Life cycle energy comparison of different polymer recycling processes

Abstract

AbstractThis article is to demonstrate a consistent, transparent approach to comparing plastic recycling technologies. The uniform comparison is based on each recycling technology having the same input (waste PET), mass basis for processing, output as new product (new PET product or fuels), and the concept of the same multiple (two) closed loops of recycling. We seek to demonstrate, at the fundamental technology level, how energy use differentiates plastic recycling technologies. Five polymer‐recycling processes are examined using a uniform, quantitative comparison of 1 kg PET bottles (about 100 single‐serve 0.5 L water bottles): direct reuse, 100% mechanical recycled content, depolymerization, and re‐polymerization of new resin and 100% to bottles, reclaiming energy value, and landfill. The life cycle energy benefit for recycle technologies with varying product recycled content can be determined by a single equation. All these recycling processes resulted in total energy reduction per kg PET bottles compared to landfilling. The base case of three cycles per 1 kg PET bottles is used to explore the influence of recycling loops. Direct reuse gave a 290% energy improvement with three cycles. Other processes, all at 100% recycle content, gave improvements: mechanical (250%), depolymerization/repolymerization (150%), and energy recovery (120%). More information would improve the analysis of the depolymerization process assessment. These preliminary data describe the analyses that are needed to quantify the benefit of recycling any polymer using these recycling methods. The Environmental Genome (“EGI”) provides valuable information for these calculations as it contains the polymers and supply chains for such evaluations.