Economic viability of multiple algal biorefining pathways and the impact of public policies

Abstract

This study makes a holistic comparison between multiple algal biofuel pathways and examines the impact of co-products and methods assumptions on the economic viability of algal systems. Engineering process models for multiple production pathways were evaluated using techno-economic analysis (TEA). These 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. 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.