J. of Supercritical Fluids 85 (2014) 31–40 Contents lists available at ScienceDirect The Journal of Supercritical Fluids jou rn al hom epage: www.elsevier.com/locate/supflu Economic analysis of a plant for biodiesel production from waste cooking oil via enzymatic transesterification using supercritical carbon dioxide Pedro Lisboa, Ana Rita Rodrigues, José Luis Martín, Pedro Simões, Susana Barreiros ∗ , Alexandre Paiva ∗ REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal a r t i c l e i n f o Article history: Received 16 August 2013 Received in revised form 25 October 2013 Accepted 28 October 2013 Keywords: Biodiesel Waste cooking oil Ethanol Lipase Supercritical CO2 Economic analysis a b s t r a c t Enzymatic transesterification is becoming a commercially competitive route to biodiesel. Supercritical CO 2 (scCO 2 ) is well established as a solvent for extraction processes. Here we analyze the economy of a scCO 2 -based, enzymatic process, for the production of biodiesel from waste cooking sunflower oil (WCO). The conversion of WCO to fatty acid ethyl esters (FAEE) catalyzed by immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM), and downstream separation to recover biodiesel conforming to the EN14214 norm, were studied in a pilot plant unit. The data generated was used to design an envisaged industrial plant, for which an energy balance was carried out. Investment and production costs were estimated for the conversion of 8000 ton WCO /year. This led to biodiesel costs of 1.64D /L and 0.75D /L (for a WCO price of 0.25D /kg; enzyme prices of 800D /kg and 8D /kg, respectively), which already reflect the ca. 10% impact of glycerol sales. © 2013 Elsevier B.V. All rights reserved. 1. Introduction World marketed energy consumption is expected to grow by nearly 50% in the period 2008–2035 [1]. Liquid fuels derived from oil remain the largest source of energy, in spite of recent and projected continued increases in oil prices that reflect not only sit- uations of increased demand from non-OECD countries but also of social and political instability around the world. The largest contri- bution to the projected growth in liquid fuels consumption comes from the transportation sector, which will continue to account for nearly 60% of world oil demand and should be the strongest grow- ing energy demand sector until 2035 [1]. The high price of fossil fuels has brought to light once more the discussion about biofuels, namely biodiesel. So far, high produc- tion costs have prevented biodiesel from being competitive with diesel fuels in the absence of government incentives. However, high crude oil prices make biodiesel a viable alternative to petrol diesel. In fact, world biofuels production is expected to grow at an average of nearly 4% per year until 2030, in spite of the impact of economic recession in some countries on biofuels development [1]. In par- ticular, the European Union 2009 Renewable Energy Directive set ∗ Corresponding authors. Tel.: +351 212 949 681. E-mail addresses: sfb@fct.unl.pt (S. Barreiros), alexandre.paiva@fct.unl.pt, abp08838@fct.unl.pt (A. Paiva). the target of 20% renewable energy by 2020, based on concerns to reduce greenhouse gas (GHG) emissions levels, as well as Europe’s energy import dependence [2]. This boosts biodiesel as part of the solution to the energy and economic problems at hand [3–5]. Of the various factors that contribute to the cost of biodiesel, feedstock is considered to be the most important. In addition to accounting for about 75–80% of the total operating cost [5], its origin is directly related with its sustainability. In fact, although biodiesel is generally regarded as a viable “green” fuel that reduces noxious exhaust emissions [5], biofuel demand can impact on the global agricultural market and food prices. The continuing controversy of food vs. energy has been an obstacle to wider public acceptance of biodiesel. This has led to the cultivation of crops that grow on land that is not adequate for, and does not compete with land used for food production, and to the use of waste fats and oils, such as waste cooking oil (WCO) [6–9]. It is estimated that about 29 million tons of WCO are generated per year [7]. Using WCO as feedstock for biodiesel production not only reduces costs but also addresses an important environmental problem. It has been shown that engine performance using biodiesel produced from WCO is essentially the same as when using biodiesel produced from virgin oils, no engine modifications being required [4,9]. The transesterification of oil triglycerides is the most com- mon technology of biodiesel production [3], and is seen to have advantages over other approaches, such as pyrolysis, dilution and microemulsion formation due to high conversion efficiency and 0896-8446/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.supflu.2013.10.018