Biogas production from the organic fraction of municipal solid waste is enhanced by nickel addition in a two-stage system compared with a conventional digester

The stability of conventional single-stage anaerobic digestion has limitations and requires strategies to enhance biogas production, including two-stage anaerobic digestion (TSAD) and trace metals addition (Ni2+). This research was focused on determining the effect of the supplementation of different concentrations of Ni2+ on a TSAD compared with a conventional process. In the first stage (hydrogen-producing reactor), the Ni2+ concentrations evaluated were 0, 0.1, and 0.5 mg Ni2+/gVSinoculum. The acidogenic effluents were fed in the second stage to produce CH4-rich biogas. The results showed that it was possible to increase the CH4-productivity and the specific methane production by 72% and 105%, respectively, by operating in TSAD compared with the conventional anaerobic digester. The Ni2+ addition improved the stability of the first and second stages, allowing higher biogas production. The microbial communities’ composition at the phylum level changed in each stage.