Static magnetic field enhanced methane production via stimulating the growth and composition of microbial community

Bo Zhao^a, Hao Sh^a, Jinwen Li^a, Shengxian Cao^a, Gong Wang^a, Yuyi Yang^b,c

School of Automation Engineering, Northeast Electric Power University, Jilin, 132012, China.

Abstract

Corn stover has a potentially valuable use as a substrate for biogas production by anaerobic fermentation. Preprocessing of corn stover, such as alkali pretreatment, is usually needed to increase substrate availability. In this study, an experimental biogas production system using a flat circular permanent magnet with a central hole to provide a static magnetic field (SMF) was devised to increase biogas production from corn stover substrate, without pretreatment, by anaerobic fermentation. The effects of varying SMF intensity on the growth of microbe populations in the activated sludge were not linear. Optimal SMF intensity was found to be 11.4 mT (±2%). At this level, the number of microbe populations increased by 85.5% compared to the control. Total gas production and CH4 content of SMF were 19.5% and 20.0% higher than those from the control NMF (no magnetic field). SMF influenced the composition of the bacterial population and significantly increased the percentage of methanogenic archaea in the overall microbe population compared to NMF. Archaea of the order methanocellales were the principal methanogenic archaea found in the decay stage. Our results indicate that SMF can potentially increase biogas production by converting agricultural waste into energy. Life cycle analysis showed that the conversion rate of chemical energy in corn stalks to CH4 was 15.2%.

Graphical abstract

Keywords: Anaerobic fermentation (AF), Corn stover, Static magnetic field (SMF), MethanogensMicrobial composition.