Enhancement of methanogenic performance of anaerobic fermentation systems by propionic acid-degrading bacteria at high straw organic loads

The imbalance between the acid-producing phase and the methanogenic phase is the main reason affecting the efficiency of dry fermentation methanogenesis under high organic loading conditions. In this paper, the effect of adding propionic acid-degrading bacteria to the anaerobic fermentation process at high concentration was investigated using straw as a feedstock for anaerobic dry fermentation. The methanogenic process of anaerobic fermentation was significantly inhibited under conditions of TS = 20 %, whereas the inhibition was lifted by the addition of propionic acid-degrading bacteria, and methane production was increased by 164 %. Under the action of propionic acid-degrading bacteria, the fermentation broth reduced the accumulation of propionic acid during the operation and stabilised the pH at around 7. Propionic acid-degrading bacteria can improve the anaerobic fermentation environment and achieve a balance between the acid-producing and methane-producing phases, which is an effective strategy to improve the efficiency of high-concentration biogas fermentation of straw-based feedstocks.