Microbial electrohydrogenesis cell and dark fermentation integrated system enhances biohydrogen production from lignocellulosic agricultural wastes: Substrate pretreatment towards optimization

The continuous surge in global energy demand, fossil fuel depletion, and related climate change issues have oriented the worldwide researchers' endeavors to the investigation and development of sustainable and coeffective technology to satisfy the global energy needs. Referring to the non-toxic properties of hydrogen, it is considered as a suitable renewable energy source that could replace fossil fuel-based energy. It is the cleanest energy carrier, combustible with high calorific value, high energy yield. Producing biohydrogen energy from renewable resources such as lignocellulosic agricultural residues could be a sustainable carbon-neutral most costeffective approach. Dark fermentation has been widely applied as a promising eco-friendly technique to produce biohydrogen from agricultural residues. However, it has shown drawbacks owing to the recalcitrance of lignocellulose structure, and the accumulation of acid-rich intermediate by-products. Microbial electrolysis cells use bio-electrochemical reactions to upgrade H2 production in a dark fermentation reactor by promoting further decomposition of the generated volatile fatty acids. Therefore, integrating microbial electrohydrogenesis with dark fermentation can be a promising strategy to optimize the straw biomass conversion to biohydrogen. This review aims in delineating the structural composition and recalcitrance of the agricultural residues and their major effects on biohydrogen production. It summarizes all possible pre-treatment methods of the lignocellulosic agricultural residues; elucidates the stable operational conditions of microbial electrolysis cell and dark fermentation integrated system and discusses its performance for biohydrogen production. This study also reviewed the current technical challenges of this integrated system application and suggested sustainable solutions towards its industrial implementation.

Automated summary

The continuous rise in global energy demand and depletion of fossil fuels have led researchers worldwide to focus on the development of sustainable and cost-effective technologies to meet energy needs. Hydrogen, known for its non-toxic properties, is seen as a suitable renewable energy source to replace fossil fuels. Producing biohydrogen from renewable resources like lignocellulosic agricultural residues is considered a sustainable and cost-effective approach.