Co-pyrolysis of Rice Straw With Polystyrene, Polyethylene Terephthalate, and LDPE With Focus on Product Distribution and Synergistic Effects

Abstract Co-pyrolysis of biomass and plastics offers synergistic effects, improves the distribution of pyrolysis products, and also enhances their quality. In this study, rice straw (RS) was co-pyrolyzed with polystyrene (PS), polyethylene terephthalate (PET), and low-density polyethylene (LDPE). Thermogravimetric analysis (TGA) and pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS) diagnostics were used to examine the co-pyrolysis characteristics, synergistic effects, and the impact of pyrolysis temperature on the product distribution. The study revealed differential kinetic properties in the co-pyrolysis reactions between the three plastics and rice straw. The weight loss peaks of the mixed systems exhibited a bimodal characteristic, and the activation energies of the mixtures were lower than those of the single feedstocks. Furthermore, the pyrolysis behaviors differed significantly from the individual components. The co-pyrolysis of RS-PET enhanced the production of oxygenated and nitrogenous compounds, while RS-LDPE significantly promoted the formation of aliphatic hydrocarbons, achieving the highest yield (91.49%) at 700 °C. In contrast, the co-pyrolysis of RS-PS markedly increased the yield of monocyclic aromatic hydrocarbons (MAHs), with a peak yield of 81.10% at 650 °C. Compared with RS-PET, both RS-PS and RS-LDPE provided effective generation of high value-added products, demonstrating superior co-pyrolysis effects. These findings indicate that altering the type of plastic and pyrolysis temperature can directionally regulate the product composition, offering new insights into improved quality of bio-oil production. The results indicate that the product composition can be directionally regulated by altering the type of plastic used and pyrolysis temperature, providing new insights for the enhanced bio-oil quality.