Biogas and Nutrient Recovery from Algal Biomass

The rise of energy demand is likely to be twice by 2050 due to the massive growth of the population forcing several researchers, academicians, and scientists to think of alternative sources of energy by utilizing food waste, cow manure, plant leaves, and algae. This chapter deals with the significance of microalgae as the best source of generating green biogas/biofuels which not only save rapidly declining stocks of fossil fuels but also mitigates environmental problems. Low or no competition with human food or crops, low amounts of lignin, and rapid growth rate are the benefits of biogas production through Algae. Conversely, issues like chemical content changes, high amounts of moisture, and other inhibition practices hinder in generation of cost-effective biogas. However, it is still more economically and environmentally affable than ordinary fossil fuels. Anaerobic digestion of algal biomass suffers from low digestibility due to cell wall resistance and inappropriate carbon-to-nitrogen ratio. A short-span method comprising fungal crude enzyme-based pre-treatment of algal biomass is introduced and the effect of it was qualitatively assessed through visual and microscopic observations and quantitatively through measuring algal biomass solubilization. Up to 50% biomass COD solubilization was observed within 150 min of pretreatment under optimal conditions. A higher production is observed in subsequent anaerobic digestion of pretreated algal biomass from untreated algal biomass. Interestingly, methane yield upsurged when pretreated algal biomass co-digested with cattle dung while sugarcane bagasse harmed algal biomass co-digestion due to its poor digestibility. Overall, the present attempt showed promising results by improving methane yield from algal biomass though pretreatment and co-digestion.