LAUSR

An integrated microalgae biorefinery producing fuels and value-added products needs to be optimally synthesized for realizing its potential. A large-scale optimization model considering biorefinery co-producing biodiesel, polar lipid, protein, and reduced sugar from microalgae has been previously developed, and biodiesel production without any co-products manufactured was found to be non-profitable. This work uses the model to study the impact of demands and selling prices of value-added co-products on the optimal biorefinery synthesis and the net annualized life cycle cost (ALCC) of biodiesel production. The simulation results showed that production of reduced sugar to the maximum extent resulted in an annualized profit of US$27.23/L of biodiesel production. Individual scenarios for mandatory production of protein and polar lipid resulted in an ALCC of US$15.11/L and US$13.20/L, respectively. The case of fluctuations in demand and selling prices of the end-products was also analyzed. Additionally, the potential of a biorefinery to sequester atmospheric carbon dioxide from a coal-fired 500 MW power plant, without any preferential product, is also modeled. Emission of carbon dioxide is considered to attract a penalty. For this study, with a low-value biodiesel selling price (US$0.48/L), the biorefinery captured 2.77% of the available carbon dioxide and recorded a net annual deficit of US$9.71 million. On the other hand, for a high price of biodiesel (US$8.74/L), 99.89% of the carbon dioxide was captured to have biodiesel and reduced sugar co-produced, yielding a net annual revenue of US$303.27 million. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd