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PLASTICS Rf CYCLING @ Viability

Resin

of Recycling Plastics by Tertiary Processes

Embodled Energy (Btu/lb) Energy Savings (Btu/lb) Secondary I Tertiary 1 Quaternary

This article takes a looks at the viability of tertiary recycling as an alternative to secondary recycling, quaternary recycling, and disposal by landfilling. A life cycle approach, addressesing both financial and environmental costs and benefits, is adopted to compare the alternatives.

HDPE

PVC

~~ ~~ ~

By T. Randall Curlee and Sujit Das, Oak Ridge National Laboratory

36,500 31,025 27,300 20,050

25,600 21,760 12,600 7,700

ne focus of the municipal solid waste (MSW) debate is on plastic wastes. Although plastics only contributed to about 9% by weight and 24%

by volume of the municipal waste stream in 1993, in some respects plastics are still a part of our “throw-away” society, and have been at the center of the debate about waste recycling. The use of plastics has been criticized because, in most cases, they do not degrade, are difficult to compact in landfills, and have the potential to emit furans and dioxins upon incineration. However, overall, the stereotypes about plastics have been discarded. For instance, arguments against landfilling so-called non-degradable plastics now carry little weight in light of evidence that even degradable materials resist degradation until placed under actual landfill conditions. In addition, recent studies failed to draw strong linkages between plastic incineration-and emissions. Nevertheless, public opposition to plastics disposal and incineration continues, and public support for recycling programs generally remains strong.

A recent twist in the debate about plastics recycling centers on the means by which recycling is achieved and the resulting products. At the core of this debate is the value of the marketable products of plastics recycling, the products or commodities for which those recycled products may be substitutes for, and the degree to which recycling of plastics is

toxic

closed loop. For many, the rationale for loop-closing is the near-permanent conservation of the subject materials; for others, it is an extended displacement of virgin production materials and the atten- dant environmental effects. For still others, its importance is informational- closed loop recycling is, in theory, easier to track and monitor compared to recycled wastes put to different or varying uses.

Current Status of Plastics Recycling The use of plastics continues to grow.

The quantity of plastics entering the municipal waste stream increased from about 3.1 million tons in 1970, about 2.5% of MSW, to about 19.8 million tons in 1994, 9.5% of MSW. The EPA pro- jects that plastics will account for about 23.3 million tons of MSW in 2000, or 10.5% of MSW. Of the 19.8 million tons of post-consumer plastic waste that entered the municipal waste stream in

Table 1. Estimated Energy Savings

1994, 5.6 million tons, or 28%, came from durable goods, 4.8 million tons, or 24%, were from nondurable goods such as plates, cups, trash bags, etc., and 9.5 million tons, or 48%, were from containers and packaging. From a resin perspective, HDPE (19.7%) and LDPE (28.7%) constitute nearly half of all plastics in the municipal waste stream.

The percentage of plastics that has been recycled in the U.S. has increased from a negligible amount in 1970 to 4.7% in 1994. This marks a rapid increase from the 2.2% recycled in 1990 and the 0.3% in 1980, but does not compare favorably with other major components of MSW. The 1994 recycling rates for other materials include 35.3% for paper and paper- board, 23.4% for glass, 37.6% for aluminum, and 35.9% for all metals. Overall, in 1994 about 23.6% of all MSW was recycled in the U.S.

Of the 930,000 thousand tons of plastics recycled in 1994, 710,000 tons (76%

PET I 48,700 I 41,395 1 24,700 1 11,400

LDPE I 38,500 I 32,725 I 28,100 I 20,000

PP I 34.200 I 29.070 I 28,000 I 20,000 I ’ I ’ I ’ I ’

PS I 34,300 I 29,155 I 23,600 1 17,800

Other Resins I 42,600 I 36,210 I 26,000 I 15,725

Source: Derived from Caines and Shen (1980).

50 SOLID WASTE TECHNOLOGIES March/Aprill998 http://www.SolidWosteTeth.tom

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ODOR CONTROL

volatile nitrous compounds and sulfides to stabilize as nitrates and sulfur or sulfates. The neutralizer reduces odor levels of hydrocarbons, aldehydes, mercaptans, amines, sulfides, ammonia, and ketones. In typical situations, odors are nothing more than a hydrocarbon combining with a nitrogen- or sulfur-based molecule or radical. These organic, odorous gases eventually degrade into carbon dioxide, water, nitrogen in the form of nitrates, and elemental sulfur. Until these odors biode- grade, if present in sufficient quantities, they are frequently very obnoxious and odorous.

Case History Briefs Transfer Stations

Washington, DC. This neutralizing system was implemented in Washington, DC's largest transfer station. Temperatures are known to exceed 90°F during July and August which, when com- bined with high levels of humidity, generate significant odor problems. Upon

Composting Activities United Kingdom. A mushroom grower

and composter in the United Kingdom experienced complaints from the local environmental agency and surrounding community. Residential properties are sit- uated approximately 400 meters from the composting windrow shed. Four spray nozzles were installed, one for each extract fan built into the gab)& end of the windrow shed. The nozzledwere initially linked to a pump syste grammed to run only w

D. Van Nostrand Company, Incorporated. (1948).

Calkin, Robert, Perfumery, Practice and Principles, John Wiley and Sons, Inc. (1993).

Odors and Deoderization in the Environment, edited by Guy Martin and Paul Laffort, VCH Publishers, Inc. (1194). ,,,I

Man$, J. , Davidson, R.S., Natural Prodwbts: their chemistry and biological sig $cance, John Wiley and Sons, Inc.

odified by the /) Odor Control for Wastewater ( !? 94).

addition of w Whenever the w

Worldwide, #9-1222 Fewster Dr., Mississauga, Ontario, L4W 1A1, (905) 625-8664. 4)

installation, the system reduced odors to a non-detectable level. Odor control has I / i been achieved in the facility, the surrounding area, and within the adjacent residential community.

Southern Ontario. After receiving complaints from the community and being assessed fines by the Ontario Ministry of Environment and Energy, this transfer station installed the neutralizing system. For immediate relief, a fogger was utilized in the wet garbage area. The full-scale installation included a system equipped to power 60 nozzles. The height of the transfer station ceiling is 50 ft. To provide easy iccess to the nozzles while servicing them, a newly designed pulley system was Implemented. Each line has a winch at :ither end of the building so a cable can 3e used to raise and lower the nozzles. rhis leaves each line in a stable state of suspension while in operation. Thus far, he odor problems and their associated :omplaints have been eliminated. landfills

Vaughan, Ontario. This neutralizing ;ystem is being implemented in stages at a andfill site near Vaughan, Ontario. The nitial implementation consisted of nstalling a portable 10-nozzle system nounted on poles. The system was placed it the workface that is currently receiving vaste materials. Complaints about the Idor problems are decreasing.

\\ The choice is yours! Qonozaire OdQr Neutralizers are waste management's answer to odor problkns. These ozone generators are ideal for use

with garbage coir\pactor/containers, and they have just been made better by the addition of a weatherproof option.

gonozaire kills many bacteria, reduces fermenfation and slime, and the odors that attract pests. It can be used in

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@PlA5l lC5 RECYCLING

of the total) came from containers and packaging. Soft drink bottles alone accounted for 320,000 tons (34% of the total). In terms of specific resins recycled, PET and HDPE each accounted for 350,000 tons (38%), and PP accounted for 110,000 tons (12%). In 1994, 50% of all soft drink bottles (primarily PET) were recycled. About 30% of all milk bottles (mostly HDPE) were recycled. Cursory evidence indicates that the vast majority of PET, HDPE, and PP, 87% of all plastics recycled, are recycled by secondary means, most of which produce goods that otherwise would be produced from virgin resins,

Overview and Approaches Plastic resins can be placed into two

broad categories. Thermoplastics, although differing widely in their specific physical and chemical properties, can be melted and reformed. Thermosets, which have cross-linked molecular structures, cannot be melted and reformed, and con- sequently are more difficult to recycle. Most of the resins familiar to consumers are thermoplastics.

Plastics recycling technologies are generally placed into four categories. 0 Primary-the manufacturing of new plastic products with material and chemical properties equivalent to those of the discarded plastics items. 0 Secondary-the manufacturing of products with material properties inferior to the original products. 0 Tertiary-processes that utilize waste plastics by altering a polymer’s chemical structure to manufacture monomers, basic chemicals, or fuels. 0 Quaternary-incineration of plastics with heat recovery, either as part of the municipal waste stream or as a segregated waste.

Although much of clean thermoplastic manufacturing waste is recycled in a primary sense, remelted and reformed, primary recycling by these methods is not, at present, a viable economic option for the vast majority of post-consumer plastics or manufacturing wastes that are contaminat- :d. Removing contaminants and separating similar plastic resins has been difficult 2nd costly. Secondary recycling has met with moderate success in the marketplace. [n fact, the overwhelming majority of all :urrent plastic recycling is by secondary neans.

Tertiary recycling is a range of techno- ogical approaches applicable to a wide

range of plastic wastes, producing a variety of products that may be substituted for different materials. Tertiary recycling can be divided into three basic categories: 1) depolymerization processes that require clean, single-resin plastic wastes and produce monomers or other basic inputs that can be used in the production of new and like-kind resins; 2) tertiary processes that are applicable to mixed and contaminated plastics waste streams and utilize waste plastics as a substitute for crude oil in refinery operations and as substitutes for basic chemicals in refinery recycling and pyrolysis; and 3) dissolution processes that can be applied to mixed and contaminated waste streams to selectively remove individual resins or classes of resins for further processing and recycling.

With the exception of dissolution, tertiary recycling achieves closed loop recycling. That is, tertiary recycling makes it possible to use recycled resins in the same applications in which they were originally used. Most of these technologies are in the developmental stage, and, with economic viability, they will substantially advance recycling efforts. Some tertiary technologies allow recovery of nearly pure polymers or their constituents from a waste mixture, and the reaction conditions destroy contaminants, allowing the recovered material to be used in food- packag- ing applications.

Depolymerization. Depolymerization technologies, such as hydrolysis, methanolysis, and glycolysis, are recog- nized as technically feasible routes to con- vert condensation polymers like PET, polycarbonate, polyester, polyurethane (PUR), and nylon into basic chemicals. Depolymerization by chemical means is also called solvolysis. These technologies involve the application of heat and pres- sure to a sorted and clean waste in the presence of a reactive chemical agent, fol- lowed by the purification of the reaction mixture which yields monomers. These monomers can then be repolymerized to produce virgin resins. Of the three depolymerization routes, only methanolysis can recover pure monomers, which can be used directly to produce recycled resins.

Refinery Recycling. Recycling plastics back to hydrocarbons using existing refinery process units is being considered by some petroleum companies. Refinery recycling, also known as full-circle recycling, is attractive. This form of recycling processes mixed plastic wastes, while tak- ing advantage of the existing refinery infrastructure. From a quality standpoint, some waste plastics are more attractive

compared to traditional refinery feeds. Plastics solutions may represent an attractive feedstock because of their high hydrogen-to-carbon ratio. Compared to crude oils, some plastics contain relatively few impurities, especially sulfur and nitrogen. Refinery recycling is preferable to pyrolysis because it produces better quality oil and significantly smaller propor- tions of solid chadblack carbon residue and gas.

Pyrolysis. Pyrolysis converts wastes into basic chemicals and oils. The capabil- ity to of handlinge a mixed plastics waste stream makes this recycling option attractive. The distribution between oil and gas products obtained depends on the compo- sition of plastic wastes. Polyolefins and polystyrene are best suited for pyrolysis, as oil can account for up to 97% of the plastics materials used as feedstock. Monomer recovery by pyrolysis is generally difficult, but may be promising in the case of acrylics and polystyrene. A yield of nearly 100% of the original monomer can be obtained in the case of pyrolysis of acrylics.

Polymer Dissolution. There is growing interest in the area of commingled plastics recycling by means of chemical dissolution. These methods are based on the prin- ciple that different polymers dissolve in different solvents, or even in the same sol- vent at different temperatures. By selec- tive chemical dissolution, the individual components of the commingled plastic wastes can be separated.

Economic Viability Current plastics recycling programs in

the U S . and other industrialized countries are the result of a variety of incentives and constraints faced by various decision- makers involved in the production and waste management of plastics. Given that only about 3.5% of all post-consumer plastic wastes are currently recycled, there are numerous plastic waste streams that might be addressed by tertiary approaches. However, to make use of those waste streams, tertiary technologies must sur- mount the barriers not overcome by existing recycling processes.

The viability of current and developmental tertiary processes to recycle plastic wastes will be determined by the abilities of those processes to either displace current plastics recycling technologies and approaches or extend plastics recycling to new segments of the plastics waste stream that are currently being landfilled or incinerated. The ability of tertiary processes to meet either or both of these conditions

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@PLASTICS RECYCLING

will, in turn, depend on the net life cycle costs of the alternative processes-tertiary recycling, secondary recycling, waste-to- energy (WTE), and landfilling.

Life cycle costs can be divided into financial and external costs. Financial costs include expenditures for collecting, sorting, transporting, and processing the waste plastics. These costs are balanced against the revenues received from the sale of products made from the recycled materials to determine the net life cycle costs or revenues associated with the recycling alternatives. The financial costs of landfilling and WTE include the costs of collection, transportation, and a tipping fee at the landfill or WTE facility. The tipping fee should reflect the cost of operating the landfill or WTE facility and any follow-on costs associated with, for example, monitoring required by existing regulations.

External costs are less concrete than financial costs, but are nonetheless very important to the overall viability of the alternatives. External costs include, for example, damages associated with environmental degradation and health effects of the alternatives. External costs are so named because they are external to the commercial transactions between buyers and sellers. That is, the price in the market does not reflect the external costs. When environmental damages are conceptual- ized as external costs, the notion of economic costs becomes very broad encom- passing both financial costs-what in other contexts might be labeled as economic costs-and environmental and health effects.

The remedies for externalities are diverse. In some cases government may impose a tax on certain types of goods, such as packaging, or mandate that some waste streams, such as plastic bottles must be recycled or at least returned to a central

cases, government agencies have stipulat- ed that recycled products be given preference in procurement decisions. The government actions in essence “level the playing field” among the various options by transforming an external cost or benefit into a financial cost or benefit. In some cases, the threat of regulation may be sufficient to elicit the desired response.

