Environmental assessment of enhanced biomethane production from biogas via membrane-based upgrading

The concerns regarding energy security and climate neutrality are increasing the need for process optimisation as well as the development of novel technologies to support a sustainable energy transition. Biomethane produced from biowaste offers a sustainable pathway and can potentially improve the environmental profile of gaseous fuels. This study presents a comprehensive environmental assessment of the enhanced production of biomethane by catalytic methanation of biogas combined with membrane-based gas upgrading. In this assessment, we developed a detailed inventory for the membrane module and implemented it with the remaining process units. Seven midpoint categories were selected from the ReCiPe 2016 (H) method, and a functional unit of 1 MWh of biomethane produced is applied. Our study shows that the electricity demand for electrolysis is significant, but using renewable sources like wind power could greatly reduce the process footprint across all impact categories evaluated. Among the configurations assessed, a single-stage membrane separation combined with off-gas recycling to the catalytic methanation step based on biogas from one-stage fermentation (PM 1F) provides the best environmental benefits: 137.15 kg CO 2 eq. for global warming potential, 0.25 kg SO 2 eq. for terrestrial acidification, 0.09 kg PM2.5 eq. for particulate matter, 0.13 kg P eq. for freshwater eutrophication, 5.37 m 2 a crop eq. for land use, 35.69 kg oil eq. for fossil resource use and 3.68 m 3 for water consumption. • Catalytic methanation of biogas combined with membrane separation for enhanced biomethane production in Austria. • Membrane module production is included in the system boundaries and benchmarked with an available dataset. • Membrane separation and off-gas recycling reduce the overall process footprint. • Electrolysis is a hotspot, but is mitigated under 2040 net-zero energy scenarios.