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TECHNICAL NOTE NoRECYCLING OF GLASS
14
Technical Note 2
Technical Note 6
Treatment of finalwaste
Technical Note 11 Technical Note 12
Recycling ofplastics
Technical Note 13
Technical Note 8
Principles for SSWM
Evaluation of theneeds for SSWM
Technical Note 1
Technical Note 3
Selection of technicalcomponents for the
establishment of a stra-tegy for SSWM
Technical Note 4
Organisation andoptimisation ofwaste collection
Technical Note 5
Technical Note 9
Micro-composting andseparate collection ofbiodegradable waste
Recycling as a wasteteatment option
Management ofhazardous waste
Technical Note 7
Composting stations
Technical Note 14
Technical Note 10
Anaerobic treatmentof organic waste
Recycling of glassRecycling of paper andcardboard
Recycling of non-ferrous metal
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RECYCLING OF GLASS
TABLE OF
CONTENTS
Technical Note 14
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TABLE OF CONTENTS............................................................. 1
LIST OF FIGURES.................................................................... 1
LIST OF TABLES....................................................................... 2
LIST OF ACRONYMS............................................................... 3
TECHNICAL NOTE NO 14....................................................... 4
RECYCLING OF GLASS........................................................... 4
1. Glass under its various forms...........................................4
1.1. Production and composition........................................... 4
1.2. Types of products...........................................................6
2. Glass recycling channels................................................11
2.1. The manufacturing channels...........................................12
2.1.1. Optimization of the deposit-and-return (DaR) system..........13
2.1.2. Optimization of colorimetric sorting.................................15
2.1.3. Optimization of the collection of clear glass and flat glass... 18
2.2. Alternative recycling options........................................... 21
2.2.1. A complementary strategy with a local dimension.............. 21
2.2.2. The integration in concrete and other construction material.22
LIST OF FIGURES
Fig 1: Representation of the colorimetry of glass according to
the addition of metallic oxides......................................... 5
Fig 2: Representation of different modes of production
of glass........................................................................ 7
Fig 3: Different types of flat glass...............................................8
Fig 4: Different types of container glass..................................... 9
Fig 5: Different types of fibre glass.............................................10
Fig 6: The three colorimetric groups..........................................16
Fig 7: Glass shredding............................................................16
Fig 8: Typology of clear glass................................................... 19
Fig 9: Selective sorting of clear glass......................................... 23
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Fig10: Representation of the production cycle for cement with addition
of recycled glass............................................................ 24
LIST OF TABLES
Tabl 1: Chemical composition of different types of glass................ 6
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TABLE OF
CONTENTS
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TABLE OF
ACRONYMS
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ABS Acrylonitril butadiene styrene
CFC Chlorofluorocarbons
DAR Deposit-and-Return
EC European Commission
ECS Eddy Current Separator
GDP Gross Domestic Product
GHG Green House Gases
ICZM Integrated Coastal Zone Management
IOC Indian Ocean Commission
LCD Liquid Crystal Display
MSW Municipal Solid Waste
NCV Net Calorific Value
NFM Non Ferrous Metals
NFP National Focal Point
NHIW Non Hasardous Industrial Waste
PCB Polychlorobiphenyl
PCM Project Cycle Management
PEhd Polyethylene high density
PEld Polyethylene low density
PET Polyethylene terephtalate
POP Persistent Organic Pollutant
PU Polyurethane
ReCoMaP Regional Programme for the Sustainable Managementof Coastal Zones of the Indian Ocean Countries
SME Small & Medium Enterprise
SWM Solid Waste Management
TN Technical Note
TOE Ton of Oil Equivalent
WEEE Waste Electrical and Electronic Equipment
PP Polypropylene
TOR Terms of Reference
PVC Polyvinyl chloride
HHW Household Waste
PS Polystyrene
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The glass is a discrete but omnipresent material. It is present in many
consumer goods and equipment, both as pure and impure material.
1 Glass under its various forms
Production and
composition
1.1
In fact, there are numerous types of glass which decline according to the
applications which are made, but the material itself present some1
inherent characteristics associated to the composition of the product :
At its origin, glass is composed of sands containing more than
99% of silica (SiO ) which plays the role of oxide forming the2
molecular structure to the networkSilica counts for about 72% in the composition of the average
glass material.
Purer sands containing low impurity level (< 0,2% of iron oxide)
are reserved for the elaboration of optical glass and crystal
manufacture.
The sodium carbonate brings the main oxide which modifies the
molecular structure of the network (Na O) and which plays the2
role of melting agent allowing the reduction of the melting point
of SiO .2
1 from J. Zarzycki « les verres et l'état vitreux, Masson 1982. »
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Under the form of bottles and other
containers it is a pure (or nearly pure)
material which constitute the totality ofthe product
In the hull of a fibreglass boat it
constitutes only a fraction, invisible and
not often disregarded.
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Figure 1: Representation of the colorimetry of glass according to the addition of metallic oxides.
Limestone and dolomite bring calcium carbonate (CaCO )3
which improves the chemical resistance of sodic glass by strongly
reducing their solubility
The borax (2B O + Na2O) brings the oxide of Boron (B O )2 3 2 3
which reduces the dilation coefficient of glass and improves its
resistance to thermal shocks.
Minium (Pb3O4) brings the lead oxide (PbO) which increases therefraction index. We can note that in the crystal glass, the PbO
content is higher then 24%. With a high content (48 to 80%), it is
used in optical glasses and those which protects against X-rays.
For more than 20 years, a large fraction of glass production has been
carried out from recovered and recycled glass, also called cullet. In
2005, in average 64% of glass produced in Europe was made of recycled
glass and this proportion is increasing. The furnaces for production of
hollow glass commonly use a mixture which contains more than 50%
cullet, the average for flat glass being 20% only. Some furnaces morecommonly used for green bottles can use up to 90% of cullet.
The color of a glass is given by the metallic oxides which are
incorporated:
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Iron and chrome oxides Nickel oxides Iron sulphite in reduction phase
Manganese oxide Cobalt oxide Copper oxide
Green Brown Ocre
Purple Blue Red and Blue-green
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Chemical composition of the maion types of glasses
Types
flat glass
container glasse
"pyrex"
fiber glass
"Kristal"
glass for bulbs
SiO2 B O2 3 Al O2 3 Na O2 K O2 CaO MgO PbO
72.5 1.5 13 0.3 9.3 3
73 1 15 10
80.6 12.6 2.2 4.2 0.1 0.05
54.6 8.0 14.8 0.6 17.4 4.5
55.5 11 33
73 1 16 1 5 4
Table 1:Chemical composition of different types of glass
Beyond the variability in the chemical composition of glass, we must also
take into account the fact that this material covers a wide range ofindustrial applications which can be distributed in 3 main groups:
Flat glass
Container glass
Glass fibers
In each group much diversified products are found but they share the
same particular mode of production. We can also note that the three
groups use cullet in different proportions to optimize their production:
Types of products1.2
As for ferrous /non-ferrous metals, plastics and paper/cardboard,
glass recycling forms an integral part of the life cycle of a glass product
From a general point of view, we must underline that glass production
has a very high energy consumption due to the transformation of silica
(in majority) which requires temperatures around 1500 °C to reach its
melting point. We can note that the melting point of cullet is of
1000°C only which represents an economy evaluated at 1 TOE for
10 T of cullet
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Figure 3: Representation of different modes of production of glass
The following figure illustrates the different channels for glassproduction:
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The group of flat glass products counts 8 types of different glasses as
represented below:
Figure 3: Les différents types de verres plats
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Container glass products can be divided in three sub-groups:
Figure 5: Different types of container glass
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Figure 5: Different types of fibre glass
Fibres include two main types:
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Textile fibersTheir composition is very poor in alkaline oxide but encompasses high quantitiesof alumina, Anhydrate Bore and some mineral alkaline oxides
Builiding and composite sector Non woven textile fibres can be incorporated into organic polymers in order toproduce armoured plastics. The production of this composite material(glass/resins) requires the major part of textile fibres
Textile sector Woven fibers are set on coils an then distributed as aprimary material for a wide range of industrial applicationssuch as safety clothes, ribbons etc.
Optical sector Glass fibers processed on continuousspinning can be employed as a lightconductor, or picture signal conductor.Their diameter is larger than textilefibers and they are coated with a glasscylinder of lower refraction rate.
Insulation glass (glass wool)it looks like a tangled mass of short fibers of very thindiameter (some microns). Their composition requires moreimportant quantities of alumina, and Anhydrate Bore forfew oxide alkaline compounds than current industrial glass.
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Glass is therefore a complex material due to the variations of
chemical composition and shape brought about by the industry. We
can find this diversity in a certain number of waste made of glass or
containing glass, which implies that their recycling require an
efficient and rational preliminary sorting.
2 Glass recycling channels
As for paper/cardboards and plastics, glass recycling is first orientated
towards the reintegration of transformed material and disposal after use
in the production cycle.Indeed, the energy costs associated to glass produced from virgin
material (silica) are much higher than those associated to the
transformation of glass waste after sorting and shredding (cullet).
The manufacturing recycling channel uses the majority of
recycled glass but it requires that recyclers sort and prepare the
waste so as to optimize the transportation and the transformation.
Alternative channels do not reintegrate recycled glass in the
production circuit but try to re-use the glass material through
various applications such as in the construction industry or in thearts and craft sector.
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We can distinguish 3 main industrial types of demand for the use of used
glass:
The
manufacturing
channels
2.1
The deposit-and-return system
for glass bottles is mainly used for
beers and soda drinks
Sorted container glass in bulk or
shredded. It is mainly generated by
non returnable beverage bottlesand other containers. It can be
collected by color or bulk.
Flat glass such as glass panes are
co l l ec ted separa te l y f rom
windscreen. Mirrors should also be
collected separately but it is rarely
the case.
Note : The market related to the purchase of fibreglass has low
visibility (specially in developing countries). Indeed this product is
essentially manufactured from cullet and not specifically from used
fibres. However fiberglass generated from composite material, such
as those used in the ship building industry starts being seriously
considered in some African countries.
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The manufacturing channels are all based on heavy technology
investments and we can distinguish two activities, often managed by
different operators:
Collection and sorting of glass waste and residual material
Washing and hygienization for hollow glass from the deposit-and-
return schemes and production of cullet
In the priority regions of ReCoMap, the recycling channel through the
DaR system and re-use of some categories of bottles is effective. The
breweries and soda manufacturers have indeed organized the re-launch
of a system which is not new but which was not proving to be efficient in
the 80’s.The present energy crisis can only reinforce this tendency and there is
room for operators who can cover proximity areas and who wish to invest
time and some means but above all, organisation work in this sector.
Optimization of
the deposit-
and-return
(DaR) system
2.1.1
We can note that a returnable bottle of beer is re-used 6 times a year
during 10 years and that its transport when empty remains not only
economically viable but also benefits in terms of GHG in a 250km
radius from the brewery (when compared to the manufacture of a new
bottle and in a collection scheme partly integrated to the distribution
logistic)
However the system has a few limitations:
Two direct factors influence the economic and environmental
viability of the DaR system: the cleanliness of the bottles and the
efficiency of transport.
Two external factors limit their extension, namely the developmentof the sales of new bottles made of cullet (and often as products
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called « glass shape ready for blowing ») or containers made of
other competing material such as aluminium or PET.
To optimize the DaR system, certain experimental projects have been set
up by breweries and soda manufacturers in an attempt to organize
rationally the system, mainly at the collection stage
Organize a primary collection for retailers (including informal
sellers) : indeed retailers do not always have the space to storeempty bottles and the informal sellers who are often hawkers have
even less storage capacity.
During primary collection, bottles must be counted and the lots
collected must be registered in a book with counterfoils. Indeed
the operation is payable and should be accounted in a systematic
way.
The proximity collection must include the rinsing of the bottles
(cleaning of the outside as well as a disinfection of the bottles is
not necessary as it must be carried out just before the filling of thebottles). The collection should also optimize the filling up of the
bottle racks, by classifying the bottles and ensuring that the racks
are full as far as possible.
The primary collector should be able to have a storage place not
far from the distribution route. Hence the distributor will be able,
in one operation, to load a complete lot of sorted empty clean
bottles as well as the statements indicating their origin.
These four operations, which can be paid by the distributor and the
brewery, contribute to the efficiency of the system at 4 levels:Optimization of the distribution of full bottles,
Reduction of sorting operations and accounting at the reception
Reduction of transport nuisances
Reduction of cleaning difficulties
This optimization also contributes to perpetuate the DaR system or even
to extend it to other selling points or products (alcohols, cosmetic,
pharmaceutical containers etc.)
We can also note that the proximity collection can envisage the collectionof caps (if they are not oxidized or soiled) as they can be recycled within
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the ferrous metal channel but it can also ensure the collection of non
returnable bottles which can go for the glass recycling (cullet)
The supply for container glass at national level, when glass-making
exists, or at international level where it does not exist, is growing for
products sorted at source by color.
Indeed, as seen above, the coloration of glass is based on complex
mixture of pigments (metallic oxides) for which each brewery or other
beverage manufacturer knows the secret and which contributes to the
communication strategy.
The removal of pigments during the melting phase of a cullet is a delicate
and costly operation which can be avoided by grouping a batch of virginmaterial together with a homogeneous cullet batch for a given
production batch. It represents therefore the possibility for the distributor
to pay less for a delivery of new bottles and therefore to buy for slightly
more the delivery of sorted returned bottles.
We can note that it is at the voluntary deposit stage at regrouping points
or at civic amenity centers that the sorting of waste by color must be
proposed and this initial sorting can eventually be optimized.
There is still a debate to find out how many colors of glass should be
sorted but a general rule tends to limit to 3 groups the colorimetric sortingfor cullet to be used for the manufacture of colored glass:
The collection of flint glass (clear) is made separately and corresponds to
a regular and constant demand. In fact, this general rule depends also on
the demand of glass-makers and therefore varies with the applications
which lead the market (flat or container glass, fiberglass etc.)
Optimization of
colorimetric
sorting
2.1.2
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Figure 6: The three colorimetric groups
Once a rigorous, colorimetric sorting has been undertaken, the filling up
of the transportation skip can be optimized with a preliminary crushing,
which is carried out preferably with a slow roller shredder which crushes
the bottles and reduces it in fragments of size required by the glass makers
and without generating dust.
Figure 8: Glass shredding
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Ocre
Red et Blue-green
Brown
Purple
Blue
Green
Red et Blue-green
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Furthermore, in any case, one must ensure that the demand of the glass
makers specially the price proposed are satisfactory knowing that at this
stage of the negotiations, criteria other than the colorimetric sorting must
be taken into account :
Minimum tonnage to be catered for per period and for each type
of product
Maximum tonnages accepted per periodThese two parameters will allow the definition of storage needs (volume
and duration of storage) which in turn will enable the determination of
needs for the washing of the shredded glass.
We can also recall that the rules for colorimetric sorting can vary from a
glass maker to another and that it is always better to have several clients
rather than one. It is therefore better to adopt quite flexible sorting criteria
in order to favor the sales in continuous flows rather than the sales with
slightly higher profit margins but subject to the risk of a restricted market.
Clear glass
We usually call clear glass container glass which is not colored. For the
majority of them, they are containers of food products but there are also a
large range of special containers of cosmetic and pharmaceutical
products.
Optimization of
the collection
of clear glass
and flat glass
2.1.3
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Figure 9: Typology of clear glass
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No particular precaution except during handling. Beware of spilling residual liquids.
Handle with care. De-metallise (capsules, bases). To be identified regarding their contentwhich can be hazardous even with very small residual quantities.
To be identified regarding their content which can be hazardous even with very small
residual quantities.
Shall be depolluted prior to transportation and treatment such as de-metallisation, shredding.
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Note: Light bulbs and fluorescent tubes do not really form part of
this category but are included in the category of special waste as
they can contain POPs. Only incandescent bulbs which are
gradually being replaced by low energy light bulbs which are
assimilated to special waste can enter this category of clear glass.
In conclusion we note that the collection of clear glass is made byseparating 2 main categories;
Clear glass (non hazardous)
Bottles and other containers which have been used for
food products
De-metallized incandescent light bulbs
Containers used for pharmaceutical products or other
special uses (eg medical laboratories) after identification
of content, harmlessness certification and de-
metallization if necessary.
Hazardous Clear glass (special waste)
Light bulbs and fluorescent tubes if not complete
Containers used for pharmaceutical products or other
special uses (eg medical laboratories) after identification of
content and no certification of harmlessness
Flat glass:
We generally distinguish 3 main categories of flat glass:
Simple or insulated glazing (rare in our targeted countries)
Vehicles windscreens and some special glass (rare in our targeted
countries)
Cathodic tubes
Except for cathodic tubes which require a complex treatment and are thus
special waste, the two first categories are easy to identify and must be
collected separately.
It is also possible to collect the first category (simple glazing) together withclear container glass used for food products.
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Windscreens are subject to a special recycling process and can be
considered as undesirable waste which « pollute » the loads of clear glass
or simple flat glass and disqualify it for sale.
In terms of quantity this category of material is not very representative
(<8%) when compared to container glass. Their collection is therefore
often neglected even if they have a certain value and are relatively easy to
store. In our targeted countries it would be opportune to envisage
grouping actions on a large territory in order to reach minimal quantities
required for negotiation on the recycling market.
Before envisaging an alternative recycling option, one must analyze the
benefits which can be drawn from this strategy.
If it is clear that the manufacturing channels are stable and that they have
capacities to absorb the recyclable glass produced in the priority regions
of ReCoMap, it not less true that the offer is not always attractive.
Indeed, in the priority regions of the programme, the situation is made
difficult due to 3 parameters:
The glass generated does not represent a large volume and is
found in a scattered way when compared to large urban areas.
There is no separate collection or accompanying measures
(information on sorting at source, or sorting at regrouping
centers) which could favor a fine selection of waste
It is sometimes necessary to drive long distances on roads with
limited practicability to bring the sorted waste to treatment centers
or to export zones. Moreover the volumic reduction is not often
carried out.
These 3 parameters increase the cost of operations preceding recycling
itself so much so that the value of the offer for the exportation of a ton of
these wastes (low quality) is probably less than the expenses associated to
the delivery of the material FOB.
2.2 Alternative recycling options
A complementary
strategy with a
local dimension
2.2.1
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Of course this analysis is based on general observations and can be
questioned, in some of the targeted countries, by the setting up of logistic
projects or selective collection, but these favorable situations are rare. It is
therefore legitimate to review possible local alternatives for glass
recycling, as it has been carried out for plastics and paper/cardboards.
We can also note that glass powders are used in numerous extruded
plastics and there is therefore an obvious technical link between this two
recycling channels.
A local recycling alternative must not only avoid the barriers which are
associated to manufacturing options but must also be able to get back
or dedicate part of the material treated to those options. In any case, acomparative analysis is essential to decide which of a manufacturing
or an alternative option, or a mix of both, will be more viable.
Glass as aggregates or powder in concrete
Cement industry has long gone beyond the experimentation stage ofintegrating glassfibre (fibre composite concrete) in special concrete and it
is engaged since recently in the integration in cement of waste and
industrial residuals such as fly ashes, silica smokes and other residual
waste from furnaces. High expectations exist about these new industrial
products for the coming decade.
In this innovation context, it is already possible to use for road works or
individual structures, glass powder as additives or as substitute to cement
and aggregates replacing basalt, flint or traditional granites.
The substitution of part of cement by powders made of used glass indeedimproves the reaction alkali-silica which can be even better controlled
The integration
in concrete andother construction
material
2.2.2.
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thanks to the addition of lithium carbonate but it is considered that the
proportion of glass powder should not exceed 15% of the fraction of
cement in concrete.
Regarding the inclusion of rough fragments of crushed used glass (with a
regular granulometry) in substitution of traditional mineral aggregates, it
is the final material resistance capacity which limits the proportion but for
structures such as ground slabs or facades, substitution up to 30% have
been undertaken. We can note that in most cases it is recommended that
in a view to comply to the requirements of the mixing proportions, the
concrete should have a ratio water/cement of 0,45.
In order to set up this alternative recycling process, we must proceed in 3
main steps as shown below:
Figure 9: Selective sorting of clear glass
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Figure 11: Representation of the production cycle for cement with addition of recycled glass
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The following steps are the usual stages for the preparation of concrete,
namely:
Dry mixing of cement and glass powder
Dry mixing of quarry aggregates, sand and glass pellets
Storage and distribution
Mixing with water and ready-to-use
Cement is necessary to the fabrication of concrete but it is a costly
material which becomes less and less accessible in developing
countries. Moreover it is generally admitted that the production of 1
ton of cement generates 1 ton of CO2 and consequently it is
responsible of approximately 5% of GHG emission on the planet.
Hence the substitution with recycled glass powder and glass
fragments is certainly a promising solution both for the recycling of
glass material at local level and for the continuity and economic
feasibility regarding the improvement of habitat in the targeted
countries of ReCoMap.
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