Lignocellulose usually requires pretreatment to improve biogas production. To enhance lignocellulose biodegradability and improve anaerobic digestion (AD) efficiency, different types (N2, CO2, and O2) of nanobubble water (NW) were applied in this study as soaking agent and AD accelerant to increase the biogas yield of rice straw. The results showed that the cumulative methane yields of treating with NW in two-step AD increased by 11.0%-21.4% compared with untreated straw. The maximum cumulative methane yield was 313.9±1.7 mL/gVS in straw treated with CO2-NW as soaking agent and AD accelerant (PCO2-MCO2). The application of CO2-NW and O2-NW as AD accelerants increased bacterial diversity and relative abundance of Methanosaeta. This study suggested that using NW could enhance soaking pretreatment and methane production of rice straw in two-step AD; however, combined treatment with inoculum and NW or microbubble water in the pretreatment needs to compare in future.
Keywords: Accelerant; Methane production; Microbial community; Nanobubble water; Soaking pretreatment.
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