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Working Group on Thermal Treatment of Waste

Management of APC residues from W-t-E Plants An overview of management options and treatment methods

Second edition, October 2008

Subgroup on APC Residues from W-t-E Plants

ISWA-WG Thermal Treatment of Waste

Subgroup APC Residues from W-t-E plants

Management of APC residuesfrom W-t-E Plants

An overview of management options and treatment methods

Thomas AstrupDepartment of Environmental Engineering

Technical University of Denmark

October, 2008

Preface

This report is produced by ISWA’s WGTT (Working Group on Thermal Treatmentof Waste). The work has been carried out by a subgroup on Air-Pollution-Control(APC) residues from Waste-to-Energy (W-t-E) Plants.

Associate Professor Thomas Astrup from Department of Environmental Engi-neering, Technical University of Denmark has produced the report with inputs fromthe subgroup.

Contributing authors

The report is produced with contributions from members of the WGTT subgroupon APC Residues from W-t-E Plants:

• Henrik Ørnebjerg, I/S Vestforbrænding, Denmark (Chairman)

• Robert Morin, Veolia Environmental Services, France

• Jean-Francois Brua, LAB SA, France

• Henning Friege, Stadtwerke Dusseldorf AG / AWISTA GmbH, Germany

• Conrad Bader, Von Roll Umwelttechnik AG, Switzerland

Coordinating authors

• Thomas Astrup, Technical University of Denmark, Denmark

• Kim Crillesen, I/S Vestforbrænding, Denmark

• Kirsten Bojsen, I/S Vestforbrænding, Denmark

Tina Benfield from The Chartered Institution of Wastes Management (UK) isgreatly acknowledged for proof-reading the text. The authors are, however, fullyresponsible for any remaining mistakes.

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Summary

Today solid residues from modern Waste-to-Energy facilities constitute the primaryemission route to the surrounding environment. Although bottom ashes are gener-ated in larger quantities, the main pollution potential is found in the air-pollution-control (APC) residues originating from cleaning the flue gases before emission toair. While a range of different types of APC residues exists the overall propertiesand environmental concerns are the same, regardless of the incinerator and countryof origin.

Research and development over the recent decades have produced numeroustreatment and disposal solutions for APC residues, some of these only tested in thelab while others are available commercially. The documentation of this range ofmanagement solutions is generally very poor: public reports may not be availableon commercial solutions while thoroughly investigated lab scale processes may nevergo beyond the lab due to market constraints. In all cases, developers and researchersmay claim that their particular solution is the best available.

This situation makes it increasingly difficult for stakeholders to compare manage-ment solutions, and for operators to select the right treatment and disposal for theresidues. This report attempts to provide an overview of available treatment tech-niques, commercial solutions, and discuss challenges and barriers as well as providesuggestions for environmental evaluation of relevant management solutions.

Currently, no general consensus appear to exist regarding residue disposal solu-tions on a worldwide level. In most countries, residues are treated to minimize futurerelease of contaminants (mainly salts and heavy metals, but also dioxins receive at-tention) and then landfilled under varying conditions (either traditional surface levellandfills with leachate collection and top covers, or subsurface disposal sites such asold salt mines). It cannot be recommended that APC residues are landfilled withoutprior treatment.

Some management solutions facilitate utilization of the residues or properties ofthe residues. This includes the use of residues for neutralization of acidic solutions,the use of residues as aggregate filler in cement or cement-like materials and asphalt.In Europe, for example, APC residues are used as backfilling material in salt minesas well as in production of asphalt for roads. As such no treatment technique andmanagement solution can be singled out as the best option; choices depend on localand regional traditions, legislation as well as market conditions (e.g. for secondaryconstruction materials).

It is recommended that management alternatives are thoroughly documentedand evaluated with respect to environmental performance before decision making.A common approach to do this systematically is by means of a life-cycle assessment(LCA); this report provides an example of an LCA-screening as well as an outlineof the data needed for such an assessment.

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A few general aspects can be emphasized:

Treatment. Residues should always be stabilized or treated to minimize futurerelease by leaching. Stabilization and treatment should naturally reflect thechoice of final disposal.

Transportation. For solutions only associated with minor emissions or energy con-sumption, the transportation of residues often represent the main environmen-tal load.

Energy. For solutions associated with significant energy consumptions, e.g. thermaltreatment, the environmental benefits from the treatment should be criticallyevaluated against the environmental load from energy consumption.

Leaching. Metal leaching from residues after final disposal may continue for thou-sands of years. Although the actual consequences cannot be determined today,the potential impacts from this long-term release should be assessed and ac-counted for.

Contaminant dispersion. Spreading of contaminants, e.g. heavy metals, via con-struction materials should be avoided. In case of utilization for constructionpurposes, the materials should be used in major projects controlled by the au-thorities and the fate of the materials after demolition should be determinedbeforehand.

Environmental assessment. Life-cycle assessments is found useful for evaluationof residue management solutions, however collection and evaluation of theneeded technology data is rather difficult, and the assessment should be ac-companied by a critical review of assumption, system boundaries, assessmentcriteria, and data.

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Contents

Preface i

Summary iii

1 Introduction 11.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Report structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Management and regulatory framework for APC residues 32.1 Residue generation and characteristics . . . . . . . . . . . . . . . . . 32.2 Environmental problems and treatment strategies . . . . . . . . . . . 52.3 Overview of management solutions . . . . . . . . . . . . . . . . . . . 62.4 Individual countries . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3 Treatment techniques 193.1 Extraction and separation . . . . . . . . . . . . . . . . . . . . . . . . 203.2 Chemical stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . 223.3 Solidification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.4 Thermal treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4 Recovery and utilization 274.1 Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274.2 Utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5 Final disposal options 315.1 Subsurface disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315.2 Surface disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

6 Commercial Technologies 33

7 Solutions and evaluation 377.1 Potentially available solutions . . . . . . . . . . . . . . . . . . . . . . 377.2 Development and documentation level . . . . . . . . . . . . . . . . . 387.3 Technology evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 387.4 Final remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

8 Recommendations 45

9 Literature 47

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Appendices 52

A Technology information A-1

B LCA-screening of residue management: An example B-1B.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1B.2 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . B-2B.3 General conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-6B.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-7

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Chapter 1

Introduction

1.1 Background

Within recent years, Municipal Solid Waste (MSW) has become a much more valu-able resource in many countries. The transition from a mere waste problem to aresource has to a great extent been enabled by modern Waste-to-Energy facilities,waste incinerators in particular.

Life-cycle thinking and more holistic approaches for evaluation of environmentalaspects has been introduced with respect to waste management; this also has con-sequences for the management of solid residues from Waste-to-Energy facilities andmay change the way these residues are managed in the future.

Today a large number of management options exists, and new potential solutionsare suggested on a regular basis. Many of these new as well as existing solutionsare not sufficiently documented. The data needed to carry out a life-cycle basedenvironmental evaluation are in by far the most cases extremely difficult to acquire.In order to assist plant owners, technology developers and public authorities inoptimizing their choice between the range of residue management technologies, thereport provides an overview of the documentation level and environmental aspectsof these technologies. The report also provides an outline of the data needed toperform a life-cycle assessment on these technologies.

1.2 Scope

This report presents a short overview of potential management options for Air-Pollution-Control (APC) residues as well as outlines potential barriers and solutions.The report focus on residues generated at Municipal Solid Waste incinerators.

The report does not provide in-depth coverage of all aspects of APC residuemanagement and treatment, for example chemical reactions in specific treatmentprocesses, and does not provide specific information on all available treatment op-tions on a global scale. The report does, however, offer a systematic overview ofpotential solutions based on research literature as well as available information fromtechnology owners.

The report is intended to serve as a catalogue and guideline for stakeholders aswell as to provide a basis for evaluating suggestions for residue management solu-tions. This is done by outlining principles of potential residue treatment, recoveryand disposal techniques. The development level of these techniques is further as-sessed and emphasized in the text.

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The report does not include discussions of treatment costs as economical aspectsmay change significantly with time and geography, and because reported cost maynot provide an accurate basis for decisions but have to be requested according tospecific needs.

The report only includes processes and technologies for which it has been possibleto acquire a reasonable level of information. The authors, however, welcome relevantinformation and data and want to encourage the readers to forward such informa-tion to subgroup chairman Henrik Ørnebjerg ([email protected], I/S Vestforbrænding,Denmark).

The report constitute a revised and updated version of the first report on APCresidue management from ISWA (ISWA, 2003).

1.3 Report structure

The report is divided into two sections: one providing the overview mentioned above,and another providing state-of-the-art data on commercially available residue tech-nologies. These data are kindly supplied by technology owners and presented inAppendix A. Appendix B provides an example of a life-cycle assessment screeningof APC residue management.

Chapter 1. Background and scope of this document.

Chapter 2. Introduction to the residues, environmental issues, overview of majormanagement strategies and legislative aspects, as well as specific informationconcerning selected countries.

Chapter 3. Introduction to residue treatment techniques, operation principles, anddevelopment status.

Chapter 4. Introduction to recovery and utilization techniques, operation princi-ples, and development status.

Chapter 5. Introduction to final disposal options, operation principles, and tech-nology status.

Chapter 6. Brief overview of major commercial residue treatment and manage-ment technologies.

Chapter 7. Overview of status for residue management solutions, documentationlevel, assessment approach for environmental impacts, outline of importantaspects for consideration, qualitative evaluation of individual treatment pro-cesses.

Chapter 8. Main recommendations based on the report.

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Chapter 2

Management and regulatoryframework for APC residues

2.1 Residue generation and characteristics

Air-Pollution-Control (APC) residues residues from waste incineration facilities existin a number of different varieties depending on the type of incinerator and the typeof flue gas cleaning equipment installed. The chemical composition of the residuesalso depends on the waste incinerated. Typically, however, APC residues are a veryfine grained powder, ranging from light grey to dark grey. If detailed informationabout flue gas cleaning equipment and residue characteristics is needed, please referto IAWG (1997) and EC (2006).

Overall, two different types of residues exist:

Dry and semi-dry residue systems. Slaked lime is injected into the flue gas,either in dry form or as a slurry. This is done to neutralize acidic componentsin the flue gas, and is typically done before removing the fly ash from the fluegas. Fly ash, reaction products, and unreacted lime is typically removed infabric filters. Activated coal may be injected for dioxin removal and removedtogether with the fly ash. Dry and semi-dry systems typically generate a singleresidue.

Wet residue systems. Fly ash is typically removed before neutralizing acidic com-ponents. After this, the flue gas is scrubbed in one, two, or a multistage ar-rangement of scrubbers. The scrubber solutions are then treated to producesludge and gypsum. Wet systems typically generate more than one residue.

It should be noted that flue gas cleaning technologies, and thereby APC residues,exist in many varieties and configurations; more than mentioned here. The abovetwo overall types of residues, however, cover most modern waste incinerators world-wide. The management of these residues is generally not depending on individualcharacteristics and variations in the residue quality. Consequently, this report treatsAPC residues collectively from a management point of view, regardless the type ofresidue.

Table 2.1 provides an overview of individual components in the two overall APCresidue types. The chemical characteristics of APC residues vary significantly fromplant to plant and region to region, however on a general level the chemical composi-tion is comparable. Table 2.2 provides typical ranges of important ash components.

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Table 2.1: Presence of individual components in residues from the two major typesof flue gas cleaning systems.

Component Dry and semi-dry systems Wet systems

Fly ash Always AlwaysBoiler ash Always AlwaysExcess lime Always (usually included) –Reactionproducts (salts)

Always (usually included) Always (in wastewater)

Dioxin sorbent Optional (usually included)Optional (usually handled

separately)

Sludge –Always (sometimes mixed

with fly ashes)Gypsum – Optional (recovery possible)Chloride salts – Optional (recovery possible)

Table 2.2: Typical ranges of important residue components (IAWG, 1997). Units inmg/kg.

Element Fly ash Dry / semi-dry WetAl 49,000-90,000 12,000-83,000 21,000-39,000As 37-320 18-530 41-210Ba 330-3100 51-14,000 55-1600Ca 74,000-130,000 110,000-350,000 87,000-200,000Cd 50-450 140-300 150-1400Cl 29,000-210,000 62,000-380,000 17,000-51,000Cr 140-1100 73-570 80-560Cu 600-3200 16-1700 440-2400Fe 12,000-44,000 2600-71,000 20,000-97,000Hg 0.7-30 0.1-51 2.2-2300K 22,000-62,000 5900-40,000 810-8600Mg 11,000-19,000 5100-14,000 19,000-170,000Mn 800-1900 200-900 5000-12,000Mo 15-150 9-29 2-44Na 15,000-57,000 7600-29,000 720-3400Ni 60-260 19-710 20-310Pb 5300-26,000 2500-10,000 3300-22,000S 11,000-45,000 1400-25,000 2700-6000Sb 260-1100 300-1,100 80-200Si 95,000-210,000 36,000-120,000 78000V 29-150 8-62 25-86Zn 9000-70,000 7000-20,000 8100-53,000

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2.2 Environmental problems and treatment strategies

Apart from working safety aspects, the main problem related to APC residues isthe potential release of contaminant to the environment. This release may poten-tially occur by several routes, however the primary is by leaching from the residuesonce landfilled or otherwise placed at their final destination. On modern plants theresidues are generally handled and transported in closed systems or under moistconditions to avoid dusting, therefore these activities are not considered importantfrom an environmental perspective.

The main environmental concern with respect to APC residues is leaching of:

Easily soluble salts such as Cl and Na. Although not toxic for humans in typ-ical concentration levels these components may significantly affect ecosystemsand spoil drinking water resources.

Heavy metals such as Cd, Cr, Cu, Ni, Pb, and Zn. Heavy metals and traceelements can potentially be present in concentrations harmful for humans aswell as for ecosystems. As such, leaching of these components has generallybeen the primary concern and has also received the greatest research focus.

Dioxins. Although dioxins and furans do not easily leach, release of these contam-inants is of major concern because of their toxicity.

In order to minimize impacts on the environment, the release of the above con-taminants should be reduced as much as possible. Ideally this means that theseconstituents should either be effectively bound in the residue matrix or simply re-moved leaving the remaining materials harmless. This may not always be possibleto achieve, however APC residues should always be treated to minimize potentialfuture release.

Research and development related to APC residue treatment and managementhas for the above reasons traditionally been aimed at developing and evaluatingtechniques for reducing leaching from residues after final placement. In the case ofdioxins, also actual destruction of these components has been a focus.

This has resulted in a range of techniques discussed in Chapter 3 (please referto this chapter for further details):

• Extraction and separation

• Chemical stabilization

• Solidification

• Thermal treatment

The overall aim has been to treat the residues so that landfill acceptance criteriaare fulfilled, but also various material related criteria may have to be fulfilled forexample in the case of utilization. The above techniques reflect different approachesto meet these goals. The reason for development of these different types of tech-niques, rather than using a single process worldwide, has been differences in localtraditions, regulations, market conditions, and political focus.

In almost all countries, some level of treatment of the residues are requiredbefore further utilization or landfilling. A commonly applicable definition of what

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is an acceptable level of “stabilization” does not exist as criteria and conditionsdiffer worldwide. Treatment and stabilization of residues should, however, provide aresidue quality appropriate for the intended final destination, regardless whether theassociated criteria are environmentally or technically based. From an environmentalpoint of view, residue treatment may not always be an issue of providing the mostinert material. As discussed in Chapter 7 using a lot of energy and resources inthe treatment phase without evaluating the achieved benefits relative to the type ofdisposal may not necessarily be environmentally sound.

2.3 Overview of management solutions

2.3.1 Residue management

Overall, three main routes for APC residues exist:

• Utilization as aggregates

• Material recovery

• Landfilling

In Europe, either of these options include some degree of treatment and/or sta-bilization: 1) the residues may not have the necessary technical quality needed forutilization, 2) the utilization option integrates stabilization of the residues, 3) the re-covery of materials requires treatment of the residue, and 4) the leaching propertiesof the residues need to be improved before final placement.

A large number of combinations of treatment, stabilization, utilization, and land-filling processes exists on an international level. These combinations are often aconsequence of local traditions and legislation. A rough estimate is that in the orderof 20–30 technologies is in use or has been suggested worldwide. Regardless of thesevariations, APC residue management can for simplicity be grouped according tothe three main options mentioned above. Chapters 3–5 provides further details onavailable treatment technologies, utilization and recovery, as well as final disposal.

2.3.2 EU Legislation

APC residues are categorized as hazardous waste and residue management is regu-lated within this framework. The EU is currently in the process of updating legisla-tion and introducing new overall strategies on waste: these initiatives will affect themanagement of APC residues. The most important of the—expected—consequencesare outlined in the following.

Thematic Strategy on the Prevention and Recycling of Waste

With this thematic strategy, the EU aims to decrease waste quantities, increase re-cycling and material recovery as well as increase energy recovery from waste, amongother issues. Introducing the principles discussed in the strategy into EU legislationand regulation, may also give rise to changes for APC residues:

• Reduction of the number of waste specific directives (e.g. merging the Directiveon Hazardous Waste into the Waste Framework Directive)

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• Definitions regarding the transition of waste to secondary products

• Quality standards for recycled and secondary materials and products

• Definitions of recovery and disposal activities

• Introduction of ”life-cycle thinking”

The above issues are not defined in detail in the thematic strategy, but willbe defined during the actual implementation process. Introduction of “life-cyclethinking” into waste management regulation may potentially have a large impact onthe way residue management is evaluated and argued. In Chapter 7, this documentprovides an example of a life-cycle assessment on residue management alternatives.

Waste Incineration Directive

The process of revising the Waste Incineration Directive is expected to start around2008. This may affect emission levels from incinerators and subsequently also thecomposition of residues. The revised directive is expected around 2012.

Waste Framework Directive

The directive provides a definition of waste utilization. This primarily affects importand export of APC residues in EU Member States. The current revision of the WasteFramework Directive suggests a new and more concise definition of utilization andend-of-waste criteria. It is unclear how this will affect APC residues in the future.The revised directive may also allow more possibilities for the mixing of hazardouswaste fractions, provided that the environmental burden is not increased.

Landfill Directive

The criteria for waste acceptance at landfills are minimum criteria and MemberStates may define more stringent criteria. In any case, APC residues do not complywith these criteria and need to be stabilized before landfilling.

Statutory Order on Transport

Exchange of APC residues between Member States is regulated according to theStatutory Order on Transport. Member States may define more restrictive standardsfor residue treatment, and may deny import/export of residues on this account.

Statutory Order on POP

The Statutory Order on Persistent Organic Pollutants (POP’s), including dioxins,regulates management of waste containing these compounds. For APC residues, thecontent of dioxins/furans is relevant with a limit value of 15 µg/kg. Generally, APCresidues are anticipated to be below this limit, however in cases exceeding the limitdioxins should be destroyed or the residues should be safely landfilled.

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2.3.3 General challenges

Treatment and management of APC residues may face various challenges: technical,economical, legislative, and environmental. Strategies to meet these challenges arehighly dependent on local and/or regional conditions, and are generally reflectedby the management option of choice in individual countries. In section 2.4 shortoverviews of the situation in selected countries are provided.

A few overall principles with respect to the environmental aspects, however,should be emphasized:

Dilution. The principle of mixing hazardous waste with other materials can beregarded as dilution should not be sanctioned. On one hand this limits thepossibilities of utilization, but on the other hand potentially uncontrolled dis-persion of contaminants in the environment is avoided.