Other non-governmental actions may, in effect, internalize actual or perceived external costs. For example, the general household preference of recycling over disposal, gives firms an incentive to pro-

locatiGn t G facilitate recyciing. !E ether

mote recycling-even in cases where the direct financial costs of disposal are lower than those of recycling.

Therefore, preferences by households for recycling and potential regulations by government to encourage recycling may serve to internalize external costs just as effectively as concrete governmental action. Significant debate exists about the extent to which alternatives impose external costs and the value of those external costs; in some cases the alternatives may be more environmentally burdensome or simply produce an environmental improvement that is not commensurate with the cost. The effectiveness of existing attempts to internalize these external costs through direct government action or indirect preferences of consumers and government officials is also disputed.

Against this background, the question arises whether it is better to take recovered plastics back to monomers through depolymerization, to chemical intermedi- ates through refinery recycling or to oils through pyrolysis. Better could mean environmentally preferred, high market output price, or flexible end use. These questions are easier to address in a life cycle framework. The best way to assess this issue is to compare incrementally the environmental effects of two competing ways of producing and disposing of plastics on a life cycle basis, with attention to what process or material is most likely to be displaced.

In financial terms, better refers to the net value of the output of competing processes. That is, PET obtained through depolymerization might command a higher price in the market than PET obtained through mechanical recycling. It is also important to understand that breaking plastics down into more primitive constituents such as a crude oil fraction or a chemical intermediate has a wider range of potential uses than does a monomer. At the same time, it requires more processing tc be transfcrmed intc a final prcdnct. A more primitive constituent is therefore less valuable for a given end use because more costs must be incurred to get that constituent into in the final product-the plastic resin.

A key aspect in determining the economic viability of tertiary recycling is the perspective from which costs and benefits are assessed and the relative power of different groups in the decision-making process. Five groups are particularly important:

0 Tertiary technology users-typically a plastics manufacturer or related firm;

0 Waste management company-pro- vides the waste services, recycling or otherwise; 0 Household and other waste genera-

tors-contributes to the economic viability of recycling by collecting, sorting, and in some cases transporting segregated plastics waste streams;

0 Local government-makes decisions on which materials will be collected and sorted for recycling; and

0 Society at large-includes an assessment of, and reaction to, the external costs and benefits of the alternatives.

Each of these groups of decision-makers will view recycling differently. Depending on the relative strength of each group, different outcomes can occur in terms of which waste management approach is adopted.

The company that makes use of tertiary recycling technology clearly seeks to make a profit-by using plastic wastes as feedstocks that are presumably cheaper than conventional raw materials and producing a product that commands a price in the market that generates profit. The companies that appear to be most interested in tertiary recycling are producers of plastic resins and related materials. They have the technological expertise and capital equipment most related to these sorts of processes. From the perspective of the entity performing the waste management function, the primary criteria are financial costs and revenues. Financial costs will include the cost of collection and transportation (in some cases borne by the municipality), separation, and processing the waste polymers into marketable products. Financial costs must be balanced against the market value of those end products.

The importance of the household’s actions and perspectives in determining the economic viability of plastics recycling are all too often downplayed or ignored. The monetary and non-monetary ccst: and benefit: cf recyc!ing tc heuse- holds are difficult to value and often are ignored in the public debate about the economic viability of recycling. While it is difficult to quantify the inconvenience that recycling imposes on households, there can be little argument that the household’s contribution to source separation and collection is essential to the success of current secondary approaches used to recycle plastics and to the potential success of the tertiary technologies discussed in this article.

Local government also plays an important role in determining the most viable

52 SOLID WASTE TECHNOLOGIES MarchlAprill998 http://www.SolidWasteTeth.tom

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waste management approach. To a great extent, the current success of plastics recycling can be traced to the willingness of local governments to pay the high cost of collecting, transporting, and sorting recyclables. Current data show that the local government’s financial cost of collecting and processing recyclables is in many cases much higher than the alternatives of landfilling and WTE. In some cases, local governments have responded to the wishes of their voters. In other cases, they have responded to mandates for recycling imposed by state government. Whatever the reason, local governments, like households, will play a major role in determining the future economic viability of plastics recycling.

The final perspective, the societal perspective, includes external costs and benefits from recycling that do not relate directly to either the household or the company overseeing the recycling activi- ty. These external costs and benefits are primarily health and the environment. To the extent that one form of waste management is less environmentally damaging than another, government actions are warranted to level the playing field such that .he environmental benefitdcosts of the ilternatives are included in the decisions If households and companies, potentially :hanging choices about what to produce, nhat to buy, and how to manage the ,esulting wastes. Other types of externali- ies based on energy and materials conser- iation may exist, that is, energy and mate- .ials may be scarce in ways that are not :aptured in market prices.

