Quantitative Comparison of Life Cycle Assessments of Advanced Recycling Technologies for End-of-Life Plastics

Abstract

There is growing urgency to both increase plastic recycling rates and reduce the impact of plastic waste on the environment. Mechanical recycling rates for plastics in the United States have only slightly increased from 6% to 9% between 2000 and 2015 and have plateaued near 9% despite continued efforts to increase the rate. Therefore, evaluation of additional options that can increase recycling rates must occur to establish a comprehensive approach to keeping used plastics in the economy. The advanced recycling (AR) technologies analyzed in this paper have the capability to address the unrecycled plastics, representing a viable future path that can improve the plastic recycling rate and reduce resource use and environmental impacts. A rigorous quantitative assessment has been done of a subset of recent life cycle assessments (LCAs) resulting in thirteen LCAs being selected using criteria based on processing capacity and technology readiness level. Comparisons across those LCAs resulted in a quantitative greenhouse gas (GHG) emissions reduction ranging from −267% to 566% with the implementation of AR technologies. Specifically, mixed plastic (MP) streams converted to polyolefins via pyrolysis produced 185% less carbon dioxide equivalent (CO2eq) emissions compared to conversion to energy for heat and power production. Alternatively, MP processed via pyrolysis produced 267% more CO2eq emissions than landfilling. Importantly, 30 other comparative scenarios were presented by the chosen LCAs as sensitivity analyses, with GHG emissions similarly ranging from increases to reductions, with the preponderance of the data indicating reductions. The various impact categories assessed, in addition to GHG emissions, for the AR technologies ranged from favorable, with the pyrolysis of MP offering a 97% reduction in fossil depletion compared to waste to energy, to unfavorable with the pyrolysis of MP offering a 400% increase in fine particulate matter compared to 30% municipal solid waste incineration and 70% refuse-derived fuel.