A techno economic analysis of the power to gas route

A successful implementation of Germany's energy transition to renewable energy supply requires a strong interlinking between different sectors such as energy supply and mobility which is labeled as sector coupling. Power-to-methane is one option for sector coupling in a future energy system. Here, a techno-economic analysis is presented that investigated different pathways with eight different scenarios. The first four use renewable hydrogen via electrolysis from wind combined with different CO2 sources, i.e., from biogas production, tail gas from power plants, provided by a supplier and from direct air capture. The remaining four scenarios based on conventional hydrogen and carbon dioxide sources are considered for the sake of comprehensive coverage. For all scenarios, a process analysis provides important insights. The economic analysis shows methane costs in the range of (sic)3.51-(sic)3.88 per kg for all optimized process schemes on the power to gas route. Therefore, no economic benefit can be achieved for a gas provider using power-to-methane in his gas grid. Nevertheless, with regard to the GHG reduction target of 80-95% through 2050, green solutions are of special interest. The results of the ecological analysis show a highly promising pathway that makes use of liquid manure. The avoidance of fertilizing soil by dispensing large amounts of liquid manure achieves improvements in acidification and eutrophication of soil and ground water. A switch from fossil diesel to fossil natural gas only yields a reduction of between 7%-22%. Good results were already achieved by applying municipal waste or dry manure offering an 87% GHG reduction. Liquid manure offers a credit of -78.1 g CO2,eq/MJ(f) CH4 instead of GHG emissions on the order of 70.4 g CO2,eq/MJ(f) CH4 using fossil CNG on a well-to-wheel basis.