Life cycle assessment of alternative biogas utilisations, including carbon capture and storage or utilisation

•Biogas upgrading is environmentally and energetically favourable over combustion.•Storage or utilisation of the captured CO2 has larger savings than biogas upgrading.•Upgrading, CO2 storage or utilisation perform well in all impact categories.•The energy system has a substantial impact on the environmental performance.•Methanation provides large climate change savings only in renewable energy systems.