Microalgae organomineral fertilizer production: A life cycle approach

Abstract

The recovery and valorization of sanitation resources are alternatives to mitigate environmental impacts. The objective of this study was to evaluate the environmental performance of an organomineral fertilizer composed of urea and microalgae biomass (MB) grown in wastewater as an alternative to chemical fertilizer. MB was produced from wastewater from a meat processing industry, thus enabling the recovery of sanitation resources. A life cycle assessment (LCA) was carried out considering the stages of cultivation, harvesting, drying of MB, pellets production, and soil application as a nitrogen fertilizer for corn plants (Zea mays L.) cultivation. The LCA was performed with primary data obtained from a previous experiment, using the ReCiPe 2016 (H) methodology at midpoint and endpoint levels. Five scenarios with increasing proportions of MB (5 % to 50 %) and urea were evaluated, compared with a commercially applied fertilizer (100 % urea). The functional unit considered in the LCA was 1 kg of corn plant cultivated for 30 days. In addition, a Monte Carlo simulation was performed to assess the uncertainty in the various data entries. The results indicate that MB-based fertilizer improved the environmental performance compared to chemical fertilizer by up to 38.65 % (scenario C1). However, the increase of MB in the final product did not favor the impact mitigation due to the processes and inputs used, mainly during the cultivation and harvest stages, in scenarios C4 (40% MB) and C5 (50% MB). For uncertainty analysis, greater variations were observed for Water Consumption and Freshwater Eutrophication. Finally, an optimized scenario (C2-O) was proposed where, during harvest, the gravitational sedimentation process was considered without adding a chemical coagulant. The adopted strategy favored the mitigation of environmental impacts by up to 52.56 % compared to chemical fertilizer, improving the overall performance of the proposed fertilizer.