Waste plastic extruder: literature review

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The following literature review has been originally conducted as part of the Waste plastic extruder for Mech 461. It now supports the Recyclebot project. Please add content.


See Also

Polymer Properties Table

Polymer Properties
Density (g/cc) Hardness Tensile Strength, Yield (MPa) Elongation at Yield (%) Modulus of Elasticity (GPa) Flexural Modulus (GPa) Processing Temperature (˚C) Middle Barrel Temperature (˚C) Die Temperature (˚C) Notes
HDPE, Blow Moulded .935 – 1.01 57.0 – 73.0 Shore D 15.2 – 42.1 6.00 – 13.00 .700 – 2.62 .586 – 2.62 160 – 260 n/a 175 – 190
LLDPE, extrusion grade .916 - .944 51.0 – 58.0 Shore D 7.58 – 17.9 n/a n/a .276 - .480 n/a n/a n/a
LDPE, extrusion grade .915 - .939 42.0 – 57.0 Shore D 7.60 – 12.0 n/a .152 - .290 .0800 - .276 108 – 340 177 - 210 204 – 221
ABS, extruded 1.03 – 1.17 68.0 – 113 Rockwell R 13.0 – 65.0 .620 – 30.0 1.00 – 2.65 1.20 – 5.50 180 – 274 190 – 250 210 -250
PP, extrusion grade .886 – 1.84 57.0 -120 Rockwell R n/a 1.60 – 30.0 .680 – 2.60 .620 – 2.55 120 – 330 190 -280 200 -310
PC, extruded 1.20 – 1.26 120 – 126 Rockwell R 58.6 – 70.0 6.00 – 50.0 1.79 – 3.24 2.09 – 3.10 270 – 343 250 – 332 n/a
PET, unreinforced 1.25 – 1.91 80.0 – 95.0 53.0 – 265 3.5 – 30.0 1.83 – 5.20 1.90 – 15.2 120 – 295 n/a n/a

all data from Matweb Material Property Data

add Coefficients of Linear Expansion


  • Waste plastic extrusion
  • RepRap
  • Fab@home
  • Open Source Rapid Prototyping
  • Thermoplastics
  • Polylactic acid
  • plastics waste developing world
  • thermoplastics emissions

Open Source Rapid Prototype Technology

RepRap - the replicating rapid prototyper

Rhys Jones, Patrick Haufe, Edward Sells, Pejman Iravani, Vik Olliver, Chris Palmer and Adrian Bowyer, "RepRap - the replicating rapid prototyper", Robotica, 29(1), pp. 177 - 191 (2011).


This paper presents the results to date of the RepRap project – an ongoing project that has made and distributed freely a replicating rapid prototyper. We give the background reasoning that led to the invention of the machine, the selection of the processes that we and others have used to implement it, the designs of key parts of the machine and how these have evolved from their initial concepts and experiments, and estimates of the machine's reproductive success out in the world up to the time of writing (about 4500 machines in two and a half years).


  • brief history of self replication and definitions of associated terms.
  • explains philosophy and motivations for the invention of the RepRap by Bowyer, as well as decision to go open source.
  • step-by-step evolution of the RepRap from first model up to the RepRap Mendel.
  • includes design process and detailed description of how the machine functions.
  • Follow Up: Look into PLA production

Additional Resources on RepRap:

A wealth of information is available at the RepRap wiki found here here. This wiki has detailed construction instructions and includes many improvement, add-ons, etc. from the open source community. Of particular interest to this project are the following two, which attempt to create feedstock from recycled plastic:



Fab@Home - the personal desktop fabricator kit

E. Malone and H. Lipson, "Fab@Home: the personal desktop fabricator kit," Rapid Prototyping Journal, vol. 13, pp. 245-255, 2007.


Purpose – Solid freeform fabrication (SFF) has the potential to revolutionize manufacturing, even to allow individuals to invent, customize, and manufacture goods cost-effectively in their own homes. Commercial freeform fabrication systems – while successful in industrial settings – are costly, proprietary, and work with few, expensive, and proprietary materials, limiting the growth and advancement of the technology. The open-source Fab@Home Project has been created to promote SFF technology by placing it in the hands of hobbyists, inventors, and artists in a form which is simple, cheap, and without restrictions on experimentation. This paper aims to examine this.

Design/methodology/approach – A simple, low-cost, user modifiable freeform fabrication system has been designed, called the Fab@Home Model 1, and the designs, documentation, software, and source code have been published on a user-editable “wiki” web site under the open-source BSD License. Six systems have been built, and three of them given away to interested users in return for feedback on the system and contributions to the web site.

Findings – The Fab@Home Model 1 can build objects comprising multiple materials, with sub-millimeter-scale features, and overall dimensions larger than 20 cm. In its first six months of operation, the project has received more than 13 million web site hits, and media coverage by several international news and technology magazines, web sites, and programs. Model 1s are being used in a university engineering course, a Model 1 will be included in an exhibit on the history of plastics at the Science Museum London, UK, and kits can now be purchased commercially. Research limitations/implications – The ease of construction and operation of the Model 1 has not been well tested. The materials cost for construction (US$2,300) has prevented some interested people from building systems of their own.

Practical implications – The energetic public response to the Fab@Home project confirms the broad appeal of personal freeform fabrication technology. The diversity of interests and desired applications expressed by the public suggests that the open-source approach to accelerating the expansion of SFF technology embodied in the Fab@Home project may well be successful.

Originality/value – Fab@Home is unique in its goal of popularizing and advancing SFF technology for its own sake. The RepRap project in the UK predates Fab@Home, but aims to build machines which can make most of their own parts. The two projects are complementary in many respects, and fruitful exchanges of ideas and designs between them are expected.


  • less geared toward self replication than RepRap, but same goal of making rapid prototyping widely available.
  • uses syringe based extrusion versus the filament extrusion of RepRap
  • open source software works solely with Windows OS at time of publication.

Additional Resources on Fab@Home:

Check out the Fab@Home wiki [1]. This page includes detailed construction guidelines, as well as improvements, add-ons, etc. developed by the open source community. A few general notes:

  • Similar project to RepRap and RapMan.
  • Developed at Cornell University by Hod Lipson and Evan Malone.
  • Uses open source developed hardware and software. Software programs are have been specifically developed for the Fab@Home but are open source.
  • Extrusion uses a syringe/piston based system – can handle diverse materials.

