Abstract
Dark fermentation appears as a promising strategy in the new energy landscape, as it enables the production of biohydrogen using a wide range of biomass substrates, thus also contributing to waste management. However, this process exhibits lower yields compared to conventional thermochemical processes for H2 production, such as reforming. To overcome this limitation, the use of additives has been explored to enhance microbial activity and increase dark fermentation yields. However, the application of additives remains limited in practice. This study aims to address this gap by examining the effects of three types of additives (zero-valent iron, activated carbon, and hydrochar) on dark fermentation and hydrogen generation. The results reveal that hydrochar shows the most promising outcomes, increasing H2 production by 20.3%, with the highest biohydrogen yield at 92 mLH2/g-glucose. Volatile fatty acid analysis reveals that butyric and acetic pathways are utilized for H2 production in this case. It is also important to consider the alkalinity of the feedstock, as high levels can increase the pH in the medium and promote methane (CH4) production as the main fermentation product instead of H2. When this occurs, Fe(0) NPs appear to be the additive that most favors methane generation, resulting in a 6.1% higher production compared to the control experiment. This confirms the interest in the use of certain additives in fermentative processes.
Keywords: Activated carbon, Addition, Dark fermentation, Fe(0) nanoparticles, Green hydrogen, Hydrochar, VFA.