High-Alkalinity Algal Cultivation with Direct Air Capture: An Economic Feasibility Analysis

Weather variability and CO2 supply costs remain key barriers to the commercial viability of algal biofuel production. Recent experimental work has demonstrated that the algae Chlorella sp. strain SLA-04 achieves high productivity in extreme alkaline growth media (pH > 10), where the solution chemistry enables direct capture of atmospheric CO2, eliminating the need for costly CO2 sparging. Despite these promising results, the commercial-scale economic and environmental implications of this cultivation approach have not yet been assessed. Here, we present the first integrated Techno-Economic Analysis (TEA)/Life-Cycle Analysis (LCA) of high-pH–high-alkalinity production. We compare four SLA-04 cultivation scenarios with a baseline strain cultivation scenario with Nannochloropsis oceanica. These scenarios also include the first incorporation of Trona, a naturally occurring carbonate mineral and the primary domestic source of bicarbonate in the United States, into our TEA/LCA framework as a low-cost alternative to commercial NaHCO3 for establishing the high-alkalinity growth medium. Our results indicate that the SLA-04-Trona scenario reduces carbon intensity and present value of lifetime expenses by 40% and 55% on a per-gallon basis, while simultaneously exhibiting lower production variability across all seasons. Quarterly revenues reflected an improvement of $6 million over the baseline strain revenue over 40,000 simulations. Modeled productivity was lower than what was observed experimentally and resulted in a MBSP of $705/ton. These findings provide the first quantitative evidence that high-pH–high-alkalinity cultivation can substantially improve both the economics and environmental footprint of commercial-scale algal biofuel production.