Consequential life cycle assessment of pretreatment strategies for a microalgae-based wastewater treatment pilot unit in a circular livestock industry bioeconomy

Abstract

This study presents a Consequential Life Cycle Assessment (CLCA) of a microalgae-based wastewater treatment system for the livestock industry, integrated with a circular bioeconomy approach through biofertilizer production and biogas generation through anaerobic digestion (AD). Three treatment scenarios were evaluated, each employing different combinations of pretreatment technologies, including bioflocculation with chitosan. A scaled-up process model was developed using SuperPro Designer, and the environmental performance was assessed using SimaPro 9.7. Results indicate that scenario with a previous pretreatment using a centrifugation and UV radiation achieved the lowest global warming potential (8129 kg CO₂-eq per ton of dried microalgae), reduced fine particulate matter emissions (38.55 kg PM₂.₅-eq), and required less water consumption (114.29 m³) due to minimal chitosan usage compared to the other scenarios. Sensitivity analysis revealed significant variations in environmental impacts based on microalgae yield and biofertilizer application rates. A 20 % increase in biofertilizer application led to a 27.68 % additional reduction in global warming potential. This research provides compelling evidence for the environmental feasibility and economic viability of large-scale microalgae-based wastewater treatment systems, offering a promising pathway towards sustainable livestock practices and a circular bioeconomy within the agricultural sector.