Catalytic co-pyrolysis of lignocellulosic biomass and plastic waste for biofuel production: a review

The rising global demand for energy, along with the growing challenges posed by biogenic waste and single-use plastics, has heightened interest in sustainable technologies that convert waste into energy. Pyrolysis has emerged as a promising thermochemical method for the concurrent valorization of organic waste into valuable products, including bio-oil, biochar, and pyro-gas. The synergistic interactions between biomass and plastics during co-pyrolysis, especially mechanisms involving hydrogen transfer and free-radical stabilization, can significantly boost bio-oil yield and quality while reducing the production of unwanted byproducts, such as excessive biochar, tar, and non-condensable pyro-gas. The addition of catalysts, such as active metals, metal oxides, zeolites, activated carbon, and bimetallic systems, is crucial in directing reaction pathways, enhancing conversion efficiency, and customizing product selectivity toward valuable hydrocarbons. This review thoroughly evaluates the impact of feedstock characteristics, operational conditions, and catalytic functions on mono-pyrolysis and co-pyrolysis performance of biomass and plastic waste, focusing on the mechanisms that control hydrogen transfer, free-radical generation, stabilization, and interactions. The specific effects of different catalysts on the production of hydrocarbons and aromatics are systematically examined. The review also reports on the opportunities and limitations of catalytic pyrolysis systems, along with the prospects for lifecycle and techno-economic analyses, and for machine learning as important aspects for technology scale-up, commercialization, and informed decision-making. By combining co-pyrolysis with advanced catalytic systems, this review highlights a viable pathway for circular carbon utilization, improved resource efficiency, and sustainable management of biomass and plastic waste. • Co-pyrolysis of biomass and plastics can improve the fuel qualities of liquid products. • Temperature, heating rate, and vapor residence time of pyrolysis impact product distribution. • Catalysts like zeolites and metal oxides enhance product quality and efficiency. • Liquid products from pyrolysis serve as a source of clean fuel and platform chemicals. • Co-pyrolysis supports circular economy and sustainable waste-to-energy solutions.