ABSTRACT

Microalgae have rich potential to be a renewable source of energy. Additionally, a suite of products such as proteins, polar lipids, and reduced sugars can be co-produced, thereby leading to the concept of a biorefinery. The comparative analysis of different process alternatives and the study of mutual trade-off aid in achieving optimized design and operation of the microalgae biorefinery. This chapter presents a model-based superstructure optimization to this end. First, the model is applied to the case of biodiesel as the only target product. The net annualized life cycle cost (ALCC) for this scenario is US$13.286/L, with the step of growth accounting for around 88% of the expenditure. The model is expanded by the inclusion of more process alternatives, as well as through co-product generation. The net ALCC for this case is US$8.53/L, with reduced sugar being a co-product. Production of reduced sugar to the maximum theoretical potential is found to make the biorefinery economically viable. The prospect of microalgae for atmospheric carbon dioxide sequestration is also analyzed, subject to variations in demand and selling price profiles of end products. The optimized protocol of design and operations is also attained for each of the scenarios studied, thereby highlighting crucial bottlenecks and scope for improvement.