Soil application of microalgae for nitrogen recovery: A life-cycle approach

Abstract

The application of algal biomass in the soil represents an alternative of efficient use of fertilizers. In the present study, the environmental impacts generated by the application of 1 kg of nitrogen from the algal biomass (biofertilizer) were analyzed through life cycle analysis. Nitrogen was recovered from a meat processing industry effluent in a high-rate algal pond. Impacts related to the entire biofertilizer chain were mainly impacting on climate changes (115 kgCO2eq). Other categories (particle formation, terrestrial acidification, freshwater eutrophication and freshwater ecotoxicity) were not very representative. Biomass cultivation was the most critical step regarding energy and time consumption. On the other hand, the use of effluent as the culture medium for microalgae growth reduced impact categories, such as freshwater eutrophication. Results showed that microalgae cultivation and harvesting steps need to be technologically developed, especially when compared to a conventional fertilizer already established in the market. In order to make microalgae biofertilizer environmental advantageous, alternatives should be beforehand: i) the use of photovoltaic energy instead of hydropower energy; ii) the use of a nitrogen richer effluent; iii) and the consideration of an environmental compensation for the treatment of effluent can be accounted for, disregarding the biomass production stage.