Energy balance and global warming potential of biogas-based fuels from a life cycle perspective

• Three gas-to-liquid fuels produced from biogas compared with CBG and LBG in simulations.
• Energy efficiency and global warming potential (GWP) were assessed.
• CBG, methanol and DME had the highest specific fuel productivity.
• CBG and LBG gave the highest GWP.
• DME showed the best overall performance of all the fuels compared.

Biogas is a multifunctional energy carrier currently used for co-generation or compressed biomethane as vehicle fuel. Gas-to-liquid (GTL) technology enables conversion of biogas into other energy carriers with higher energy density, facilitating fuel distribution.The energy efficiency and global warming potential (GWP) for conversion of biogas to compressed biogas (CBG), liquefied biogas (LBG), Fischer–Tropsch diesel (FTD), methanol and dimethyl ether (DME) were studied in a life cycle perspective covering the technical system from raw biogas to use in city buses.CBG, methanol and DME showed the best specific fuel productivity. However, when fuel distribution distances were longer, DME, LBG and methanol showed the best energy balance. Methanol, FTD and DME emitted half the GWP of LBG and CBG. Choice of electricity mix had a large impact on GWP performance. Overall, taking into account the different impact categories, combustion properties and fuel yield from raw biogas, DME showed the best performance of the fuel conversion scenarios assessed.