Improving the efficiency of anaerobic digestion: Domesticated paddy soil microbes enhance the hydrolytic acidification of rice straw and pig manure

Abstract

Improving the efficiency of hydrolytic acidification is critical for methane production from agricultural waste. This study is the first to apply domesticated paddy soil microbes to (DPSM) enhance the hydrolytic acidification of rice straw (RS) and pig manure (PM) to obtain acidizing fluid for anaerobic digestion (AD). At a substrate concentration of 20%, the inoculation of an RS-PM mixture (1:3) with 35% DPSM degraded the volatile solids by 48.1% and yielded 6.8 g/L of volatile fatty acids and 4.7 g/L of acetic acid after seven days of hydrolytic acidification. After 10 days of subsequent AD, the cumulative methane production of the acidizing fluid was 304.96 mL/g COD, similar (P ＞ 0.05) to the control (318.27 mL/g COD). However, the methane production time decreased by 43.4% (from 30 to 17 days), thereby improving the AD efficiency. Inoculation with DPSM is therefore an effective pre-treatment for agricultural waste for methane production.

Keywords: Domesticated paddy soil microbes; Hydrolytic acidification; Methane production; Pig manure; Rice straw.