Hazardous waste utilization. In extension of the above, the actual concept ofutilization of hazardous waste may be questionable: from an overall environ-mental point of view, it may be wiser to keep contaminants concentrated andconfined, and then attempt to minimize and control the release (e.g. by leach-ing in the case of residues).

Resource consumption. Extensive treatment/stabilization and material recoverymay involve consumption of significant quantities of resources such as energyand water. From an overall environmental perspective this may not be benefi-cial (e.g. material recovery requiring more energy than the energy representedby the actual material substituted).

2.4 Individual countries

The following sections present country specific information on management andtreatment of APC residues with focus on current management practices, specificlegislation and regulation, and important barriers and challenges for residue man-agement and further development.

2.4.1 Denmark

Management practices

The current solution in Denmark is to export APC residues to either Norway orGermany. In Norway the residues are utilized for neutralization of waste acid, and inGermany for backfilling of salt mines. This solution is not considered permanent bythe Danish EPA, however it is unlikely that a permanent solution can be determinedat the moment as relevant EU legislation is under revision. In 2004, the majorDanish incinerator operators1 initiated a research and development program withthe focus to improve APC residue management in Denmark, including evaluatingand supporting relevant technologies as well as providing the necessary scientificbasis for decision making. The initiative is carried out in accordance with the DanishEPA and finishes in 2009 with conclusions on future solutions for Denmark.

1DONG Energy A/S, I/S Amagerforbrænding, and I/S Vestforbrænding

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Specific legislation

No specific statutory order regulates management of APC residues in Denmark.The current policy is not to allow landfilling or temporary storage of APC residuesin Denmark, treated or not treated. This policy is maintained until a long-termsolution is found for management of APC residues from Danish incinerators. Untilthis, final disposal in Germany and Norway is allowed.

Barriers and challenges

So far, a major focus has been to avoid (uncontrolled) spreading of contaminantsin the environment and the society. This results in reluctance from authorities tosanction utilization options including production of construction materials based onAPC residues. It is unlikely that this will change in the future. Currently, themain challenge for the operators in Denmark is that the Danish authorities haveyet to decide whether relevant technologies should be categorized as utilization ordisposal. Until such a decision exists, investments in new treatment and utilizationtechnologies in Denmark are unlikely.

2.4.2 France


APC residues are classified as hazardous waste and are treated as such by all Frenchmunicipal waste incinerators. The most common treatment is to stabilize and solidifythe residue with addition of cement and chemicals. The process is changing boththe chemical and physical nature of the APC residues and ensures that even if themonolith deteriorates that the contaminants will remain in the matrix. It is a meansto reduce the solubility of traced metals contained in the residues. Once stabilizedthe residue is buried in a landfill permitted for hazardous waste disposal. In 2007,the treatment cost was around 235 Euro/ton of residue, including a 20 Euro/tonenvironmental tax but excluding transportation costs.

The French regulations governing the possibility of exporting APC residues toother countries for underground disposal in abandoned salt mines are facing someinterpretation problems and it is difficult at this point in time (2008) to estimatewhat will be the final situation with regards to this mode of disposal for APC residuesproduced by French incinerators.

APC residues produced from Flue Gas treatment systems using dry sodiumbicarbonate for HCl and SO2 abatement are in some case collected in order tobe washed, filtered and partially recycled in the production of sodium carbonate.In France, the Resolest platform has a 50,000 tons (APC residues) per year ofproduction capacity.

One incineration plant is equipped to provide a thermal treatment of APCresidues. A plasma torch system is used to vitrify the APC residues.


The French adaptation of applicable EU directives for Hazardous Waste call for thetreatment of solid wastes from flue gas treatment as an hazardous waste associatedto the EU Waste Catalog number 19 01 07*.

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Different processes have been studied and tested to wash, separate and recycle someof the APC residues constituents or to use them as an acid neutralizing agent.Due to their specific waste classification it is unlikely that APC residues could avoidbeing disposed of under anything but hazardous waste regulations unless thoroughlytreated by an industrial process that will separate some basic constituents thatcan be reused as feedstock to other industrial processes. Therefore the barrier topartial recycling is essentially economic, especially when considering the challengeof getting through the required REACH regulation requirements that may apply tothis approach.

2.4.3 Germany


Most German W-t-E plants are equipped with a dry or a semi-dry flue gas cleaningsystem, the decreasing number of wet systems in recent years is due to high costsfor chemicals and waste water handling. APC residues are treated as hazardouswaste and are generally processed within the country. There is no relevant exportof residues from flue gas cleaning.

Former or active salt mines represent the most prominent sink for APC residues.Due to good geological preconditions in the region between the cities of Braunschweigand Halle, many salt mines were founded in the 19th and 20th century. Potassium,Magnesium and Sodium chlorides number among the most important salts mined inthis area. The seams are found between 500 and 800 m below ground. The cavernsare large enough for the use of heavy trucks. The height of the caverns is in the rangeof 5 to 10 m. The caverns may break down due to static reasons, especially causedby incautious exploitation as has been practiced in the former GDR. Therefore,backfilling of the mines fulfills a need. Due to the high amount of soluble salts, APCresidues in general, especially all salts from wet scrubber systems are suitable forbackfilling thus replacing natural resources otherwise needed. This storage methodis looked at as extremely safe because of the geological history of the mines. Othermines (coal, iron ore) used for the disposal of APC residues in former years, havebeen closed down.

Few APC residues are used as asphalt construction materials. Small amounts ofAPC residues are disposed of in normal landfills after various stabilization processes.Recently, Germany introduced ambitious criteria for leaching tests used as a decisioncriterion for waste disposal. It may therefore be concluded that the amount of moreor less stabilized APC residues will decrease again.

Less than 10 % of all APC residues are disposed of in underground storagefacilities or on landfills suitable for hazardous waste.

In 2005, more than 350,000 tonnes APC residues were produced from W-t-Eplants. About 200,000 tonnes were recycled without further processing by backfillingof salt mines. About 30,000 tonnes were landfilled mostly in underground storage.About 120,000 tonnes were processed, partially by stabilization techniques.


In Germany, waste management has changed enormously since 2005, when the land-filling of organic waste (i.e. household waste or other waste with more than 3 %

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TOC) was banned after a long transition period. Therefore, the mass flows reportedfor APC residues in 2005 may not be representative for the years 2006 and 2007.Probably, backfilling of salt mines has become even more important.


The solidification of APC residues with the aim to use these materials as a layerfor landfills might be restricted by a forthcoming regulation on the recycling of sec-ondary minerals. Due to their experience with the classical leaching test (DEV H 14,EN/ISO) they prefer the so called pH stat test where the residues are exposed to anacid with a constant pH over some time. With this test, acidic rainfall is simulated.Very often, this test leads to more critical results because normal water used in theclassical leaching procedure normally does not destroy solidified materials.

2.4.4 Italy


Most of the waste to energy plants in Italy are equipped with a dry or a semi-dry fluegas cleaning system, using lime or sodium bicarbonate as alkaline reactant. The useof sodium bicarbonate is now increasing, especially during the revamping of existingplants, in order to comply with emission limits in the EU, without installing anyadditional wet treatment system.

No thorough survey on the APC residues management has been carried out sofar in Italy. However, it is known that most facilities dispose of the residues tolandfills after a specific treatment, aimed to stabilize and solidify the residues bymeans of the addition of cement and chemicals so complying with regulatory limitvalues for waste acceptance in landfill. Treatment is mainly performed outside theincineration plant, but there are also some plants that treat APC residues on site.

Some Italian facilities, located in Northern Regions, export their untreated APCresidues to German salt mines as backfilling materials, similar to other Europeancountries. There are nevertheless some examples of alternative forms of manage-ment. For instance, in the case of using dry sodium bicarbonate the alkaline saltsare collected by the seller and treated in a plant having a capacity of 30,000 tons peryear; so a brine suitable for sodium carbonate production is recovered. This practicerequires a flue gas double stage filtration system, in order to pull apart alkaline saltsfrom fly ash.

In 2004 about 4.22 million tons of waste was incinerated in 52 W-t-E plants witha total APC residue production of about 200,000 tons.


The Italian legislation (Government Decree n. 152/2006) classifies APC residuesfrom waste-to-energy plants as hazardous waste according to the EU Waste Cata-logue. The Environment Ministry decree n. 36/2003 also prescribes that landfillscan accept only waste whose contaminants content respect the limit values listed inTable 2.3.

Also a leaching test (according to the CEN EN 12457 standard) shall be compliedwith; pollutant concentrations in extracted eluate shall not exceed the limits shownin Table 2.4.

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Table 2.3: Limit values for waste acceptance in landfill, as per decree n. 36/2003.Parameter Unit Limit valuePCB mg/kg 50PCDD & PCDF mg/kg 0.01Solid content % ≥ 25TOC % < 6

Table 2.4: Limit values in eluate for waste acceptance in landfill, as per decree n.36/2003.

Parameter Unit Limit valueCr mg/l 7Cd mg/l 0.2Cu mg/l 10Hg mg/l 0.05Mo mg/l 3Ni mg/l 4Pb mg/l 5Sb mg/l 0.5Se mg/l 0.7Zn mg/l 5Chloride mg/l 2500Fluoride mg/l 50Aromatic organic solvents mg/l 4Nitrogen organic solvents mg/l 2Chloro-organic solvents mg/l 20Cyanides (CN) mg/lSulfates (SO2−

4 ) mg/l 5000DOC mg/l 100TDS mg/l 10000


At present it seems that there are no drivers pushing waste managers for towardsalternative options to landfill disposal, and it is unlikely that this will change in thenear future.

Possible use of APC residues in cement kilns or for construction material arehampered by a strict and unclear legislation that makes recovery of material fromhazardous waste such as APC residues difficult and costly.

Probably only the recovery of alkaline salts from APC residues coming fromplants that use sodium bicarbonate will be further implemented, as it can partlyovercome the issues related to APC residues management.

Also some thermal treatment methods were evaluated and tested in the past, butthey were abandoned, because there is no chance that this technology can becamecommercially viable.

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2.4.5 The Netherlands


The Dutch policy with regard to the residues from Waste to Energy Plants (WtEplants) aims towards maximization of useful application and minimization of re-quired volume for disposal of these residues. This policy has led, to date, to arecovery rate of the APC residues of around 50 %. The other half is disposed of inconditioned landfills after cementation (fly ash) or in big bags (fly ash and flue gastreatment salts). The policy has been put into practice successfully for municipalsolid waste incineration (MSWI) fly ash and led to the use of this material as a fillerin asphalt (as a substitute for lime stone) for road construction. The demand forasphalt fillers containing MSWI fly ash, however, is limited. As a result only 30 %of the MSWI fly ash produced has been utilised as an asphalt filler. A considerableamount of fly ash and flue gas treatment salts are being utilised for fortification inGerman coal and salt mines (it has been adopted by the Council of State in theNetherlands that application of APC residues is called utilisation if it is identifiedas such in the country of application). The Dutch Waste Management Association(DWMA) has started a project group which is going to identify potentially successfulalternatives for fly ash utilisation.


Annex II (Council decision 2003/33/EC) of the European Directive on the Landfillof Waste (Directive 1999/31/EC) is implemented in Dutch legislation.


Implementation of Annex II makes it more difficult (i.e. more costly) to landfillhazardous waste in its untreated form it’s already forbidden in the Netherlands.Since it is a waste of effort and money to continue with disposal Annex II serves asan incentive for more recovery of APC residues. This may lead to utilization of thesulphates in the form of gypsum and chlorides in the form of calcium chloride.

2.4.6 Norway


APC residues are categorized as hazardous waste, and thus specific legislation applies(see below). Current practice is that all APC residues are landfilled in specificlandfills (rock structures). NOAH Langøya holds the largest market share.


No specific legislation exists for the handling of APC residues. As for waste cate-gorized as hazardous waste this may only be handled and treated by parties withspecific permission.


There is a general political wish to maximize the reuse/recycling of incineratorresidues, but no real political will. When it comes to APC residues these con-

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tain toxic components, and will very likely maintain the classification as hazardouswaste, and their disposal will only be categorized as disposal.

2.4.7 Sweden


The amount of APC residues in Sweden 2006 was 180,000 tonnes and the trend isincreasing. The increase is mainly caused by increased incineration capacity. Thetotal amount of waste treated in WtE-plants during 2006 was 4,000,000 tonnes.Approximately half of the waste incinerated was household waste.

Currently there are two major ways to handle the APC residues. One way isto send the residues to landfill after stabilization. This is still the most commonway to treat APC residues. This however will change after 2008 when the landfilldirective comes in to force. The other way is export to Norway where the residuesare utilized for neutralization of waste acid. This method is used by an increasingnumbers of WtE plants.

Only three of 30 plants handles their APC residues in other ways than the onespresented above. One plant has succeed in classifying their APC as non-hazardouswaste and can send the APC residues to a landfill for non-hazardous waste. Oneplant having access to old petroleum storages in the ground beneath their plant isusing their residues to refill these storages. The third plant has installed equipmentto wash the APC residues with the aim to get them classified as non-hazardous.Although the process is still under development they have succeeded in washing outthe chlorides below the acceptance criteria, which means they can send the APC toa landfill for hazardous waste.


Annex II (Council decision 2003/33/EC) of the European Directive on the Landfillof Waste (Directive 1999/31/EC) is implemented in Swedish legislation.

The flue gas treatment from the WtE-plants is classified as hazardous waste as inthe EU Waste Catalogue number 19 01 07*. If the APC residues exceed the leachinglevels in the acceptance criteria the residues have to go to recycling or treatment.


After 2008 all of the landfills have to fulfill the EU landfill directive. The plantssending their APC residues to these landfills then have to find other alternatives. Ifresult from the plant that attempts to clean the APC residues are not promising,the major part of Swedish APC residues will be exported to either Norway or Ger-many. An alternative currently being looked into is if there can be found a need forneutralization or back-filling in Sweden similar to those in Norway or Germany.

2.4.8 Switzerland


Most of the 29 W-t-E plants in Switzerland are equipped with sophisticated wetscrubbers as APC systems, a few only still have semi-dry systems using spray dryers.All plants are equipped with Electrostatic Precipitators that separate the filter dust,before the de-dusted flue gas is treated in a scrubber section.

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Therefore, the main quantity of APC residues consists of filter dust, which istreated in several different ways, usually on site. Effluents from the scrubber sectionand a possible APC residues treatment plant (typically acid fly ash washing) are inall cases cleaned by precipitation and filtering steps, where solids are separated assludge. The cleaned effluent, still containing the main part of the soluble salts, isusually discharged to the next river. A few plants evaporate the effluent to producesalt or brine, which is used for the regeneration of ion exchangers or for de-icingroads during winter time.

In 2004 the 29 plant incinerated a quantity of 3,131,809 tonnes of waste inSwitzerland, thereby producing 60,726 tonnes of fly ash, which was roughly disposedof as follows:

• 18 % was acid washed, back-mixed with bottom ash and landfilled in Swisslandfills

• 36 % was exported to German salt mines

• 46% was washed, solidified with additives, in some cases also including thewater treatment sludge, and land filled in Swiss landfills

• A small amount was exported to France and disposed of in a heavy metalsrecovery and smelter plant

The sludge quantity resulting from the effluent cleaning of the wet flue gas treat-ment and wet fly ash treatment systems totalled 9,460 tonnes in 2004.

• 32 % of this was disposed of without solidification, mainly in German saltmines

• 12 % was solidified with additives and landfill in Swiss landfills

• 56 % was exported to smelter plants for zinc recycling

Today Swiss W-t-E plants have the choice of either exporting untreated APCresidues to German salt mines for backfilling purposes or landfill the treated andmainly also solidified APC residues in Swiss landfills. For new plants fly ash washingand zinc recovery is considered to be state-of-the-art.


APC residues are considered hazardous waste. A special landfill class for residues isdefined (Reststoffdeponie). Residues to be landfilled have to fulfill a special two-stepleaching test (continuous acid test).


The main barriers are costs for treatment and local landfilling versus export costs.Utilization of residues or fly ashes in any form is prohibited due to the risk of dilutionand dissipation in the environment.

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2.4.9 United Kingdom


In the UK APC residues are classified as hazardous waste at the point they aregenerated at EfW facilities. APC residues as generated in the UK may differ fromother EU arisings, in that some boiler dusts are excluded from the APC residues aspart of the process, in some cases effecting final composition. APC residues arisingin the UK currently constitute around 200,000 tonnes per annum, and this figure ispredicted to continue rising.

The most common treatment is to undertake physical chemical treatment withacidic wastes in order to partially stabilize the residue. The process changes boththe chemical and physical nature of the APC residues. The product of the treatmentis a “solid” non-hazardous or hazardous residue. The residue is currently sent tolandfill.

Once treated, the residue is sent to either a non-hazardous or hazardous landfilldepending on the assessment of hazardousness normally linked to either compositionor H14 ecotoxicity test. The total treatment and disposal cost (including tax) isaround £60/tonne for non hazardous landfill and £120/tonne for hazardous landfill(2008). The treatment takes place either in mixing pits (see the first bullet pointbelow), facilitated by mechanical shovel mixing, pan mixers or more sophisticatedsilo and metered enclosed mixing units.

There is one salt mine in Cheshire authorized to accept APC residues untreatedfor storage. There is no export of APC residues outside of the UK.

The UK hazardous waste market is still evolving and the Environment Agencyis working on the issue of interpreting and introducing legislation that adopts aEuropean model into a market that has an infrastructure developed around 30 yearsof co-disposal. The key issues potentially impacting further on APC residues in thefuture being:

• UK Environment Agency stated policy is to ban open pit mixing (in 2008, dueto issues relating to homogeneity of treated mixtures), and in the long term,seek the requirement of solidification and stabilization of inorganic hazardouswastes

• UK Environment Agency are considering the cessation of WAC (Waste Accep-tance Criteria) derogation for Hazardous landfill sites and this would, in themajority of cases, prevent the landfill of APC treated residues as a “HazardousWaste” unless they are stabilized

• UK Environment Agency is looking at whether hazardous wastes should re-main hazardous even after treatment i.e. become partially treated hazardouswastes even if hazardous components are below the threshold for being haz-ardous

• The introduction of Pollution Prevention Control Permits is starting to makethe operation of hazardous waste facilities far more stringent and onerous

The most likely future treatment at some point will include the introductionof hydraulic binder (cement or other pozzolanic waste stream) solidification andstabilization. There are some proposals for washing processes for APC residues inorder to produce re-saleable materials. There are also some developments in thermal

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treatment, e.g. plasma torch, but it remains to be seen if, after many years, thistechnology can become commercially viable.


The UK landfill regulations adaptation of the applicable EU directives for HazardousWaste call for the treatment of solid wastes from flue gas treatment as an hazardouswaste associated to the EU Waste Catalogue number 19 01 07*.

The EU Waste Catalogue number for the partially stabilized residue from phys-ical chemical treatment with acidic wastes is 19 02 05 (hazardous) or 19 02 06(non-hazardous).


The main barrier is an economic one, e.g. cost of binders and the EA is unlikely toconsider the stabilized APCR as non-hazardous (although efforts are being made toascertain the hazardous or non-hazardous nature of monoliths from this process).

There are a wide range of operators treating APC residues and the processesrange from bespoke treatment with enclosed mixing systems to ’open pit’ mixingthrough to wetting APC residues with leachate prior to direct landfill. The UK Envi-ronment Agency is trying to bring consistency to the way hazardous waste is treatedand is expected to provide some guidance in order to facilitate the development anddemonstration of processes.

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Chapter 3

Treatment techniques

Treatment of APC residues should always be considered an integral part of anymanagement, utilization and disposal option. Although, a specific technology orsolution does not explicitly involve residue treatment, it is most likely that one ormore of the processes included contain some level of modification of the physicaland/or chemical properties of the residues. As such, understanding relevant residuetreatment techniques are very important when discussing APC residue management.

Within the last few decades, a large number of specific residue treatment tech-niques have been suggested. Although significant variations exist, these treatmenttechniques may be grouped according to the main principle of operation:

Extraction and separation. Processes involving extraction and removal of spe-cific components in the residues.

Chemical stabilization. Processes involving binding and immobilization of con-taminants by chemical reactions.

Solidification. Processes involving physical binding and encapsulation of residues,and in some cases also chemical stabilization.

Thermal treatment. Processes involving heating of the residues, and changes ofthe physical and chemical characteristics.

Only a small fraction of the suggested treatment techniques are currently incommercial use, often techniques have only been tested in lab- or pilot scale applica-tions. Many of the techniques are comparable by their principle of operation, manytreatment technologies also include several of the above processes.

It should be noted that traditionally the main focus for research and developmentof treatment techniques have been to improve the environmental properties of theresidues in case of landfilling. This means that most processes aim to reduce leachingof metals and in some cases also salts. In spite of this, the processes used forutilization and recovery are generally similar.

This chapter provides an overview of the most important processes and treatmenttechniques. The techniques are presented according to their main principle, althoughthey may include several individual processes. For each of the processes, examples ofrelevant technologies are mentioned and it is stated whether the process/techniquein question is in commercial use.

It is thus the intention to provide an overview that forms a simple basis for eval-uation of new treatment technologies not specifically mentioned in this document.

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For a number of the technologies, Appendix A provides further details to the extentavailable.

3.1 Extraction and separation

Extraction and separation processes include all processes whose main purpose is toremove or recover specific components or fractions from the residues. The maindevelopment focus has been placed on removing heavy metals and to some extentsalts from the residues, mainly using water or acidic solutions. The processes aretypically relatively simple, but are in some cases integrated with other processessuch as chemical stabilization or solidification. A subgroup of extraction processesare related to thermal treatment as the actual extraction occurs integrated with thethermal treatment due to differences in melting temperatures of metals. Thermaltechniques are discussed separately in section 3.4.

The main advantage of extraction and separation processes are the use of rela-tively simple techniques. The main disadvantage is the generation of metal and saltcontaining process water; this may, however, be utilized for further recovery.

Water

Mixing water and APC residues results in an extremely alkaline suspension with pHaround 11–13 and high concentrations of salts like Cl, Na, and sulphate, and heavymetals like Pb, Zn, Cr, and As. Using water, most of the salts can be extracted butonly a small fraction of the heavy metals (typically less than 1 %). Although saltleaching can be significantly reduced with water extraction processes, the leachingof metals are generally not reduced significantly.

Water extraction—or washing of residues—is typically used in combination withother processes as washing alone is generally not considered to be sufficient. Washingprocesses may, however, constitute a relatively significant element in some treatmentprocesses. Typical residence times are 0.5–1 hour at liquid-to-solid (L/S) ratios ofabout 2–5 l/kg; about 10–30 % of the total mass can easily be removed with waterextraction (Lundtorp, 2001).

Technology status: The technique is used in several commercially available tech-nologies, such as: Ferrox, DHI, cement solidification in Switzerland.

Acid

Extraction with acidic solutions are in many respects similar to water extraction,pH is however significantly lower typically around 3–6. Like water, acidic solutionsalso extract salts, however most heavy metals are much more soluble at lower pHresulting in improved removal of these components as compared with water extrac-tions. Typically, around 30-60 % of cationic heavy metals may be removed from theresidues using acid (Arcangeli et al., 1996; Gong and Kirk, 1994; Hong et al., 2000).It should, however, be noticed that increased metal removal may not always be cor-related with improved leaching as the mineralogy of the treated residues generallydetermines metal leaching rather than the actual metal contents.

Acid extraction has been suggested in a range of treatment technologies, in manycases acid from the first scrubber stage on plants with wet flue gas cleaning systemshas been utilized. Acid extraction has been combined with other processes likethermal treatment and solidification.

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Technology status: The technique is used in several commercially available tech-nologies, for example FLUWA.

Microorganisms

Biohydrometallurgy is a well established technique for metal recovery from solidmaterials such as low-grade ores. The technique—also termed bioleaching—hasbeen suggested for a range of waste materials, including APC residues (Krebs etal., 1997; Brombacher et al., 1997, 1998; Bosshard et al., 1996). Extraction bybioleaching makes use of microorganisms to 1) facilitate redox reactions, 2) to formacids, or 3) to form complexing agents. Indirectly, the technique involves waterand/or acid extraction.

Removal of large fractions (50–90 %) of specific heavy metals has been reportedin the lab, however this requires large quantities of water (L/S above 20 l/kg) andvery low pH (around 0.5–5). These requirements make the technique less suited forAPC residues on an industrial scale.

Technology status: The technique is not commercially available, and has beentested in small scale only.

Electrodialysis

Metals can be extracted by applying a current thereby facilitating a migration ofions in a residue suspension toward an anode or cathode. Ion exchange membranescan then be used to separate metal ions from the residue suspension (Pedersen etal., 2003; Ottosen et al., 2003). The technique requires metals to be in the aqueousphase; the release from the solid may be enhanced by use of complexing agents. Inpractice therefore, this technique first involves aqueous extraction of metals fromthe solids; the electrodialysis process then serves as a separation process.

Removal rates of around 20–70 % for metals like Zn has been reported at L/Sratios of about 5 l/kg. Effective extraction requires good mixing.

Technology status: The technique is not commercially available, and has beentested in small scale only.

Particle size fractionation

Separation based on particle size fractionation has been suggested only in a singlecase (Crillesen, 2005). The technique is based on the settling velocities of residueparticles in a water filled reactor: small particles are removed at the top of thereactor. The process has been suggested for separation of unreacted lime from dryand semi-dry residues. As the technique involves an aqueous suspension, waterextraction processes are also included.

Particle size fractionation should be used in combination with other treatmenttechniques as removal of the small particles will not render the remaining fractionsuitable for final disposal or utilization.

Technology status: The technique is not commercially available, and has beentested in pilot scale only (in combination with the DHI treatment process, see section3.2).

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3.2 Chemical stabilization

Chemical stabilization processes include all processes whose main purpose is to bindand immobilize pollutants in the residue matrix. Development focus has primarilybeen placed on binding heavy metals by alterations to the residues geochemicalproperties. The processes are typically relatively simple subprocesses, such as waterextraction, chemical reactions, and then de-watering. It should be noted that severalother treatment processes also involve elements of chemical stabilization, for examplein cement solidification techniques.

The main advantage of chemical stabilization processes is a significant improve-ment of the leaching properties of the residues and the use of relatively simpletechniques. The main disadvantage is the generation of metal and salt containingprocess water.

FeSO4

Addition of Fe-oxides to a residue suspension may significantly increase the sorp-tion capacity for heavy metals. The technique involves several steps: first waterextraction of easily soluble salts and mixing of FeSO4, then oxidation of Fe for pre-cipitation of Fe-oxides, adjustment of pH to about 10–11, and finally de-watering ofthe product (Jensen et al. 2002, Lundtorp et al. 2002a, 2002b).

The technique has been tested in pilot scale by means of the Ferrox treatmentprocess, and has been thoroughly documented (Lundtorp, 2001). The treated prod-uct has also been suggested to be sintered with the bottom ashes by re-introducingthe (treated) residues to the furnace (Baun et al., 2004; Bergfeldt et al., 2004), andto be solidified with cement (Cai et al., 2003, 2004).

Technology status: The technique is commercially available.

CO2 and H3PO4

Stabilization with CO2 and H3PO4 involves changes to the geochemical binding ofheavy metals similar to stabilization with FeSO4, however in this case the metals(primary focus on Pb, Cd, and Zn) are bound as relatively insoluble carbonates orphosphates. The technique includes a multi-step procedure similar to the Ferroxprocess.

The technique has been tested in pilot scale by means of the DHI treatmentprocess (Hjelmar et al., 1999, 2001). Similar processes, however only using CO2 forthe stabilization, has been suggested and tested in the lab by several researchers (e.g.Ecke et al., 2002, 2003; Ecke, 2003). A Danish process (DHR treatment process),similar to the DHI process but without the use of phosphate, has been tested inpilot scale in Switzerland.


Phosphate

A variety of the above stabilization processes also utilize phosphate as the stabilizingagent and bind the heavy metals as phosphate minerals. Originating from USA, thisprocess mixes reagents and residues more or less “dry”, often only with a little waterto avoid dusting (Lyons, 2003; Eighmy et al., 1997; Iretskaya et al., 1999; Kim etal., 2003). As such, the process does not include water extraction of salts but onthe other hand generates no process water.

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Technology status: The technique is in commercial use (e.g. in USA, Japan andTaiwan).

Sulphide

Similar to phosphates and carbonates, sulphides can bind heavy metals in ratherinsoluble compounds. This technique is used on a regular basis for treatment ofprocess and waste waters. One process utilizing this technique has been suggestedbased on the sulphide containing sludge from cleaning the scrubber solution onplants with wet flue gas cleaning systems (Reimann, 1990). This sludge containsunreacted sulphide compounds that—mixed with the residues—can improve theleaching properties of the final product (Bamberg product). This also has the benefitof reducing the number of products leaving the plant. Another process, the AES(Acid Extraction Sulphide) process, combines acid extraction with sulphide addition.Also stabilization with Na2S has been suggested (Youcai et al., 2002).

Technology status: The technique is in commercial use as the Bamberg method(rather extensively used in Europe).

3.3 Solidification

Solidification processes include all processes whose main purpose is to physically andhydraulicly encapsulate the residues. The primary development focus has been tominimize leaching of heavy metals after final disposal. In the literature, solidifica-tion processes are often discussed as stabilization processes (S/S: solidification andstabilization). This illustrates that in many solidification processes, metals are alsosubjected to chemical stabilization and immobilization reactions with componentsin the hydraulic binder (e.g. binding of heavy metals in cement minerals).

The main advantages of solidification techniques are a decrease of leaching andimprovement of the mechanical properties. Solidification techniques often also makeuse of relatively simple technology. The main disadvantages are that the physicalintegrity of the product may—depending on the choice of binder—deteriorate overtime and that mass and volume increases with the treatment.

Water

Residues have pozzolanic properties and may harden if mixed with water. Relativelylarge quantities of water may be incorporated due to the high content of for exampleCa salts. The resulting geochemical changes are similar to those occurring in waterextraction processes, except in this case residue components are not extracted.

Technology status: The technique is primarily used as a subprocess in othermulti-step procedures. As a stand-alone technique it has been investigated in labscale only (Todorovic et al., 2003).

Cement

Cement solidification is probably the most widespread treatment technique for APCresidues worldwide. Simplified the process involves mixing of residues, cement, wa-ter, and other additives. The additives may be other types of waste materials and/orspecific components enhancing strength development; often companies use their ownspecific recipe for the mixing. These processes have been investigated extensively

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within the recent decade (e.g. Polettini et al., 2001; Sabbas et al., 2003), in partic-ular with respect to metal binding, strength development, and leaching properties.Cement solidification exists in numerous variations on a worldwide level and maybe used in combination with other treatment processes, for example after acid ex-traction and chemical stabilization. Focus for the solidification can be either land-filling or utilization of the final product for construction purposes (e.g. backfillingin mines).

Technology status: The technique is in commercial use in many countries world-wide.

Asphalt

Residues may be used as a filler material substitute in asphalt production. Thisis done in The Netherlands where about 25 % of the filler used in asphalt is flyashes from waste incineration. The aspalt is then used in road construction. Thetechnique has also been used in Japan, but with the purpose of landfilling (IAWG,1997). The involved processes are significantly less investigated than in the case ofcement; it is however likely that the longevity of the encapsulation is better thanthe case for cement.

Technology status: The technique is in commercial use in The Netherlands.

Gypsum

The process is based on formation of a gypsum containing product by mixing ofresidues, water and acid. The residues are suspended in water, and then mixed withacid and lime at a pH of about 5–7. At this point gypsum precipitates. Finally,pH is increased to around 8–10 by addition of hydrated lime. Heavy metals areco-precipitated with gypsum.

Technology status: The technique is in commercial use in Norway (NOAH, 2003).

Others

Residues are also solidified by mixing with other materials than those mentionedabove, typical examples are other waste materials that are suited for a similar dis-posal and in combination with the residues form a material that can be used as fillermaterial. The exact choice of waste materials added to the residues often vary fromcase to case depending on availability. This practice is used to produce “cement-like” solidified materials as mentioned above but also mixing with other materialssuch as wastewater sludge, soil, and waste glass is carried out, for example in theNetherlands and Belgium (Hydrostab).

3.4 Thermal treatment

Thermal treatment processes all involve a heating of the residues and thereby chang-ing the physical and chemical properties, and in some cases also encapsulation.Overall, the main focus has been to produce a stable product with sufficient leach-ing properties; however, also utilization solutions has been investigated. Thermaltreatment may also serve as a basis for separation of metallic phases due to differ-ences in melting temperatures.

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A main advantage is a very dense and stable product with good leaching prop-erties. Another very important aspect is destruction of POP’s such as dioxins. Themain disadvantages are high energy demands for the process and generation of fluegas containing volatile metals. Three major types of thermal treatment exist: vitri-fication, melting, and sintering.

Vitrification

Vitrification processes involves melting of a mixture of residues and glass precursors(i.e. Si). This mixture is typically heated to around 1300–2000 ◦C (Reimann, 1990)in order for an amorphous glassy material to form. In this process, residue com-ponents are bound in the glassy materials thereby also encapsulating the residues.The glass forming materials could be other types of mineral waste products, andthe properties of the final product are to some degree dependent of these additives.The products are often quenched directly after leaving the melting furnace; thus,vitrified residues appear as a dark, granular and hard material.

Technology status: The technique is commercially available. Vitrification israther extensively used on a commercial basis in Japan (about 30–40 vitrificationand melting plants) and other Asian countries. Also a few plants in Europe andUSA exists.

Melting

Melting processes are very similar to vitrification processes, however in this caseno glass forming materials are added. The final product consists of multiple metalphases (Nishigaki, 1996, 2000; Fujisawa et al., 1998; Traber et al., 1999; Sakai andHiraoka, 2000; Katou et al., 2001; Washizu et al., 2002). Utilizing differences inmelting temperatures of individual metal phases, it is possible to separate theseduring the process. Temperatures are similar to vitrification. Melting is in somecases carried out on a mixture of waste materials; adding organic materials to theresidues may thereby add energy to the process. It should be noted that bothvitrification and melting processes may originally have been developed for wastematerials other than APC residues, APC residues have been added at a later stage.

Technology status: The technique is commercially available and is used to asimilar extent as vitrification.

Sintering

Sintering processes involves heating to a level at which individual particles are boundtogether (Lee et al., 1999; Mangialardi, 2001; Ward et al., 2002). Sintering ofAPC residues has primarily been suggested in connection to bottom ashes, typicallyinvolving re-introduction of the residues to the incinerator furnace (i.e. the grate).Temperatures are around 900–1300 ◦C, and a denser and less porous material isproduced.

Sintering is less common than vitrification and melting, however a number ofEuropean companies market treatment technologies including routing APC residuesback to the furnace for sintering with the bottom ashes. One example is theSYNCOM-PLUS process (Gohlke and Busch, 2001; Gohlke et al., 2003) althoughthis process focuses on bottom ash treatment. Other technologies combine sinteringwith other processes such as acid extraction: 3R and MR (Stubenvoll, 1989; Vehlow

25

et al., 1990), and chemical stabilization: Ferrox (Bergfeldt et al., 2004; Baun et al.,2004).


Pyrolysis

Pyrolysis of organic waste materials (e.g. plastic) has been suggested combinedwith APC residue treatment. Residue components are then essentially heated (e.g.melted) and mixed with the other products from the pyrolysis process. As such,the characteristics of the final products highly depend on the accompanying wastematerials.

Technology status: The technique is not commercially available, and has beeninvestigated in lab scale only.

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Chapter 4

Recovery and utilization

Residues—or specific residue constituents—should always be utilized or recovered iftechnically possible and environmentally beneficial. Based on the range of treatmenttechniques presented in Chapter 3, this is feasible to a certain extent. However,research and development activities have primarily focused on improving leachingproperties of the residues rather than on techniques for recovery and utilization.Only within the recent decade, interest into these aspects has increased significantly.Consequently, only a limited number of recovery and utilization solutions exist today.One of the reasons for the lack of commercially available recovery and utilizationtechnologies is likely difficulties related to achieving satisfactorily technical qualitiesof products based on APC residues and readily available virgin materials.

Recovery and utilization solutions are generally derived from and associatedwith the treatment technologies. In many cases, the actual treatment processes areintegrated with the utilization solution.

4.1 Recovery

Specific components present in the residues may be recovered and used again, forexample in other industrial processes. The primary interest is centered aroundmetals and salts. Recovery is characterized by production of a material which maysubstitute a similar virgin material and be used in a similar manner.

Salts

Evaporation of water from treated waste water from wet scrubbers can producea very concentrated salt solution, or recrystallized salt. This may be performedby plants with no permission for discharge of waste water. Salt recovery directlyfrom the residues is also possible after water extraction of salts (i.e. “washing”of the residues). This has been considered in conjunction with several treatmenttechnologies generating salt containing process water.

Technology status: The technique is in commercial use.

Acid

The solution from a first scrubber stage in a multi stage setup is essentially concen-trated hydrochloric acid. Depending on use and management of this solution, HClmay be further concentrated and utilized, e.g. for residue treatment.


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Gypsum

Production of gypsum may be achieved based on scrubber solution from an alka-line scrubber, typically a second stage in a multi stage scrubbing system. Sulphiteions are oxidized to sulphate; gypsum can then be precipitated by addition of Cacarbonates and pH adjustment with NaOH. The suspension is then dewatered. De-pending on the metal content in the scrubber solution, heavy metal removal may benecessary before precipitation of gypsum.


Metals

From a technical point of view, residues represents low-grade ores that may besubjected to metal recovery using traditional upgrading methods. This has, however,only been attempted in a limited number of cases. Overall, metals are primarilyrecovered based on two approaches:

• Extraction techniques: mainly acid extraction

• Thermal techniques: melting

Acid extraction is a well known method for dissolution of solid materials, andprovided pH is sufficiently low most metals will dissolve into solution. The recoveryrate is limited by the dissolution level, and the quality of the recovered metals bythe solution composition. The recovered metal product may need further upgradingbefore a suitable quality is achieved.

Appropriate control of residue melting processes may facilitate recovery of spe-cific metal phases, depending on process temperatures.


4.2 Utilization

APC residues have properties to some extent comparable with cement (e.g. poz-zolanic behavior and contents of Ca, S, Al, Si), and may be utilized as filler materialor aggregates. However due to the high contents of easily dissolvable salts and apotential for hydrogen generation, APC residues cannot directly substitute cement.Utilization is characterized by substitution of materials in products or applicationsto which the residues can contribute with useful properties.

Utilization of APC residues for the applications mentioned in the following shouldalways be associated with a detailed description of the residue amounts used, theplacement, and the fate of the residues in case of demolition of the involved struc-tures. Registration by the responsible authorities should be a prerequisite for uti-lization.

