Biogas upgrading for use as a fuel in buses appears as the most relevant option with respect to most non-toxic impact categories and ecotoxicity, when considering average values for trace gas concentrations and combustion emission factors. Biogas combustion in an engine for CHP production shows the best performances in terms of climate change, but generates significantly higher photochemical oxidant formation and marine eutrophication impact potentials than flaring or biogas upgrading for use as a fuel in buses.