Balancing Water Sustainability and Productivity Objectives in Microalgae Cultivation: Siting Open Ponds by Considering Seasonal Water-Stress Impact Using AWARE-US

Microalgae have great potential as an energy and feed resource. Here we evaluate the water use associated with freshwater algae cultivation and find it is possible to scale U.S. algae biofuel production to 20.8 billion liters of renewable diesel annually without significant water-stress impact. Among potential sites, water-stress is significantly more variable than algae productivity across location and season. Thus, it is possible to reduce water-stress impact, quantified as water scarcity footprint, through the choice of algae site location. We test three site-selection criteria based on (1) biomass productivity, (2) water-use efficiency, and (3) water-stress impact and find that adding water-stress constraints to productivity-based ranking of suitable sites reduces water-stress impact by 97% and water consumption by half, compared with biomass-productivity ranking alone, with little productivity impact (