Prospective water impact assessment of algal biofuels: a climate-driven spatiotemporal approach

The environmental sustainability of algal biofuels is directly influenced by climatic conditions, yet their long-term impacts in the future remain currently unexplored. To address this gap, this study develops a novel framework to integrate spatiotemporal dimensions in prospective environmental assessments, in order to investigate the effect of climate change on water-related impacts. The estimation of the water scarcity footprint and freshwater eutrophication impacts of biodiesel production from Chlorella vulgaris in Belgium is chosen as a case study, capturing both water availability and quality challenges. By dynamically modelling biofuel production with projected meteorological data from 2025 till 2075, an improved productivity is identified after mid-century, reaching up to 6.8 g/m²/day, particularly for the intensified climate change scenarios. The environmental impact results indicate significant fluctuations over the 50-year period, with maximum deviations up to 95 % for freshwater eutrophication and 68 % for water scarcity footprint impacts across all climate change scenarios. A comparison between the two different Representative Concentration Pathway scenarios indicates that, as climate change intensifies, the uncertainty in the projections increases significantly, particularly for water scarcity footprint impacts, as the uncertainty range expands to nearly 50-fold compared to its minimum value. These findings highlight the need of dynamic, climate-driven evaluation of the long-term environmental performance of algal biofuels, towards more robust prospective assessments.