Mechanical Recycling of Plastics

FIGURE 9.11 The avoided energy and carbon emissions per kilogram of PET mechanically recycled. GWP (Global warming potential in CO equivalents). The numbers from other LCA studies can vary shghtly. Source Data from source Kuczenski and Geyer (2009). 

In 1988, the Society of Plastics Industry developed the now-widely used set of seven identification codes for six classes of plastics (the seventh is a catch-all category). These symbols (see Fig. 9.13) molded into the products are intended to 

FIGURE 9.12 A general scheme for recycling of plastics recovered from MSW, illustrating closed- and open-loop pathways. 

FIGURE 9.13 Recycling symbols. PETE is polyester (PET), V is vinyl plastics, and the other category covers aU other resins. 

Over 94% of the US population have access to PET and HDPE recycUng facilities. Therefore, in the United States, PET beverage bottles and HDPE milk jugs enjoy 32.6 and 22.2% rate of recycling, respectively, compared to the single-digit rates for other classes of plastics. Only a smaller group (57%) have access to faciUties that can 

Mechanical recycled plastics can have two forms, recycled sources, post-industrial or post-consumer plastics. Post-industrial recycling of plastics can occur with most plastic products, wherein the plastic from the sprues runners and extrudate is added back into the virgin plastic at the plastic manufacturing plant. Post-consumer recycling process occurs when plastics are made into products, for example, bottles, bags, film, packaging, used by a consumer, collected by a waste disposal company, processed into recycled pellets at a materials recovery facility (MRF), and then sold to plastic companies. 

Mechanical recycling has the appropriate recycling infrastructure established in the United States, Europe, Australia, and Asia. 

Consumer places plastic item in a recycling container. 

Recycling container is collected by a waste management company. 

Materials recovery facility collects the recycling container and segregates the plastics by type into collapsed pallets. 

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Finally, other relevant treatment options for plastics waste include landfill and mechanical recycling. Since these options (unlike Vinyloop and cement kiln incineration) are not even similar to feedstock recycling we discuss them here only very briefly. Mechanical recycling of plastics (be it PVC or other plastics), needs dedicated collection of the plastic waste in question. This is only possible for selected plastic flows (high volumes, recognisable products, products consisting mainly of one plastic). Landfill can accept plastic waste in any waste context (pure plastic type, MPW, mixed materials). I will only address the costs of these alternative technologies. 

The severe limitations on the mechanical recycling of plastic wastes highlight the interest and potential of feedstock recycling, also called chemical or tertiary recycling.17,18 It is based on the decomposition of polymers by means of heat, chemical agents and catalysts to yield a variety of products ranging from the starting monomers to mixtures of compounds, mainly hydrocarbons, with possible applications as a source of chemicals or fuels. The products derived from the plastic decomposition exhibit properties and quality similar to those of their counterparts prepared by conventional methods. 

Pfaendner R. Additives for mechanical recycling of plastics. In Zweifel H, editor. Plastics Additives Flandbook. 5th ed. Munich Hanser Publisher 2001. p 1006. 

The problems with the mechanical recycling of plastic from used cars include ... 

Figure 13.36. Cost-benefit analysis for mechanical recycling of plastics packaging from households in Austria 1996 (/t collected material [21]).

Mechanical recycling of plastic parts can provide the least environmental burdens than waste to energy and sending the plastics to landfill. Use of landfill for plastic parts can provide the highest environmental burdens. 

Automated disassembly of electronic and automotive products would be of considerable benefit to the mechanical recycling of plastics fractions. The results of a Delphi Study [3] provided an indication of the full or partial technical feasibility and economic viability of automated disassembly. 

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