Environmental impact of microalgal biomass production using wastewater resources

The current study provides a life cycle assessment (LCA) of microalgal biomass production using the effluent collected from the stabilization lagoon of a municipal sewage treatment as culture medium. Strains of two native microalgae from the stabilization lagoon (Desmodesmus sp. and Scenedesmus sp.) were grown in three different media: filtered effluent, autoclaved filtered effluent and conventional medium for cultivation of freshwater microalgae. Environmental analysis was carried out within the methodological framework of the LCA, by the life cycle impact assessment method ReCiPe 2008. A comparative analysis was performed for three endpoint categories: damage to human health, damage to ecosystem diversity and damage to resource availability. For both microalgal strains, the results confirmed that microalgal biomass production in non-autoclaved effluent has the lowest potential environmental impact. An additional analysis indicated that the potential environmental impact caused by discharge of effluents treated with microalgae is higher than the impact of untreated effluents. Despite the decrease in N and P in the effluent after microalgal treatment, the potential environmental impact of its discharge is strongly correlated with the electric consumption required for microalgal cultivation. This consumption could be lowered by decreasing the expenditure for illumination and mixing using outdoor microalgal cultivation.