Rapid Prototype Manufacturing System

A.Tan, T. Nixon, "Rapid Prototype Manufacturing System", Unpublished undergraduate paper, The University of Adelaide, Adelaide, Australia,(2007)


  • covers applications and benefits of small scale rapid prototyping technology.
  • summary of existing small scale and commercial technologies. Comprehensive review of process methods. (i.e. Fab@home uses solid freeform fabrication (SFF) while RepRap uses fused deposition method (FDM)).
  • information on rapid prototyping materials including good review of thermoplastics.
  • some testing of materials with Rapid Prototyper (properties include viscosity, cure time, layering time, flow rate).
  • develop alternative deposition system for Fab@Home. Seems to be successful granule extruder.
    • interesting idea - 2 heated sections, one for melting, the other to maintain desired temperature through nozzle.
    • incorporate heated hopper for pre-melting of material
    • screw extruder for material deposition.
    • some optimization completed.


  • commercially available, proprietary version of RepRap Darwin.
  • kits available retailing at approximately $1000.
  • some proprietary components.

More information:


  • another open source 3D printer which is sub-$1000.

More information:

Plastics Recycling

An Investigation of Mechanical, Thermal and Creep Behavior of Recycled Industrial Polyolefins

S. Haider Rizvi, S. H. Masood, Igor Sbarski. "An Investigation of Mechanical, Thermal and Creep Behavior of Recycled Industrial Polyolefins" Progress in Rubber, Plastics and Recycling Technology." 23(2), 97 - 110. 2007


  • recycling industrial plastics ex. plastic pails and containers
  • polyolefins - PP, HDPE, most common is a mix of polyethylene and polypropylene
  • blend - physical mixture of 2 or more polymers, goal = get desired properties, done by diluting engineering resins w. low cost commodity polymers
  • as recycled percentage in HDPE increases --> decrease in tensile modulus, flexural modulus and lower yield pt shifted toward the lower strain, no changes in tensile and flexural strength, over 40% recycled - significant decrease in crystallinity
  • as recycled percentage in PP increases --> tensile modulus decreased , flexural modulus increases slightly, no changes in tensile and flexural strength, until 60% recycled PP - crystallinity decreases linearly, past 60% no change in crystallinity
  • Creep
     * fast creep --> elastic deformation
     * slow creep --> viscoelastic deformation (most of creep process), permanent deformation
     * dependent upon temp and stress

Recycling and Recovery Routes of Plastic Solid Waste (PSW): A review

""S.M. Al-Salem, J.Baeyens, P. Lettieri, “Recycling and Recovery Routes of Plastic Solid Waste (PSW): A review” Waste Management, 29(10), 2625-2643, 2009. doi:10.1016/j.wasman.2009.06.004""


Plastic solid waste (PSW) presents challenges and opportunities to societies regardless of their sustainability awareness and technological advances. In this paper, recent progress in the recycling and recovery of PSW is reviewed. A special emphasis is paid on waste generated from polyolefinic sources, which makes up a great percentage of our daily single-life cycle plastic products. The four routes of PSW treatment are detailed and discussed covering primary (re-extrusion), secondary (mechanical), tertiary (chemical) and quaternary (energy recovery) schemes and technologies. Primary recycling, which involves the re-introduction of clean scrap of single polymer to the extrusion cycle in order to produce products of the similar material, is commonly applied in the processing line itself but rarely applied among recyclers, as recycling materials rarely possess the required quality. The various waste products, consisting of either end-of-life or production (scrap) waste, are the feedstock of secondary techniques, thereby generally reduced in size to a more desirable shape and form, such as pellets, flakes or powders, depending on the source, shape and usability. Tertiary treatment schemes have contributed greatly to the recycling status of PSW in recent years. Advanced thermo-chemical treatment methods cover a wide range of technologies and produce either fuels or petrochemical feedstock. Nowadays, non-catalytic thermal cracking (thermolysis) is receiving renewed attention, due to the fact of added value on a crude oil barrel and its very valuable yielded products. But a fact remains that advanced thermo-chemical recycling of PSW (namely polyolefins) still lacks the proper design and kinetic background to target certain desired products and/or chemicals. Energy recovery was found to be an attainable solution to PSW in general and municipal solid waste (MSW) in particular. The amount of energy produced in kilns and reactors applied in this route is sufficiently investigated up to the point of operation, but not in terms of integration with either petrochemical or converting plants. Although primary and secondary recycling schemes are well established and widely applied, it is concluded that many of the PSW tertiary and quaternary treatment schemes appear to be robust and worthy of additional investigation.


  • re-extrusion (primary recycling) - reintroduction of scrap/industrial/single polymer plastic into exrusion cycle
  • scrap must be semi-clean = unpopular w. recyclers
  • process scrap - products made that don't meet standards of producer
      * in UK process scrap = 250,000 tons --> 95% primary recycled
  • recycling household waste challenges
      * large # of sources supply small quantities of PSW
      * resource drain, high operating costs

Examination of the possibility of recycling and utilizing recycled polyethylele and polypropylene

Cemal Meran, Orkun Ozturk, and Mehmet Yuksel, Examination of the possibility of recycling and utilizing recycled polyethylele and polypropylene, Technical Report (Kinikli, Denizli, Turkey: Pamukkale University, Mechanical Engineering Department, n.d.).

  • manufactured in the following percentages: 31% polyethylene (PE), 17% polyvinyl chloride (PVC), 15% thermosets, 14% polypropylene (PP), and 9% polysty- rene (PS)
  • plastics best suited for recycling are PE, PP, PVC, and polyethylene terephthalate (PE)
  • The recycled plastics should not be used in the medicine and food sec- tors. However, recycled plastics could be used in 90% of applications, such as in manufacturing contractile films, some kinds of pipe, sandwich structured laminates, and some containers targeted for industrial us
  • results of the experiments demonstrated that the usability of the recycled low-density polyethylene, high- density polyethylene, and polypropylene is 100%
  • polypropylene- tensile strength, even in bars pressed from the highly recycled polypropylene, decreased 15% compared with the pure material.
  • HDPE 24% decrease
  • LDPE 36% decrease

Characterization and recovery of polymers from mobile phone scrap

Angela C Kasper, Andréa M Bernardes and Hugo M Veit. "Characterization and recovery of polymers from mobile phone scrap" 
Waste Manag Res 2011 29: 714 originally published online 7 March 2011. DOI: 10.1177/0734242X10391528


  • users keep particular models of mobile phones for from 9 to 18 months before replacing them with newer or better equipment
  • estimated that the global number of such obsolete mobile phones is now more than 500 million and is growing constantly
  • In developing countries such as China and India, waste is ‘processed’ in backyards or small workshops using very primitive methods (burning in the open air or washing with acids) to recover only any metal of economic interest. Normally in these artisanal procedures, the polymers are lost and atmospheric pollution is inevitable.
  • suitable industry-level mechanical processing emerges as a reasonable alternative where it can be arranged to concentrate the metals into one group and the polymers and ceramics in another
  • 95% of the components were made from a blend of PC/ABS
  • tensile strength of recycled material is similar to that of virgin material, and the density presented (1.08 g cm^3) is closer to the density of ABS, indicating a high content of ABS in the blend. The recycled material demonstrated greater hardness value than virgin material, probably due to the presence of inorganic elements in the blend. Table 4

Collection, transfer and transport of waste: accounting of greenhouse gases and global warming contribution

Eisted, R., Larsen, A., and Christensen, T., 2009, "Transfer and Transport of Waste: Accounting of Greenhouse Gases and Global Warming Contribution," Waste Management & Research, 27(8) pp. 738-745.


