A strategy for commercialization of macroalga biorefineries

Abstract

The transportation sector significantly contributes to global warming due to the extensive use of fossil fuels. Biofuels have the potential to eliminate inherent problems associated with the combustion of fossil fuels. However, large-scale deployment of biorefineries is limited because of high capital and operating costs as well as the low market value of biofuels that make such plants economically unfavorable. Additionally, using sustainable feedstock (algae, cyanobacteria, etc.), i.e., with no social, environmental, or technological challenges, is another major bottleneck for biorefineries. Considering these challenges, this study presents a strategy for the commercialization of macroalga-derived bioethanol via a circular economy-based integrated biorefinery concept. A standalone (conventional) process was designed for bioethanol production at 50.0 million gallons (189.3 million liters) per year capacity in Aspen Plus V12.2. Economic and environmental indicators were assessed through discounted cash flow and cradle-to-grave (SimaPro V9.4.0.7) analyses, respectively. Once the potential targets are identified, a novel integrated process was designed for biofuel and biochemical production, which is not only economically favorable in the current market but also has a better life cycle profile compared to that of a standalone process. The results showed that the integrated design has a minimum ethanol selling price of USD 0.35/L and a global warming potential of 0.35 kg CO2 eq/L of ethanol, which is 45% and 82.7% lower than that of the standalone design. Sensitivity analysis showed that the Bio-SA selling price, total capital investment, and seaweed price are the most critical economic parameters for the economic feasibility of the process.