Effect of Nano-Magnetite and Ethanol on Methane Production in the Anaerobic Digestion of Wheat Straw

Abstract

HighlightsStudied mesophilic and thermophilic anaerobic fermentation of wheat straw with nano-magnetite (Fe3O4) and ethanol.The maximum biogas yield of 421.5 mL/g in mesophilic AD was 60.8% higher than control.Revealed the mechanism of nano-Fe3O4 and ethanol addition to promote biogas production.Abstract. This study investigated the mesophilic and thermophilic anaerobic fermentation of wheat straw with nano-magnetite (Fe3O4) and ethanol addition. The effects of ethanol addition on the biogas yield, the degradation of lignocellulose, and the bacterial community were explored. The results showed that the biogas yield and methane content increased as the ethanol concentration increased. The ethanol concentration of 4 g/L resulted in highest biogas yield in mesophilic anaerobic fermentation at 421.5 mL/g, which was a 60.8% improvement compared to the control. The corresponding methane content was 66.2%. For the lignocellulose degradation, the cellulose and hemicellulose contents in mesophilic anaerobic fermentation were reduced from 55.42% and 17.19% of the pretreated wheat straw to between 22.88% and 25.98% and 11.60% and 13.05%, respectively. The microbial community results showed that as the ethanol content increased, the relative abundance of Firmicutes initially increased before it decreased. Among the microbial community results, the relative abundances of Firmicutes and Bacteroides in the biogas residue of the mesophilic anaerobic fermentation with the addition of 3 g/L of ethanol were the highest, at 31.26% and 30.94%, respectively. Keywords: Anaerobic Digestion, Biogas, Ethanol, Nano-Fe3O4, Wheat Straw.