Environmental Impact of Microalgae Production in an Industrial-Scale Plant: a Comparative Scenario Analysis

This study conducts a comparative life cycle assessment to explore the potential for improvement in the environmental profile of an industrial-scale microalgal production system. The base case regards a pilot plant with vertically stacked photobioreactors for cultivating Chlorella vulgaris, where electricity (from the Italian grid) and chemical fertilizers emerge as the key impact drivers. To address these hotspots, renewable energy and circular bioeconomy approaches were assessed in a scenario analysis. Specifically, these included the use of on-site photovoltaic panels (PV) for energy supply and reclaimed wastewater (WW) for nutrient provision. The results showed that the PV scenario can reduce the global warming potential by 55%, demonstrating its decarbonisation potential, though it increased other impacts (some toxicity-related categories and abiotic depletion). Instead, the WW scenario yielded reductions across all impact categories, albeit to varying degrees. The PV+WW combination outperformed the base case in all impact categories and emerged as the best option in the impact categories not adversely affected by the deployment of photovoltaic panels. Finally, an uncertainty/sensitivity analysis on biomass productivity under wastewater-based cultivation highlighted potential risks of poor environmental performance, but also opportunities for improvement through the use of native microalgal strains.