Quantitative analysis of the mechanism of biochar in alleviating product inhibition in different fermentative hydrogen production processes
Weiming Li, Qinglan Zhang, Chi Cheng, Yan Xie, Min Liu, Nanqi Ren, Shaofeng Wang, Xiangfeng Zeng, Yongfeng Jia
Abstract
Abstract Dark fermentation is a biological process that converts organic molecules into molecular hydrogen and stands out as one of the most promising methods for extracting bioenergy from wastewater. The accumulation of end-products causes varying inhibitory effects on the process, posing a key challenge. This study explored the efficacy and mechanisms of biochar as a cost-effective solution to mitigating the inhibitory effects of end-products in major types of dark fermentative hydrogen production processes and provided for the first time a quantitative analysis of the relative contribution of each mechanistic pathway. Results showed that biochar was more effective in butyrate-type than ethanol-type fermentations. In butyrate-type fermentation facing endogenous and exogenous volatile acid inhibition, biochar increased hydrogen production by 145.74% and 64.95%, respectively. In ethanol-type fermentation, biochar increased hydrogen production by 10.53% and 18.09% under endogenous and exogenous inhibitions from ethanol, respectively. Mechanistic analyses revealed three primary pathways through which biochar mitigated product inhibition: pH buffering, cell colonization, and inhibitor adsorption. The relative contribution of each pathway varied by fermentation type. In butyrate-type fermentation, pH buffering was critical, accounting for 42.9% of the mitigation effect, while cell colonization was primary in ethanol-type fermentation, contributing 32.4%. This study demonstrated the different roles of biochar in mitigating production inhibition in diverse fermentation types, highlighting its potential to enhance hydrogen energy recovery in dark fermentation. Graphic Abstract