LAUSR

Abstract Activated carbon can not only alleviate toxicity of harmful substances to microorganisms but also enhance direct interspecies electron transfer (DIET) during anaerobic digestion. Therefore, this study aimed at investigating the effect of powder activated carbon (PAC) on anaerobic digestion of Flammulina velutipes residues which were pretreated by aerobic composting with production of alcohols and volatile fatty acids (VFAs). Results show the starting time of methane production peak period emerged at the 4th day for the PAC-treatment comparing with the 15th day for the control, implying PAC application enhanced methane production rate significantly by alleviating the inhibitory effect of isopropanol and propionic acid regarding remarkable biodegradation of alcohols and VFAs from composting. A Gompertz curve fitting also indicated that the PAC-treatment possessed the greatest rate constant of biogas (0.1847) and methane (0.1793) production. Fourier transform infrared spectra analysis indicated that PAC could facilitated to the decomposition of recalcitrant cellulose, protein, lipid and polysaccharides. Furthermore, addition of PAC could enrich more vadinBC27_wastewater-sludge_group with electrochemical activity and Methanosarcina with ability to accept electrons from carbon-based mediator, suggesting that vadinBC27_wastewater-sludge_group might participate in DIET with Methanosarcina and therefore PAC could promote syntrophic association between bacteria and methanogens via DIET. Graphic Abstract