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

Abstract

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 (<1.7% per-site on average). With 20.8 billion liters, algae could meet 19.7% of U.S. jet fuel demand with a freshwater demand of less than 1.4% of U.S. irrigation consumption. Evaluating water-stress impact is important because the impact of unit water consumption on water stress varies significantly across regions and seasons. Considering seasonal water balances allows producers to understand the combined seasonal effects of hydrologic flows and productivity, thereby avoiding potential short-term water stress.

Microalgae Commercialization Using Renewable Lignocellulose Is Economically and Environmentally Viable

“…7,8 This inherent limitation results in considerable water, nutrients, and energy consumption for algal production in commercial scale. 9,10 Further, biomass productivity relies closely on local weather conditions, including intensity and duration of sunlight and temper-ature, 11,12 which cannot be easily controlled outdoors. Additionally, mono-cultivation of desired species is difficult to maintain due to airborne contamination, 13 resulting in unreliable biomass quality and limiting the algal biomass for high-value applications that require pure strains.…”

“…However, several bottlenecks limit the scale-up of this cultivation method. Self-shielding of algal cells hinders light transmission during phototrophic cultivation, leading to low algal growth rate and terminal density and therefore longer cultivation durations. , This inherent limitation results in considerable water, nutrients, and energy consumption for algal production in commercial scale. , Further, biomass productivity relies closely on local weather conditions, including intensity and duration of sunlight and temperature, , which cannot be easily controlled outdoors. Additionally, mono-cultivation of desired species is difficult to maintain due to airborne contamination, resulting in unreliable biomass quality and limiting the algal biomass for high-value applications that require pure strains.…”

Regionalized Life-Cycle Water Impacts of Microalgal-Based Biofuels in the United States

“…In previous assessments, the water consumption of algal systems has been estimated using the discussed methods. However, studies often employed one method exclusively resulting in either a WF − or WSF accounting , and fail to provide a complete assessment of the water impacts. Previous studies do not account for geographic considerations or are restricted to a few locations. ,,, In addition, multiple studies do not use a LCA framework and neglect water consumption of upstream processes or the direct consumption of the conversion to fuel process, ,,, which underestimates the total water consumption of the algae-to-fuel process, , particularly in high-energy-expenditure pathways.…”

“…7 In previous assessments, the water consumption of algal systems has been estimated using the discussed methods. However, studies often employed one method exclusively resulting in either a WF 8−13 or WSF accounting 14,15 and fail to provide a complete assessment of the water impacts. Previous studies do not account for geographic considerations or are restricted to a few locations.…”

Effects of Iron-Oxide Nanoparticles (Fe3O4) Released From Synthesized Iron-based Thiourea Catalyst on the Growth, Cell Density, and Pigment Content of Chlorella Vulgaris

“…Over the past decade, microalgae have gained signi cant attention among environmentalists due to their advantageous properties in aquatic ecological balance [23]. Many studies have been conducted concerning the toxic effects of metal contaminants on the biological aspects of microalgae, including growth rate, yield rate, pigment content, reproduction, and nutrient content [24]. Copper nanoparticles caused growth inhibition in Skeletonema costatum in exposing to microplastics [23].…”