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.