The generation of biohydrogen from pretreated algal biomass in batch fermentation mode

Hydrogen is considered to be a green fuel for the future. Among the several substrates capable of producing biohydrogen, microalgae are one of the most promising sources. So algae-based biofuels have drawn the attention of the scientific community. Microalgae for biohydrogen production are chosen based on their carbohydrate content. For the present study, Chlamydomonas reinhardtii with a carbohydrate content of 0.23 (g/g) was chosen as the substrate. The biophotolysis method of hydrogen production didn't give significant biohydrogen with the yield being only 0.1 L L⁻¹. Further biohydrogen production studies by dark fermentation were carried out using algae as the substrate and facultative acidogenic mixed consortium as the inoculums, and an algal biomass concentration of 18 g L^-1 was found to be the most suitable condition with 0.73 L L⁻¹ biohydrogen production. On imparting pretreatment to algal biomass for improving hydrogen production, autoclave treatment gave the most satisfactory results, verified morphologically as well with the lowest crystalline index of 2.1% and highest hydrogen production of 1.543 L L⁻¹ compared to other treatments. Batch fermentation with pretreated algal biomass gave hydrogen production of 2.08 L L⁻¹ and hydrogen yield of 0.85 mol H₂/mol of reducing sugar consumed, with an energy recovery close to 8%.