The viability of tertiary recycling turns )n its economics compared to other recy- :ling and waste management approaches when viewed from the perspectives of the :ompany, the household, the local govern- nent, and society at large. If all life cycle :osts and benefits can be determined and ialued, then the best approach to manag- ng plastic wastes can be selected. For ter- iary recycling to be viable, the processes nust be attractive to the people who, ndependently or in collaboration, make he final selection.

:osts and Benefits Costs. Information on the financial

osts of tertiary recycling processes is carce and often incomplete. Most esti- nates do not include the costs of collect- ng, sorting, and transporting wastes to the daste processing site. Assessments often ssume that required feedstocks are readi-

ly available and free. However, depolymerization requires sorted and clean resin in flake form, and the cost of recycled resin flake (including collection, sorting, grinding, washing, and drying) is estimated to be in the range of $0.20 to $0.31/lb. In the case of clean PET flakes, costs range from $0.25 to $0.30/lb. As a point of comparison, some secondary recycling technologies currently being used to recycle clean resin flakes have end product values (i.e., market prices) of $0.30 to $l.OO/lb with net revenues in the range of $10 to $40/ton.

The limited information currently available suggests that depolymerization is not a particularly financially attractive approach, especially in light of the costs and revenues of available secondary processes. Current secondary technologies that utilize clean PET and HDPE appear to be superior in a purely financial sense. In the near term, depolymerization is likely to be adopted by firms that can benefit from the public’s likely positive reaction to closed-loop recycling and where the infrastructure is already in place to collect and process clean, single-resin waste. In future years, the viability of depolymerization from the perspective of the company will turn on future technology improvements that may lower the relative financial costs of depolymerization and on the public’s continued support for closed- loop recycling.

Refinery recycling, pyrolysis, and dissolution processes offer the potential to cap- ture a significant segment of the plastics waste stream that currently is not captured by secondary approaches. Applications to highly contaminated, mixed waste streams, e.g., automobile shredder residue, could open opportunities for firms that must currently pay to have these wastes disposed of in landfills or, to a much more limited extent, incinerated. However, current estimates of the financial costs of these developmental technologies do not suggest that they will be competitive with the financial costs of landfill or incineration. Future technology advances may place these processes in a more competitive position from the perspective of firms pursuing plastics recycling.

Refinery recycling, pyrolysis, and dissolution processes have also been men- tioned as an alternative to secondary recycling of commingled plastics. Although not currently competitive in terms of financial costs, these forms of tertiary recycling could be an alternative to technologies that produce bulky items that compete with similar items made from

lumber or concrete. Logistics and capital cost of the recycling facility are particularly important to the financial viability of refinery recycling. Currently, construction and start-up costs for refinery recycling are high. For now, U.S. companies have redirected their efforts-focusing on improving the overall economics of the refinery process.

Pyrolysis processes generate olefins and oils as valuable substances; hence, the price of petroleum dictates the value of products from these processes. Little information on the costs of advanced pyrolysis processes is currently available. High capital and operating costs of pyrolysis processes remain a concern for pyrolysis processes. No detailed information was identified on the economics of polymer dissolution processes, as most of them are still in the experimental stage.

From the perspective of households and local governments, these tertiary processes offer potential benefits. Dissolution processes, for example, offer the potential for separating individual resins from a commingled stream and thus may allow households to reduce the degree to which they must source separate. In addition, households may have fewer restrictions in terms of what can go in the plastics recycling bin. Resins for recycling may no longer be limited to PET and HDPE, as is the case with most current curbside collection programs.

Benefits. Many argue that the environmental damages caused by recycling are less than the environmental damages caused by landfill or incineration. In addition, many believe that some forms of recycling are less environmentally damaging than others. To the extent that one form of waste management is less environmentally damaging than another, government actions are warranted to level the playing field such that the health and environmental externalities of the alternatives are included in the decisions of households and firms.

The various arguments concerning environmental impacts and energy and materials conservation suggest that government should subsidize directly or indirectly those waste management options that impose lower environmental damages and consume fewer energy and material resources.

Health and Environmental Perspective. According to some experts, plastics pose very few environmental problems when placed in landfills. The fact that most resins do not degrade rapid- ly under landfill conditions is viewed as a

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@PlAiT lC i RECYCLING

benefit in that air emissions and leachate generation are reduced. Plastics may contribute to difficulties in compacting a landfill in post closure activities and may indirectly contribute to leaching of other materials in the landfill. However, the consensus opinion is that landfilling of plastics poses few environmental problems. The incineration of plastics is more controversial. Although, for the most part, empirical evidence does not provide a strong link between the incineration of plastics and furan, dioxin, or heavy metal emissions.

Energy Perspective. Given that plastics are made for the most part from petroleum and natural gas, plastics recycling them has been supported on the basis of energy conservation. Quaternary recycling could directly retrieve the heat energy of waste resins. Tertiary recycling could potentially retrieve monomers that embody significant amounts of energy. Secondary recycling, if used to manufacture products that would otherwise be made from virgin resins, could reduce the overall demand for virgin resins and the energy embodied in those resins.

Four energy estimates for various resins have been defined by others as follows:

0 Net heat of feed combustion-the sum of the heats of combustion of all feedstocks entering into a process sequence, starting with oil and gas.

0 Net process energy-the total fuel required to complete all steps of a manufacturing process minus the heat of combustion of any by-product fuels not burned within that process sequence. 0 Total energy input-the sum of the heat of combustion of the

feed and the net process energy. It is the total energy embodied in the final product.

0 Product heat of combustion-the sum of the heats of combustion of all process products and non-fuel by-products. It is the energy that would be recovered if the final products were burned.

Preliminary, first-cut estimates of the energy savings associated with secondary, tertiary (refinery), and quaternary (incineration with heat recovery) recycling of selected resins are given in Table 1. With respect to secondary recycling, it is assumed that 85% of the total embodied energy in plastic waste is recovered. The energy savings associated with refinery recycling are assumed to equal the net heat of feed combustion. Refinery recycling of plastics displaces crude oil feedstocks. Thus, the energy savings associated with refinery recycling are equivalent to the energy embodied in the crude oil that is being displaced. With respect to quaternary recycling, it is assumed that energy savings can be estimated as the product heat of combustion as defined by others. Energy savings estimates for “other fesins” are based on the average of estimates for “other thermoplastics” and “other thermosets” categories.

Summary. At this point in time, depolymerization processes do not appear to hold significant advantages over currently available secondary processes for the recovery of plastics in the municipal waste stream. There is no strong evidence that depolymerization results in lower overall emissions or damages. This position is supported by the fact that both secondary recycling and depolymerization displace virgin resins. From an energy balance perspective, tertiary recycling appears to hold no particular advantage. In fact, preliminary data suggest that current secondary processes targeted at clean PET and HDPE are superior to tertiary recycling from an energy perspective. Finally, tertiary recycling holds no advantage to secondary recycling in terms of conservation of materials-once again because tertiary and secondary recycling of clean, single-resin waste streams both displace virgin polymers. Closing the loop by adopting tertiary processes as compared to secondary recycling is of ittle value from a materials conservation perspective if, in fact, no

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Environmental Liners, Inc , . , . , . , .73 . , . , . ,970-565-9540, Fax: 970-565-8844 , , , , ,

EPG Companies Inc. . , , . . . . . . . . . .60. . . . . ,800-443-7426 . , . , . . , . . , , . . , , . . . . . . . . . .#406

The Fogmaster Corp . , . , . . . , . . . . .58 . . . . . ,954-481-9975 General Kinematics . . . . . . . . . . , . .57 . , . , , ,847-381-2240, Geneva Recycling Separators . . , . .41 . . , , , ,701-845-1 017, Global Equipment

Marketing Inc , . . , . . . . . . . . . . . .64 . . . . . ,561-750-8662, Fax: 561-750-9507 . . . . . . . . .#236 Guthrie Trailer Sales, Inc . . . . . . . . .69. . , . . ,800-835-9382 or 316-793-541 #240 Hardy Instruments . , . . , , . , . , . , , .71 , . , . ,300-821 -5831 , . . . . , . . . . , . #250 Howe-Baker Engineers Inc . . . . . . . .49 . . . . . ,903-597-0311, Fax: 903-581-6178 . , . , , . . . .#234 I-Corp International . . . . . . . . . . . . .60 , . . . , ,561-369-0795 . , . . . , . , . . , . . , . . . . . . . . , . .#408 International Chimney Corp , . , . , , .6 , , . , . , ,800-828-1446, Fax: 716-634-3983 , , , , , , , , .#204

Eriez Magnetics . . . . Flagship Corporation 209-478-7353 . . . . . . . . .

888-800 ERiEZ . . . . . . . . . . . . . . . . . , , , , , , .#398

International Press &. Shear Corporation . . . . . . . ,

Jeffrey . . . . . . . . . . . . . . . . . . . Jones Manufacturing Company Keith Mfg. Co , , . , . , , , . , , , , , Kewanna Screen Printing, Inc . Landlill Gas & Environmental

. . . .25 . . . . . , . , .47 , , . . . . . , .21 , , . , . , . . .59,82 . . . . . .48,61 . .

,800-280-2313, ,800-61 5-9296 .402-528-3861, ,800-547-6161, ,800-348-2454,

Fax: 91 2-366-9559 . . . . . . . . . . . . . . . . . Fax: 402-528-3239 ,

Fax: 541-475-2169. Fax: 219-653-2737

, . . . . .#216 . . . , . .#231 , , . , . .#212 .#397, #247 .#233, #417

Products, Inc . , . . , , . . , . , . , . , .63 . , . , ,388-533-5343, Fax: 619-596-9088 . . , . . , . , .#237 Legend Valley Products . . . . . . . . . .59. . . . . ,800-638-1901 , . , . . . , . , . , , , . . , . . . . . . . . .#400 McNeilus Truck & Mfg. Co . . , . , . . .60. , . , . ,507-374-6321 . . . . . . . . . . . . . . . . , . . . , , , , .#409 Mirror Lite Co., Inc . . , , . . , . , . , . , .60. , , , . ,800-843-4981 . . . . . . . . . . . . . . . , . , , . . . . . .#410 Morbark Sales Corp . , , . . . . , . . . . .27 . . . . . ,800-233-6065, Fax: 517-866-2280 . , , , , . , . .#217 Moretrench . . . . . . . . . . . . . . , . , . , .38 . , . , , .E1 3-831-1 871, Fax: 813-831-9662 . . . . . . . . .#238 Municioal Waste r-. ..I-.- . . . . -.

Management LLC . , . , . , . . . , . , .70 . , . . . ,770-998-5200 . , . , , , , , , , , , , , , , , , , , , , , , .#241 Northside Tire Company . . . , . . . . .38 . . . . . ,800-555-4483, Fax: 904-765-2832 . . . . . . , . .#225 Packer Industries. Inc . . . . . . . . . . .18. . . . . ,404-505-0522, Fax: 404-505-1450 . . . #210 ~~~ ~~~~

Peerless Corporation . . , , , . , . , , . .67 . . , . , ,501-236-7753: Fax: 501 -239-2230 , . . , , . . , .#239 Petersen Industries, Inc , . . , , . , . . .39 . . . . . ,800-930-5623, Fax: 941 -676-1493 , . . , , , . , .#226 Peterson Pacific Corp . , , . , . . . . . .15,59 . . ,541-689-6520, Fax: 541-689-0804 , . . .#208, #404 Power Strateaies LLC . . . . . . , . , . .33,59 . , ,281-893-2020, Fax: 281 -893-2059 . . . .#220. #399 Raven lndustiies Inc . . , . . , . , , , . .61 . . . . , ,800-635-3456 . , . , . , . , . , , . . , , , , . . . . , . .‘.#416 Rehrig Pacific Co . , . . . , . . , . . , , . .60. . . . . ,800-421-6244 . . . , . , . , . , , . . , , , , . . . . . . . .#411 Rochem Separation Systems . . . . , .34-35 , , ,310-370-3160, Fax: 310-370-4988 . . . . , , , , .#221 Rust Environment &

Infrastructure . . , . . . , , . , . , . , . .23 , . . . . ,800-868-0373 , . , , . . , . . , , . , , , , . . , . . . . . .#214 Ryko , , . , . , . . . . . . . . . . . . . . . . . . .7,59 . . , ,888-234-7267, Fax: 51 5-986-3621 . . . .#205, #401 Safety Vision, Inc . , . . . , , . , . , . , . .45 , . , . . ,800-880-8855, Fax: 71 3-589-7432 . . , . , . , , .#230 Saturn Shredders

on 01 MAC Corp . , . . . . . . . .36. .

and Leasing Inc , . . . , , . , . , . , . .61 , . 972-790-7800, Fax: 972-790-8733 . . . . . . , , .#222

SCARAB Manufacturing 806-883-6804 . . . , . . . . . . , . , . . . . , . , , . . . .#415

Smart Truck Systems . . , . . , . . . . . .43 . . . . , ,888-868-1511 , . , . . . , . . . , , , . . . . . . . . . . . ,6252

Svedala Industries, Inc , , . . . ,800-366-2051, Fax: 31 9-369-5440 . , . , , , . . .#246 Synthetic Industries , . . , , . , . ,423-899-0444, Fax: 423-899-7619 . , . , . . . . .#211 Tarpomatic Inc . . . . . . . . . . . . . . . , .2 , , , , , , ,800-500-5069 , , . . . . . . . . . . . . . . . . . Tire Resource Systems, Inc . . , . , . .48,59 . . ,800-755-8473, Fax: 712-255-9239 , . . .#232, #402 TMS Solutions, LTO , . , , , , , , , . , . .32 . . . . . ,888-238-7646 , , , . , . , . , . . , . , , . , . . . . . . . .#228 TMT Soltware . . . . , . . . . . . . . 919-493-4700 , , , . . . . . . . . . . . . . . . . . , , , , .#213 Universal Reliners . . . . . . . . . 360-249-441 5 . . , , .#412 U.S. Manulacturing Inc . . . . . 800-800-1 81 2 . . . . .#414 Waste Technology Corporation . . . .24 . . , , , ,800-231-9286 . , . . , , . , , , . . . . . . . . . . . , , , .#215 Weigh-Right Inc . . . . . . . . . . . . . , , . 6 0 , , , , , ,316-665-1 1 2 3 . . . . . . . . . . . . . . . . . . . . , , , , .#413 Wildcat . . . . . . . . . . . . . . . . . , . . . , .9 , , , . , . ,800-627-3954, Fax: 605-925-7536 . . , , , , . , .#206

Spectra Gases . . . . . . . . . . . , ,800-932-0624 . . . . . . . . . . . . . . . . . . . , , , , , ,8393

This directory IS published for the reader convenience, every care is taken to make it accurate. Solid Waste Technologies assumes no responsibility for errors and/or omissions.

