Exergy Analysis for third Generation Biofuel Production from Microalgae Biomass

In the search for renewable energy, third generation biofuels have become an innovative alternative that offers a wide variety of exceptional benefits. A major advantage of third generation fuels is that the raw materials used as a source does not compete with food sources also have a high percentage of yields per unit area. Nowadays the production of biodiesel from microalgae is an option that has attracted strong interest of the scientific community and should be evaluated to determine the technical, technological, economic and environmental sustainability of the process. Exergy analysis is a useful tool for measure the quantity and quality of the energy sources and analyze the process sustainability previously mentioned, besides, exergy analysis has been widely used in the design, simulation and the global evaluation and improvement of the processes. The relationship between exergy, energy and environment can recognize that the exergy is closely related to sustainable development. This methodology requires analyzing material and energy flows of each stage of the production process. In this study exergy analysis was applied on two scenarios taking a production capacity of 100,000 t/y of biodiesel from microalgae biomass. Chlorella vulgaris (Chlorella sp) was used as reference algae. This algae has been widely studied and their characteristics are well known, also one of the algae that have a higher percentage of lipids. In this work a basic process for biodiesel production is showed, comprising the following steps: transesterification, separation and washing the biodiesel. Thermodynamic variables as entropy, enthalpy, Gibbs free energy were determined for all process steps and exergetic losses using the software ASPEN-PLUS ® . Finally the exergetic efficiency was calculated for the overall process. The results confirm the potential of third generation biofuels microalgae as an energy source.