Study on the performance of HNO_3-modified biochar for enhanced medium temperature anaerobic digestion of food waste

摘要

Biochar can help promote direct interspecies electron transfer (DIET) and increase methane production; the surface redox groups play a constructive role in these processes. This study attempted to improve the anaerobic digestion (AD) performance by modifying biochar with HNO_3 to increase its redox activity. A comparative experimental study, raw biochar (BCO) and biochar treated with HNO_3 for 6 h (BC6), were conducted to investigate the effect of HNO_3 treatment on the medium temperature AD performance of food waste. Both BCO and BC6 can enhance CH_4 yield and facilitate the degradation of volatile fatty acids. The enhanced yield of CH_4 was 36% for BCO and 90% for BC6, respectively. Biochar can also enhance methanogenesis, presumably owing to direct interspecific electron transfer (DIET). Compared with BCO, BC6 had a higher redox activity and a smaller conductivity. It was supposed that BCO mediated DIET through its conductivity, whereas BC6 accelerated DIET by surface redox groups.