Electrochemical hythane production for renewable energy storage and biogas upgrading

This study investigates the feasibility of using an electrochemical process to convert excess renewable electricity and biogas into hythane gas, which has higher value than biogas and can be stored and transported using current natural gas infrastructure. The electrochemical process utilizes the protons generated in water electrolysis to liberate cations in silicate minerals, which in turn forms metal hydroxide and efficiently captures the CO2 present in biogas. The H2 produced in electrolysis is blended with purified biogas to generate mixed hythane product, which has a higher combustion rate in methane fueled vehicles. Results show that under a voltage of 3.5-4.0 V, the system reduced CO2 in biogas from the original 40% to less than 15% and increased the heat value of the gas product from 534 kJ/mol to over 669 kJ/mol. Preliminary techno-economic analysis showed a net profit of $0.28 per thousand ft.cu hythane generated when standard grid electricity is used, and the profit may be increased by orders of magnitude if excess renewable electricity is used. The process offers a new route for renewable energy storage and upgrade.