Current state and future direction of algal based biorefineries: An economic and life cycle perspective

J.C. Quinn, J. Cruce, M. Somers, B. Beckstrom, P. Chen, K. DeRose, A. Beattie, D. Quiroz, J. Greene
Colorado State Univeristy,
United States

Keywords: algae, techno-economic, life cycle assessment

Summary:

Various biorefinering pathways have been identified as potential pathways to sustainable algal production. The objective of this work is to understand the current state of the economic viability and environmental impact of algal based biorefineries. A survey of the literature illustrates the need for harmonization of studies. Results from growth rate and system boundary harmonization are shown to not dramatically impact the end result mainly due to process assumptions. Based on this result engineering process models of various processing pathways was completed and leveraged to understand the economics and life cycle impacts on a systems level across consistent assumptions. The pathways included baseline hydrothermal liquefaction (HTL), protein extraction with HTL, fractionation into high-value chemicals and fuels, and a small-scale first-of-a-kind plant coupled with a wastewater treatment facility. This foundation is then used to explore the impact of co-products and methods assumptions on the economic viability of algal systems. The impact on economic results from policy scenarios was then examined. The type of depreciation scheme was shown to be irrelevant for durations less than 9 years, while short-term subsidies were found to capture 50% of the subsidy value in 6 years, and 75% in 12 years. Carbon prices can decrease fuel costs as seen by the production facility through carbon capture credits. TEA tradeoff assessments determined that $7.3 of capital costs are equivalent to $1 yr-1 of operational costs for baseline economic assumptions. Comparison of algal fuels to corn and cellulosic ethanol demonstrates the need for significant co-product credits to offset high algal capital costs. Higher value co-products were shown to be required for algal fuel economic viability.