Organic waste to biohydrogen: A critical review from technological development and environmental impact analysis perspective

The increasing worldwide population and rapid urbanization have led to huge amount of fossil fuels consumption and waste generation. The awareness of living in a sustainable society is pushing people to target a low-carbon energy structure. Hydrogen, a carbon-free energy source, draws more and more attention. Particularly, biohydrogen from organic waste calls great interest by generating hydrogen and disposing waste simultaneously. Therefore, the three main technologies convening waste to biohydrogen: biological fermentation, thermochemical gasification and microbial electrolysis cell, were reviewed in this study from both technological and environmental perspective. The results showed that a variety of waste streams have been tested to produce hydrogen and different production efficiency were reported. The most favourable waste material for fermentation and microbial electrolysis cell were different types of wastewater, and agricultural lignocellulosic waste was also intensively studied in fermentation. Whereas wooden waste and municipal solid waste were the two wastes investigated the most in gasification. Optimization of the operational parameters was proved to improve the hydrogen production. However, researches focusing on scale-up of these technologies are still needed. On the other hand, life cycle assessment demonstrated that waste gasification had a better environmental profile compared to other technologies. However, the majority of the reviewed life cycle assessment studies failed to further explain the robustness due to the lack of sensitivity and uncertainty analysis, indicating high quality life cycle assessment studies are needed in the future.