Methane production from waste organic substrates in bioelectrochemical systems

In this research a fully microbial bioelectrochemical system that couples methane production to acetate oxidation has been developed. A hydrogenophilic methanogenic culture and a Geobacter sulfurreducens culture were used as electrocatalytic agents for CO2 reduction into methane (at the cathode) and acetate oxidation (at the anode), respectively. The reactor was operated at ambient temperature and by applying a voltage difference of +900 mV between the electrodes. In spite of methane being formed at low rate because of both low working temperature (18÷21 °C) and low microorganisms' concentration, the coulombic efficiency (i.e. the recovery of electric current into methane) was high (around 80%). Overall, the process needs to be improved in terms of methane production rate and it is expected that higher performance could be achieved over time in the reactor by gradually increasing the biocatalyst’s density.