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Environmental assessment of shredder residue management

TitleEnvironmental assessment of shredder residue management
Publication TypeJournal Article
Year of Publication2006
AuthorsBoughton B, Horvath A
Journal TitleResources, Conservation & Recycling
KeywordsCement manufacturing, Life-cycle assessment, Resource recovery, Shredder residue, Supplemental fuel
AbstractMetal recycling from automobiles, appliances and scrap steel occurs at dedicated metal shreddingoperations. Shredder residue (SR) consists of glass, rubber, plastics, fibers, dirt, and fines thatremain after ferrous and nonferrous metals have been removed. The over 3 million tonnes of SRgenerated in the U.S. each year are managed by landfilling. Material recovery or energy recoveryalternatives to landfilling can be beneficial because of conservation of non-renewable resources andreduction of waste disposal. In this study, the human health and environmental impacts of landfillingand three recovery options (supplemental fuel and mineral feed for cement manufacturing, hydrolysisto light fuel oil, and material recovery for recycling) were quantified and characterized using a lifecycleassessment (LCA) approach. Comparisons were carried out after characterization of emissionsrelative to potential impact categories of global warming, freshwater aquatic toxicity, acidification,eutrophication, human toxicity, photochemical oxidant creation, and terrestrial ecotoxicity. SR recoveryin cement manufacturing could result in 1 million tonnes of coal conservation each year for theU.S. Compared to landfilling, recovery of the fuel and mineral value of SR in cement manufacturingprovides net benefits for all environmental impact characteristics considered primarily due to avoidedcoal mining and landfilling impacts. As much as 750,000 tonnes of recyclable materials could berecovered from SR. Material recovery system impact results were very sensitive to process energyrequirements as well as the assumptions of percent recovery and the specific material types recovered.Hydrolysis of SR could produce 250 million gallons of light fuel oil equivalent per year. Thehydrolysis process requires a significant amount of electricity, the impacts of which are somewhatoffset by the avoided impacts of producing fuels from crude oil resources. Primarily due to high electricityconsumption, both the hydrolysis and material recovery scenarios yielded trade-offs (some netbenefits and some net higher impacts) compared to landfilling. The results of this end-of-life impactassessment showed that the supplement for cement manufacturing option was environmentally bene-ficial to the current practice of landfilling and appears better in comparison to the other managementmethods studied.
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