(298a) Economic and Environmental Analysis of Plastics Pyrolysis after Secondary Sorting of Mixed Plastic Waste

Plastic usage has skyrocketed in recent years as plastics have become an essential material to everyday life. Unfortunately, recycling rates have not matched the increased growth, with the majority of waste plastic (approximately 80%) currently landfilled in the United States. New chemical recycling technologies, i.e., pyrolysis, are needed to increase the recycling rates of waste plastics. However, pyrolysis faces challenges because of bridging the feed into the hot reactor and with the high cost of waste plastic feedstock. In this work, a novel liquid-fed pyrolysis process, designed to eliminate bridging, was modeled through process simulation using Aspen Plus and then assessed over a range of processing conditions. A secondary sortation of inexpensive mixed plastic waste from material recovery facilities provided a low-cost feedstock (PE, PP) for pyrolysis.

A techno-economic analysis was conducted using a discounted cash flow analysis to analyze the minimal selling price (MSP) of pyrolysis oil as an alternative to fossil naphtha. Naphtha is a commodity chemical feedstock for plastics production. A life cycle assessment was conducted to determine the "gate to gate" greenhouse gas emissions and energy consumption of pyrolysis oil compared to fossil naphtha using SimaPro. Our analysis found favorable economic and environmental results for pyrolysis oil when compared to fossil naphtha ($561/t, 0.52 kg CO₂ eq./kg). A sensitivity analysis found the economic results most responsive to waste plastics feedstock costs, pyrolysis gas sales, operating capacity, and waste disposal costs. Finally, a comprehensive interrogation of the TEA and LCA parameter space will be presented to provide an understanding into the relationships and trade-offs between the economic and environmental impacts of this novel process. The lowest minimum selling price and greenhouse gas emissions for pyrolysis oil were achieved by recovering and selling sorted PET from the mixed plastic bale and implementing process heat integration surrounding the pyrolysis reactor.