Biogas production from algae and cyanobacteria through anaerobic digestion: A review, analysis, and research needs

Abstract

Anaerobic digestion is a common process for the treatment of a variety of organic wastes and biogas production. Both, macro- and microalgae are suitable renewable substrates for the anaerobic digestion process. The process of biogas production from algal biomass is an alternative technology that has larger potential energy output compared to green diesel, biodiesel, bioethanol, and hydrogen production processes. Moreover, anaerobic digestion can be integrated into other conversion processes and, as a result, improve their sustainability and energy balance. Several techno-economic constraints need to be overcome before the production of biogas from algal biomass becomes economically feasible. These constraints include a high cost of biomass production, limited biodegradability of algal cells, a slow rate of biological conversion of biomass to biogas, and high sensitivity of methanogenic microorganisms. The research opportunities include a variety of engineering and scientific tasks, such as design of systems for algae cultivation and anaerobic digestion; optimization of algae cultivation in wastewater, nutrients recycling and algal concentration; enhancement of algal biomass digestibility and conversion rate by pretreatment; deep integration with other technological processes (e.g., wastewater treatment, co-digestion with other substrates, carbon dioxide sequestration); development and adaptation of molecular biology tools for the improvement of algae and anaerobic microorganisms; application of information technologies; and estimation of the environmental impact, energy and economical balance by performing a life cycle analysis.