Economics of Recycling Thermosets 920802

The technology to recycle thermosets exists as reported in the bibliography. The purpose of this article is to explore the economics of recycling thermosetting sheet molding composite (SMC) wastes generated by the molding plants. The principles discussed here equally apply to other thermoset composites and, in general, to other plastics. A recycling model is presented that will accept waste SMC as input and delivers value-added end product for reuse as output. Recycling methods considered are briefly reviewed. A cost model is developed to illustrate the economics of various proposed recycling paths. SMC is assumed to be shredded at the molding sites and delivered to the “RECYCLING PLANT” (RP) in lieu of being shipped to a landfill site. A fee equal to landfill fees is charged for this service; a source of income for the RP. It is further assumed that the RP has various pieces of equipment to separate metals, grind, mill, recover fiber, pyrolyze and to reprocess the waste stream into reusable and value-added products.
Operating variables were altered to determine the effects of tipping fees, re-sale value of the recycled materials and volume, among others. The model shows that as the tipping fees rise and higher value-added uses are found for the end products, the profitability of the operation improves. The model shows that, based on the assumptions made, the fiber recovery path is currently the most economically desirable, followed by fine milling and pyrolysis. However, fine milling and fiber recovery without pyrolysis do not offer a complete solution as uncured SMC cannot be directly processed by these methods. This will remain true until the value of pyrolysis end products and/or tipping fees increase, or pyrolysis costs can be decreased, or some combination of these movements makes pyrolysis economically viable. Furthermore, compliance with the Clean Air Act may make handling and disposal of these materials more stringent due to styrene emission.


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