Advances in photo-fermentative biohydrogen and biomethane production from organic waste: a comprehensive review of processes, parameters, and integrated pathways

The depletion of fossil fuels and rising environmental concerns have accelerated the search for clean and sustainable energy alternatives. Photo-fermentative bioenergy production is a promising, eco-friendly approach for generating renewable fuels such as biohydrogen and biomethane. This review critically examines photo-fermentation’s biological and technological aspects using organic waste and wastewater as feedstocks, focusing on process efficiency and optimization. Key parameters – light intensity, carbon-to-nitrogen (C/N) ratio, microbial consortia, and reactor design – are analyzed for their influence on hydrogen and methane yields. The integration of dark fermentation, photo-fermentation, and anaerobic digestion is also explored to highlight synergistic benefits in energy recovery and waste reduction. Findings reveal that optimized photo-fermentative processes significantly enhance hydrogen yields, while integrated systems boost biogas productivity. Including less-studied photo-fermentative biomethane pathways underscores additional potential for circular waste management and energy diversification. This review concludes that combining biohydrogen and biomethane production improves feedstock utilization and enhances economic and environmental sustainability. It outlines recent innovations and suggests directions for future research, positioning photo-fermentation as a vital component in the transition to low-carbon, sustainable energy systems.