Evaluation of alternatives for microalgae oil extraction based on exergy analysis Y. Peralta-Ruiz, A.-D. González-Delgado, V. Kafarov ⇑ Research Center for Sustainable Development in Industry and Energy, Department of Chemical Engineering, Industrial University of Santander, Colombia highlights " Exergy analysis was used as decision-making tool for evaluation of microalgae oil extraction. " A robust composition of Chlorella sp. biomass was modeled and used for simulation. " Three solvent-based microalgae oil extraction methods at large scale were compared. " Hexane based extraction presented the highest exergetic efficiency. article info Article history: Received 10 December 2011 Received in revised form 19 June 2012 Accepted 29 June 2012 Available online 24 August 2012 Keywords: Microalgae biomass Exergy analysis Oil extraction Third generation biofuels abstract Several technologies for microalgae oil extraction are being evaluated in order to find the most adequate for large scale microalgae processing. In this work, exergy analysis was used as an instrument for screen- ing three design alternatives for microalgae oil extraction in a large-scale process and as a decision- making tool for evaluation and selection of novel technologies from the energy point of view. Routes were simulated using dedicated industrial process simulation software, taking as feedstock a representative and robust modeled composition of Chlorella sp. microalgae biomass. Mass, energy and exergy balances were performed for each alternative, and physical and chemical exergies of streams and all specific mic- roalgae constituents modeled were calculated with the help of the thermodynamic properties of biomass components and operating conditions of streams. Exergetic efficiencies, total process irreversibilities, energy consumption and exergy destruction were calculated for all solvent-based microalgae oil extraction pathways evaluated. It was shown that exergy analysis led to identify the hexane-based oil extraction (HBE) as the most adequate alternative of the routes assessed for scaling up from the energy point of view, presenting a maximum exergy efficiency of 51% and exergetic losses of 982,000 MJ considering a production of 104,000 t of microalgae oil per year. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, the continued use of fossil-derived fuels is recog- nized as unsustainable due to the exhaustion of supplies and their contribution to environmental pollution. This kind of fuels has to be replaced with clean and renewable energy. In response to this issue, environmental policies worldwide have favored the increase in research, development and the use of biofuels, mainly those that can replace fossil fuels used in transportation. Biofuels offer many benefits associated with energy security, economic stability and reduction of the environmental impact of greenhouse gases [1]. Third-generation biofuels are derived from microorganisms, such as yeast, fungi and microalgae, some of these microbes can biosynthesize and accumulate large amounts of lipids and/or sug- ars [2], fungi like Trichosporon fermentans have been studied for microbial oil production and biodiesel preparation [3,4], however, the most attractive source for third generation biofuels production are microalgae. They have recently been rediscovered as promising candidates for biotechnological applications and efficient energy production systems [5]. Depending on the strain, microalgae can grow in a wide range of temperatures, pH and nutrients availabil- ity. They have a growth rate between 20 and 30 times higher than other sources for biofuels, some microalgae species have the ability to produce up to 20 times more oil per unit area than palm [6], oil content of certain strains in some cases exceeds 80% in dry weight biomass under appropriate conditions [7]. Microalgae can grow in warm, tropical, and subtropical climates, for biomass production it only requires water, some nutrients, a carbon source and a high and constant sun irradiance. Microalgae can be cultivated in pho- tobioreactors which offer high biomass productivities and an adaptable illumination, open ponds which can be natural systems 0306-2619/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apenergy.2012.06.065 ⇑ Corresponding author. Address: Research Center for Sustainable Development in Industry and Energy, Department of Chemical Engineering, Industrial University of Santander, K 27 Cll 9 Bucaramanga, Colombia. Tel.: +57 7 6344000x2603. E-mail address: Kafarov@uis.edu.co (V. Kafarov). Applied Energy 101 (2013) 226–236 Contents lists available at SciVerse ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy