Renewable hydrogen production via biological and thermochemical routes: Nanomaterials, economic analysis and challenges.

The urgent need to address greenhouse gas (GHG) emissions, particularly in relation to climate change, is driving the demand for new sustainable renewable fuels. This demand is promoting the expansion of de-carbonization efforts, which hold tremendous potential as a renewable energy source. One area of focus is the production of hydrogen (H 2), which has long been a popular subject of discussion. Currently, large quantities of H 2 are generated using conventional fossil fuels. However, the finite nature of these resources has compelled the global community to explore alternative, more environmentally friendly options like biomass. Generating H 2 on a large scale from various biomasses presents a complex challenge. Researchers have identified thermochemical (TC) and biological (BL) processes as the primary methods for converting biomass into H 2 , although other techniques exist as well. Commercializing H 2 as a fuel presents significant technological, financial, and environmental hurdles. Nevertheless, nanomaterials (NMs) have shown promise in overcoming some of the obstacles associated with H 2 production. This review focuses on the use of NMs in TC and BL processes for H 2 generation. Additionally, the paper provides a brief overview of the methods and financial considerations involved in enhancing biomass-based H 2 production. Studies indicate that the production of bio-H 2 is relatively expensive. Direct bio-photolysis costs range from $2.13 kg−1 to $7.24 kg-1, indirect bio-photolysis costs range from $1.42 kg−1 to $7.54 kg−1, fermentation costs range from $7.54 kg−1 to $7.61 kg−1, biomass pyrolysis costs range from $1.77 kg−1 to $2.05 kg−1, and gasification costs $1.42 kg−1. The paper also explores various challenges related to biomass conversion and utilization for H 2 production, aiming to better understand the feasibility of a biomass-based H 2 economy. [Display omitted] • The biological and thermochemical routes for renewable H 2 are elucidated and compared. • Biological routes basically have low H 2 production rate than thermochemical ones. • Ni and Fe are the most promising nanomaterials for H 2 production. • Economic analysis and challenges associated with both routes are explained. • Future research directions are presented based on identified literature gaps. [ABSTRACT FROM AUTHOR]