Microbial mechanism for improving biogas production performance from boiling acidified pig manure feedstock

A short heat treatment (HT, 90 °C-100 °C, 5 min) was applied to two-phase anaerobic digestion (TPAD) of pig manure (PM) to investigate its effect on microbial inactivation in the acidified feedstock during the methanogenic phase. The results showed that no differences in biogas production at organic loading rate (OLR) below 4.28 g volatile solid (VS)/(L·d). However, as the organic load increased, the TPAD with HT exhibited greater biogas production and volatile organic acids removal than the control. By stabilizing pH, digestion of HT acidified feedstock at 9.56 g VS/(L·d) OLR resulted in a biogas yield of 340.1 mL/g VS, exceeding the control by 35.6 %. HT enriched syntrophic bacteria, Methanothrix and Methanobacterium methanogens, and one-carbon metabolizing genes in the methanogenic phase, enhancing energy storage and conversion. Accordingly, acidification followed by HT could be a potential method to improve microbial community and load tolerance in methanogenic phase of TPAD.