One possibility for renewable energy is the use of biogas out of the anaerobic fermentation. To achieve a supply at the point of the need, biogas can be upgraded and fed into the gas grid. The scope of the study is to identify the scenario with lowest overall GHG emissions. The study is based on a holistic life-cycle perspective, taking into account greenhouse gas emissions resulting from cultivating of renewable agricultural products as well as methane losses of upgrading processes etc. Two substrates have been taken into account: 1) ley crops with liquid manure and 2) municipal organic waste. The study provides results for four different upgrading technologies: pressure swing adsorption (PSA), water scrubbing, purification with membranes and the BABIU (Bottom Ash for Biogas Upgrading) method. Bottom Ash from waste incineration plants is used to sequester carbon dioxide as CaCO3. For this method the transport of Bottom Ash is a critical factor. Therefore, five scenarios with different transport distances and means of conveyance (lorry, train) are considered. Other parts of the assessment are biogas compression before feeding into the gas grid and energy conversion of (upgraded) biogas in a combined heat and power plant. GHG emissions of exploration, transport and energy conversion of natural gas have been estimated for the reference-scenario, which is combustion of pure natural gas. The calculation of the scenarios has been carried out by GaBi 4.0 under the use of its scientific databases. Milestones of the comparison between 33 upgrading scenarios are: The overall reduction of GHG emissions may be rather small, e.g. the PSA-scenario for an agricultural biogas plant emits only 10% less greenhouse gases than the use of natural gas for energy supply. Another result shows that the BABIU-method can be regarded as a carbon sink even if the bottom ash has to be transported by train or by lorry.