Cement based applications

APC residues have been suggested to substitute cement in concrete for constructionpurposes, for example construction elements for buildings, shore protection blocks,and artificial reefs. While solidification of residues by addition of cement is relativelysimple, substitution of cement by APC residues in concrete can be rather difficult.Even 10–20 % substitution significantly affects strength development and settling

28

times (Geiker et al., 2006). The presence of metallic Al in fly ashes can under moistconditions result in hydrogen generation (Astrup et al., 2005); this may lead tocracks and disintegration of concrete with APC residues (Geiker et al., 2006).

Considering the technical limitations related to producing concrete products withAPC residues and the availability of cement, residue utilization as general construc-tion materials is not particularly widespread. APC residues are, however, used asmaterial for backfilling of mines to avoid collapse. This is done on a large scale inGerman salt mines (see section 3.3).

The properties of the residues used for utilization may be improved by washing,either with water or acid. Although not with a focus on utilization, this has beenpracticed in Europe with subsequent addition of cement in order to cast blocks forlandfilling.


Filler materials

Investigations of coal fly ash utilization, and similar materials such as APC residues,as filler material has been carried out for many years, examples are embankments,highway ramps, noise barriers, harbour facilities, etc. Compared with coal fly ashes,APC residues are much less suited for those purposes due to the high contents ofeasily soluble salts resulting in potential problems with settling. However, due tothe pozzolanic properties of the residues, uptake of water can induce hardening andresult in a rather hard material over time.

Utilization of APC residues as filler material for construction works are generallynot accepted today due to the environmental aspects, but may have been practicedearlier.

Technology status: The technique is not commercially available.

Asphalt

Utilization of APC residues in bituminous structures has been investigated in a num-ber of cases, primarily with a focus to stabilize the residues and minimize leaching(Ali et al., 1996; Sawada et al., 2001). Fly ash can, however, be utilized as a sub-stitute for filler material in asphalt production. Fly ash is used for this purpose inThe Netherlands for road construction on a regular basis: fly ash is ground, homog-enized and mixed with other materials to produce a combined filler material witha maximum of about 25 % fly ash. Utilization of residues in asphalt production inThe Netherlands is accepted on the premise that used asphalt is recycled and theresidues therefore are part of a closed loop.


Neutralization capacity

The very alkaline nature of APC residues may serve as neutralization capacity ofacidic waste materials. This is utilized in Norway (NOAH, 2003) on acid wastefrom the titanium industry. After neutralization, the remaining solid products arelandfilled. Utilization of APC residues for neutralization purposes is also carried outin the United Kingdom (Veolia, 2007).


29

Chapter 5

Final disposal options

Residues should always be treated to minimize leaching and/or utilized in the bestpossible manner (see Chapters 4 and 3). However even after the most sophisticatedtreatment process, a risk for leaching and thereby future release of contaminants fromthe processed residues remains. To minimize such a risk, the treated residues—orresiduals from residue treatment processes—should be safely landfilled.

Landfilling of the residues can be carried out using one of two solutions: disposalat a surface level landfill, or disposal at a subsurface landfill. Depending on thelandfill, final disposal may in some respects be similar to utilization as filler materialin construction works: the landfill site is well known and documented, the placementof the residues registered, and the potential environmental impacts similar.

Residues should be treated before final disposal in order to reduce future leachingand comply with the relevant acceptance criteria.

5.1 Subsurface disposal

Disposal of residues in subsurface landfills or disposal sites is typically done in oldmines. This technique is used as a utilization option primarily in Germany but alsoin the United Kingdom. Disposal in mines may be done after wet mixing with otherwaste materials, and perhaps cement, and then transport to the final destination inthe mine by pumping of the slurry. Disposal in mines may also be done directly byplacement of the residues, for example in big bags, in the mines.

Salt mines are considered a viable disposal option as natural salt deposits arecharacterized by practical no hydraulic contact with the surrounding groundwaterbodies. Consequently any leaching, or other contaminant release, from the residuesis considered effectively hindered over geological time scales, i.e. millions of years.The salt content of APC residues is—in contrast to other options—not a concernhere because of the “salty” environment. Salt mines are generally regarded as safedisposal sites in Europe.


5.2 Surface disposal

Final disposal of residues at traditional surface level landfills have been practicedin many countries for decades, and is still the most common option. At earliertimes, the residues have been placed in landfills without any treatment, howeverincreasing focus on leaching properties has provided incentives for improvement

31

of leaching properties before landfilling. Most of the research and developmentactivities focusing on residue treatment has been directed at decreasing leachingafter landfilling. Worldwide most of the APC residues generated are landfilled inone way or the other, most of these at surface level landfills. It is unclear how largea fraction of the residues are treated before final disposal; however this is generallyconsidered to be the case in Europe, USA, and Japan.

Residues may be landfilled in granular form, for example after chemical stabi-lization or thermal treatment, or in big bags. As mentioned previously, the residueswill harden upon contact with infiltrating water. Surface level landfilling of residuesshould follow modern landfilling practices: i.e. construction of bottom liners, topcovers, as well as leaching collection and treatment. Reaching final storage qual-ity requires specific treatment of the residues prior to landfilling, e.g. by chemicalstabilization.

Residues may also be landfilled in monolithic form i.e. after solidification, typ-ically with cement. For example, blocks of one by one meter are then cast andlandfilled. This practice has been used in several cases, for example in Switzerland(Baur et al., 2001).


32

Chapter 6

Commercial Technologies

While the previous Chapters 3–5 discussed available treatment, recovery and dis-posal techniques, this chapter focuses on commercially available technologies, i.e.residue management technologies that are currently on the market. These commer-cial technologies make use of a range of the specific techniques and processes furtherdescribed in Chapter 3:

• Extraction and separation

• Chemical stabilization

• Solidification

• Thermal treatment

Table 6.1 outlines a range of major technologies available commercially and usedon a larger scale. It should be realized that this list of technologies is not complete,however examples of all major technology types currently in use around the worldare included here. A brief description of these technologies is provided below (forfurther details please refer to Chapters 3–5 and Appendix A):

AshRock: Residues are mixed with various reagents and additives to produce asolid material. The material is then landfilled. It has not been possible to finddetailed data on this process; it is, however, included in Table 6.1 for the sakeof completeness.

Asphalt: Residues are grinded, homogenized and mixed with additives to producea filler material to be used in asphalt production. The filler content in thefinal asphalt is about 5 % per weight.

Backfilling material for mines (Bulk Material Blending): Residues are mix-ed with various waste materials (solids and liquids) to produce a materialsuitable for backfilling of mines. The overall principle is to physically andchemically bind the contaminants in a solid matrix thereby minimizing watercontact. The solidified material is typically placed in old salt mines and uti-lized as backfilling material. Mines in for example Germany, France, and UKaccept APC residues.

DRH: Residues are mixed with water to extract easily soluble salts, then heavymetals are precipitated by flushing with CO2, for example using flue gas. The

33

Table 6.1: Overview of major commercial residue management technologies. If thetechnology is further described in appendix this is noted.Technology Company Country AppendixAshRock/Solicendres SARP Industries FranceAsphalt The Netherlands

√

Backfilling material (bulk) Liebherr/GTS GmbH & Co. KG Germany√

DRH Dansk Restprodukthandtering Denmark√

Ferrox Bacbcock & Wilcox Vølund Denmark√

FLUWA Von Roll Switzerland√

INERTEC Stabilization INERTEC France√

Langøya NOAH Norway√

NEUTREC SOLVAY France√

Melting: Furnace Takuma Japan√

Melting: Electric Arc Daido Steel Japan√

Melting: Electric Resistance JFE Engineering Japan√

T.I.L. LAB France√

WesPhix Wheelabrator Technologies Inc. USA√

residues are dewatered and landfilled. Heavy metals in the process water areremoved and returned to the residues.

Ferrox: Residues are washed with water to extract easily soluble salts, then heavymetals are fixed with Fe-oxides. The residues are finally dewatered and land-filled. The process chemically binds heavy metals to the residue matrix therebyminimizing leaching after final placement.

FLUWA: Residues are washed with acidic scrubber solution from wet flue gascleaning systems to extract soluble heavy metals. The residues are dewateredand landfilled after mixing with bottom ashes or solidification with additives.Extracted metals (zinc) are recycled.

INERTEC: Residues are mixed with water and reagents to chemically bind heavymetals and produce a solid matrix suitable for landfilling.

Langøya: Residues are utilized to neutralize waste acid, then mixed with lime toproduce a gypsum-like material that is landfilled. The solidified residues areutilized to fill an old lime quarry.

NEUTREC: Reacted neutralization products from the gas cleaning process (re-acted sodium bicarbonate) are washed with water and dewatered. The processwater is cleaned by activated coal and ion exchange systems to produce a brine,which can be recycled in the sodium carbonate production. The dewateredresidues are landfilled.

Melting: Residues are heated by electricity or fuel to produce a mixture of meltedphases. Metals or metal phases may be recovered. The melted residues aretypically quenched and landfilled or utilized for construction purposes. De-pending on the additives and temperatures used in the processes, the residuescan be vitrified as well.

34

T.I.L.: Residues are washed with acidic scrubber solution from wet flue gas cleaningsystems in order to extract heavy metals. The residues are then dewatered andlandfilled.

WesPhix: Residues are mixed with soluble phosphate to chemically bind heavymetals. Typically, the stabilized residues are then landfilled.

35

Chapter 7

Solutions and evaluation

Management and disposal of APC residues from municipal solid waste incinerators isnot a trivial task and requires critical consideration of solutions prior to employment,in particular of the environmental aspects. It is important to realize that although aspecific residue management option may appear promising, the entire chain of pro-cesses and activities related to the solution should be carefully considered, includingindirect and avoided activities.

Specific management solutions have specific benefits and drawbacks, and specificregions and countries have specific requirements. Consequently, it is not possible topinpoint a single residue management solution that fulfills all requirements through-out the world. As such only general recommendations can be given in this document.

This chapter focuses on aspects relevant for evaluating residue management so-lutions, new or existing, and provides recommendations for assessment approaches.

7.1 Potentially available solutions

The residue management solutions and techniques discussed in the previous Chap-ters 3–6, can be categorized as follows:

Experimental: Processes or techniques tested only in small scale. The techniquesmay be in use on ashes from other combustion processes, such as coal firedpower plants.

Promising: Processes or techniques specifically tested on APC residues and sys-tematically documented. These techniques may or may not be in commercialuse, however they are often tested at a minimum in bench or pilot scale.

Commercial: Technologies involving one or several individual processes or tech-niques. These techniques may or may not be tested and documented.

Although specific residue management solutions are commercially available andin widespread use, the involved techniques may not necessarily be publicly identifiedand documented nor may the relevant technical requirements and environmentalaspects be apparent for users. On the other hand, treatment processes may beinvestigated in detail in the lab by researchers but unlikely to be picked up byinvestors due to economical aspects.

Currently, most of the treatment techniques mentioned in the literature falls inthe Experimental or Promising category. It should be realized that each type of

37

treatment (i.e. extraction and separation, chemical stabilization, solidification, andthermal treatment) is today represented by a substantial range of specific technolo-gies, some of which are commercially available. As such, most Commercial solutionsmake use of processes similar in type to some of the Experimental or Promisingtechniques.

For operators and authorities to navigate in this field and choose between differ-ent management solutions, a localized evaluation of the solution is necessary as wellas a technical description of the involved processes.

7.2 Development and documentation level

Researchers as well as entrepreneurs suggest new residue treatment technologieson a regular basis, most of these—although appearing promising—may never bedeveloped further than lab scale or may never be appropriately documented. Athorough evaluation and assessment of a technology requires detailed documentationof the processes involved.

Although detailed technical data on individual commercial technologies may notbe publicly available, information about similar techniques and processes can oftenbe found in research literature. However as researchers typically focus on leachingbehaviour and mechanical properties of the residues, an exhaustive description ofa process may not be available: e.g. energy consumption and air emissions fromthermal treatment processes are often not measured.

Table 7.1 provides a qualitative assessment of the development status of thetechniques discussed in Chapters 3–5 as well as an assessment of the availabilityof descriptions and data related to technical aspects, leaching, and emissions ingeneral. It should be noted that the table lists individual processes that may notnecessarily be compared directly. It should also be realized that the table does notcover actual commercial solutions (i.e. backfilling of salt mines), but rather focuseson the individual processes. Commercial treatment and management solutions oftenconsist of several steps combining a technical process and a disposal or utilizationstep. Some examples are:

• Stabilization with FeSO4 and surface disposal

• Solidification with asphalt and controlled utilization in construction works

• Solidification with cement and utilization as backfilling materials in salt mines

This approach for Table 7.1 has been chosen because of a general lack of sufficientdata and information about commercial solutions, and because the table providesmore flexibility for the reader to create their own understanding of a specific solutionby combining information for the relevant processes mentioned in the table.

7.3 Technology evaluation

7.3.1 Aspects to consider

Processes and technologies for residue treatment and management should ideally beevaluated at least with respect to the following aspects:

• Technical

38

Tab

le7.

1:Q

ualit

ativ

eas

sess

men

tof

deve

lopm

ent

leve

lwit

hre

spec

tto

full

scal

eco

mm

erci

alus

eof

the

indi

vidu

alte

chni

ques

,as

wel

las

gene

ral

avai

labi

lity

ofdo

cum

enta

tion

and

data

desc

ribi

ngth

ete

chni

ques

.1–

5st

ars

are

give

n,fiv

est

ars

indi

cate

shi

ghde

velo

pmen

tle

vel

and

publ

icav

aila

bilit

yof

deta

iled

docu

men

tati

on.

Ava

ilabi

lity

ofda

tare

late

dto

:P

roce

ss†

Dev

elop

men

tle

vel

Tec

hnic

alpr

oces

ses

Lea

chin

gO

ther

emis

sion

sE

xtra

ctio

nan

dse

para

tion

:W

ater

?????

???

????

??

Aci

d?????

???

????

??

Mic

roor

gani

sms

??

??

Ele

ctro

dial

ysis

???

???

Par

ticl

esi

ze?

??

?

Che

mic

alst

abili

zati

on:

FeSO

4?????

?????

?????

????

CO

2/

H3P

O4

?????

?????

?????

?????

Pho

spha

te?????

?????

?????

?

Sulp

hide

????

???

????

??

Solid

ifica

tion

:W

ater

???

?????

Cem

ent

?????

?????

?????

???

Asp

halt

?????

???

??

Gyp

sum

?????

???

??

The

rmal

trea

tmen

t:V

itri

ficat

ion

?????

????

?????

?

Mel

ting

?????

????

?????

?

Sint

erin

g?????

???????

??

Pyr

olys

is?

??????

?†

Only

indiv

idual

pro

cess

esare

cover

edin

this

table

,i.e.

the

“buildin

gblo

cks”

of

com

mer

cial

solu

tions.

Rea

der

sare

enco

ura

ged

tobuild

thei

row

nass

essm

ent

on

rele

vant

managem

ent

solu

tions

by

com

bin

ing

the

info

rmati

on

inth

eta

ble

.

39

• Environmental

• Economical

The priority of the above aspects can always be discussed, and may vary inindividual cases depending on the management option in question (e.g. level of doc-umentation and development, political framework and regulations, existing man-agement solutions, local conditions and requirements, etc). Fulfilling the technicalrequirements can be regarded as a pre-requisite as it makes little sense to proceedwith a technique if technical aspects make it unpractical to use on APC residues.The same, however, can be argued for environmental and economical aspects as well.The techniques discussed in this document can all be applied to APC residues, thetechniques may, however, not all be environmentally and economically viable. Theremainder of this chapter focuses on the environmental aspects of residue manage-ment and the economical aspects are not discussed further.

An evaluation of the environmental aspects should include all relevant environ-mental consequences and potential impacts of the process chain. This means thatalso indirect consequences (e.g. on other material flows) and avoided activities (e.g.previous landfilling of waste materials now co-treated with the residues) should beconsidered. Such an assessment can be done using several approaches, it is how-ever important to do this systematically. A commonly applied approach is life-cycleassessments (LCA).

7.3.2 Life-cycle assessments (LCA)

In a simplified form LCA is an account of all resource and material consumptionsas well as all emissions related to a given service, including all relevant upstreamand downstream processes. In this case the service could be: “management of onetonne of APC residues”. An LCA may then include all activities and processes fromthe point where the residues leave the incinerator until the residues (and all derivedproducts) are finally disposed. As such, an LCA should include consumptions andemissions related to the activities “today” but also include “future” activities andprocesses, such as demolition and final disposal of construction works, leachate con-trol activities, and future emissions from landfilled residues or bi-products from theprocesses.

It should be realized that performing an LCA can be a relatively complicatedtask, the most critical activity is however to provide the necessary documentation ofthe solution in question. In a European context, use of “life-cycle thinking” has beenintroduced by the EU Commission (see Chapter 2). Although vaguely defined, it isanticipated that LCA will become important in the future as an argument for se-lecting specific residue management solutions throughout the EU and for companiesin marketing their specific solutions.

Systematic evaluations of environmental aspects of APC residue management,such as life-cycle assessments, are very limited although a few examples exist inDenmark and the Netherlands (e.g. Fruergaard and Astrup, 2007; Afval OverlegOrgaan, 2002). It should be realized that although life-cycle aspects are included inan environmental assessment, such an assessment may not necessarily be character-ized as a “full” LCA (for further details see Wenzel et al. 1997; ISO 14040, 1997).A few issues should be realized with respect to LCA:

40

• LCA is an analytical tool used for decision support, it is not a decision makingtool

• The result of an LCA is highly dependent on system boundaries, assumptions,assessment criteria, time horizons, data quality, etc

• Several methodologies exist for performing LCA

It is not the intention to provide a detailed description of LCA methodology inthis report, however a Danish example of an LCA-screening is given in Appendix Bwhere the main aspects related to LCA on APC residue management are introduced.Readers are strongly encouraged to seek further information about LCA. Please notethat LCA on waste management in general (e.g. municipal solid waste, includingwaste incineration) is relatively well investigated and several scientific papers existon this topic (e.g. Christensen et al., 2007).

Life-cycle assessments includes a number of steps as outlined in Textbox 1. Inpractice an LCA is centered around defining a set of scenarios which are compara-ble with respect to the service provided (e.g. “management of one tonne of APCresidue”). Then all relevant emissions, consumptions and productions, etc. are ac-counted for in each scenario and the potential environmental impacts (e.g. globalwarming) calculated for each emission, etc. The resulting LCA is then typicallypresented in the form of graphs showing environmental impacts in a number of dif-ferent “impact categories” (such as global warming, etc. See Textbox 1). Potentialbenefits from a specific scenario can then be realized by comparing these impactswith other scenarios.

As mentioned above, only a few life-cycle assessments have been carried outfocusing on APC residue management. However, some countries, e.g. Denmark,have accepted this approach as a basis for decisions regarding waste managementincluding APC residues. It is anticipated that the use of environmental assessmentsusing a life-cycle perspective will grow in the future. It is, however, important torealize that although LCA’s are carried out following identical methodologies in twocountries, the results may vary according to local conditions. Therefore, it may notbe possible to provide a generic LCA with conclusions about how to manage APCresidues for example throughout Europe. Differences in energy production, existingAPC management, emissions, etc. between countries may result in different con-clusions. However, using LCA methodology provides a systematic and comparableapproach to the evaluation.

7.4 Final remarks

Ideally, the management solution with the least environmental impact should bechosen. As discussed in the previous sections, individual technologies have differentenvironmental profiles and choices between management solutions should be arguedwith respect to local conditions. A number of aspects should however be discussedin all cases:

Treatment. Residues should always undergo some level of treatment to minimizefuture release, for example by leaching. The treatment should naturally reflectthe choice of final disposal.

41

Textbox 1: Outline of important steps in life-cycle assessment (LCA) and the typeof results gained.The following environmental “impacts” are often assessed in LCA’s (and termed“impact categories”). They represent a range of “environmental aspects” generallyconsidered to be important, although choices of impact categories varies betweenLCA’s:

• Global Warming

• Acidification

• Nutrient Enrichment

• Photochemical Ozone Formation

• Stratospheric Ozone Depletion

• Ecotoxicity (in Water and Soil)

• Human Toxicity (via Air, Water and Soil)

LCA includes the following main steps (for further details see Wenzel et al., 1997;ISO 14040, 1997):

Goal and scope definition. Definition of the “functional unit”, system bound-aries, assessment criteria, methods for accounting indirect and avoided pro-cesses and activities.

Inventory analysis. Data collection and preparation of an inventory of inputs andoutputs for the involved processes. Assessment of data quality.

Impact assessment. Four sub-steps: selection of impact categories to assess (e.g.global warming, acidification, etc.), characterization (e.g. quantification ofan emissions contribution to a specific impact category), normalization (e.g.normalization of the results to a common unit such as average impacts relatedto one person, a person equivalent), and finally weighting (e.g. weighting ofthe results according to assessment goals, society or political interests, etc.).

Interpretation. Interpretation of results, including sensitivity analysis for examplewith respect to system boundaries, assumptions, data, etc.

42

Transportation. The transportation of residues from incinerators to the treatmentor disposal facility may account for a significant part of the environmental load,in particular in cases with simple or less energy intensive treatment.

Energy. Consumption of energy during treatment and related to disposal activi-ties may account for very significant parts of the overall environmental load,in particular in case of thermal treatment. Environmental benefits from thetreatment should be critically evaluated against the environmental load fromenergy consumption, in particular.

Leaching. Metal leaching from residues after final disposal may continue for thou-sands of years. Although the actual consequences cannot be determined today,the potential impacts from this long-term release should be assessed and ac-counted for.

Contaminant dispersion. Spreading of contaminants, for example heavy metals,via construction materials should be avoided. In case of utilization for con-struction purposes, the materials should be used in major projects controlledby the authorities and the fate of the materials after demolition should bedetermined beforehand.

Life-cycle assessments (LCA) of APC residue management solutions are founduseful as a decision support tool, however these assessments cannot serve as theonly basis for a decision. Collecting and evaluating technology data is extremelytime-consuming, and the final results can be highly affected by system boundariesand assumptions. In spite of these limitations, LCA is a useful tool for systematiccomparison of management alternatives and is likely to become increasingly used inthe future.

Table 7.2 provides a qualitative overview of major environmental benefits anddrawbacks related to the various types of treatment processes discussed in this re-port. The table does not provide specific and quantitative information about howmuch is leached from treated residues, but rather provides a relative overview. Itshould be realized that the individual processes act differently on the residues andthat the “stabilization quality” may not be comparable (e.g. washing with waterwill produce residues with higher leaching than vitrified residues). The table alsoillustrates the potential for recovering residue components such as metals and saltsbased on the individual processes. It should be noted that complete commercial so-lutions have not been evaluated in Table 7.2, only the individual technical processessimilarly to the approach used in Table 7.1. The potential for utilizing the treatedresidues for construction purposes has not been evaluated.

It may be realized from Table 7.2 that a number of treatment processes existproviding low leaching potentials and thereby good stabilization of the residues. Ifthese techniques are combined with appropriate disposal technologies, the combinedsolution may effectively represent a sink of substances in the APC residues.

43

Table

7.2:Q

ualitativeassessm

entofm

ajorenvironm

entalbenefitsand

drawbacks

forindividualprocesses.

The

number

ofclosedcircles

(0–5)reflects

the“level”

ofenergy

requirements

neededto

treatthe

residues,theneed

fortreatm

entof

processw

aterand

fluegas

cleaning,andthe

“pollutionpotential”

ofleachate

fromthe

treatedresidues:

0indicates

alow

levelof

energyuse,

pollutionpotential,

etc.O

pencircles

(0–5)reflects

thepotential

forrecovery

ofcom

ponentslike

metals

andsalts

fromthe

residues:5

indicatesa

highpotential

forrecovery.

Process †

Energy

Process

water

Air

emissions

Leaching

Recovery

potentialE

xtractionand

separation:W

ater•

••••

•••••

◦◦A

cid•

•••••

••••

◦◦◦

Microorganism

s••

••••

••••

◦◦E

lectrodialysis•••

••••

◦◦◦

Particle

size•

••••

•••••

◦

Chem

icalstabilization:

FeSO4

•••

••

CO

2/

H3 P

O4

•••

••••

Phosphate

•••

••••

Sulphide••

•••

•••

Solidification:W

ater•

••••

Cem

ent••

••A

sphalt•••

•G

ypsum••

•••••

Therm

altreatm

ent:V

itrification•••••

••••••

•◦◦◦◦◦

Melting

•••••

••••••

•◦◦◦◦◦

Sintering•••

••••

••◦◦◦

Pyrolysis

••••

••••••

•◦◦◦◦◦

†In

div

idual

com

mercia

ltech

nolo

gies

(e.g.

back

fillin

gof

salt

min

es)are

not

specifi

cally

addressed

as

limited

info

rmatio

nare

typica

llyava

ilable

ab

out

these

technolo

gies.

Only

indiv

idual

pro

cessesare

covered

inth

ista

ble,

i.e.th

e“build

ing

blo

cks”

of

the

com

mercia

ltech

nolo

gies.

Rea

ders

are

enco

ura

ged

tobuild

their

own

assessm

ent

on

relevant

managem

ent

solu

tions

by

com

bin

ing

the

info

rmatio

nin

the

table.

The

assessm

ent

isdirectly

related

toth

epro

cess,i.e.

exclu

din

gin

direct,

secondary,

and

avoid

edpro

cesses.It

should

be

realized

that

the

“sta

biliza

tion

quality

”is

not

the

sam

efo

rall

pro

cesses,and

that

oth

erasp

ectsth

an

those

men

tioned

ab

ove

should

be

consid

eredas

well.

44

Chapter 8

Recommendations

Today a long range of APC residue management solutions exists worldwide. Someof these management solutions are commercially available, while others have onlybeen tested in the laboratory. Common for most of the involved techniques andprocesses are, however, that the documentation is very limited and not sufficientto support choices between these techniques with respect to environmental criteria.It is recommended that individual residue management solutions are evaluated sys-tematically with respect to potential environmental impacts: this should be doneusing a life-cycle approach and accounting for local conditions.

This report presents data on individual residue treatment technologies, processes,etc. to the extent it has been possible to collect these. Technology owners are, how-ever, strongly encouraged to provide the necessary data: this enables incinerators,authorities, and other stakeholders to evaluate specific residue management solu-tions with respect to environmental criteria and thereby provide environmentallybased arguments for choosing one solution from the other. From incinerators andauthorities point of view, the availability of technical data may therefore be seen asa market advantage in the future.

The outline below provides an overview of the information and data needed tocarry out a life-cycle assessment of residue management. Appendix A provides asuggestion for a relevant data table format.

Technical description of involved processesConsumption of (per ton of residue):• chemicals and materials• water (water quality specified: e.g. surface or groundwater)• energy (type specified: e.g. diesel, electricity, gas, etc.)

Outputs of (per ton of residue):• by-products (composition specified)• treated residues (composition specified)

Emissions (per ton of residue):• waste water (composition specified)• air emissions (composition specified)• leaching from solid products (composition specified)

Technical description of fate of solid products (e.g. landfilling, construction, etc.)

45

Chapter 9

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Appendices

53

Appendix A

Technology information

This appendix provide data for a range of APC residue treatment and managementtechnologies. The data has been collected from technology owners, incinerators,literature, etc. and may be used as a guideline and a basis for performing a life-cycle assessment (LCA) on residue management. It should be clearly stressed thatthe supplied data are not sufficient for carrying out a full LCA and that the data areprovided “as is”. Any use of these data should be accompanied by a critical reviewof assumptions, data quality, sensitivity of results, etc. and an LCA should followbest-practice, see for example ISO standards 14040, 14041, 14042, and 14043.

The technologies, treatment techniques and processes described in this appendixare grouped in three categories: Commercial, Promising, and Experimental. Thetable below provides an overview. Technology owners, incinerators and stakeholdersin general contributing with data and information are greatly acknowledged.

Process name Tech info In-Out data LeachingCommercial:

Asphalt xDRH x xBulk Material Blending x xFerrox x x xFLUWA xINERTEC Stabilization x x xLangøya x x xNEUTREC xMelting: Furnace x x xMelting: Electric Arc x x xMelting: Electric Resistance x x xT.I.L. x x xWesPhix x

Promising:3R xCTU x x xDHI x x xSemi Fluid Slurry x x

Experimental:Electrolysis xWatech x x

A-1

Comments to the data tables in Appendix A

For some of the technologies reported in this appendix, expenses are mentioned astreatment costs and in some cases as price margins (the table field “Economics”). Insome cases no information is mentioned. Cost information is supplied by the processowners, however it should be acknowledged that there might be a big differencebetween price and cost.

When reading the data tables in this appendix, attention should be drawn tothe following aspects. Generally cost information for the technologies: Backfillingmaterial for mines (Liebherr/GTS GmbH), Langøya (NOAH) and also Inertec ap-pear to be real price margins (for final disposal) whereas for the technologies: Ferrox(B&WV), Fluwa (von Roll), WesPhix, DHI and Semi fluid slurry (GTS GmbH) costinformation are considered as (incomplete) coarse estimates which in some cases donot even include final landfilling costs. It is not specified whether cost informationreflects only the treatment costs of the specific process or to which extent the totalcosts for treatment and (final) disposal are included.

A-2

Standard for documentation of APC residue management solutions

TECHNOLOGY NAME Manufacturer/developer Name of company, institution, etc. Contact Contact information Process type Type of process according to descriptions in this report Technical description Technical description of involved processes, procedures, and activities Achieved environmental benefits Main environmental benefits from the point of view of the residues handled Cross-media effects Any indirect effects on other media, e.g. wastewater, air emissions, etc. Operational information Specific information regarding operation of the processes

Lab Bench Pilot Full

Current scale of implementation

Commercial Applicability of technique Types of residues, situations, etc. in which the technology is applicable Economics Information about cost estimations, economical aspects, etc. Driving force of implementation Main driving forces for implementing the technology References & examples Reference to current implementations of the technology, examples of use, etc. Main public reports References to public reports, including point of access.

Inputs Units Per ton of residue treated Electricity kWh Water m3

Quantification of inputs needed to carry out the techniques, processes, and activities described above. Should include all

inputs and be expressed per ton of residue treated or handled.

Outputs Units Per ton of residue treated Liquid output m3 Quantification of liquid outputs, e.g. wastewater, etc.

pH mg/l Cl mg/l Sulfate mg/l Cd mg/l Cr mg/l Cu mg/l Hg mg/l Pb mg/l Zn mg/l

Composition of this output. All liquid outputs should be quantified individually by volume and composition.

Treated residue kg Quantification of solid outputs, e.g. treated residue, slags, etc. Cl mg/kg Sulfate mg/kg Cd mg/kg Cr mg/kg Cu mg/kg Hg mg/kg Pb mg/kg Zn mg/kg

Composition of solid outputs. All solid outputs should be quantified individually by mass and composition.

Residue leachate

pH mg/l Cl mg/l Sulfate mg/l Cd mg/l Cr mg/l Cu mg/l Hg mg/l Pb mg/l Zn mg/l

Composition of leachate from solid outputs. Leaching from all solid outputs should be quantified individually by composition.

The leaching test used should be noted.

Flue gas Nm3 Quantification of gaseous outputs, e.g. flue gas Cl mg/Nm3 Sulfate mg/Nm3 Cd mg/Nm3 Cr mg/Nm3 Cu mg/Nm3 Hg mg/Nm3 Pb mg/Nm3 Zn mg/Nm3 Dioxin ng-TEQ/m3

Composition of gaseous outputs. All gaseous outputs should be quantified individually by volume and composition.

All inputs and outputs should be described and quantified as indicated above for the full process, including for example pretreatment of the residues, mixing, actual treatment, as well as transport to final placement if this is an integral part of the technology. Relevant outputs should be added if necessary. The composition parameters illustrated above should not be viewed as exhaustive: all relevant data should be included.

Asphalt Manufacturer/developer Ankerpoort nv, The Netherlands Contact Process type Solidification + utilization Technical description The residues are transported dry to a temporary storage and pretreatment

facility. Here the residues are grinded, homogenized, and mixed with other materials to produce a filler material which can be used in asphalt production. The filler content of the final asphalt is about 5 % per weight. In the Netherlands, maximum about 25 % of the filler is substituted by fly ashes.

Achieved environmental benefits The residues are solidified thereby limiting release of contaminants to the surrounding environment. At the same time natural resources are saved.

Cross-media effects The technique substitutes limestone on a 1:1 basis per weight of fly ash. Operational information



x Commercial Applicability of technique The technique is only applicable for dry fly ashes without neutralization

products from neutralization of acidic components. Economics Driving force of implementation In the Netherlands, several different materials are routinely used as filler in

asphalt production thereby substituting natural resources. The produced asphalt is later recycled in a closed loop.

References & examples The technique is well established in the Netherlands, but also Belgium has experiences with the technique.

Main public reports Data mainly from: Milieueffectrapport Landelijk Afvalbeheerplan, Achtergronddocument A25, Uitwerking "AVI-vliegas", Afval Overleg Orgaan, 2002

Inputs Units Per ton of residue treated Energy kWh ? Limestone kg 4000 River sand kg 29,200 River grind kg 45,800 Bitumen kg 3300

Outputs Units Per ton of residue treated Wastewater m3 0 Treated residue (asphalt) kg 83,300

Cl mg/kg ? Sulfate mg/kg ? Cd mg/kg ? Cr mg/kg ? Cu mg/kg ? Hg mg/kg ? Pb mg/kg ? Zn mg/kg ?

Leachate pH ? Cl mg/l ? Sulfate mg/l ?

Cd mg/l ? Cr mg/l ? Cu mg/l ? Hg mg/l ? Pb mg/l ? Zn mg/l ?

DRH Manufacturer/developer Dansk Restprodukthåndtering A.m.b.a. Contact Finn Petersen, [email protected] Process type Water extraction + chemical stabilization Technical description The DRH includes a combined washing and stabilization step. The residues

are mixed with water to extract easily soluble components, then the suspension is flushed with CO2 (e.g. treated flue gas from an incinerator or industrial process). Heavy metals are bound primarily as carbonates (similar to the DHI process). The treated residues are then dewatered and landfilled.

Achieved environmental benefits Leaching from treated residues are generally below EU acceptance criteria for non-hazardous waste landfills.

Cross-media effects The process generates salty waste water which has to be treated and discharged. The use of CO2 in the process may facilitate net reductions in emissions from the source of flue gas (e.g. the incinerator).

Operational information Lab Bench Pilot Full


x Commercial Applicability of technique Can be used on fly ashes as well as residues from dry and semi-dry systems Economics Driving force of implementation Reduction of leaching from the residues. References & examples The process has been tested in lab and pilot scale setups. No full scale plants

are currently available. The manufacturer has an agreement with von Roll to supply full scale plants.

Main public reports None available. Information about the process has been obtained from the Dansk Restprodukthåndtering A.m.b.a.

Inputs Units Per ton of residue treated Electricity kWh 63 Water m3 4 NaOH kg 4.3 HCl kg 8.4 TMT kg 0.5 CO2 kg 169

Outputs Units Per ton of residue treated Treated residue kg 1375

As mg/kg 240 Ca mg/kg 230 Cd mg/kg 160 Cr mg/kg 600 Cu mg/kg 11,000 Hg mg/kg 4.4 Mn mg/kg 0.88 Na mg/kg 13 Ni mg/kg 1,200 Pb mg/kg 9,100 S mg/kg 96,800 Zn mg/kg 52,000

Wastewater m3 3.5

As μg/l <10 Cd μg/l <10 Cl μg/l <35,000,000 Cr μg/l <5 Cu μg/l <10 F μg/l <5,000 Hg μg/l <2 Ni μg/l <10 Pb μg/l <20 Zn μg/l <100

Residue leachate pH mg/l ? Cl mg/l ? Sulfate mg/l ? Cd mg/l ? Cr mg/l ? Cu mg/l ? Hg mg/l ? Pb mg/l ? Zn mg/l ?

Bulk material blending Manufacturer/developer Liebherr / GTS GmbH & Co. KG Contact [email protected] Process type Solidifcation + utilization Technical description The residues are blended in charges of about 1.5 m³ with mud cake and waste

fluids within a modified mixer from the cement industry. The setting properties of the residue causes the former dustlike and fluid material to become a bulk material which can be handled in an open fashion with load-haul-dump technology. Mud cake e.g. from waste water purifying plants is firstly used as a filler and secondly as a supplier of fluid components for the mixing recipe. The produced bulk material is then used as backfill of excavations leftover from the mining activities in the former potash mine. The backfilling is necessary in order to prevent future earthquake like rock bumps caused by the collapse of pillars within the mine.

Achieved environmental benefits The waste materials used as components for the backfill are contaminated with hazardous elements in such a small concentration which makes a recycling process nearly impossible from a financial and technical point of view. The build up within the mine extracts therefore these hazardous waste materials from the biosphere for a geological long-term period of time.

Cross-media effects The main advantage is the utilization of waste material as backfill which otherwise would have been composed of building material which again would have to be produced. Either by recycling or newly mined material. The technique therefore substitutes otherwise usable resources. Lab Bench Pilot Full


X Commercial Applicability of technique The technique can be used on all types of APC residues as long as the

concentration of hazardous materials keeps within the limits which are defined by German law for underground mining. While keeping in mind that the blending with other Materials (fluids and mud cake) dilutes up to a certain extend.

Economics The treatment and utilization within the backfilling of the mine with residues arise from 70,- up to 100,-€/ton. This is an indicative price margin for average waste material which is used in the above described utilization.

Driving force of implementation The main reason for the application of the described technique is firstly the stabilization of underground pillars and secondly in the commercial value of the business.

References & examples A similar technique was used on the mine Wohlverwahrt-Nammen near Minden, Germany. It is being applied comparable in Kochendorf, Germany, but where the blended material is filled into big-bags before it is backfilled under ground.

Main public reports

Inputs Units Per ton of residue treated Electricity kWh 29 Water m3 0.115 Diesel l 1.5 Waste mud cake kg 277 Waste fluids kg 208

Outputs Units Per ton of residue treated Wastewatera) m3 none

pH mg/l 7.5 Cl mg/l 24000 Sulfate mg/l 7800 Cd mg/l 0.0056

Cr mg/l < 0.05 Cu mg/l 0.01 Hg mg/l < 0.0002 Pb mg/l < 0,005 Zn mg/l 0.18

Treated residueb) kg 1485 pH 11.8 Cd mg/kg 130 Cr mg/kg 269 Cu mg/kg 739 Hg mg/kg 14.7 Pb mg/kg 2400 Zn mg/kg 10720 Dioxins Ng-TEQ/kg 839

a) Wastewater only is produced from the treatment of water within a clarifying tank from the bath of the mine. b) Threshold values which have to be respected from German law are fixed in “Versatzverordnung Anlage 1” and determine when a material primarily should be recycled.

