A comparative review of biohydrogen and biomethane production from biowaste through photo-fermentation

Given the depletion of fossil fuels and the environmental issues they cause, the search for alternative, clean, and renewable energy sources has made significant progress. Among them, the photo-fermentative production of bioenergy stands out as an attractive and environmentally friendly approach. This review comprehensively examines the key biological and technological characteristics and mechanisms involved in the production of biohydrogen and biomethane through photo-fermentation. Specifically, it discusses the use of wastewater or biowaste as feedstocks for photobiological hydrogen production, key factors influencing biohydrogen yields, and various enhancement methods. Building on the insights gained from biohydrogen production, we further explore the processes, methods, and mechanisms for enhancing photo-fermentative biomethane production areas that have not been thoroughly reviewed elsewhere. By linking biohydrogen and biomethane production, this study underscores the complementary roles of these bioenergy sources within a unified photo-fermentative framework. Additionally, it offers a comparative analysis of biohydrogen and biomethane in terms of mechanisms, feedstock utilization, environmental impact, economic viability and efficiency. The aim is to highlight recent advancements in this field, identify challenges and future perspectives, and discuss the potential of photobiological biohydrogen and biomethane as sustainable bioenergy sources.