Assessment of biomass-to-syngas process routes involving pyrolysis/gasification reactions coupled with a liquid metal bath reactor

The transition to renewable carbon sources requires efficient thermochemical processes to convert biomass into synthesis gas. This study evaluates six biomass-to-syngas process configurations, combining either high-temperature pyrolysis or steam gasification with downstream upgrading in a liquid metal bath reactor. The contribution of this work lies in the first systematic thermodynamic comparison of integrated biomass-to-syngas routes under consistent boundary conditions. Gasification and gas pyrolysis were modelled using a thermodynamic equilibrium approach, while biomass pyrolysis was represented by literature-based product distributions. Process schemes differ in the utilization of pyrolysis-derived charcoal, the implementation of steam gasification, and the inclusion of water separation steps. Across all configurations, the dry syngas composition ranges between 50 and 56 mol-% H₂ and 36–49 mol-% CO. Routes involving only pyrolysis (PR1-PR2) exhibit the lowest heat demand (0.76–0.88 kWh kg−1PG,dry) but have limited carbon and energy efficiencies due to the production of unutilized charcoal. Integrating gasification (PR3-PR6) increases carbon efficiency to 93% and improves energy efficiency from 39 to 47 to 57–65%, reaching approximately 75% when heat recovery is considered. Depending on the selected performance criteria (syngas quality, heat demand, carbon utilization, or process simplicity) multiple routes (notably PR3, PR4, and PR6) offer favorable trade-offs. The results are calculated as thermodynamic upper-bound benchmarks for route comparison. They provide a basis for further experimental validation and process development, particularly regarding tar conversion, carbon reactivity, ash behavior, and scale-up effects in liquid metal bath reactors.