A review on interactions and reactor implications during pyrolysis of biomass- and plastic-based waste

Meeting the growing demand for sustainable fuels and chemicals requires the adoption of alternative raw materials to replace those obtained from fossil fuels. The co-pyrolysis of biomass- and plastic-based waste is seen as a highly promising avenue for the creation of sustainable fuels and chemicals. A comprehensive knowledge of the components' interactions during co-pyrolysis is essential for understanding the formation pathways of valuable compounds and realizing a viable and sustainable valorization of biomass and plastic waste. This review presents an integrated interactions-to-reactor perspective on co-pyrolysis of biomass- and plastic-based wastes. Co-pyrolysis chemistry of lignocellulosic and non-lignocellulosic biomass with different types of plastics is discussed with an emphasis on hydrogen transfer, mineral-assisted cracking and deoxygenation, heteroatom migration, and secondary vapor-phase reactions. Non-lignocellulosic biomass-based wastes including marine biomass, sewage sludge, food waste and other lipid-rich residues that introduce high ash, protein, and oxygen functionalities are discussed to understand reaction pathways. Mechanisms that provide insights into char formation during co-pyrolysis are also included. The review further highlights recent advances in reactor concepts (fixed-bed, fluidized-bed, auger, microwave-assisted, and catalytic systems) and examines how heat and mass transfer couple with chemistry to control selectivity. Finally, applications of CFD tools to co-pyrolysis systems are also outlined.