Synergetic promotion of direct interspecies electron transfer for syntrophic metabolism of propionate and butyrate with graphite felt in anaerobic digestion.

Acetate and H2 are the two main substrates for CH4 production, while the CH4 generation from H2 can be regarded as the process of transferring electrons from volatile fatty acids or alcohols to CO2 and H2 acts as an electron carrier. This process is called interspecies H2 transfer (IHT). In addition to IHT there is a direct interspecies electron transfer (DIET) pathway between syntrophs and methanogens in syntrophic metabolism, which can directly transfer electrons to reduce CO2 to CH4 with lower electron losses. In this work, the DIET process is strengthened by adding graphite felt as an electron carrier.