(684a) Conversion of Material Recovery Facility-Rejected Municipal Solid Wastes Via Anaerobic Digestion and Pyrolytic Combined Approaches

Landfilling and incineration remain the primary methods of waste disposal which contribute significantly to greenhouse gas emissions, water contamination, and habitat loss. As the volume of plastic and organic wastes continues to increase, material recovery facilities (MRFs) play a crucial role in managing these streams through mechanical recycling. However, wastes are frequently rejected by MRFs and diverted to landfills or incineration due to their low quality and contamination. This underscores the need for alternative waste management methods such as chemical recycling. In our study, we explore an innovative upcycling strategy to convert MRF-rejected waste by which the organic waste fraction (OWS) is first subjected to anaerobic digestion (AD) to produce biogas and the residue digestate is co-pyrolyzed with the plastic waste fraction (PWS). By employing different microbial inoculum during AD, we investigate how inoculum selection influences its thermal behavior when co-pyrolyzed with unwashed mixed plastics.

In this study, the OWS was subjected to pilot-scale AD with sewage sludge/food waste-derived inoculum or dairy manure-derived inoculum. It showed that the digestion using sewage sludge/food waste inoculum exhibited a higher methane yield and a shorter lag phase compared to using the inoculum from dairy manure. Co-pyrolysis of the digestate and PWS was performed using a laboratory-scale fluidized bed reactor to produce waxes, oils, chars, and gases. It was found that when co-feeding digestate with PWS produced a lower wax yield and a higher oil and char yield compared to pyrolysis of PWS alone. Furthermore, it was found that co-pyrolysis of PWS with the digestate with dairy manure inoculum produced fewer wax and more oil than co-pyrolyzing PWS and the digestate with sewage sludge/food waste inoculum. Additionally, more char was produced from co-pyrolysis with the digestate with dairy manure inoculum due to the higher fixed carbon content in the given digestate. The wax/oil and char produced from the co-pyrolysis are being explored for their additive applications in asphalt binder and concrete.