The collection, transfer and transport of waste are basic activities of waste management systems all over the world. These activities all use energy and fuels, primarily of fossil origin. Electricity and fuel consumptions of the individual processes were reviewed and greenhouse gases (GHG) emissions were quantified. The emission factors were assigned a global warming potential (GWP) and aggregated into global warming factors (GWFs), which express the potential contribution to global warming from collection, transport and transfer of 1 tonne of wet waste. Six examples involving collection, transfer and transport of waste were assessed in terms of GHG emissions, including both provision and use of energy. (GHG emissions related to production, maintenance and disposal of vehicles, equipment, infrastructure and buildings were excluded.) The estimated GWFs varied from 9.4 to 368 kg CO2-equivalent (kg CO2-eq.) per tonne of waste, depending on method of collection, capacity and choice of transport equipment, and travel distances. The GHG emissions can be reduced primarily by avoiding transport of waste in private cars and by optimization of long distance transport, for example, considering transport by rail and waterways.


  • provide LCA of transport, collection and transfer for waste
  • GHG emissions and Global Warming Potential of these activities under various conditions.
  • greatest for rural and remote areas, or situations where individuals drop waste at a central point. Lower for urban areas and curbside collection. Still some emissions in each scenario.

Municipal Solid Waste Management: Can Thermodynamics Influence People's Opinions about Incineration?

Norman Kirkby and Adisa Azapagic, “Municipal Solid Waste Management: Can Thermodynamics Influence People’s Poinions about Incineration?,” in Sustainable Development in Practice, vol. 1, 1 vols. (John Wiley and Sons Ldt., 2004), 117-200.

  • each person produces an average of 500 kg of solid waste per year
  • developed countries produce twice as much as undeveloped countries
  • reusing and recycling waste to recover materials is a sustainable way to deal with municipal solid waste - difficult because of high costs of collection/sorting/recycling
  • MSW in U.S is 10.7% plastic
  • MSW in Mexico is 4.4% plastic
  • Asia - slum areas often denied waste collection services
  • Africa - lack of financial resources, trained staff, and poor enforcement of legislation

Factors influencing waste separation and utilization among households in the Lake Victoria crescent, Uganda

Ekere, W., Mugisha, J., and Drake, L., 2009, "Influencing Waste Separation and Utilization among Households in the Lake Victoria Crescent, Uganda," Waste Management, 29(12) pp. 3047-3051


Wastes, which are the by-products of consumption, are a growing problem in the urban and peri-urban areas of the Lake Victoria region largely due to high urban population growth rates, consumption habits, low collection rates and hence waste accumulation. Whereas the biodegradable proportion is high and could be reutilized, a few have tapped the economic potential of this waste. This study was conducted to explore the potential alternatives and determinants of waste separation and utilization among urban and peri-urban households in the Lake Victoria crescent. A random sample of households in five urban and peri-urban areas of the crescent were selected and surveyed. Logit models were used to establish the factors influencing waste separation and utilization in urban and peri-urban areas of the lake crescent. Results indicate that, gender, peer influence, land size, location of household and membership of environmental organization explain household waste utilization and separation behaviour. Campaigns for waste separation and reuse should be focused in the peri-urban areas where high volumes of wastes are generated and accumulate. Social influence or pressure should be used to encourage more waste reuse and separation.


  • evaluation of waste separating practices in region of Uganda.
  • attempts to explain factors contributing to compliance with separation and recycling guidelines.
  • Mention of profit gaining activities using recycled goods.

Stability of ABS compounds subjected to repeated cycles of extrusion processing

Karahaliou, E. -., and Tarantili, P. A., 2009, "Stability of ABS Compounds Subjected to Repeated Cycles of Extrusion Processing," Polymer Engineering & Science, 49(11) pp. 2269-2275


  • No changes found in ABS mechanical properties through 5 extrusion cycles
  • Some changes in colour and chemical composition indicate that two parallel processes may be occurring which balance each other, but no conclusive evidence.
  • indicates ABS should be useful for RepRap through multiple use cycles.

Energy Audit of Kerbside Recycling Services

Metcalfe, P. (2008) "Audit of the Kerbside Recycling Services." The London Borough of Camden. Energy Audit Camden Report 3. ADAS, Wolverhampton, UK.


  • includes graphs showing percentage of GHG from recycling process in Camden results from transport and collection.
  • new system implemented from study has greatly reduced collection impact, but it is still significant.

The ecological relevance of transport in waste disposal systems in Western Europe

Salhofer, S., Schneider, F., and Obersteiner, G., 2007, "Ecological Relevance of Transport in Waste Disposal Systems in Western Europe," Waste Management, 27(8) pp. S47-S57.


With the development of modern waste management systems in Western Europe, a remarkable increase in the distances for waste transportation has been observed. The question thus arises whether recycling with longer transport distances is ecologically advantageous or whether disposal without recycling is to be preferred. This situation was analysed using selected product and waste streams. This included refrigerators, paper, polyethylene films and expanded polystyrene. For each of these streams, a life cycle analysis was conducted with an emphasis on waste transport. The system boundaries were set in terms of the generation of waste to recycling or landfilling. The comparison included several scenarios with recycling and different transport distances. Landfilling was used as the reference scenario. The results obtained demonstrated how transport distances influence the ecological benefit of recycling. In the case of expanded polystyrene, the ecological boundaries are reached in practical situations, while with other materials these boundaries are far from being attained. In these cases, more complex and elaborate collection schemes, such as kerbside collection, which is economically convenient and shows the highest collection rates, can also be recommended.


  • wide range in results based on material transported and availability of recycling materials.
  • for HDPE films, found transport accounted for 1%-11% of GHG and GWP.
  • in almost all cases, impact less for recycling than landfilling.

Life cycle assessment of a plastic packaging recycling system

Arena, U., Mastellone, M., and Perugini, F., 2003, "Life Cycle Assessment of a Plastic Packaging Recycling System," The International Journal of Life Cycle Assessment, 8(2) pp. 92-98.


