Bioconversion of industrial wastes to hydrogen: A review on waste-to-wealth technologies

Energy plays a significant role in attaining the sustainable growth of the industrial sector of any nation. The resources for getting energy are limited and cannot fulfill the huge demand for energy supply in the near future. Generating fuels from various waste materials and biomass is widely viewed as a sustainable energy source and a viable option for the future. Currently, researchers are particularly interested in synthesizing hydrogen (H₂) without emitting CO₂ and other greenhouse gases (GHGs). Hydrogen is recognized as a pristine and environmentally friendly energy source, presenting an optimal substitute for fossil fuels due to its high energy content of 122 kJg^-1. The traditional methods for the production of H₂ are cost-intensive and heavy input requirements are needed. Thus, the synthesis of H₂ through biological approaches is cost-effective and eco-friendly alternating with easy operational requirements with ambient reaction conditions. The most common drawback of the biological production of H₂ is the low yield and production rates of gas during scale-up conditions. This review is focused on different processes used to convert the wastes into H₂ energy along with their pattern of utilization and the effect on the environment.