Integration of biomass gasification and water electrolysis: Importance of sweep gas selection

Water electrolysis and biomass gasification have emerged as promising renewable and environmentally friendly methods for producing hydrogen, and there is growing interest in integrating these two technologies. However, the role of sweep gas, a crucial factor in overcoming challenges associated with water electrolysis, has been largely overlooked in most integrated studies. To bridge this gap, the effects of three types of sweep gases (air, oxygen, and steam) on the performance of integrated systems were evaluated in this study. The process utilizing steam as the sweep gas achieved the highest energy efficiency of 72.42 %, whereas the use of air resulted in the lowest efficiency of 70.00 %. A similar trend was observed in the exergy analysis, where the use of steam resulted in the highest exergy efficiency of 64.53 %, while air led to the lowest exergy efficiency of 62.27 %. The process using air as the sweep gas demonstrated the most cost-effective levelized cost of hydrogen (LCOH) of $1.28/kg, which was 9.0 % and 3.0 % lower than those of the processes using oxygen and steam, respectively. This study is the first to examine the influence of sweep gas types on integrated process performance, highlighting the importance of sweep gas selection. The proposed approach can be a viable alternative, as most previous studies either overlooked sweep gas or used oxygen and steam as sweep gases. These findings provide new strategies for optimizing integrated system performance and are expected to significantly contribute to the integration of green hydrogen production systems with processes other than biomass gasification.