Techno-economic and Sensitivity Analysis of Microalgae-based Biorefinery

Abstract

Microalgae possess tremendous potential to meet the ever-increasing demand for food, feed, energy and fuels in a sustainable manner. However, to be commercially viable, the entire supply chain of microalgae production including harvesting and conversion needs to be thoroughly investigated and better understood. To this end, a comprehensive theoretical approach was used in the present study involving first-principles based detailed modeling, simulation and analysis. Mathematical models were developed to quantify microalgae productivity potential and the associated feed stock costs in commercial scale biorefineries. In addition, detailed process modeling of the conversion of algae to multiple value-added products and the associated technical and economic feasibility and environmental assessment were conducted for the different geospatial locations. Using a first principles-based approach, algae growth and productivity were modeled considering an open raceway pond reactor and a flat panel photobioreactor to understand the implications of reactor geometry on microalgae growth and harvesting. Economic analysis was also conducted to determine algae production costs in the two different reactor systems, and across several geographic locations, thereby offering direct comparisons to facilitate selection of the most productive algae reactor system and the location. Then process models were developed for the conversion of microalgae to natural astaxanthin and eicosapentanoic acid (EPA) and docosahexanoic acid (DHA). These process models were used to assess the cost of production of the above products using different bioreactor systems and at various geospatial locations. In addition to value-added products, utilization of the residual algae biomass was also included in the overall techno-economic analysis to understand the economic competitiveness of microalgae-derived natural products and algal biorefinery in a fossil fuel-dominated market. The results obtained here suggest that microalgae productivity potential as well as production costs are heavily influenced by geographic location. Predicted yields and corresponding costs for astaxanthin and EPA and DHA suggest that the production of these high-value products may be more successful in locations characterized by favorable environmental profiles that are more conducive to algae growth. While the costs of production in algal biorefineries were found to be higher than those of their petroleum-based counterparts, with further research and development the commercial production of microalgae-based natural products is highly promising for future industrial applications.