Biohydrogen: Production, promising progressions and challenges of a green carbon-free energy

[Display omitted] •Biohydrogen is the cleaner and eco-friendly alternative energy source of fossil fuels.•It has 2.75 times greater energy efficiency than petroleum-based fuels.•Photosynthetic microorganisms can directly convert water into biohydrogen gas.•Most reliable and cost-effective way of biohydrogen production is dark fermentation.•To boost biohydrogen production, dark fermentation needs to be applied at pilot scale. The global energy landscape is currently dominated by the extensive use of fossil fuels, which, unfortunately, has severe environmental consequences, including the release of carbon dioxide compounds that contribute to global warming. To address these pressing environmental challenges, there is an urgent need to transition away from fossil fuels and embrace renewable energy sources. In this context, biohydrogen has emerged as a highly promising and environmentally friendly energy alternative. Biohydrogen is a natural and sustainable energy source that offers several distinct advantages. Unlike conventional energy sources, biohydrogen production does not involve the emission of harmful compounds, making it a cleaner and greener option. Biohydrogen can be generated through various methods, often relying on microorganisms in biological pathways. Importantly, biohydrogen production can occur in both the presence and absence of light, offering flexibility in its implementation. Comprehensive investigations into biohydrogen production methods, as well as efforts to enhance production efficiency, are essential to bridge the gap between laboratory-scale success and practical, large-scale applications. In summary, this review underscores the remarkable qualities of hydrogen as a future energy carrier, emphasizing its promise as a renewable and sustainable energy source. The article also highlights various biohydrogen production methods and sheds light on the challenges that must be overcome to realize the vision of biohydrogen as a pivotal player in the global shift towards cleaner and more sustainable energy solutions.