Biohydrogen production from wastewater: Production technologies, environmental and economic aspects

Biohydrogen (bio-H2) production from wastewater can be a sustainable and innovative approach that uses biotechnological processes to convert organic waste into hydrogen, a clean energy source. Technologies such as dark fermentation, photo-fermentation, microbial electrolysis cells, and biophotolysis are widely utilized, with emerging technologies like anaerobic membrane bioreactors and microalgae processes also gaining prominence. Integration between these systems aims to enhance process efficiency. This study reviews the hydrogen production from wastewater, analyzing its potential as a source for bio-H2 production and evaluating environmental and economic issues. The performance of various processes in bio-H2 production from different wastewater sources is discussed, focusing on challenges, opportunities, and trends. Wastewater, including cassava (225.2 mL H2/gVS) and corn (265 mL H2/gVS) processing, dairy (54.5 mL H2/gVS), domestic (154–180 mL H2/gVS), fruit (104.9 mL H2/gVS) and starchy (153–200 mL H2/gVS), show promising potential for bio-H2 production. Economically, indirect biophotolysis is the most cost-effective technology per kg of bio-H2 produced, followed by microbial electrolysis cells, photo-fermentation, dark fermentation, and direct biophotolysis. Furthermore, from an environmental and sustainability perspective, bio-H2 production presents a strategic tool for global decarbonization efforts, reducing CO2 emissions and facilitating transformation towards clean energy solutions. Bio-H2 generation during wastewater treatment holds potential by concurrently producing clean fuel and enabling safe disposal of wastewater. Continued research and development efforts are essential to overcoming current challenges. Achieving this will require targeted investments, policy support, and technological innovations to make biohydrogen a viable and sustainable energy solution. [Display omitted] •Bio-H2: a clean energy from wastewater, merging fuel production with waste removal.•Key conditions for maximizing H2 production by different processes are summarized.•Anaerobic membrane bioreactors increase bio-H2 production 3.5x over other reactors.•Challenges for bio-H2 from wastewater: improve efficiency, scalability, and cost.•Future studies should aim to reduce bio-H2 costs below US$ 2.00/kg for viability.