Impact of protein co-production on techno-economic feasibility of microalgal biodiesel

Integrated microalgae biorefinery co-producing various valuable products is desirable for techno-economic feasibility. However, it is difficult to design due to numerous process alternatives at each processing stage. Moreover, the economic impact of such an integrated biorefinery on biodiesel production cost needs to be rigorously quantified. This work implements model-based superstructure optimization to optimize the biorefinery design and operation, and quantify the impact of co-production of protein on biodiesel production from Chlorella sp. The mixed integer linear programming (MILP) model first optimized the biorefinery that produced only biodiesel. The results showed that the net cost of biodiesel production was US $ 16.262/L, with lipid extraction contributing 78% of the cost. Subsequently, an integrated biorefinery was optimized that co-produced protein from lipid extracted biomass. The cost of biodiesel production got reduced by about 16% to US $ 13.726/L when protein was a co-product. For both scenarios, the model recommended the optimal operation strategies and equipment sizing for each process step. This study highlights the utility of co-producing protein for better economics of the entire system.