Goal, Scope and Background. The object of the study is the Italian system of plastic packaging waste recycling, active until 2001, that collected and mechanically recycled the post-consumer PE and PET liquid containers. The phases of collection, compaction, sorting, reprocessing and refuse disposal were individually analysed and quantified in terms of energy and material consumptions as well as of emissions in the environment. The work is the result of a joint research project with the Italian Consortium for Packaging (CONAI), carried out in co-operation with the main Italian companies active in the field. The main aim was the quantification of the real advantage of plastic container recycling and the definition of criteria, at the same time environmentally compatible and economically sustainable, for their management. Main Features For each of the unit processes, and in order to increase the data quality, all the data of interest were collected during technical visits to several selected plants active in Italy or deduced by official documents and certificate declarations of the same companies. To allow comparison of resource consumption and environmental pollution from different management scenarios producing different products, thebasket of products method was applied. Results The results indicates that the production of 1 kg of flakes of recycled PET requires a total amount of gross energy that is in the range of between 42 and 55 MJ, depending on whether the process wastes (mainly coming from sorting and reprocessing activities) were sent or not to the energy recovery. The same quantity of virgin PET requires more than 77 MJ. The energetic (and then environmental) saving is so remarkable, even for PE, being 40–49 MJ for the recycled polymer and about 80 MJ that for the virgin polyolefin. The calculations were made with the reasonable assumption that the final utilisation can use the virgin or the recycled polymer without any difference. Conclusions and Outlook The analysis defined and verified a suitable tool in the field, based on objective data, for comparing different coherent scenarios of waste management politics. This allows one to propose the extension of the tool under different collection schemes, as well as for different systems of packaging recycling. As an immediate consequence of the success of the present study, the joint-research programme with CONAI has been extended for another three years. The focus will be the Italian system for paper and paperboard recycling and that for all plastic packagings. In parallel, a different study has been scheduled with reference to the integrated solid waste management of the Regione Campania, the largest and most populated area in the South of Italy.


  • transportation and collecting found to have the biggest environmental impact on the recycling process.

Small scale recycling of plastic waste

H. Vest, "Small scale recycling of plastic waste," Appropriate Technology, vol. 29, pp. 51-53, January-March, 2002. Available online here

  • originally written in 1995, published in Appropriate Technology in 2002. Open source - available online at URL above.
  • speaks to potential of plastics recycling to be a profitable venture in developing countries due to low labour cost
  • description of recycling process for various plastic types
  • outline of existing technology (extruders, pelletizers, manual injection moulding, etc.)
    • larger scale than targeted for this project (i.e. commercial vs. domestic).
  • raises concern of difficulty of sorting plastics, though notes it can be done by eye with experience.
    • sorting is necessary for high quality feedstock

Reactive Extrusion of Recycled Bottle Waste Materials

R. Hettema, J. Pasman, L.B.P.M Janssen, “Reactive Extrusion of Recycled Bottle Waste Materials”, Polymer Engineering and Science, April 2002, Vol. 42, No. 4.

  • States challenges of plastic recycling
    • mixing waste streams (ie. HDPE and PP) results in undesirable engineering properties.
    • hard to recreate properties of virgin material
  • Authors conducted experiments with reactive extrusion (chemicals added during process)
    • peroxides added during extrusion process.
    • found to be beneficial in improving properties such as toughness
  • Extrusion settings also tested for effects on material properties.
    • mass flow rate, screw speed and termperature tested.
    • linkage found between these parameters and % elongation, Young's modulus and yield strength.


  • Reactive extrusion could be explored to improve properties of expanded materials. Need to ensure such chemicals are domestically available in a development setting.
  • Extrusion parameters will have to be tested to determine optimal conditions for quality feedstock production.

Plastics recycling and waste management in the US

Subramanian, P. M., 2000, "Plastics Recycling and Waste Management in the US," Resources, Conservation and Recycling, 28(3-4) pp. 253-263.


The increasing awareness of the environment has contributed to concerns regarding our life styles and our indiscriminate disposal of wastes. During the last decade, we have been trying to address this complex problem, more aggressively. Discussed here briefly, are our efforts in the United States in addressing the issue of solid wastes and in particular, plastic wastes. These efforts have begun to show promising results. The municipal solid waste (MSW) produced annually, has begun to decrease, e.g. from 211.5 million tons in 1995 to 209.7 million tons in 1996. Recycling rates and composting rates are increasing. Disposal in landfills is decreasing (from 60.9 to 55.5% in 1996). Waste disposal by combustion is also increasing. This is primarily due to the increased efficiencies of the new incinerators and their ability for the removal of particulates and harmful gases. Plastics are a small but a significant component of the waste stream. It is encouraging to note that the amount of plastics being recycled has grown significantly. In 1997, about 317 million kg of high density polyethylene (HDPE) bottles and 294 million kg of polyethylene terephthalate (PET) bottles were recycled. Recycling of durable goods, such as automotive parts, carpets, electronic and appliance housings and parts are being explored. Environmental compatibility and recyclability are being considered during the designing of new parts. Life cycle analyses and management are also being studied as tools for decision making.


  • General review of plastics recycling in the US.
  • some good data, but potentially out of date (data from early to mid 1990s)

Optimal Recycling of Waste Materials in a Plastic Extrusion Production Process

S.P. Ladamy, K.C. So, “Optimal Recycling of Waste Materials in a Plastic Extrusion Production Process”. European Journal of Operational Research, 79(1994), pg 13-24.

  • Recycling process overview.
  • Recyled plastic mixed with virgin material to retain engineering properties
    • Less virgin material in plastic each cycle
  • Authors attempt to determine optimal number of cycles of mixing reclaimed and virgin material
  • Based on factors such as sale price, value of recovered waste material, raw material cost, production, etc.
  • Numerical model developed to determine optimum cycling.


  • Some useful insights into engineering properties of recycled plastics.
  • Virgin material mixing may be utilized.

An efficient method of material recycling of municipal plastic waste

I. Fortelný, D. Michálková, and Z. Kruliš, “An efficient method of material recycling of municipal plastic waste,” Polymer Degradation and Stability, vol. 85, no. 3, pp. 975-979, Sep. 2004.

  • goal is to find a compatibiliser for PE/PP/PS to reduce the need for sorting
  • tested mixes of 5% EMP, 5% SBS and 5% EPM/SBS and charted tensile strength
  • adding 5% of EP(D)M/SBS and .5% of a stabiliser with proper mixing conditions leads to a mixture with toughness comparable w. virgin polyolefins
  • EPM - ethylene-propylene-diene statistical terpolymer
  • SBS - styrene-butadiene block copolymer

Plastic and Plastic-Composite Materials

Phase Structure and Properties of Poly(ethyleneterephthalate)/High-Density Polyethylene Based on Recycled Materials

Yong Lei et al., “Phase Structure and Properties of Poly(ethyleneterephthalate)/High-Density Polyethylene Based on Recyced Materials,” Journal of Applied POly Science 113 (2009): 1710-1719.

  • PET and PE combinations - less brittle, stiffer, better flowing, cool faster than HDPE so can be made faster
  • Recycled PET - higher flexural strength, flexural modulus, tensile strength, tensile modulus compared to recycled HDPE
  • Recycled HDPE - higher impact strength
  • Mixing recycled PET and HDPE - almost linear changes in flexural strength, flexural modulus, tensile strength and tensile modulus between values found for PET 100% and HDPE 100%
  • Impact strength at a minimum w. 50/50 blend of HDPE and PET because of incompatibility
  • HDPE crystallinity increases when blended with PET
  • PET crystallinity decreases w. addition of HDPE
  • adding 2% PE-g-MA and 5% SEBS suppressed crystallinity in HDPE and PET, and improved impact strength
  • adding .5% increased tensile modulus but lowered tensile and impact strength

Processing Technologies for poly(lactic acid)

Lim, L. -., Auras, R., and Rubino, M., 2008, "Processing Technologies for Poly(Lactic Acid)", Progress in Polymer Science, 33(8) pp. 820-852.


Poly(lactic acid) (PLA) is an aliphatic polyester made up of lactic acid (2-hydroxy propionic acid) building blocks. It is also a biodegradable and compostable thermoplastic derived from renewable plant sources, such as starch and sugar. Historically, the uses of PLA have been mainly limited to biomedical areas due to its bioabsorbable characteristics. Over the past decade, the discovery of new polymerization routes which allow the economical production of high molecular weight PLA, along with the elevated environmental awareness of the general public, have resulted in an expanded use of PLA for consumer goods and packaging applications. Because PLA is compostable and derived from renewable sources, it has been considered as one of the solutions to alleviate solid waste disposal problems and to lessen the dependence on petroleum-based plastics for packaging materials. Although PLA can be processed on standard converting equipment with minimal modifications, its unique material properties must be taken into consideration in order to optimize the conversion of PLA to molded parts, films, foams, and fibers. In this article, structural, thermal, crystallization, and rheological properties of PLA are reviewed in relation to its converting processes. Specific process technologies discussed are extrusion, injection molding, injection stretch blow molding, casting, blown film, thermoforming, foaming, blending, fiber spinning, and compounding.


  • Good resource for properties and conventional processing of PLA.
  • effects of heat, extrusion on PLA properties - may affect recyclability.

Polylactic Acid Technology

R. E. Drumright, P. R. Gruber and D. E. Henton, "Polylactic Acid Technology," Advanced Materials, 12(23), pp. 1841-1846, 2000. Available online[2]


Polylactic acid is proving to be a viable alternative to petrochemical-based plastics for many applications. It is produced from renewable resources and is biodegradable, decomposing to give H2O, CO2, and humus, the black material in soil. In addition, it has unique physical properties that make it useful in diverse applications including paper coating, fibers, films, and packaging.


  • Polylactic acid (PLA) is a biopolymer made from starch sources (i.e. corn, beets).
  • Has been used successfully with the RepRap machine.
  • Biodegradable plastic means reduction in waste... if a domestic source could be obtained it may be a useful feedstock.
  • This article provides basic review of PLA:
    • production
    • degradation
    • properties
    • applications
    • treatment options (i.e. peroxide treatment to promote branching and therefore increase strength)

Plastics Processing Technology

Muccio, E.A., 1994, "Plastics Processing Technology", ASM International, Materials Park, OH, pp. 302.

  • comprehensive review of plastics and processing technologies.
  • 4th printing in 1999. Slightly outdated, but still useful for information on material properties and conventional processing practices.
  • preview available on Google books.

Society of the Plastics Industry (SPI), Resin identification codes

  • set of codes developed in 1988 to be applied to plastic objects to identify their composition
  • allows for simplied sorting during the recycling process.
  • system is used internationally.
  • may help with plastic sorting for waste plastic extruder

See the SPI website for more information: available here

The American Chemical Council has also published a chart showing the appropriate SPI symbol and summarizing the properties and applications of each resin type. The chart is online here.

A kinetic model of polymer degradation during extrusion

E. G. El’darov, F. V. Mamedov, V. M. Gol’dberg, and G. E. Zaikov, “A kinetic model of polymer degradation during extrusion,” Polymer Degradation and Stability, vol. 51, no. 3, pp. 271-279, Mar. 1996.

  • focuses on PE
  • processing degradation caused by formation of alkyl R radicals that interact w. oxygen to make peroxide R02.
  • molecular weight decreases because peroxide causes bonds in the macromolecular bonds to break
  • includes equations that determine possible changes of molecular weight and the amount of absorbed oxygen * breakage or changes in the amount of crosslinking is not the cause of the of the changes in molecular weight, caused by the oxidation reaction
  • at low temps molecular weight decreases bc. of mechanically initiated breaks, medium temps (up to 190 C) molecular weight increases, between 210 - 220 C macromolecular weight stable and above 220 C macromolecular weight decreases

Addition Compatibilization of PP/PS Blends by Tailor-Made Copolymers

M. Diaz, S. Barbosa, and C. Numa, “Addition Compatibilization of PP/PS Blends by Tailor-Made Copolymers,” Polymer Engineering and Science, vol. 46, no. 3, pp. 329-336, Mar. 2006.

  • Taylor Made Compatibilizer (TMC) is added to PP/PS blend
  • benefits - uses small amounts of low cost reactants, process is not affect by secondary reactions that can degrade/modify the blend, allows for optimization of amount/quality of the copolymer formed
  • incomplete homogenization of the compatibilizer caused samples to break before the cold drawing-strength zone meaning that the interfacial PP/PS adhesion is lower than the shear stress of the matrix
  • TCM concentration doesn't affect yield strength
  •  % elongation at break highest when TMC concetration (wt %) is between .5 - .75,
  • applicable to the recycling of mixed plastics from urban/industrial waste sources.

Combined kinetic analysis of thermal degradation of polymeric materials under any thermal pathway

P. E. Sánchez-Jiménez, L. A. Pérez-Maqueda, A. Perejón, and J. M. Criado, “Combined kinetic analysis of thermal degradation of polymeric materials under any thermal pathway,” Polymer Degradation and Stability, vol. 94, no. 11, pp. 2079-2085, Nov. 2009.

  • experimental curves for the thermal degradation of polytetrafluoroethylene and polythylene under linear heating
  • may be useful for determining the impact of long term heating on PE

Molecular Modification and Compatibilization of Collected Polyethylene

M. Sjoqvist and A. Boldizar, “Molecular Modification and Compatibilization of Collected Polyethylene,” J polym environ, no. 19, pp. 335-340, 2011.

  • PE extruded at 200, 300, 350 °C
  • 350°C had highest Elastic modulus, 200°C lowest
  • adding 5% EPDE ( Ethylene- propylene diene rubber ) to PE w. 5% PP leads to better interfacial adhesion, increased tensile strength

Processing and Characterization of Recycled Poly(ethylene terephthalate) Blendes with Chain Extenders, Thermoplastic Elastomer, and/or Poly(butylele adipate-co-terephthalate)

Y. Srithep et al., “Processing and Characterization of Recycled Poly(ethylene terephthalate) Blendes with Chain Extenders, Thermoplastic Elastomer, and/or Poly(butylele adipate-co-terephthalate),” Polymer Engineering and Science, vol. 51, no. 6, p. 1023, 2011.

  • recycled PET shows hydrolytic and thermal degradation, reducing molecular weight and viscosity which negativley impacts mechanical properties and moldability
  • can add reinforcing fillers and toughening modifiers to help compensate
  • chain extenders (CE) increases molecular weight and melt viscosity, diepoxides, diisocyanates,
  • adding PBAt (poly(butylene adipate-co-terephthalate)) improves toughness
  • adding CE and PBAT doesn't affect melting temp of recycled PET
  • RPET + 25%PBAT + 1.3% CE had the highest impact strength of 5.17
  • RPET + 1.3% CE had the greatest Ultimate tensile strength and tehnsile modulus (53.2 and 1450.3 respectably)
  • heat treating improved all mechanical properties

Processing of Ternary Polymer Blends Based on Polyvinyl Chloride, Thermoplastic Polyester Polyurethane and Polyethylene-Co-Acrylate-Co-CO.

M. Modesti, F. Simioni, M. I. Tiberio, M. Veronelli, G. Zinelli, and M. Passudetti, “Processing of Ternary Polymer Blends Based on Polyvinyl Chloride, Thermoplastic Polyester Polyurethane and Polyethylene-Co-Acrylate-Co-CO.,” Journal of Elastomers and Plastics, vol. 32, no. 15, 2000.

  • mix of PVC (poly(vinyl cholride)), TPU (thermoplastic polyester polyurethane) and ENBACO (polyethylene-co-n butyl acrylate-co-CO) has possible application in footwear industry
  • TPU increases abrasion resistance and tensile characteristics, reduces thermal stability
  • Increased ENBACO decreases specific gravity, resistance to abrasion, increases flexibility of chains reducing performance at low temps

Extrusion Process and Technology

Fundamentals of Extrusion

O. Vongeheur, “ Fundamentals of Extrusion”, Candy Industry. January 2008.

  • Basic outline of extrusion processes
    • describes major steps in extrusion and examines three methods – screw, piston and roller
  • Originally written for Candy Industry – therefore may not apply to RepRap. But does describe mechanical processes for plastic
  • Note also that RepRap extruders have been designed to extrude paste, as has the piston system of Fab@home.

An experimental study on shear stress characteristics of polymers in plasticating single-screw extruders

Atakan Altinkaynak, Sam L. Crabtree, Mahesh Gupta, Mark A. Spalding, “An experimental study on shear stress characteristics of polymers in plasticating single-screw extruders” Polymer Engineering and Science, 49(3), p471, 2009.

  • ABS resin inside barrel temp 160-130˚C bc. stresses at interface at maximum and provide maximum forwarding forces at barrel wall.
  • Barrel zone temp may need to be 210 ˚C for inside to be at 160˚C.
  • LDPE 90˚C screw and 130˚C Barrel stress at interface = .24 MPa (screw) and .27 MPa(barrel) = enough to conval LDPE resin
  • LDPE resins can be extruded using an exturder w. short melting section

Reactive Extrusion of Recycled Bottle Waste Material

Hettema, L.P.B.M Janssen, J. Pasman, “Reactive Extrusion of recycled bottle waste material” Polymer Engineering and Science, 42(4), p665, 2002.


  • HDPE mixed w. PP / different grades HDPE --> poor mechanical properties
  • Increase in PP = increased young’s modulus, decreased impact strength and elongation at break, Figure 8
  • Processing Conditions - increasing screw speed @ constant thoughput = improved mixing, impact strength and elongation at break decrease, young’s modulus increases (single screw extruder)

Plastics Processing Data Handbook

Rosato, Dominick (1997). Plastics Processing Data Handbook (2nd Edition).. Springer - Verlag. (Online) [3].


  • Very comprehensive text on a wide range of plastics processing technologies. Particularly useful sections for the report include:
    • Chapter 1 - Fundamentals - includes material properties, process overviews, general information.
    • Chapter 3 - Extrusion - extrusion processes and technology
    • Chapter 16 - Auxiliary Equipment - includes material and parts handling, other processes.
  • Focus is on large industrial applications but background will be usefull.

Volatile Emissions During Thermoplastics Processing - A Review

Patel, S. H., and Xanthos, M., 1995,"Volatile Emissions during Thermoplastics processing—a Review", Advances in Polymer Technology, 14(1) pp. 67-77.


Types and amounts of volatiles emitted during thermoplastics processing depend upon the chemical structure of the material and the choice of processing conditions. The identification of volatiles and the development of analytical techniques for measuring their concentration in the workplace are of paramount importance to establish or revise threshold limit values that would minimize exposure to hazardous chemical substances and lead to corrective action. In this review, information related to the types of volatiles emanating from injection molding machines and extruders as well as analytical methods for their measurement was collected, analyzed, and tabulated. Emphasis was placed on the four major commodity plastics, viz., polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). Although the main emphasis is on emissions during processing, related literature under simulated conditions is also mentioned.


  • detailed recording of volatiles emitted from various plastics under different temperatures and process.
  • recommend exposure limits not included - relevant for health effects of producing feedstock from waste plastic.

Rapid prototyping of electrically conductive components using 3D printing technology

J Czyewski et al., “Rapid prototyping of electrically conductive components using 3D printing technology,” Journal of Materials Processing Technology 209 (2009): 5281-5285.

  • electrically conductive, carbon-black-filled thermoplastic polymer compounds.
  • have a volume resistivity of 10^1 -10^3 ohms and a surface resistivity of 10^2 - 10^4 ohms
  • steps 1) model made of powder deposited layer-by-layer and bound by inkjet printed liquid binding agent 2) structure impregnated by a hardenable infiltrant (epoxy based resin)
  • can be made electrically conductive if an electrically conductive filer to the infiltrate
  • using carbon nanofibers - require low concentration and don't affect infiltrant
  • surface resistivity below 800 ohms/sq reached with less than 4 weight% of CNF's
  • works at a lower weight% if the CNF's are aggregated vs. being well dispersed

Feasibility study on developing productivity and quality improved layered manufacturing method for rapid prototyping/tooling/manufacture

Ajantha K. Egodawatta, D. K. Harrison, A. De Silva, G. Haritos, “Feasibility study on developing productivity and quality improved layered manufacturing method for rapid prototyping/tooling/manufacture,” Journal of Materials Processing Technology 149 (2004): 604 - 608.

  • Rapid prototyping needs to reduce time to market to compete with conventional manufacturing processes (injection moulding)
  • Shell assisted layer manufacturing improves quality and productivity
  • 1. develops out shell of specific layer of the part
  • 2. fill shell with UV curable resin
  • 3. repeat until built
  • uses a print head of 1536 nozzels
  • benefits - faster, can be made smoother
  • drawbacks - complicated, need to remove shell, cannot be used for extremely fine applications

Emissions from Processing Thermoplastics

Forrest, M. J., Jolly, A. M., Holding, S. R., 1995,"Emissions from Processing Thermoplastics", The Annals of Occupational Hygiene, 39(1) pp. 35-53.


  • Various processes and materials tested
  • all tested levels well below legislated standards.
  • extrusion found to have higher fumes than injection moulded. Worker position important.
  • Some toxins, (i.e. aldehydes) not tested.

Thermal and Mechanical Degradation During Polymer Extrusion Processing

C. Capone, L. Di Landro, F. Inzoli, M. Penco, and L. Sartore, “Thermal and Mechanical Degradation During Polymer Extrusion Processing,” Polymer Engineering and Science, vol. 47, no. 11, 2007.

  • found that processing with the extruder screw at a higher rpms had little to no effect on the shear viscosity

Existing Waste Plastic Extrusion Technology


"RecycleBot," May-June 2010, RecycleBot blog, [online], http://recyclebot.tumblr.com/archive.


  • student project at Victoria University in Wellington
  • hand crank device built to extrude plastic filament.
    • appears fairly successful.
    • no information on MakerBot mounted adaptation.

More information RecycleBot blog

Plastic Extruder for Growing Media

Web4Deb, "Plastic extruder for growing media," December 10, 2010. The Adventures of Bigelow Brook Farm blog. 2010


  • Web4Deb is online avatar. Name to be found.
  • developed to extrude HDPE as a growth medium for aquaponics.
  • automated system extrudes at 200ft/ hour.
  • could be modified to extrude filament.

More information:

The Adventures of Bigelow Brook Farm: Plastic Extruder for Growing Media.

Also: Web4Deb extruder, RepRap wiki

Developing a plastics recycling add-on for the RepRap 3D printer

Braanker, G.B., Duwel, J.E.P., Flohil, J.J., & Tokaya, G.E. (2010), "Developing a plastics recycling add-on for RepRap 3D Printer". (Online) Available: http://reprapdelft.files.wordpress.com/2010/04/reprap-granule-extruder-tudelft1.pdf (June 30, 2010).


The main theme of this paper is using domestic waste plastic to create new plastic products. A brief research is conducted in the granule-making field. This research functions as the foundation in selecting the right domestic appliance for creating granule of the right size for a small extruder. This had to be done in a way that regular people must be able to copy this process, so this should be as easy as possible. Parallel to this a literature review was conducted to find the right extruder principle for the creation of a mini extruder. A principle was selected and with the help of experts in the field of 3D printing and extruding this principle was evolved to a design. After lots of trial and error this design has been transformed into a working prototype.

With this prototype five tests were conducted. These tests proved to be very valuable in obtaining new insight in problems that still have to be overcome. The most important problems that were faced are getting the right accuracy in the tolerances, heat development in the granule making process and creating a good granule feed flow for the extruder. While trying to solve these problems other point of interest came along. This research can be seen as the starting point of the development of a new kind of domestic extruder.


  • background review of RepRap project and rapid prototyping technology
  • similar goal to this project - conversion of domestic plastic waste to usable feedstock technology.
  • blender used to grind plastic - feedstock for granule extruder.
  • Some successes
    • able to extrude some material into filament
    • groundwork on background research and granule extruder design
    • prototypes constructed and tested
  • further work
    • consistent product of printing quality
    • reduction of wear on screw and extrusion barrel
  • further research and alternatives
    • safety concerns with melting of plastics and hot components
    • effectiveness of tapered screw system
  • things to consider - lateral extrusion (used by most commercial processes) and automation.

Follow Up: different method for grinding plastic - developing world context.


3-D Printing of Open Source Appropriate Technologies

J. M Pearce, C. Morris Blair, K. J. Laciak, R. Andrews, A. Nosrat and I. Zelenika-Zovko, “3-D Printing of Open Source Appropriate Technologies for Self-Directed Sustainable Development”, Journal of Sustainable Development 3(4), pp. 17-29 (2010). Full text: [4]

  • covers the use of 3D printers and open design to improve self-directed sustainable development.
  • a research trajectory is outlined that includes the use of a waste plastic extruder to extend the existing technology to provide complete village-level fabrication of OSATs.

Understanding Open Source Design

Richard Doyle, Erick Froede,David Saint John,Richard Devon, Understanding Open Source Design: A White Paper, In the Beginning Was the Noösphere: Community and Collaboration in Open Source Evolution of Technology, ASEE Proceedings, 2010.

Solid Domestic Wastes as a Renewable Resource: European Experience

V.S Fridland and I. M. Livshits, “Solid Domestic Wastes as a Renewable Resource: European Experience,” Thermal Engineering, vol. 58, no. 1, pp. 79 - 84, 2011.

  • in europe - recycling ratio at 50%
  • 10% of solid domestic waste is plastic
  • only 10% of the total mass of polymeric wastes can be used as primary polymers because polymers can't be mixed due to thermodynamic incompatibility

Public participaton in plastics recycling schemes

Seonaidh McDonald and Rob Ball, “Public participaton in plastics recycling schemes,” Resources, Conservation, and Recycling, vol. 22, pp. 123-141, 1998.