Ferrox stabilization Manufacturer/developer Babcock & Vilcox Vølund Contact Kasper Lundtorp: [email protected] Process type Water extraction + chemical stabilization Technical description Ferrox stabilization involves five steps: residues are first mixed with a FeSO4

solution and then aerated with atmospheric air at L/S 3 l/kg in order to oxidize Fe(II) to Fe(III) and precipitate iron oxides. This step also includes extraction of soluble salts. The pH of the suspension is maintained at pH 10-11 for about 0.5 to 1 hour to allow dissolved heavy metals to bind to the precipitated iron oxides. The fourth step involves dewatering of the treated residues and finally a washing step to exchange the remaining water and remove salts. The final stabilized product has a water content of about 50 %.

Achieved environmental benefits The main advantage is improved leaching properties of the final product. The pollution potential of the treated residues is documented rather detailed and the treated residues are expected to be physically more stable than cement stabilized products because most salts are removed. Ferrox stabilized residues typically have far better leaching properties than cement solidified residues.

Cross-media effects Utilization of the stabilized product in road construction after mixing with cement has been investigated. Also, utilization after sintering with bottom ashes has been suggested. The FeSO4 used in the process is a waste product from titanium production.

Operational information Parameters like water consumption, mixing of water and residues, Fe(II) oxidation rate, reaction time, pH and pH controlling additive have been optimized in pilot scale. The process is robust with respect to the residue input. Typical process times are 20-50 minutes aeration and 30-60 minutes reaction. In the current set-up, dewatering of the treated residues was done with a plate and frame filter press.

Lab Bench

X Pilot (200 kg batchwise corresponding to 1:20 of full scale) X Full (drafted, no full scale plants installed)


X Commercial Applicability of technique The stabilization unit can be implemented as an integrated part of the

incinerator but may also exist as a centralized treatment plant handling residues from several incinerators. The technique has been demonstrated on semidry APC residues as well as fly ash alone and fly ash combined with sludge from the wet scrubbers (Bamberg product); all with good results. About 80 test runs have been performed in pilot scale.

Economics Treatment cost for Ferrox stabilization is estimated to about €65/ton with a plant capacity of 20,000 ton/year; including investment costs.

Driving force of implementation The main reason for implementing this technology is the very good leaching properties of the treated residues and the fact that this is expected to last in a long-term perspective.

References & examples Pilot plant at I/S Vestforbrænding (DK) Main public reports Lundtorp, K. (2001): The Ferrox-process in an industrial scale. Ph.D. Thesis.

Environment & Resources DTU, Technical University of Denmark. (http://www.er.dtu.dk/publications/fulltext/2001/MR2001-221.pdf) Jensen, D.L., Christensen, T.H. & Lundtorp, K. (2002): Treatment of waste incinerator air-pollution-control residues with FeSO4: Laboratory investigation of design parameters. Waste Management and Research, 20, 80-89. Lundtorp, K., Jensen, D.L., Sørensen, M.A., Christensen, T.H. & Mogensen, E.P.B. (2002): Treatment of waste incinerator air-pollution-control residues with FeSO4: Concept and product characterization. Waste Management and

Research, 20, 69-79.

Inputs Units Per ton of residue treated Electricity kWh 31 Water m3 3-4 FeSO4 kg 30-130

Outputs Units Per ton of residue treated Wastewater m3 2-3

pH mg/l 10.5-11 Cl mg/l 30000-50000 Sulfate mg/l 300-1100 Cd mg/l 0.003-0.006 Cr mg/l 0.07-0.09 Cu mg/l 0.005-0.007 Hg mg/l 0.0003-0.001 Pb mg/l 0.03-0.07 Zn mg/l 0.02-0.1

Treated residue kg 860 Cl mg/kg 1500 Sulfate mg/kg 30000-70000 Cd mg/kg 200-300 Cr mg/kg 200-800 Cu mg/kg 900-1800 Hg mg/kg 3-17 Pb mg/kg 5000-7000 Zn mg/kg 20000

Residue leachate pH mg/l 11.2 Cl mg/l 700-900 Sulfate mg/l 600-800 Cd mg/l < 0.0005 Cr mg/l 1-4 Cu mg/l < 0.001 Hg mg/l 0.0002-0.0005 Pb mg/l 0.007-0.009 Zn mg/l 0.01-0.03

FLUWA Manufacturer/developer von Roll, Switzerland Contact Martin Brunner, [email protected] Process type Acid extraction Technical description The process is only used in combination with wet flue gas cleaning technology

combines an acid extraction of soluble heavy metals and salts by using the (acidic) scrubber blow down. Before using the scrubber liquid, mercury is removed by either a filtration (when activated carbon is introduced into the scrubber) and/or a specific ion exchanger. Both boiler ash and fly ash are treated this way. The L/S-ratio in the extraction step is about 4; pH is controlled at 3.5 by addition of hydrated lime. Within the residence time of about 45 minutes, sulphate (from the SO2-scrubber) is precipitated to gypsum. The residue is dewatered, then counter current washed on a belt filter and finally landfilled, normally as a mixture with bottom ash. The filtrate has to be treated in order to remove heavy metals by neutralisation, precipitation and ion exchange. The dewatered and rinsed filter cake contains about 25 % zinc and is therefore recycled in metallurgical processes.

Achieved environmental benefits The process removes a significant part of the total amount of heavy metals from the residues (Cd: = 85 %; Zn: = 85 %; Pb, Cu: = 33 %; Hg: = 95 %); the leachability of the residue is reduced by a factor 102 – 103. Zinc, cadmium and mercury are recycled.

Cross-media effects The dioxin content of the bottom ash increases when the treated ash is disposed of in combination with bottom ash; however, the leaching properties of the mixture are even better because of a higher density. The dioxin content can, however, be reduced by recirculating the treated residues trough the incineration.

Operational information Start-up of the first plant was 1996. Most of the plants are operating 24h and are adapting the weekly operation period (4 – 7 days) according to the generated APC residues.



X Commercial Applicability of technique The system is preferably used on incinerators with a wet APC system having a

permit for discharge of treated waste-water. If salts cannot be discharged with the spent water, the feasibility of the process has to be evaluated case by case.

Economics Process costs of treating the APC-residues are about 150 – 250 EUR/t (including charges for recycling the zinc filter cake)

Driving force of implementation The technique provides a method to treat residues according to the Swiss legislation with competitive (to the export in German underground disposal in salt mines) costs.

References & examples Switzerland: Berne, Buchs SG, Emmenspitz, Niederurnen, Thun, Lausanne. Czech Republic: Liberec.

Main public reports Faey R (1991): Ein Verfahren zur behandlung von flugstäuben. AbfallwirtschaftsJournal, 3, 194. Frey, R., Brunner, M.: Recycling von Zink aus Elektrofilterasche, in: Optimierung der Abfallverbrennung März 2004, TK Verlag, Berlin

Inputs Units Per ton of residue treated Energy kWh ? Water m3 0 (water recycled from wet scrubbing process) Acid l ?

Outputs Units Per ton of residue treated Wastewater m3 No additional waste used in the process

Treated residue kg ? Residue leachatea)

Cd mg/l < 0.01 Cr(III) / Cr(IV) mg/l < 0.05 / < 0.01 Cu mg/l < 0.2 Hg mg/l < 0.005 Pb mg/l < 0.1 Zn mg/l < 1.0

a) Maximum values according to TVA (Vehlow 1.4.1996). Evaluation by Swiss Leaching Test.

Langøya Manufacturer/developer NOAH AS, Norway Contact [email protected] Process type Water extraction + acid extraction + solidification with gypsum Technical description The residues are crushed in order to remove aggregates. First, residues are

mixed with water at a density of about 1,5 ton/m3 and stored in tanks with stirring devices. The slurry is pumped through a grinder in order to remove granulates and larger particles. The residue slurry is then mixed with waste acid and slaked lime. The addition of residue and limestone slurry to the acid is controlled to maintain a pH of 4-5. In this step gypsum is precipitated along with some of the heavy metals (hydroxides). In the third step, remaining metals (iron as well as other heavy metals) are precipitated by adding slaked lime in order to raise the pH to about 8-9. The final mixture is pumped to an old limestone quarry. Remaining residue solids, gypsum and precipitated metals are then deposited at the bottom by sedimentation and consolidation of the gypsum. Water is recycled and used in the neutralization process. Surplus water from the process is treated to remove heavy metals before discharge.

Achieved environmental benefits Excess lime and buffer capacity in the APC residues are utilised in the neutralisation process, and a part of the available heavy metals is precipitated mainly as metal hydroxides as well as incorporated in the gypsum. This probably results in some level of heavy metal retention, however it is not likely that this type of processing - in a long-term perspective - significantly reduces leaching. The deposit is not hydraulically connected to the surrounding sea but excess water from the deposit is treated to remove heavy metals and discharged to the sea. This is likely to continue while the facilities are in operation, however when the area is reclaimed the long-term leaching is determined by the contact with infiltrating water.

Cross-media effects The utilization of excess lime in the residues substitutes limestone from the quarry on the island. As a result of this, the heavy metal content of the excess surface water from the facilities is increased.

Operational information None available. Lab Bench Pilot Full


X Commercial Applicability of technique The technique can be used on all types of APC residues with equal success.

Also other types of ashes could be used in the process. Economics A typical cost for treatment and disposal is estimated to €50 without transport

to the treatment facility (Langøya, Norway). Driving force of implementation The authorities in Norway accept the utilization of APC residues in the acid

neutralization process, and the deposit prolongs the lifetime of the limestone quarry.

References & examples The technique is used only at the Langøya Island in Norway. About 100.000 ton APC residues are treated annually.

Main public reports Information about the process has been obtained from Miljøstyrelsen (2005) and NOAH AS (www.noah.no).

Inputs Units Per ton of residue treated Electricity kWh 13 Diesel l 0.6 Waste acid kg 1600 Slaked lime kg ? Water m3 0.9 Chemicals (waste water) kg 0.002

Outputs Units Per ton of residue treated Wastewater m3 1.7

Cl mg/l 5400 Sulfate mg/l 480 Cd mg/l 0.0018 Cr mg/l 0 Cu mg/l 0 Hg mg/l 0.00004 Pb mg/l 0.00018 Zn mg/l 0.0084 Dioxins ng-TEQ/l 0.0042

Treated residue kg 3400 pH 9.5 Cl mg/kg 35000 Sulfate mg/kg 0 Cd mg/kg 50 Cr mg/kg 50 Cu mg/kg 50 Hg mg/kg 10 Pb mg/kg 200 Zn mg/kg 500 Dioxins ng-TEQ/kg 0.0012

INERTEC Stabilization and Solidification Manufacturer/developer INERTEC Contact Philippe de Rochebouët / Marie-Claire Magnié / Stéphane Lebrave Process type Solidification and stabilization Technical description Stabilization : transform the polluting agents contained in the waste into stable

and non soluble products by chemical fixation Solidification : change the waste into a solid matrix with low porosity and low permeability which ensures physical and chemical stability (Patented processes)

Achieved environmental benefits Insolubilisation of polluting agents Mechanical properties are improved so stability of the landfill site is improved too

Cross-media effects Reutilization of output products : impossible in France for hazardous waste, depends on legislation of the considered country Possibility of using wastewater or leachates instead of clean water Possibility of using sub-products of industrial processes instead of reagents Possibility of mixing different wastes in order to optimize chemical reactions (for example acid waste and alkaline waste)

Operational information Physico-chemical treatment of Hazardous Waste (for example fly-ashes from incineration plants)

• Storage of water and reagents

• Test and choice of the right formula for the specific waste

• Mixing of waste with the different reagents and water

• Solidification and storage of the mortar in the landfill Lab Bench Pilot Full


X Commercial Applicability of technique Applicable to all kinds of incinerators and fly ashes

Applicable to many different kinds of hazardous waste Analysis of new hazardous waste before creating a new formula : adaptation of the process (reagents, mix…) to each waste or waste type characteristics Database of treatment formulations for over 2.000 different hazardous waste

Economics Fly-ashes : 200-220 €/ton including landfill of the stabilized waste Other hazardous waste : between 150 and 220 €/ton (in France) Costs can be different according to legislation and local context

Driving force of implementation Legislation Technical compromise between objectives of the law and costs Applicability to every kind of fly-ashes and hazardous waste No output of secondary waste after treatment Automatic process Proved technique

References & examples More than 2 000 000 tons of hazardous waste treated with Inertec processes in inertization plants on landfill sites : Jeandelaincourt (F-54) : 30.000 ton per year, since 1993 Bellegarde (F-30) : 60.000 ton per year 1995 Villeparisis (F-77) : 100.000 ton per year since 1995 Drambon (F-21) : 20.000 ton per year since 1998 Champteussé-sur-Baconne (F-49) : 30.000 ton per year since 1995

Vaivre (F-52) : 40.000 ton per year since 1996 Laimont (F-55) : 20.000 ton per year since 1996 Valorsul (Portugal) : 30.000 ton per year since 1999

Main public reports FNADE study on storage of hazardous waste 2002 ALBI, WASTEENG 2005 / Mai 2005 “Modeling of the impact of a hazardous waste storage centre : sensitivity

study” M.A. Aubry (Inertec) – M.C. Magnié (Inertec) – A. Budka (Sita France) – I. Martin (Sita FD)

“Stabilisation / Solidification Experience in France” P.Y. Klein (Inertec) – M.C. Magnié (Inertec) TRAVAUX n° 800 / 2003 “Rehabilitation of ballast pond in Brest by active barrier and in situ

stabilisation“ M.C. Magnié (Inertec) – A. Barbier (Inertec) – J.J. Kachrillo (Soletanche-

Bachy) TRAVAUX n°769 / November 2000

"Use of household bottom ash in civil engineering : strengthening of underground quarries" JY Cojan (Inertec) - MC Magnie (Inertec) - E Gastine

CONGRES STAB&ENV / Avril 1999 "Industrial feedback about stabilisation / solidification of industrial waste" A Bouchelaghem (Inertec)

Inputs Units Per ton of residue treated Water m3 0.1 to 0.6 (can be replaced by “dirty” water) Reagentsa) kg 200-500 Sludgeb) kg 500-1500

Outputs Units Per ton of residue treated Treated residuec) kg 1200-2000

pH 11-12.5 Cl mg/kg 4000-200,000 Sulfate mg/kg 2000-5000 Cd mg/kg 50-500 Cr mg/kg 100-1000 Cu mg/kg 100-2000 Hg mg/kg < 100 Pb mg/kg 200-5000 Zn mg/kg 200-40,000

Residue leachated) pH mg/l 11-12.5 Cl TDS < 10 % Sulfate TDS < 10 % Cd mg/l < 5 Cr mg/l < 70 Cu mg/l < 100 Hg mg/l < 2 Pb mg/l < 50 Zn mg/l < 200

a) Reagents depending on waste type and local availability b) Depending on waste to be treated, availability and characteristics c) About 1 m3/ton d) According to French regulation for HW: EN 12 457 –2 (granular waste) and NF X 31-211 (monolithic waste)

NEUTREC Manufacturer/developer NEUTREC / Solvay S.A. Contact Process type Solidification + water extraction + recovery Technical description Several variations of this process exist depending on whether fly ashes are

collected separately or not. The process is used in combination with dry flue gas cleaning systems (sodium bicarbonate): "residual sodium chemicals" (i.e. neutralization products) are dissolved in water with a controlled pH and certain additives. The suspension is filtered and the resulting solution then filtered by activated coal and ion exchangers to produce a brine suitable for sodium carbonate production. If fly ashes are collected separately, these may be washed separately but the filtrate may used for washing of the neutralization products from the dry process (the dewatered residues are then chemically and thermally stabilized before landfilling). If fly ashes are collected together with the neutralization products (i.e. a single filter), hydraulic binders (and other additives) may be added before washing. Again, the dewatered residues are landfilled.

Achieved environmental benefits The brine may substitute raw materials in the production of sodium carbonate. Lower leaching from treated residues than without treatment.

Cross-media effects Substitution of raw material for sodium carbonate production. Operational information



x Commercial Applicability of technique The technique is only applicable for dry/semi-dry systems Economics Driving force of implementation References & examples Main public reports NEUTREC web site: http://www.neutrec.com/process/0,0,1000052-

_EN,00.html

Inputs Units Per ton of residue treated Energy kWh ? Water m3 ? Additives kg ?

Outputs Units Per ton of residue treated Recyclable brine kg 7-101)

Treated residue kg 1-31)

Cl mg/kg ? Sulfate mg/kg ? Cd mg/kg ? Cr mg/kg ? Cu mg/kg ? Hg mg/kg ? Pb mg/kg ? Zn mg/kg ?

Residue leachate pH mg/l ? Cl mg/l ? Sulfate mg/l ?

Cd mg/l ? Cr mg/l ? Cu mg/l ? Hg mg/l ? Pb mg/l ? Zn mg/l ?

1) In cases where only reacted sodium bicarbonate (i.e. the dry product) is treated. If fly ashes are co-treated up to about 16 kg of brine can be produced, but also about 30-50 kg of (treated) fly ashes are produced.

Melting: Electric Arc Manufacturer/developer Daido Steel Contact Koichiro Kinto (http://www.daido.co.jp/english/index.html) Process type Melting Technical description Vibrating sieve, magnetic separation, drying, melting furnace, gas cooler, bag

filter, APC residue stabilization (exhaust gas go to incinerater) Achieved environmental benefits Extending the life of landfill sites and decomposition of dioxins. Cross-media effects Operational information Arc plasma of 3000-5000 deg C and slag temperature of 1400-1600 deg C,

oxidized conditions. Lab Bench Pilot Full


X Commercial Applicability of technique Mixture of bottom ash and APC residue Economics Driving force of implementation Extending the life of landfill sites and decomposition of dioxins References & examples Ohta Seisou Koujo Second Plant, Tokyo 23-Ku Seisou Jimukumiai, Japan Main public reports K. Kinto (1998): Ash melting system and reuse of products, Denki-Seiko

(Technical Paper of Daido Steel), Vol. 68, No. 4, pp.269-278 Inputs Units Per ton of residue treated Electricity kWh 550 Graphite electrode kg 6-12

Outputs Units Per ton of residue treated Treated residue kg 900 (including 90 kg of metal)

Cl mg/kg 20-400 Sulfate mg/kg 10-150 Pb mg/kg 10-60 Zn mg/kg 30-190 Dioxins ng-TEQ/m3 0.003

APC residue kg 60-100 Air emissions

Dioxins ng-TEQ/m3 0.4 Residue leachate

Cd mg/l < 0.01 Cr mg/l < 0.05 Cu mg/l < 0.05 Hg mg/l ? Pb mg/l 0.01 Zn mg/l < 0.01

Melting: Electric Resistance Manufacturer/developer JFE Engineering Contact Eiichi Shibuya Process type Melting Technical description Vibrating sieve (< 25mm), drying, melting furnace, secondary combustion

chamber, bag filter, APC residue stabilization (exhaust gas goes to bag filter in incineration plant).

Achieved environmental benefits

Extending the life of landfill sites, decomposition of dioxins, and control of heavy metal leaching from slags.

