Environmental sustainability of syngas biomethanation integrated with a power-to-gas system

• Integrating water and heat reuse improves the sustainability of the PtG system. • Biomethane shows evident environmental benefits over natural gas systems. • Six different scenarios were designed to test the sensitivity of the PtG system. • In all scenarios, electricity demand for the electrolysis unit was the hotspot. The increasing demand for renewable energy and the acute need to mitigate climate change have accelerated interest in sustainable energy solutions such as the production of biomethane. The gasification of lignocellulosic biomass coupled with syngas biomethanation, and a Power-to-Gas (PtG) system offers a promising pathway for producing gas grid-quality biomethane. Although a techno-economic analysis (TEA) for the above technological approach has been performed, its environmental feasibility remains unexplored. Conducting a life cycle assessment (LCA), in addition to TEA, can help to identify the trade-offs between economic and environmental factors in bio-based chemical production. This study integrates an existing TEA study with an LCA study for a small-scale PtG system for gas grid quality biomethane production. The results show that water recirculation and heat reutilization in the PtG system have considerable environmental advantages, such as a reduction in the impact category global warming and fossil resource scarcity by 65–92 %. Sensitivity analysis assessed the effect of biomass type, wastewater treatment, electricity mix, and scale of the system. The findings underscored the potential of the small-scale PtG system as a sustainable substitute for traditional natural gas. Future studies should focus on optimizing the scaling up of the system and incorporating green electricity to enhance environmental and economic performance.