Synergistic application of thermally-pretreated-biocatalyst and dark-fermentative process coupled with bioelectrohydrogenesis promotes biohydrogen production from agricultural straw wastes
Fabrice Ndayisenga, Zhisheng Yu, Bobo Wang, Gang Wu, Hongxun Zhang
Abstract
• DF-MEC integrated system enhanced biohydrogen production from wheat straw biomass. • Thermally-pretreated activated sludge significantly influenced bioH 2 production. • The achieved bioH 2 yield was 5.416 mmol H 2 /g-straw with an energy recovery of 94.4 %. • DF-MEC promoted further conversion of lignocellulosic fibers and VFAs into bioH 2 . • The maximum COD and NH 3 -H removal efficiency were 81.32% and 42.25% respectively. This work investigated the feasibility of enhancing biohydrogen yield from agricultural wheat straw by introducing an electrohydrogenesis process into dark fermentation (DF) and using heat-pretreated activated sludge as inoculum as a strategy to inhibit the methanogens’ growth. The achieved maximum biohydrogen yield was 5.416 mmol H 2 /g-straw with an energy recovery efficiency of 94.4 %. It reported a maximum coulombic efficiency of 74 % and chemical oxygen demand (COD) removal efficiency of 81.32 % whereas the maximum NH 3 -H removal efficiency was 42.25 %. The main volatile fatty acids (VFA) detected at the end of DF were acetic acid, propionic acid, and butyric acid, respectively, reduced by 84.07 %, 77.38 %, and 75.52 % at the end of the second phase of electrohydrogenesis. Moreover, this novel strategy promoted the conversion of lignocellulosic components compared to the non-pretreated activated sludge-catalyzed fermentative bioreactors, where the cellulose, lignin, and hemicellulose removal rates rose by 58.4 %, 55.5 %, and 79.5 %, respectively. These results revealed that coupling the electrohydrogenesis with dark fermentation in the process biocatalyzed by a thermally-pretreated activated sludge remarkably inhibited methanogen growth and improved the biohydrogen yield from agricultural straw residues. Hence, this investigation provides a novel technology utilizing agricultural straw biomass as a bioresource other than waste.