Improvement in biohydrogen and volatile fatty acid production from seaweed through addition of conductive carbon materials depends on the properties of the conductive materials

Abstract Fermentative production of biohydrogen and volatile fatty acids (VFAs) from advanced feedstocks such as seaweed provides opportunities in the carbon-neutral bioeconomy. The gap in the state of the art exists in overcoming both the low fermentation efficiency associated with the rigid structure of seaweed and the inefficient metabolic electron transfer within the microbial communities. This study evaluated the effects of carbonaceous additives (such as graphene and various biochars) on biohydrogen fermentation of glucose, cellulose, and the brown seaweed Laminaria digitata. The impacts of carbonaceous additives varied significantly in terms of hydrogen production, VFA profiles, and microbial communities. Graphene and wood-derived biochar (Wood_Biochar) were shown to be superior to draff-derived biochars. In the fermentation of L. digitata, graphene and Wood_Biochar significantly reduced the lag-phase time by 47% and 49%, respectively. Microbial analysis revealed that the enhanced fermentation was ascribed to the enrichment of Thermoanaerobacterium genus in response to carbonaceous additives. Kinetic correlations between the fermentation parameters and the properties of the additives suggested that the graphitic structure and electrical conductivity might play a crucial role in facilitating the fermentation. The mechanisms might be ascribed to (1) the supported biofilm growth and (2) enhancement in microbial electron transfer induced by the additives.