Synergistic effects between cellulose and low-density polyethylene (LDPE) during their co-pyrolysis for polygeneration

Co-pyrolysis of biomass and plastic enables simultaneous production of biochar, bio-oil, and gaseous products and also offers a pathway for waste recycling and valorization. This research investigates the synergistic effects of co-pyrolysis of cellulose and low-density polyethylene (LDPE) by TG-FTIR and a fixed bed reactor. Kinetic analyses by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models showed that the average activation energy ( E a ) for pyrolysis of cellulose and LDPE individually was 184.1 and 267.4 kJ/mol, respectively, whereas that of 1:1 cellulose/LDPE mixture decreased to 150.4 kJ/mol. Pyrolysis experiment showed that co-pyrolysis suppressed biochar formation while enhancing yields of bio-oil and gaseous products. Co-pyrolysis enriched carbon and removed oxygen in biochar, resulting in maximum graphitization degree and higher heating value (HHV) of 31.51 MJ/kg at 700 °C. Additionally, co-pyrolysis decreased the relative content of light oxygenated compounds in bio-oil. The inhibitory effect of co-pyrolysis on aldehydes, ketones, and acids was maximum at 600 °C. Co-pyrolysis enhanced CH 4 and H 2 formation and suppressed CO 2 and CO. At 700 °C, CH 4 and H 2 proportions peaked to 19.3 vol% and 13.1 vol%, respectively, during co-pyrolysis. This research provides fundamental insights into the synergistic mechanisms of biomass and plastic co-pyrolysis for polygeneration.