Life-cycle performance of hydrogen production via indirect biomass gasification with CO2 capture

The implementation of CO2 capture into biohydrogen-production systems is seen as a potential solution for greening the energy sector. However, the performance of biocapture strategies needs to be assessed thoroughly in order to guarantee their suitability. In this work, the Life Cycle Assessment methodology is used to evaluate an energy system producing hydrogen from short-rotation poplar biomass through gasification coupled with carbon dioxide capture. The biomass feedstock is dried and milled before being fed to a low-pressure char-indirect gasifier. The syngas produced is conditioned and undergoes a water gas shift process. Biohydrogen is separated from the rest of compounds in a pressure swing adsorption (PSA) unit. The PSA off-gas is burnt for electricity production and the exhaust gas from this power-generation section goes through a two-stage gas separation membrane process for CO2 capture. The results show that the system succeeds in obtaining a negative (i.e., favourable) global warming impact with a low cumulative non-renewable energy demand. Direct emissions to the air, external electricity production and biomass production are the key processes contributing to the evaluated impacts. When it comes to replacing conventional (fossil-based) hydrogen, the biohydrogen product is found to be a better alternative than biohydrogen without CO2 capture only under global warming aspects.