Nanobubble water promotes anaerobic digestion of high-solids cattle manure under mesophilic and thermophilic conditions

Abstract

The gradual increase in cattle farming has led to a huge production of cattle manure (CM), but the conventional treatment methods are less efficient. In this study, the treatment method of anaerobic digestion (AD) of high-solids CM by combining nanobubble water (NBW) with different gases was proposed to present a new idea for the reduction, harmlessness, and resourcefulness of CM. It was found that the performance of the digester with added NBW was better than the control. Among them, the cumulative methane yield T-Air: 227.09 mL g−1 VSadded and T-CO2: 226.12 mL g−1 VSadded increased by 17.72 % and 17.22 %, respectively, compared with the control T: 192.90 mL g−1 VSadded under thermophilic conditions. Under mesophilic conditions, M-Air: 162.39 mL g−1 VSadded increased by 9.68 % compared with control M: 148.05 mL g−1 VSadded. Microbial communities analyzed at the genus level revealed that the relative abundance of bacteria favorable to hydrolysis and acid-producing processes, such as Defluviitalea, Haloplasma, and Bacillus, increased to varying degrees. Moreover, the relative abundance of archaea favorable for methanogenesis, such as Methanoculleus, Methanobrevibacter, and Methanosarcina, also increased to varying degrees. Therefore, the addition of NBW promoted the hydrolysis of high-solids CM, enhanced the stability of the reaction, improved the methanogenic performance, and increased the RA of favorable genera, which ultimately led to a better performance of the AD of high-solids CM.