Autothermal Biomass and Plastic Cogasification for Hydrogen-Rich Syngas Production: Process and Sustainability Assessment

Abstract Transitioning to sustainable energy and chemical systems requires circular pathways that valorize waste, manage carbon emissions, and meet global energy demands. Plastic waste and biomass cogasification in the presence of CO2 to produce hydrogen-rich syngas offer viable pathways for power generation and chemical synthesis, but their technical feasibility and environmental implications remain underexplored. To address this gap, we present a holistic framework for this emerging technology, including gasification, water–gas shift reaction (WGSR), CO2 capture and recycle, and life cycle assessment (LCA). Our analysis reveals an optimized plastic-to-biomass ratio of 1:4 and a steam-to-feed ratio of 0.3:1 at 900 °C and produces syngas containing 62 mol % combined H2 and CO, at a 1.2:1 ratio and a lower heating value of 8.6 MJ Nm3–. Process intensification of the produced syngas via the WGSR increased the H2/CO ratio to 2:1 while preserving its energy content, and 91% of the CO2 in the syngas is removed via amine absorption and partially recycled to the cogasification feed stream. Finally, LCA highlights that syngas from plastic–biomass cogasification outperforms fossil feedstocks for electricity generation and methanol synthesis. Impact reductions exceed by 40% across multiple endpoint indicators, including global warming, fossil depletion, terrestrial acidification, and particulate matter formation potentials. Our results underscore plastic–biomass cogasification as a circular strategy for syngas production aimed at renewable energy or chemical synthesis.