Valorization of microalgal biomass for biohydrogen generation: A review

Third generation biomass, i.e. microalgae, has emerged as a promising alternative to first and second generation biomass for biohydrogen production. However, its utilization is still low at present, due to several reasons including the strong and rigidity of the microalgal cell wall that limit the hydrolysis efficiency during dark fermentation (DF) and photofermentation (PF) processes. To improve the utilization efficiency of microalgal biomass, it is crucial that important aspects related to the production of the biomass and the following processes are elaborated. Thus, this article provides detailed overview of algal strains, cultivation, and harvesting. It also presents recent research and detailed information on microalgal biomass pretreatment, and biohydrogen production through DF, PF, and co-digestion of microalgal biomass with organic materials. Furthermore, factors affecting fermentation processes performance and the use of molecular techniques in biohydrogen production are presented. This review also discusses challenges and future prospects towards biohydrogen production from microalgal biomass.