Cross-media effects Metal from furnace is used as materials for copper refinement Operational information Particle size of < 30mm, under 5 % water content of bottom ash in outlet of

drier, slug temperature of 1400-1500 deg C, reducing conditions, residence time of more than 10 hours



X Commercial (40 ton/24h * 2 furnace) Applicability of technique Mixture of bottom ash and APC residue Economics Driving force of implementation Extending the life of landfill sites, decomposition of dioxins, and control of

heavy metal leaching from slags. References & examples Kasugaisi Clean Center, Aichi, Japan Main public reports E. Shibuya, et al.(1996): Vitrification for fly ash using electric-resistance

furnace, NKK Technical Reprot, No. 166, pp.7-11 Inputs Units Per ton of residue Electricity kWh 700-900 Co-treated waste kg 0.9

Outputs Units Per ton of residue Treated residue kg 700-800

Pb mg/kg 15 Dioxins ng-TEQ/g < 0.01

Metal product kg 40-150 APC residue kg 20-60

Sn g/kg 3 Cu g/kg 2 Zn g/kg 180-250 Pb g/kg 4070 Dioxins ng-TEQ/g 0.25

Residue leachate Cd mg/l < 0.01 Cr mg/l < 0.04 Se mg/l < 0.002 Hg mg/l < 0.0005 Pb mg/l < 0.005 As mg/l < 0.005

Air emissions Dioxins ng-TEQ/m3 0.41

Melting: Furnace Manufacturer/developer Takuma Contact Satoshi Yoshimoto Process type Melting Technical description Magnetic separation, vibrating sieve (< 30mm), melting furnace, secondary

combustion chamber, heat exchanger, quenching chamber, bag filter, APC residue stabilization

Achieved environmental benefits Reduction in MSWI residue to 80 % in weight, decomposition of dioxins in MSWI residue (73 % is removed, the rest is moved into APC residues and exhaust gas), and no heavy metal leaching from slags.

Cross-media effects Operational information Particle size of <30mm, furnace temp of 1280-1350 deg C



X Commercial (13t/24h) Applicability of technique Mixture of bottom ash and APC residue. Economics Driving force of implementation Decomposition of dioxins in MSWI residue and control of heavy metal

leaching from slags. References & examples Hitachi-Ota Chihou Jimusyo Seiso center, Ibaraki, Japan Main public reports S. Yoshimot and S. Shibano (2002), A new film melting furnce, its

development and operation, Takuma Technical Report, Vol.10, No.2, pp.46-54

Inputs Units Per ton of residue treated Oil l 240

Outputs Units Per ton of residue treated Treated residue kg 11,000

Cd mg/kg < 5 Cr mg/kg < 0.5 Cu mg/kg < 0.005 Hg mg/kg 85 As mg/kg 1.6 Se mg/kg < 1 Dioxin ng-TEQ/g 0

Residue leachatea) Cd mg/l < 0.01 Cr mg/l < 0.05 Cu mg/l < 0.0005 Hg mg/l < 0.01 As mg/l < 0.01 Se mg/l < 0.01

Raw flue gas from process m3 3700 (Combustion chamber outlet), 5500 (Bag filter outlet) HCl mg/Nm3 500 SOx mg/Nm3 2.4 Dioxin ng-TEQ/g 0.068

APC residue from processb) kg 51 Cd mg/kg 400 Cr mg/kg < 0.5

Cu mg/kg 48 Hg mg/kg 22,800 As mg/kg 74 Se mg/kg < 1 Dioxin ng-TEQ/g 0.38

a) JLT46 b) Dioxin (Secondary Combustion Chamber outlet), SOx-HCl (quench chamber outlet)

T.I.L.® Integrated LAB ash Treatment process Manufacturer/developer LAB S.A. Contact Process type Technical description The LAB Integrated T.I.L.® ash Treatment, is a group of processes applicable

to the specific flue gas cleaning unit of the plant. It could be integrated in a wet scrubbing process (acid T.I.L.®) or separated (neutral T.I.L.®) from the scrubbing system. Here is detailed the acid ash treatment process which involves several steps: - the boiler ashes are crushed and mixed with fly ashes from ESP, - the humidified product is transferred to the acid scrubber, - the scrubbing water with ashes is sent to a settler where flocculent is added, - the continuous over-flow is sent to the waste water treatment plant, - the under-flow composed of treated ashes and gypsum is rinsed using water or an additional reagent and dewatered on a vacuum band filter, - the dewatered ashes with a water content of 50% about and a salt content lower than 5% of dry matter are mixed with slag and discharged from the plant.

Achieved environmental benefits Reduction of ash eco-toxicity and ash quantity. On-site ash stabilization process to produce a potential by-product in order to achieve compliance with different leaching or percolation test protocols.

Cross-media effects Land-filling of residual product as non-hazardous residue instead of hazardous residue fulfillment of EU Directive 2033/33/EG.

Operational information Lab Bench Pilot Full


X Commercial Applicability of technique All flue gas cleaning equipped with a wet scrubbing system. Driving force of implementation Integral part of a wet flue gas cleaning (acid T.I.L.®) or not (neutral T.I.L.®). References & examples Acid T.I.L.® ash treatment process: in operation since 2001 in SAIDEF

Fribourg Waste-to-Energy plant (Switzerland). Neutral T.I.L.® ash treatment process: in 2006 in Sundsvall Energi Waste-to-Energy plant (Sweden).

Main public reports B.Siret, F.Gourmelon, A.Praud-Tabaries (2004): Reduction of fly ash eco-toxicity by an integrated wet scrubbing process. Laboratoire RCMO, Université de Toulon et du Var. B.Siret (2004) : Reduction of fly ash eco-toxicity by an integrated wet scrubbing process. ITTT 2004, Phoenix (Arizona). F.Tabaries (1995) : Contribution à l’étude de la paragénèse et des traitements des résidus solides issus de l’incinération des déchets ménagers et industriels. Thèse en chimie et chimie physique, Université de Toulon et du Var.

Inputs Units Per ton of residue treated Electricity kWh 5,9 Water m3 0 (water is re-cycled to the wet scrubbing process) Sulfide organic reagenta) l 3-10 NaOH 50% kg 3-5 Co-treated boiler ash kg 15 ? Co-treated ESP ash kg 17 ?

Outputs Units Per ton of residue treated Treated residue kg 20-30 (50 % dry)

Cd mg/kg 30-65 Cu mg/kg 0,15-0,25 Hg mg/kg 40-80 Pb mg/kg 0,5-1 Zn mg/kg 0,9-1,6

Residue leachate Cd mg/l 0,02-0,1 Cr mg/l 0,01-2 Cu mg/l 0,02-0,5 Hg mg/l 0,001-0,1 Pb mg/l 0,09-1 Zn mg/l 2-10

Waste water from plant Waste water is re-cycled to the process and sludge is combined and treated in the waste water treatment plant

Cl mg/l 10000-20000 Cd mg/l 0,01-0,05 Cr mg/l 0,01-0,1 Cu mg/l 0,02-0,1 Hg mg/l 0,001-0,005 Pb mg/l 0,04-0,1 Zn mg/l 0,2-0,5

a) Or or H3PO4 or Na2CO3 or HCl or water

WesPhix Manufacturer/developer Wheelabrator Technologies Inc, NH, USA Contact Mark Lyons, [email protected] Process type Chemical stabilization Technical description Chemical stabilisation with phosphate as the stabilisation agent is used in the

WESPHix stabilisation process. The treatment process is relatively simple, and consists of a mixing device (such as a pug mill) into which the residues are fed at a controlled rate. A proprietary form of soluble phosphate is then added to the mixer. After the phosphate is thoroughly mixed with the residues, a conveyor at the end of the mixer then removes the treated product. In some cases, depending of the characteristics of the residue input, other additives such as lime are used. Reaction kinetics are fast and the residue is considered fully treated without further curing (Wheelabrator, 2002).

Achieved environmental benefits The process retains salts in the treated product, thus facilitating a substantial leaching of these and increased solubility of some heavy metals (e.g. Pb and Cd) after landfilling. Compared to the Ferrox and VKI processes relatively small amounts of water are added along with the phosphate. The release of salt and heavy metals is expected to be higher than is the case with Ferrox and VKI treated residues.

Cross-media effects The process produces no wastewater. There are currently no suggestions for utilisation of the treated product.

Operational information The specific amounts of water and phosphate as well as other additives are likely to vary according to the residue properties, however no quantification of this has been available.



X Commercial Applicability of technique The process is in all but one case implemented as an integrated unit at the

incinerator, but can also be set up as a centralised plant treating residues from more than one incinerator. The process was originally developed to treat MSWI residues, however several other waste types (e.g. contaminated soil, slags, sludges, etc.) have been suggested and tested (Wheelabrator, 2002).

Economics The treatment cost for WES-PHIX stabilisation is about €15 per ton of APC residue. In addition to this a royalty is charged for use of the patented process amounting to €5-10 per ton. Investment costs are in the order of about €150,000-500,000 per installation depending on existing equipment (Wheelabrator, 2002).

Driving force of implementation The main reason for implementation of the technique is simplicity of operation and, at least currently, extensive commercial use in the United States, Japan and Taiwan. The treated product is generally accepted as suitable for landfilling in these countries

References & examples The process is currently used in North America, Japan and Taiwan at about 90 MSWI facilities treating over 2 million tons of bottom ash and APC residues per year.

Main public reports Eighmy et al. (1995), Eighmy et al. (1997)

Inputs Units Per ton of residue treated Electricity kWh ? Water m3 ? Reagents kg ?

Outputs Units Per ton of residue treated Treated residue kg ? Residue leachate ?

3R Manufacturer/developer Forschungszentrum Karlsruhe GmbH Contact Jürgen Vehlow Process type Acid extraction + sintering Technical description The process combines an acid extraction of boiler and fly ash with sintering of

the acid treated product with bottom ashes on the grate. Hg is separated from the acidic scrubber solution before mixing with the ashes at L/S 7-10 and pH 3-4 for about 30 minutes. Extraction efficiency is about: 90 % (Cd), 70 % (Zn), 20-40 % (other metals). In total about 20 % of solids are extracted. Residues are dewatered and routed to the waste hopper together with the normal waste. Heavy metals in the waste water have to be removed.

Achieved environmental benefits Improved leaching properties of fly ashes. Cross-media effects Only a single solid residue is produced, i.e. the amount of bottom ashes are

increased. Operational information None Available.

Lab Bench Pilot

X Full


Commercial Applicability of technique Incinerators equipped with wet flue gas cleaning systems Economics Driving force of implementation Reduction of residue leaching References & examples TAMARA pilot plant, Karlsruhe, Germany Main public reports Vehlow J, Braun H, Horch K, Merz A, Schneider J, Stieglitz L, Vogg H

(1990): Semi-technical demonstration of the 3R process. Waste Management & Research, 8, 461. Vehlow J, Geisert H (1993): Characterization of the leaching behaviour of 3R products. 3rd. Int. Concerence on Municipal Waste Combustion, March 30- April 2, 1993, Willamsburg, VA.

Inputs Units Per ton of residue treated Energy kWh ? Acid m3 ?

Outputs Units Per ton of residue treated Wastewater m3 ? Treated residue kg ? Residue leachate ?

CTU Manufacturer/developer Conzepte Technik Umwelt AG Contact Martin Schaub, [email protected] Process type Melting Technical description The residues are mixed with pretreated car shredder waste (crushing, metal

removal) in a primary melting furnace heated by a gas burner to about 2000 °C. Slag, dust and gases moves to a secondary furnace kept at 1400 °C. Melted slag and metals are removed from the bottom of this furnace, while gases are treated in a wet cleaning system and also utilized for electricity production and heat. Wastewater from gas cleaning is treated for heavy metals. Slags are quenched, and can be separated from molten metals.

Achieved environmental benefits

Improved leaching properties of the residues, and potential utilization of residues as construction material. Destruction of POP's.

Cross-media effects The use of car shredder waste as energy supply and energy recovery in the process minimizes the use of other fuels. A Zn containing metal product may be routed to further recovery.

Operational information None available. Lab Bench

X Pilot Full


Commercial Applicability of technique The process can be used on all APC residues, but cannot be performed solely

on residues. Economics Driving force of implementation Treatment of car shredder waste and residues, and possible reutilization of

solid residues. References & examples Currently investigated in a pilot plan at MEFOS, Sweden. A full scale plant

(100,000 tons annually) has been drafted in Switzerland. Main public reports None available. Information gathered from Danish EPA, 2005

Inputs Units Per ton of residue treated Electricity kWh 9.6 Natural gas (CH4) kg 8 Car shredder waste kg 962 Oxygen (O2) kg 587 Nitrogen (N2) kg 7 Lime kg 117 Water kg 3990 TMT-15 kg 0.1 HCl kg 0.2 Active carbon kg 0.6 Ammonia kg 1.2

Outputs Units Per ton of residue treated Electricity kWh 188 Heat kWh 2606 Slag kg 1000

Cl mg/kg 600 Sulfate mg/kg 300 Cd mg/kg 2 Cr mg/kg 2700

Cu mg/kg 1800 Hg mg/kg 1 Pb mg/kg 180 Zn mg/kg 3900 Dioxin ng-TEQ/g < 100

Metal alloy kg 98 Cl mg/kg 33,000 Sulfate mg/kg < 1000 Cd mg/kg 3000 Cr mg/kg 200 Cu mg/kg 12,000 Hg mg/kg < 20 Pb mg/kg 96,000 Zn mg/kg 258,000 Dioxin ng-TEQ/g

Gypsum (flue gas) kg 135 Cl mg/kg < 20,000 Sulfate mg/kg 186,000 Cd mg/kg < 4 Cr mg/kg < 2 Cu mg/kg < 4 Hg mg/kg < 10 Pb mg/kg < 5 Zn mg/kg < 10 Dioxin ng-TEQ/g 100

Sludge (wastewater) kg 0.4 Hg mg/kg 150,000

Treated wastewater m3 2.3 pH 6.5-8.5 Cl mg/l 44,000 Sulfate mg/l 0.6 Cd mg/l 0.0001 Cr mg/l 0.0001 Cu mg/l 0.0001 Hg mg/l 10-7 Pb mg/l 0.0001 Zn mg/l 0.002 Dioxin ng-TEQ/g < 10-6

Flue gas m3 5100 Cl mg/Nm3 7 Sulfate mg/Nm3 25 Cd mg/Nm3 0.01 Cr mg/Nm3 < 0.01 Cu mg/Nm3 0.02 Hg mg/Nm3 0.02 Pb mg/Nm3 0.08 Zn mg/Nm3 ? Dioxin ng-TEQ/m3 0.02

DHI Stabilization Manufacturer/developer DHI - Water and Environment, Denmark Contact Ole Hjelmar, [email protected] Process type Water extraction + chemical stabilization Technical description The VKI stabilisation resembles in many respects the Ferrox stabilisation

process, however the chemical agents used here are CO2 and/or H3PO4. The VKI-process involves a two-step procedure where the residues are first washed at L/S 3 l/kg in order to extract soluble salts. After this the residues are dewatered and washed again in a plate and frame filter press at L/S 3 l/kg. The residues are then re-suspended, and CO2 and/or H3PO4 are added. The stabilisation reactions are allowed to occur for 1-1.5 hours while pH decreases, and another hour where pH is maintained around pH 7. Finally, the residues are dewatered again and washed at the filter press with another 3 l/kg. The final product has a water content of about 50 %. The use of CO2 and H3PO4 as stabilising agent ensures that heavy metals are bound as carbonates or phosphates.

Achieved environmental benefits VKI stabilisation shows very good leaching properties similar to the Ferrox stabilisation. Metal carbonates and phosphates are known to generally have low solubilities, and the leaching characteristics of VKI stabilised residues are expected to remain good for extended periods of time. The pollution potential of the treated residues is documented extensively and physical disintegration of the treated residues in a long-term perspective is expected to be less important than in the case of cement stabilisation, because of the fact that most salts are removed. VKI stabilised residues typically have far better leaching properties than cement solidified residues. The VKI process reduces the amount of residue by about 15 % per dry weight.

Cross-media effects No reutilisation strategies have yet been demonstrated. The process produces wastewater from first dewatering step. All other process water is recycled in the process. The wastewater needs to be treated for dissolved heavy metals in a standard unit, for example using pH adjustment and TMT addition.

Operational information The process has been demonstrated in pilot scale at a plant treating residues in batches of about 200 kg dry weight. Parameters like water consumption, mixing of water and residues, CO2 and H3PO4 addition, reaction time, pH and pH controlling approach have been optimised. It has been demonstrated that the process is robust with respect to the properties of the residue input, although some variations in process parameters arise. Depending on residue composition, either CO2 or H3PO4 or both have been used. It has also been demonstrated that flue gas can be used as a CO2 source. Typical process data for 1 ton of residue are: 5-20 kg of CO2, 0-40 kg H3PO4 and 3 m3 water.

Lab Bench

X Pilot X Full


Commercial Applicability of technique The stabilisation unit can be implemented as an integrated part of the

incinerator but may also exist as a centralised treatment plant handling residues from several incinerators. The technique has been demonstrated on semi-dry APC residues as well as fly ash alone and fly ash combined with sludge from the wet scrubbers (Bamberg product; Reimann, 1990); all with good results.

Economics Treatment cost for VKI stabilisation is estimated to about €80/ton with a plant capacity of 20,000 ton/year; including investment costs.

Driving force of implementation The main reason for implementing this technology is the very good leaching properties of the treated residues and the fact that this is expected to last in a long-term perspective.

References & examples The process has only been demonstrated in pilot scale, however it has also been designed in full scale. No full-scale plants have yet been implemented.

The technique has been developed at DHI - Water and Environment, Denmark in collaboration with I/S Vestforbrænding and I/S Amagerforbrænding.

Main public reports Hjelmar O; Birch H; Hansen JB (2001): Treatment of APC residues from MSW incineration: Development and optimisation of a treatment process in pilot scale. Proceedings Eighth International Waste Management and Landfill Symposium, 1, 667-675.

Inputs Units Per ton of residue treated Electricity kWh ? Water m3 3 CO2 kg 5-20 H3PO4 kg 0-40 Chemicals (wastewater) kg ?

Outputs Units Per ton of residue treated Wastewater m3 3 Sludge (wastewater) kg ? Treated residue kg 850 Residue leachatea)

pH mg/l 10 Cl mg/l 780 Sulfate mg/l 1600 Cd mg/l 0.004 Cr mg/l 0.1 Cu mg/l 0.003 Hg mg/l 0.0077 Pb mg/l 0.009 Zn mg/l 0.01

a) EN 12457 (L/S 2 l/kg)

Semi fluid slurry Manufacturer/developer GTS GmbH & Co. KG Contact [email protected] Process type Solidification + utilization Technical description The residues are continuously blended within a mixer as part of a recipe which

is composed of residues, fluids and a small portion of cement. Goal of the recipe is to produce a slurry which can be transported via pipes under ground. The produced slurry is then pumped as backfill into excavations leftover from the mining activities in the former potash mine. The backfilling is necessary in order to prevent future earthquake like rock bumps caused by the collapse of pillars within the mine. The goal of the recipe is to create a material which will tie off without producing overflow water. Excess water in a salt mine can damage pillars which are necessary for the stabilization of the under ground strata.

Achieved environmental benefits The waste materials used as components for the backfill are contaminated with hazardous elements in such a small concentration which makes a recycling process nearly impossible from a financial and technical point of view. The build up within the mine extracts therefore these hazardous waste materials from the biosphere for a geological long-term period of time.

Cross-media effects The main advantage is the utilization of waste material as backfill which otherwise would have been composed of building material which again would have to be produced. Either by recycling or newly mined material. The technique therefore substitutes otherwise usable resources.

