Data in Table 3 show, that scenarios that purify and upgrade biogas to biomethane (Base LS-A(U), Base LS-B(U), Base LS-C(U)) increased the CC impacts, in contrast to reductions in all other small and large-scale biogas utilization scenarios. For instance, Base LS-A(U) generated 191.68 kg CO2-eq, in contrast to 60.58 kg CO2-eq reduction in CHP generation (Base LS, Table 2). This disparity for Base LS-A(U) could be attributed to the use of natural gas based heating to meet internal heat requirements, and the potential CH4 leakage associated with the upgrading and purifying process, which was assumed to be 3% (Pöschl et al., 2010). As CH4 has up to 25 times higher global warming potential of CO2, the CH4 leakage and CC impacts caused by natural gas based heating, easily offset the CC benefits from substituting natural gas with biomethane.