Effects of initial microbial community structure on the performance of solid-state anaerobic digestion of corn stover

Abstract

High organic loading can easily lead to the accumulation of volatile fatty acids (VFAs) during the early stage of solid-state anaerobic digestion (SS-AD). The accumulated VFAs inhibit the activity of methanogens resulting in digestion failure. This problem represents a major obstacle to the industrialization of SS-AD. A strategy to improve the initial microbial community structure was proposed to prevent acid inhibition in the early stage of SS-AD. To obtain inocula with different initial microbial community structures, the inoculum was treated with acetic acid to increase the abundance of acid-tolerant methanogens and then mixed with the untreated inoculum in different proportions. The effects of the initial microbial community structure on the performance of SS-AD of corn stover were investigated. The results showed that the concentrations of VFAs in the reactors inoculated with the acid-tolerant inoculum alone (treatment 100%) were significantly lower than those of the reactors inoculated with the original inoculum alone (treatment 0%) during the early stage of SS-AD. The peak values of the methane contents and daily methane yields of the reactors inoculated with the acid-resistant inoculum occurred on day six, which was four days earlier than in the reactors inoculated with the original inoculum alone. The results of this study verified that an appropriate initial microbial community structure prevented acid inhibition during the start-up stage and improved the performance of the SS-AD process.