The population of the U.S. has almost doubled over the last 55 years; increasing from 180 million residents in 1960, to 321 million residents in 2015. MSW generation over the same timeframe has steadily increased from 88.1 MT (million U.S. tons) to 262.4 MT. Although the population almost doubled, the amount of waste produced over the same timeframe has increased by almost three fold.
Municipal Solid Waste (MSW) consists of paper and paperboard, glass, steel, aluminum, and other nonferrous metals, plastics, rubber, textiles, wood, food, yard trimmings. The traditional approach to handling MSW is disposal in landfills. In urban areas where space is already limited, landfill locations are becoming more difficult to acquire and maintain, and the waste problem continues to intensify.
The USEPA has developed a hierarchy for the most preferred methods of MSW management, which include: limiting use, recycling (including composting), energy recovery through combustion, and landfilling. Most preferably, consumers and manufacturers are encouraged to reduce their contribution to MSW.
Recycling offers a socially attractive solution to handling MSW and involves separating materials into individual components (paper, glass, metals, plastics, rubber, wood, etc.) and processing the materials into another usable form. Under current recycling methods, plastics, require further separation according to polymer type before further processing.
The burden imposed by additional sorting is significant, and is a major setback to the recycling industry.
To alleviate the burden, plastic materials are often compressed, baled together, stored in shipping containers, and then sent to other countries for manual sorting where the cost of labor is low.
Despite many municipalities offering recycling services, recyclable materials are still destined for landfills, contributing 46.7 percent of the total landfilled MSW in 2015.
Plastics are by far the most landfilled recyclable material, with almost 75.4 percent of all plastics ending up in landfills in 2015.
Pyrolysis is an option for recovering energy and low molecular weight products from MSW, and more specifically waste plastics. Members of the SET team have developed a patented technology to thermally convert unsorted waste plastics from MSW into a low molecular weight distillate distilling in the naphtha boiling range. The produced distillate is useful as a chemical feedstock or as a gasoline blending stock .
In addition, the team has filed two pending patent applications for processes to recover value added products from co-mingled MSW .