Improved methane production from anaerobic digestion of liquid and raw fractions of swine manure effluent using activated carbon

Abstract

The capacity of granular activated carbon (GAC) to increase methane productivity during the anaerobic digestion of liquid and raw fractions of swine effluent was evaluated. Microbial incubations were conducted with GAC at a particle size of 0.6 mm and inoculated with anaerobic sludge. The volume of methane produced was 1.42- and 1.33-fold higher in the raw effluent (RE) and liquid fraction (LF), respectively, compared to the controls lacking GAC. The conversion efficiency was also improved up to 94.1% by GAC addition. The methane production rates in GAC incubations with RE were increased 37.8% and 11.5% with LF in relation to the controls. The addition of GAC also impacted the lag phase, which was evidenced by a decrement of 66.6% and 18.7% for LF and RE respectively, compared to controls. High percentages of Methanosaeta species were found in all experimental conditions ranging from 74 to 88% of the archaeal community. However, when RE was employed as the substrate for methanogenesis, the presence of GAC increased 13.2% the composition of Methanosaeta respect to the control.