Operational information Lab Bench X Pilot Full


Commercial Applicability of technique The technique can be used up till now only on a small number of APC

residues which have the suitable setting properties for the recipes and do not produce overflow water.

Economics The treatment and utilization within the backfilling of the mine with residues arise from 60,- up to 90,-€/ton. This is an indicative price margin for average waste material which is used in the above described utilization.

Driving force of implementation The main reason for the application of the described technique is firstly the stabilization of underground pillars and secondly in the commercial value of the business.

References & examples A similar technique is used on the potash mine Unterbreizbach in Germany.

Main public reports

Inputs Units Per ton of residue treated Electricity kWh 8 Water m3 not yet determine Cement kg 50 Waste fluids kg 700

Outputs Units Per ton of residue treated Wastewatera) m3 ?

pH mg/l 7.5 Cl mg/l 24000 Sulfate mg/l 7800 Cd mg/l 0.0056 Cr mg/l < 0.05 Cu mg/l 0.01 Hg mg/l < 0.0002 Pb mg/l < 0,005

Zn mg/l 0.18 Treated residue kg 1700 a) Wastewater only is produced from the treatment of water within a clarifying tank from the bath of the mine.

Electrolysis Manufacturer/developer BYG·DTU, Denmark Contact Lisbeth Ottosen; [email protected] Process type Water extraction Technical description The residues are mixed with water at L/S 1-7 l/kg. Ammonium citrate is added

as desorption agent. The suspension is stirred in order to enhance release to solution. An electrical potential is applied to the suspension to facilitate separation of ions. Ion exchange membranes separate the suspension from the electrodes. Metal cations are collected at the cathode while anions are collected at the anode.

Achieved environmental benefits Removal of metal content in residues. Cross-media effects Extracted metals may be reutilized after refinement. Operational information None available.

X Lab X Bench X Pilot Full


Commercial Applicability of technique The process may be applied on all residues. Economics Driving force of implementation Metal recovery. References & examples The technique is a well known process for separation of elements in solutions

(e.g. H2 and O2 from water), and has in this setup been tested on several soils and ashes.

Main public reports Pedersen et al. (2003), Ottosen et al. (2003)

Inputs Units Per ton of residue treated Electricity kWh ? Water m3 ? Reagents kg ?

Outputs Units Per ton of residue treated Wastewater m3 ? Treated residue kg ? Residue leachate ?

Watech Manufacturer/developer RGS90 Watech AS Contact Erik Rasmussen, RGS90, Denmark Process type Acid extraction + pyrolysis Technical description The process involves co-treatment of other waste fractions (PVC, car shredder

waste, WEEE) in several process steps. First residues are mixed with waste acids to extract metals and salts. The extracted residues are then transferred to a reactor together with the other waste fractions for pyrolysis. Outputs from this step are: coke, gases, acid solution, and oil/condensate. Non-soluble residue particles are most likely primarily contained in the coke, which is further washed and used as energy input to the process (i.e. decreasing the organic content). The remaining ash then constitutes the "treated residue".

Achieved environmental benefits Improvement of residue leaching properties, recovery of salts, destruction of POP's and potentially utilization of the treated product.

Cross-media effects Use of car shredder waste and plastics as energy supply in the process minimizes the use of other fuels (energy recovery is also applied). Several secondary products are produced: brines, metal products, ash.

Operational information Not available. X Lab Bench

X Pilot Full


Commercial Applicability of technique The process can be applied on all APC residues, but cannot be performed

solely on residues. Economics Driving force of implementation Suitability of process to handle residues, and possibilities of utilization of

treated products. References & examples Tested with APC residues in lab scale. Test runs in pilot scale are expected

completed in 2005. Main public reports

Inputs Units Per ton of residue treated Electricity kWh 137 PVC kg 174 Shredder waste kg 207 WEEE kg 77 Waste acid (5 % HCl) kg ~1000 Lime kg 29 Chemicals/detergents kg 0.02 Diesel L 0.7

Outputs Units Per ton of residue treated Oil/condensate kg 118 Cl mg/kg 80 Hg mg/kg < 0.0002 Pb mg/kg < 0.04 Dioxin ng-TEQ/g 0.003 Heat MJ 2820 Ca-product kg 472

Cl mg/kg 492,000 Sulfate mg/kg 300 Cd mg/kg < 0.05

Cr mg/kg < 0.05 Cu mg/kg < 0.01 Pb mg/kg < 0.01 Zn mg/kg < 0.05

K-product kg 36 Cl mg/kg 486,000 Cd mg/kg < 0.05 Cr mg/kg < 0.05 Cu mg/kg < 0.01 Pb mg/kg < 0.01 Zn mg/kg < 0.05

Na-product kg 43 Cl mg/kg 600,000 Cd mg/kg < 0.05 Cr mg/kg < 0.05 Cu mg/kg < 0.01 Pb mg/kg < 0.01 Zn mg/kg < 0.05

Metal product kg 139 Cd mg/kg 250 Cr mg/kg 400 Cu mg/kg 6000 Pb mg/kg 30,000 Zn mg/kg 50,000

Ash kg 227 Sulfate mg/kg 23,000 Cd mg/kg 30 Cr mg/kg 200 Cu mg/kg 1000 Pb mg/kg 2500 Zn mg/kg 10,000

Metals phases kg 23 Flue gas Nm3 3028

CO2 mg/Nm3 204914 HCl mg/Nm3 0.5 SO2 mg/Nm3 1 NOx mg/Nm3 0.02 Dioxin ng-TEQ/M3 0.08

Appendix B

LCA-screening of residuemanagement: An example

B.1 Introduction

Systematic evaluations of environmental aspects of APC residue management, suchas life-cycle assessments, are very limited although a few examples exists (e.g. Fruer-gaard and Astrup, 2007). It should be realized that although life-cycle aspects areincluded in an environmental assessment, such an assessment may not necessarilybe characterized as a “full” LCA (for further details see Wenzel et al. 1997; ISO14040, 1997). A few issues should be realized with respect to LCA:

• LCA is an analytical tool used for decision support, it is not a decision makingtool

• The result of an LCA is highly dependent on system boundaries, assumptions,assessment criteria, time horizons, data quality, etc

• Several methodologies exist for performing LCA

It is beyond the scope of this document to provide a detailed account of anLCA on residue management, however the main aspects related to such an LCA isintroduced here. On this basis readers are encouraged to seek further information.Please note that LCA on waste management in general (e.g. municipal solid waste,including waste incineration) is relatively well investigated.

An LCA includes the following main steps (for further details see ISO 14040,1997):

Goal and scope definition. Definition of the “functional unit”, system bound-aries, assessment criteria, methods for accounting indirect and avoided pro-cesses and activities.

Inventory analysis. Data collection and preparation of an inventory of inputs andoutputs for the involved processes. Assessment of data quality.

Impact assessment. Four sub-steps: selection of impact categories to assess (e.g.global warming, acidification, etc.), characterization (e.g. quantification ofan emissions contribution to a specific impact category), normalization (e.g.normalization of the results to a common unit such as average impacts related

B-1

to one person, a person equivalent), and finally weighting (e.g. weighting of theresults according to the assessment goals, society or political interests, etc.).

Interpretation. Including sensitivity analysis for example with respect to systemboundaries, assumptions, data, etc.

The following sections provides an example of an LCA-screening of managementof Danish APC residues carried out by Fruergaard and Astrup (2007). It shouldbe strongly emphasized that this LCA-screening is based on generalized data ratherthan (measured) data referring to specific and concrete cases. The main purposeincluding this LCA-screening is to provide an example of how this can be done. Thismeans that the results discussed in the following should be viewed as what they are:general guidelines and indications.

B.2 Results and discussion

B.2.1 Goal and scope

This LCA-screening is based on Danish requirements and conditions. The overallaim is to evaluate various potential management alternatives for Danish residues.The following sections provides examples of such management alternatives only, andshould not be viewed as final decisions on behalf of the Danish incinerators.

The functional unit of the LCA-screening is treatment and final disposal of oneton of APC residue, including secondary and avoided processes. The time horizonis 100 years. The following environmental impact categories are assessed:

• Global Warming

• Acidification

• Nutrient Enrichment

• Photochemical Ozone Formation

• Stratospheric Ozone Depletion

• Ecotoxicity (in Water and Soil)

• Human Toxicity (via Air, Water and Soil)

These impact categories represent a range of “environmental aspects” generallyconsidered to be important. Further details can be found in Wenzel et al. (1997).

B.2.2 Assumptions

To carry out a full LCA, a range of assumptions/decisions about system boundarieshas to be made: processes and activities to include/exclude, energy supply tech-nologies, allocation of impacts to by-products, etc. This is beyond the scope of thistext to discuss these aspects, however the importance of the assumptions should berealized. Another likewise as important aspect is that it is not practically possibleto find high-quality quantitative data for all involved processes, including indirectprocesses. An LCA will therefore always to some extent be based on third-party

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data for which uncertainties and data quality are not reported. Therefore: betterdata, better results.

A number of general assumptions is needed in order to carry out this LCA-screening, for example but not excluding: type, design, and operation of the land-fills, transportation type, distances and load, origin of electricity used, handlingof leachate, etc. These assumptions should be valid for the scenarios in question.In this LCA-screening, choices reflect Danish conditions and are the same for allthe discussed management alternatives: landfills fulfill EU regulation for hazardouswaste, leachate is collected and treated within the active period, transportation isassumed to be either by truck or ships, for further details please refer to Fruergaardand Astrup (2007).

A number of specific assumptions relevant only for individual management alter-natives are also needed. Examples are: avoided handling and disposal of co-treatedwaste materials, handling of waste water generated during treatment of residues,etc.

In all cases these assumptions illustrate that relatively detailed information abouttreatment and handling of the residues has to be available in order to properlyperform an LCA. Please note that such detailed data has not been available to theextent needed for this specific LCA. Please observe that all such data has not beenavailable for the LCA-screening carried out in this appendix.

B.2.3 Management alternatives and inventory analysis

In this LCA-screening, five different treatment and management alternatives areevaluated:

1. No treatment (Denmark): Transportation of untreated residues to a landfill inDenmark by truck (100 km), leachate collection and treatment included.

2. Disposal at Langøya (Norway): Transport to Norway by truck (300 km) andbulk carrier (300 km). Neutralization of waste acid and substitution of vir-gin lime from quarry, waste water treatment and discharge from the facilityincluded. No leaching.

3. Disposal in salt mines (Germany): Transport to Germany by truck (600 km).Mixing with additives and other waste materials, pumping to mine. No leach-ing.

4. Ferrox treatment (Denmark): Stabilization by the Ferrox treatment processand subsequent landfilling in Denmark, transportation by truck (100 km),leachate collection and treatment included.

5. Asphalt production (Denmark): Substitution of limestone as filler material inasphalt production, similar to the practice in The Netherlands, transportationby truck (100 km). No leaching.

The associated data inventories (i.e. the data describing the individual alterna-tives above) can be found in Appendix A. As can be realized from the technologydata in the appendix, the information level varies (which may also be realized fromTable 7.1 in this report) to a great extent: Disposal in Norway and Germany (Alter-natives 2 and 3) and asphalt production (Alternative 5) are based on data providedby the contractors and the literature, Ferrox treatment (Alternative 4) are based

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on a feasibility study on a full scale plant in Denmark, and the reference scenario(Alternative 1: landfilling in Denmark) is based on typical data for Danish landfillsin current operation.

It should be realized that these data are approximate only and that the resultspresented here should serve as an example. The data presented in Appendix A areof the best possible quality currently available, however in a real application thecontractors should be allowed to update the data.

B.2.4 Impact assessment

The results of the LCA-screening are normalized with respect to the impacts froman average person, i.e. given in person equivalents (PE) where 1 PE represents theannual impacts from an average person in a given area. For Global Warming andStratospheric Ozone Depletion the scale is global, for all other categories exceptStored Ecotoxicity the results apply to Europe. Positive values correspond to anenvironmental load, whereas negative values represent a saving.

The figures B.1–B.4 therefore shows environmental loads or savings relative tothe average load from one person per year according to the various impact cate-gories evaluated. The actual values plotted in the figures are referred to as “impactpotentials”, i.e. potential impacts in a specific category such as Global Warming.

Figure B.1 and B.2 show normalized impact potentials for non-toxicity impactcategories. In figure B.2 transport impacts are excluded. Overall from Figure B.1 itappears that transport to Germany and disposal in salt mines (Alternative 3) hasthe highest impact while utilization in asphalt production in Denmark (Alternative5) has the lowest impact in the non-toxicity categories. From the scale it should,however, be realized that the impacts overall correspond to less than 2 % of theimpacts from an average person, and that the differences between Alternatives 2–4in practical applications are minimal. Comparing with Figure B.2 it can be realizedthat most of the impacts in alternative 2–4 are caused by the transportation includedin these scenarios. The remaining impacts in Figure B.1 and B.2 are primarilyrelated to energy consumption in the processes. This corresponds well with thefact that Alternative 1 does not include treatment of the residues, only landfilling.Alternative 5 appears to be a net benefit (i.e. negative values), this is howevermainly because no data on energy consumption for residue handling in this processhas been found and therefore not included in the modeling. As such, the result forAlternaive 5 may likely change if better data can be found which clearly illustratesthe importance of obtaining a detailed description of the processes involved. Thiswas, however, not possible in this case.

Figure B.3 and B.4 show normalized impact potentials for the toxicity categories.In figure B.4 transport impacts are excluded. Compared with Figures B.1 and B.2,quite a different result can be seen here. Now the alternatives with no treatment(Alternative 1) and the Ferrox treatment (Alternative 4) show the highest impacts.This is primarily related to the leaching after landfilling of the residues as well aswastewater in case of the Ferrox process. The fact that the Ferrox treatment actuallyperforms worse than no treatment is caused by the fact that the residues had highleaching of molybdenum (Mo). This may not be an issue in a real scale application,and illustrates that focus should be paid to leaching of this element. ComparingFigure B.3 and B.4 it may be realized that transport only has small effects on thetoxicity categories, mainly in the case of Alternatives 2 and 3 which include thelongest transportation distances. Overall, the toxicity impacts for Alternatives 2,

B-4

-0.004 0 0.004 0.008 0.012 0.016

Asphalt (alt 5)

Ferrox (alt 4)

Salt mine (alt 3)

Limestone quarry (alt 2)

No treatment (alt 1)

PE/tonne

Global WarmingAcidificationNutrient EnrichmentPhotochemical Ozone Formation (low NOx)Stratospheric Ozone Depletion

Figure B.1: Normalized environmental impact potentials per tonne of residue for thenon-toxicity categories during the first 100 years, including transportation (Fruer-gaard and Astrup, 2007).

-0.004 0 0.004 0.008 0.012 0.016

Asphalt (alt 5)

Ferrox (alt 4)

Salt mine (alt 3)



PE/tonne

Global WarmingAcidificationNutrient EnrichmentPhotochemical Ozone Formation (low NOx)Stratospheric Ozone Depletion

Figure B.2: Normalized environmental impact potentials per tonne of residue for thenon-toxicity categories during the first 100 years, excluding transportation (Fruer-gaard and Astrup, 2007).

B-5

-0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30

Asphalt (alt 5)

Ferrox (alt 4)

Salt mine (alt 3)



PE/tonne

Ecotoxicity in Water Ecotoxicity in Soil

Human Toxicity via Air Human Toxicity via Water

Human Toxicity via Soil

Figure B.3: Normalized environmental impact potentials per tonne of residue for thetoxicity categories during the first 100 years, including transportation (Fruergaardand Astrup 2007).

3, and 5 are similar, while the impacts for Alternatives 1 and 4 appear somewhathigher.

It should be noted that contaminants remaining in the residues (or any otherproducts produced during residue treatment and subsequently landfilled) after thetime horizon of the LCA (i.e. in this case 100 years) are often summarized andrecalculated into a “potential impact” (often termed “stored toxicity”). This is notincluded here for simplicity reasons, but a specific assessment of the potential forfuture releases of contaminants in the evaluated scenarios after the 100 years timehorizon should always be carried out before final conclusions are reached. A fullLCA also includes a discussion of consumptions of resources (e.g. consumption ofmetals). This is not included here for the sake of simplicity.

B.3 General conclusions

The LCA-screening discussed above is based on an incomplete dataset and shouldbe viewed as preliminary results only. As such, it is not concluded which of thealternatives are the best on an absolute scale. A few general conclusions, however,can be made:

• In cases when treatment and final disposal are not associated with majoremissions or energy consumptions, then transportation will often representthe main environmental load (e.g. in case of disposal of residues in Germanmines or in Norway, Alternative 2 and 3)

• The main impacts related to chemical stabilization solutions like Ferrox treat-ment are often caused by the treatment process itself and the leaching after

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-0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30

Asphalt (alt 5)

Ferrox (alt 4)

Salt mine (alt 3)



PE/tonne

Ecotoxicity in Water Ecotoxicity in Soil

Human Toxicity via Air Human Toxicity via Water

Human Toxicity via Soil

Figure B.4: Normalized environmental impact potentials per tonne of residue for thetoxicity categories during the first 100 years, excluding transportation (Fruergaardand Astrup 2007).

landfilling of the residues. Specific contaminants may need to be addressed inorder to lower the impacts further

• If data are not available, and therefore cannot be included in an LCA, theassociated impacts will not appear in the results (as was the case with asphaltproduction in Alternative 5). This may “improve” the results for a particularalternative and give rise to wrong conclusions. As such, it is very importantto have a clear understanding of the data and processes which are evaluated

Although a detailed sensitivity analysis is not included here for simplicity rea-sons, the general conclusions mentioned above are still valid although reasonable un-certainties in the supplied data are assumed. However, it should be realized that—aspreviously mentioned—the assessment should be localized in order to account forappropriate types of energy production, wastewater treatment and discharge, land-fill operation, etc. These aspects (among others) may potentially alter conclusionsif one management solution includes significant use of such activities while othersolutions do not.

It should—again—be emphasized that this LCA-screening is based on generaldata and a range of assumptions have been made. If an LCA should be used tosupport specific decision regarding residue management, specific data should beacquired and critically reviewed with respect to quality and uncertainty.

B.4 References

Fruergaard T, Astrup T (2007): Life cycle assessment of management of APCresidues from waste incineration. Proceedings Sardinia 2007, Eleventh In-

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ternational Waste Management and Landfill Symposium, Italy, 1–5 October2007.

ISO 14040 (1997): Environmental management - Life-cycle assessment - Princi-ples and framework, International Organization for Standardization, Geneva,Switzerland.

Wenzel H, Hauschild M, Alting L (1997): Environmental assessment of products.Volume 1: Methodology, tools and case studies in product development. Chap-man & Hall, London, England.

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ISWA General SecretariatThe International Solid Waste AssociationVesterbrogade 74, 3rd � oor DK-1620 Copenhagen VDenmarkPhone: +45 3296 1588Fax: +45 3296 1584 e-mail: [email protected]: www.iswa.org

This report is produced by ISWA's Working Group on Thermal Treatment of Waste. The work has been carried out by a subgroupon Air-Pollution-Control (APC) residues from Waste-to-Energy (W-t-E) Plants.

Associate Professor Thomas Astrup from Department of Environmental Engineering,Technical University of Denmark, has produced the report with inputs from the subgroup.

This report is the second edition published October 2008

management of apc residues from w-t-e plants · working group on thermal treatment of waste...

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