  • Plastics make up 7% of the UK domestic waste stream
  • found a lack of differentiation between groups in terms of age, socio-economic group or household size

Assessment of Plastic Waste Generation and its potential recycling of household solid waste in Can Tho City, Vietnam

"Nguyen Phuc Thanh, Yasuhiro Matsui, Takeshi Fujiwara “Assessment of plastic waste generation and its potential recycling of household solid waste in Can Tho City, Vietnam” Environ Monit Assess. DOI 10.1007/s10661-010-1490-8"

  • 1 month survey of 130 households - ave plastic waste generated/day = 17.24 g/cap/day, 95.6% plastic containers, 45.72% plastic bags

Solid Waste Characterization, Quantification and Management Practices in Developing Countries

Al-Khatib, I. A., Monou, M., Abu Zahra, A. S. F., 2010, "Solid Waste Characterization, Quantification and Management Practices in Developing Countries. A Case Study: Nablus District – Palestine," Journal of Environmental Management, 91(5) pp. 1131-1138

Available online [5]


Solid waste management (SWM) is one of the most challenging issues faced by developing countries that suffer from serious pollution problems caused by the generation of large waste quantities. This paper presents the case study of SWM in the Nablus district – Palestine. Surveys for household residents' and SWM program operators, field investigations, on-site waste measurements and characterizations were conducted. Per capita waste generation rates varied between different localities although trends were similar. Overall, the majority of waste was organic (65.1% by weight), suggesting a strong resource recovery potential in terms of animal feed or compost. Recyclable waste (plastic, paper and card) made up 16.7% by weight the waste composition suggesting an incentive to introduce source separation. Household attitudes complemented the waste characterization study, revealing the main problems faced. SWM operators quoted on the current status, highlighting problems with disposing in unsanitary landfills, ineffective solid waste fees system, increasing solid waste quantities and lacking equipment and experienced personnel. To enhance sustainable SWM, public awareness, funding, expertise, equipment and facilities and other provisions currently lacking or inappropriate must be provided.


  • found significant percentage (7.6%) of waste was plastic.
  • survey included cities, villages and refugee camps in Palestine.
  • shows instance of availability of plastic waste for feedstock in developing world

Open Design-Based Strategies to Enhance Appropriate Technology Development

Buitenhuis, A. J., Zelenika, I., & Pearce, J. M. (2010). Open Design-Based Strategies to Enhance Appropriate Technology Development. Proceedings of the 14th Annual National Collegiate Inventors and Innovators Alliance Conference : Open, March 25-27th 2010, pp. 1-12.

Available online [6]

  • covers the use of the open source philosophy in facilitating appropriate technology and sustainable development.
  • discusses technical, economic and social barriers to such a strategy.
  • frames the philosophy of this project.

Waste for Life: Student learning through international development projects. Who Pays and who benefits?

C. Baillie, "Waste for Life: Student learning through international development projects. Who pays and who benefits?" Materials Today, 11(10) , pp. 6, 2008.

online here


  • Author's experience with a development inititive in Buenos Aires, Argentina.
  • states the importance of good project planning, consultation with local communities and collaboration with reputable organizations when working on development projects.
  • outlines the process Waste for Life undertook in launching their project.
    • first met with interested groups in Argentina
    • designed low cost prototype after determining local needs.
  • developed low cost hot press/compression moulder with the help of Darko Matovic at Queen's University. Used to create cardboard-plastic composite sheets from recycled materials.


  • similar project initiative... low cost means of turning waste plastic in usable material.
  • precautions for projects targeting third world. Proper research, consultation and cost/benefit evaluation must be conducted before implementing development projects.

Assessing Informal Waste Recycling in Kanpur City, India

Zia, H., Devadas, V., and Shukla, S., 2008, "Assessing Informal Waste Recycling in Kanpur City, India", Management of Environmental Quality: An International Journal, 19(5) pp. 597-612.


Purpose – The purpose of this paper is to outline the socio-economic and environmental implications of the informal sector engaged in waste recycling in the city of Kanpur, with special emphasis on the lives of lowest group of people, i.e. waste-pickers, and to discuss various possible scenarios to integrate them with the formal sector.

Design/methodology/approach – The study involved field survey of secondary material markets, followed by the administration of questionnaires to 40 respondents belonging to various segments of the informal sector. The questionnaires were designed to elicit information on the socio-economic characteristics of the respondents. The study was conducted in 2004.

Findings – The study has attempted to delve into the socio-economic conditions of the waste and dump-pickers, the lowest segment of the informal recycling sector. The study of the status of existing alliances of formal-informal sector and the community shows that there is a lot of scope for improvement in the management of solid waste and the condition of the informal waste-recycling sector. Stronger alliances have the potential to improve the services as well as the socio-economic condition of the informal waste-recycling sector.

Research limitations/implications – A very small sample size was selected for this study in the absence of any prior database pertaining to the size, socio-economic conditions of the informal waste-recycling sector.


  • example of plastics availability in developing world context
  • analysis of informal sector recycling
    • perhaps potential for adding value to this process with WPE?
    • social implications?

Solid Waste Recycling and Reuse in Bangkok

Muttamara, S., Visvanathan, C., and Alwis, K. U., 1994, "Solid Waste Recycling and Reuse in Bangkok", Waste Management & Research, 12(2) pp. 151-163.


Materials recovered from solid waste in Bangkok are mainly glass bottles, paper and paper products, plastic products and metals. Materials are separated at three different stages of the collection process: at the source, prior to collection; by the crews of the collection vehicle; and by the scavengers at the dump site. The total daily tonnage of recyclable garbage collected at the source by the waste pickers is estimated at 286 tonnes, about 5% of the garbage collected by the city. There are small scale recycling shops (SSR) located around the main disposal sites where collected materials are sold by the collection crews and the scavengers. The quantity of materials delivered to the SSR shops by the collection crew vary between 1-6 tonnes per day. The amount of materials recovered by the scavengers (at the dump site) varies between 50-150 kg person-1 day-1. Therefore around 7.5% of the solid waste is recycled. In Bangkok both formal and informal sectors manufacture paper pulp, cardboard boxes and magazines from the recyclable paper. Paper products which account for 55% of the total waste stream are considered as the largest "product group" in the municipal solid waste. Recyclable glass (1-3% of the total waste stream) or cullet is used to manufacture plain glasses or cups. Plastics constitute about 10-15% of the waste stream. The benefit/cost ratios of production of most of these industries were reported to be higher than 1.5. In order to enhance recycling, legislative measures need to be introduced and enforced. In Thailand, there is, however, no law concerning recycling. There is no incentive for the consumer to separate solid waste for recycling, as the prices of waste in Bangkok are low and inconsistent. Therefore the pricing system should be more organized for recycling to be more effective.


  • further example of availability of plastics for recycling.
  • evaluation of existing recycling systems
  • potential for value added to recycling process?