Design of biodiesel and bioethanol production process from microalgae biomass using exergy analysis methodology

Abstract

Microalgae are a promising source of energy and its principal advantage that does not compete with the feeding supply. Besides, microalgae have other benefits, such as the use of infertile land for its cultivation and seawater and flue gas as nutrients source. Exergy analysis is a useful tool for measure the quantity and quality of the energy sources and studies the sustainability process. This methodology requires analysing material and energy flows of each stage of the production process. In this study, exergy analysis was applied to one scenario taking a production capacity of 100 t/y of biodiesel from microalgae biomass. Chlorella sp was used as reference species. This strain has been widely studied, and their characteristics are known. The process designed have five stages: cultivation, harvesting, drying, oil transformation, and residual biomass transformation. The process was simulated using specialized software. The mass, energy and exergy balances were performed for each stream of the process. Finally, the exergy analysis was developed, and it was found that the residual biomass transformation stage with 32 % value present the lowest exergy efficiency of the process, followed by oil extraction stage with an efficiency of 52 %. The overall exergy efficiency of the process was 89 %, which indicates that designed process is adequate and have potential from the energy point of view.