Flexible control of biohythane composition and production by dual cathodes in a bioelectrochemical system

Flexible control of CH₄/H₂ ratio in biohythane is important to its applications but remains a challenge. Herein, a dual-cathode bioelectrochemical system (BES) was developed for achieving biohythane production with controllable composition through adjusting external resistance. The BES was started as a microbial electrolysis cell to produce hydrogen in both cathodes ("H₂-cathode") and then evolved to produce methane production in one cathode with inoculation of anaerobic sludge ("CH₄-cathode"). When increasing the external resistance of the H₂-cathode from 10 to 330 Ω, its H₂ production decreased from 173 ± 11 to 8 ± 2 L m^-3 d^-1. This redistribution of electrons has benefited the CH₄-cathode that had an increased CH₄ production from 25 ± 3 to 90 ± 5 L m^-3 d^-1. The CH₄/H₂ ratio increased from 0.14 to 11, making biohythane more applicable to natural gas engines. Those results will help to formulate a BES-based approach to accomplish controllable biohythane production.