Methanogenic Digestion of Lignocellulose Residues under Conditions of High-Rate Acidogenic Fermentation

Abstract

A semicontinuous module reactor was operated under methanophilic conditions to effect rapid solid anaerobic digestion of lignocellulose substances for waste utilization and stabilization. This was achieved by recovering the methanogenic phase from the high-rate acidogenic fermentation phase. The influence of a total carbon to nitrate ratio (C/N(NO3)) of the lignocellulose feed on the development of methanogens from a high-rate acidification fermentation phase was first investigated. The effects of pH adjustment and dilution of the high-rate acidification fermentation phase using the two-phase anaerobic digestion configuration were subsequently evaluated. The results showed that an increase in the C/N(NO3) ratio of the feed substrate could promote the development of methanogens as a result of the restraint of denitrification during or after the acidification fermentation phase. In-process neutralization of the digestion pH and dilution of the digestion intermediate products could reduce the inhibition from the high-rate acidification fermentation phase. The integrated digestion process promoted the biotransformation of lignocellulose residues from the high-rate acidification phase to the methanogenic phase and ultimately stabilized digestion.