Techno-Economic Perspectives of Bioremediation of Wastewater, Dewatering, and Biofuel Production From Microalgae

Microalgae have an exceptionally faster growth rate (approximately 20 times) than terrestrial plants. With the help of solar energy, microalgae assimilate nutrients present in culture medium. They can accumulate a substantially high amount of oil (approximately 70%) in their cells compared to other-oil yielding crops and have tremendous potential for wastewater treatment. Algal feedstock is an excellent source of food, animal feed, fertilizer, and also used for the production of variety of biofuels. Algal biomass is produced in open ponds, high rate algal ponds (HRAP), and photobioreactors. Past experiences have shown that pilot-scale production of algal biomass in photobioreactors with the use of freshwater and fertilizers is uneconomical, due to the high capital costs including running and maintenance costs. Algal technologies face economic challenges due to the energy-intensive cultivation, harvesting, pretreatment, oil extraction, and conversion to biofuels. Therefore, the concept of advanced HRAPs emerged which has been found to be excellent for the treatment of wastewater as well as the production of algal biomass as a byproduct of the treatment. Previous studies have demonstrated the commercial feasibility of HRAPs. In the long run, HRAPs based wastewater treatment covers the capital cost and the running cost byproducts produced can be used in various applications. This chapter deals with the techno-economic challenges and opportunities associated with microalgal-based wastewater treatment, issues in harvesting and pretreatment techniques as well as the production of various types of biofuels.