54 SOLID WASTE TECHNOLOGIES March/Aprill998 http://www.SolidWosteTeth.com

@ PLASTIC5 RECYCLING

materials are conserved. And there is no evidence to suggest that additional secondary recycling of clean plastic waste is limited by potential market size.

Technical and cost improvements in refinery recycling, pyrolysis, and dissolution processes offer the potential for significant expansion of plastics recycling, in that plastic waste streams currently landfilled or incinerated might be recycled. However, whether this transition is advis- able from a societal perspective must await further research. The question of environmental emissions from these tertiary processes as compared to landfilling and incineration remains open. From an energy perspective, these processes hold obvious advantages as compared to landfilling, but less obvious benefits when compared to incineration with heat recovery. These processes may also allow resins that are currently recycled into products that displace wood or concrete and to be recycled into products that displace virgin resins. The environmental, znergy, and materials tradeoffs associated with these various transitions await the

findings of a comprehensive life cycle assessment.

Conclusions The viability of different approaches to

plastics recycling will depend on the life cycle costs and benefits of the alternatives from the perspectives of the various parties involved in the decision-making process. Our discussion underscores that many of the costs and benefits of recycling are non- financial or result in financial costs and benefits that are difficult to quantify. Many costs and benefits to households are non- monetary, and many benefits to firms that participate in recycling activities result from public support for recycling andlor the avoidance of regulatory pressures. While it may be difficult to attach numbers to these costs and benefits, they are very important to any discussion of plastics recycling or any issue related to municipal waste management.

Tertiary recycling is not particularly attractive from a financial perspective, especially when compared to the current costs and revenues of available secondary processes. From this larger perspective, which includes all financial and external

costs and benefits, tertiary recycling may be viable. The current viability of plastics recycling is due in large part to the willingness of households to source separate materials and the willingness of local governments to pay the costs of collecting and sorting recyclables, as compared to the costs of landfilling and incineration. In some cases, it is likely that tertiary recycling of some plastics will be preferable to secondary processes, landfill, and incineration. However, in other cases, recycling of post-consumer plastics, whether by tertiary or secondary means, will not be the method of choice when viewed from this larger perspective.

References For a complete list of references, con-

tact the Editor at (440) 248-1 125. For more information, contact the

authors, at Energy Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, (423) 574-5182. 4

number on the Reader Service Card to indicate your level of interest in this article/topic.

High 306 Medium 3 0 7 Low 308

Efficient, performance proven vibrating classifier for MRF systems With three decades of experience in custom design and building vibratory equipment, General Kinematics brings new efficiency to recycling operations The single knife DE-STONER is capable of separating and classifying MSW, RDF fuel, and other commingled materials, even in the toughest applications

Completely dry system operation. H Unique vibratory action plus high

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To order your FREE information use the Reader Service Card

Curlex@ Blankets have long been proven to be the best erosion control blanket for slopes and channel linings. American Excelsior is the only national full-line supplier of erosion control products and has 30 U.S. locations. In addition to Curlex@ Blankets, American Excelsior markets H.V. Blankets, FiberCel'", and Tn-Lock Concrete Revetment. American Excelsior Co., P.O. Box 5067, Arlington, TX, 7601 1, (800) 777-7645.

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This free catalog describes the complete line of CEM gas standards, EPA protocol gas standards, certified and preliminary gas standards, VOC calibration gas standards including BTEX 1 and 2, PAMS, TO-14, TO-15, EPA Method 25, formaldehyde gas standards, CEM and VOC zero degrade gases, portable gas calibration kits with lightweight aluminum cylinders, and related gas- handling equipment. Spectra Gases, 277 Coit St., Irvington, NJ, 0711 1, (800) 932-0624.

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WASTE REDUCTION MACHINE 1

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I From the company that introduced the first commercial-size eddy current separator comes this complete line of products for processing commingled materials. A new 4-page brochure reviews them all; proven eddy current separators for removing valuable non-ferrous metallics from non-ferrous materials, magnetic separators, conveyors, feeders, metal detectors, and other equipment designed to boost productivity and profits. Flow charts and photos support the text.

Eriez Magnetics, P.O. Box10608, Erie, PA, 16514, (888) 800 ERIEZ.

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58 SOLID WASTE TECHNOLOGIES MorchlAprill998 http://www.SolidWosteTech.com

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viability of recycling plastics by tertiary processes › ref › 31 › 30213.pdfmanufacturing...

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