Economic assessment of membrane-based power-to-gas processes for the European biogas market

Four different power-to-gas process chains implementing catalytic methanation and membrane upgrading are presented. Their economics for synthetic natural gas production and hydrogen storage are assessed for the first time in the context of multiple different European gas grid standards by simulation. Influence of two different fermentation setups for biogas production as well as pressure levels from 6 to 15 bar and catalyst specific flow rates from 100 to 150 Nl/(h g(CAT)) were considered. Based on this simulation an economic analysis was done. Capital expenditures and operational expenditures for electrolysis, methanation, membrane gas upgrading, and compressors of each chain are presented. It is shown that the integration of a simple recycle of the off-gas stream can reduce the costs from up to 2.93 (sic)/Nm(3) produced synthetic natural gas to at least 1.63 (sic)/Nm(3). Hydrogen storage cost can be decreased from up to 1.81 (sic)/Nm(3) stored hydrogen to at least 0.95 (sic)/Nm (3). Variation of the fermentation setup only leads to savings in the range of 0.03-0.08 (sic)/Nm (3) synthetic natural gas if off-gas recycling is included. Catalyst specific gas flow rate is shown to be of neglectable influence, contributing less than 0.01 (sic)/Nm(3) produced synthetic natural gas or stored hydrogen. Pressure influence is more pronounced at up to 0.10 (sic)/Nm(3) produced synthetic natural gas and up to 0.05 (sic)/Nm(3) stored hydrogen. Optimal operation pressure for simple off-gas recycling is shown to be below 10 bar.