Simultaneous addition of CO-nanobubble water and iron nanoparticles to enhance methane production from anaerobic digestion of corn straw.

In this research, CO-nanobubble water (CO-NBW) and iron nanoparticles (FeNPs) were added simultaneously to exploit individual advantages to enhance the methanogenesis process from both the stability of anaerobic digestion (AD) system and the activity of anaerobic microorganism aspects. Results showed that the AD performance was enhanced by supplementing with CO-NBW or FeNPs individually, and could be further improved by simultaneous addition of the two additives. The maximum methane yield was achieved in the CO-NBW + FeNPs reactor (141.99 mL/g-VS), which increased by 26.16% compared to the control group. Similarly, the activities of the electron transfer system (ETS) and enzyme were improved. The results of microbial community structure revealed that the addition of CO-NBW and FeNPs could improve the abundance of dominant bacteria (Anaerolineaceae, Bacteroidales, and Prolixibacteraceae) and archaea (Methanotrichaceae and Methanospirillaceae). Additionally, the functional metabolic prediction heatmap indicated that metabolic functional genes favorable for AD of corn straw were enhanced.