Stimulation of Biomethane Productivity in Anaerobic Digestion Using Electro-Conductive Carbon-Nanotube Hollow-Fiber Media

The production of biogas was promoted via direct interspecies electron transfer (DIET) by employing electro-conductive carbon-nanotube hollow-fiber media (CHM) in anaerobic digestion. Experimental results showed a positive effect of CHM presence on CH4 productivity with 34% higher CH4 production rate than that of in the presence of non-electroconductive polymeric hollow fiber media. An increased CH4 production rate was due to the shift in the microbiome with more abundant Pelobacter (10.0%), Geobacter (6.9%), and Methanosaeta (15.7%), which play key roles in promoting CH4 production via syntrophic metabolism associated with DIET. Microscopic morphology analysis, using confocal laser scanning microscopy and scanning electron microscopy, exhibited that several living cells were attached with electro-conductive pili on the CHM surface, thereby facilitated electron transport between microbial cells.