Progress on co-processing of biomass and plastic waste for hydrogen production

Sustainable energy sources are a solution to the increase in energy demand as a result of population growth. Pyrolysis and gasification are thermochemical processing techniques that can be used to convert biomass and plastic waste into energy. Co-processing (co-pyrolysis or co-gasification) has been identified as one of the major thermal techniques, which provides a significant framework for converting waste into fuels with higher hydrogen concentrations. The production of hydrogen from biomass and plastic waste using these techniques is being explored for its high conversion efficiencies and low processing costs. Catalysts and acid pre-treatment are used to improve gas production while reducing tar content. The best gasification agent is steam with oxygen. A thorough review of the literature revealed only a few studies on the co-pyrolysis and co-gasification of plastics and biomass for syngas production, particularly hydrogen-rich syngas. Therefore, this review focuses on H2 production from plastics and biomass by using co-pyrolysis and co-gasification. This critical discussion is aimed at improving the understanding of the subject, its relevant aspects, and its significant perspectives. In addition, it also deals with the mechanism and relevance of these techniques, along with their techno-econome evaluation. Compared to pyrolysis or gasification of plastic waste or biomass alone, co-processing often has significant impacts with improved final products. The reaction of molecules during co-processing and the transition of hydrogen from plastics to biomass derivatives account for these improved properties. H2 concentrations increase with increasing temperature in the presence of different catalysts. Even at lower temperatures, CO2 adsorption increases H2 production and enhances syngas quality while reducing the tar content. Finally, to provide sustainable energy for future generations and enasure an efficient system for sustainable waste management, further research is required to increase efficiency and hydrogen yields.