Abstract
Volatile fatty acids and ammonia nitrogen (AN) accumulate during anaerobic digestion (AD) of high N substrates, such as chicken manure (CM), causing decreases in methane yield. Previous research found that the addition of nano-Fe3O4 biochar can alleviate the inhibition caused by acids and ammonia and increase methane production. The mechanism of enhanced methane production in nano-Fe3O4 biochar-mediated AD of CM was explored in depth in this study. The results showed the lowest AN concentration in the control and nano-Fe3O4 biochar addition groups were 8,229.0 mg/L and 7,701.5 mg/L, respectively. Methane yield of volatile solids increased from 92.0 mL/g to 219.9 mL/g in the nano-Fe3O4 biochar treatment, which was attributed to the enrichment of unclassified Clostridiales and Methanosarcina. The mechanism of nano-Fe3O4 biochar in AD of CM under high AN level was to improve methane production by promoting syntrophic acetate oxidation and facilitating direct electron transfer between microorganisms.
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