An Investigation on the Economic Feasibility of Macroalgae as a Potential Feedstock for Biorefineries

Macroalgal biomass has been considered as a prospective feedstock for biofuel production as, among other benefits, it is an abundant source of renewable sugars and its growth does not require arable land, fresh water, or intense care. Successful commercial deployment of macroalgae-based biorefineries, however, depends on their economic viability at industrial scales. A key objective of this study was to carry out a detailed technoeoconomic analysis (TEA) of a macroalgae biorefinery to understand the economic potential and cost drivers of macroalgae as a feedstock for the production of biofuels and biochemicals. Ethanol was used as a representative macroalgae-derived product, given the wealth of public information available to model this option, and the analysis was extended to biomass-derived sugars in order to explore the production of other fermentation-derived chemicals. Sensitivity analysis was performed on various cost drivers, such as macroalgae price, yield, solids loading, and enzyme loading during hydrolysis. With a feedstock price of $100/MT, depending on the maturity of the other key process parameters (i.e., yield, solids loading, and enzyme loading), the minimum ethanol selling price (MESP) was observed to be in the range of $3.6–8.5/gal and reduced to $2.9–7.5/gal with macroalgae priced at $50/MT. For production of chemicals, sugar prices were in the range of ¢21–47/lb or ¢16–40/lb with macroalgae priced at $100/MT and $50/MT, respectively. Given the challenging economics of the macroalgae biorefinery, coproduction of alginate was used to show the importance of multiple revenue sources, though issues regarding market saturation continue to arise when dealing with products of disparate market sizes.