Deep Dive into the Microaeration of Lignocellulose-Based Anaerobic Digestion at Pilot Scale: Performance, Stability and Microbial Community Analysis

Abstract

Microaeration has emerged as a promising strategy for enhancing anaerobic digestion (AD) of lignocellulosic biomass, although inconsistent results highlight the need for further study especially beyond laboratory-scale. This study tested three different aeration rates (1, 5 and 8 mLO₂/gVS) on pilot-scale anaerobic co-digestion of wheat straw and cattle manure under thermophilic conditions (55°C). Daily injection of 5 mLO₂/gVS achieved the highest methane yield, with a 20.6% increase compared to the non-aerated control digester. Under these conditions, cellulose and hemicellulose degradation reached maximum levels of 75% and 66.3%, respectively. In the microaerated digester, remarkable changes in microbial population were observed. Injection of 1 mLO2/gVS/d and 5 mLO2/gVS/d increased the relative abundance of Lentimicrobium, Turicibacter, and O_MBA03 as well as hydrogenotrophic Methanothermobacter that could contribute to enhanced lignocellulose degradation and biogas generation. At the final and highest oxygen dose (8 mLO₂/gVS/d), methane yield began to gradually decrease. Under these conditions, the microbial profile shifted back to that of the non-aerated digester, suggesting that the activity of certain microbial groups was inhibited. These findings underscore the potential of controlled microaeration to enhance both methane yield and lignocellulosic degradation, offering valuable insights for optimizing AD processes.

Keywords: anaerobic digestion, hydrogen sulfide, manure, microaeration, 16S rRNA gene amplicon sequencing, wheat straw