Microalgae cultivation in wastewaters for energy purposes: a life-cycle based comparison

The developement of renewable energy systems spread over the last decades, due to growing energy demands and environmental impacts of conventional fossil fuels. Biogas is an important bio-energy carrier and its production can contribute to valorize wastewaters (WW) residues and to recycle nutrients by producing soil fertilizers. Microalgal biomass is an optimal source for renewable biofuels, due to high productivities and the possibility to capture CO2 from flue gases. However, several studies show that producing microalgae biofuel is often limited by nutrients and water availability. Cultivating microalgae on WW could overtake this limitation and could be integrated into treatment plants provided with anaerobic digesters, growing on digestate’s nutrients. In this study, relevant publications are reviewed, focusing on Life Cycle Assessment of microalgae production systems situated in biogas plants treating wastewater residues.