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 (H₂), which has long been a popular subject of discussion. Currently, large quantities of H₂ 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 H₂ 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 H₂, although other techniques exist as well. Commercializing H₂ as a fuel presents significant technological, financial, and environmental hurdles. Nevertheless, nanomaterials (NMs) have shown promise in overcoming some of the obstacles associated with H₂ production. This review focuses on the use of NMs in TC and BL processes for H₂ generation. Additionally, the paper provides a brief overview of the methods and financial considerations involved in enhancing biomass-based H₂ production. Studies indicate that the production of bio-H₂ 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 H₂ production, aiming to better understand the feasibility of a biomass-based H₂ economy.