Integrated Synthesis of Biodiesel, Bioethanol, Isobutene, and Glycerol Ethers from Algae Veró nica de la Cruz, † Sara Herna ́ ndez, † Mariano Martín,* ,† and Ignacio E. Grossmann ‡ † Department of Chemical Engineering, University of Salamanca, Pza. Caídos 1-5, 37008 Salamanca, Spain ‡ Department of Chemical Engineering, Carnegie Mellon University. Pittsburgh, Pennsylvania 15213, United States ABSTRACT: In this paper, we design an integrated process for the production of diesel substitutes, biodiesel and glycerol ethers, from algae with internal production of the intermediates ethanol and isobutene. The starch from the algae is converted into glucose. Part of it is fermented to ethanol so that we produce the alcohol needed to transesterify the algae oil while the rest is fermented to isobutene, which is needed in the production of glycerol ethers to enhance biofuels production capacity. We use CHEMCAD coupled with MATLAB for the rigorous simulation of the integrated biorefinery and evaluate the algae composition for such integrated facility. This is followed by energy integration using SYNHEAT and a detailed economic analysis. The integrated facility has promising production cost for liquid fuels, 0.46 $/gal, and an investment costs of $205M, almost half the production cost and only and investment $40M above the plant that buys the isobutene from the market. 1. INTRODUCTION For quite some time biodiesel facilities have been designed for the production of this particular biofuel from cooking oil, algae, or vegetable oil. Even though they are regarded as biorefineries, they actually are focused on the production of one main product, biodiesel, and some byproducts (i.e., fertilizers, glycerol) while some raw materials came from fossil resources, for instance, methanol. Even though the use of methanol was traditionally supported by its lower price and faster reaction times, Severson et al. 1 proved that it is economically competitive to produce biodiesel using ethanol. Furthermore, Martı ́ n and Grossmann 2 integrated the production of bioethanol and biodiesel from algae oil resulting in competitive production costs compared to those resulting from the use of methanol. With the current need for sustainable liquid fuels, a number of alternatives have been presented to increase the production of biofuels using the byproducts of the current biorefineries. For instance, the production of biodiesel generates glycerol. The high price as a result of its use in the cosmetic and food industries has been an asset for the production of biodiesel and it has improved the economics of such plants. However, the increase in the production of biodiesel is saturating the market, and new uses for glycerol are being developed to help reduce our dependence on fossil fuels. Recently, Cheng et al. 3 developed a process for the use of glycerol to produce oxygenated derivates, glycerol ethers. The advantage is that they can also be used as diesel substitutes increasing the yield to biofuels. 4 The drawback is that, apart from glycerol, the second raw material is isobutene, an expensive C4 chemical typically obtained in the fractionation of crude. However, van Leeuwen 5 proved that it is possible to produce isobutene from sugars and recently Martı ́ n and Grossmann 6 found that its production from biomass containing glucose and xylose is economically promising. Algae are a particularly rich raw material whose composition consists mainly of lipids, starch, and protein. Therefore, from algae we have all the components to design an integrated facility that produces ethanol and isobutene from starch as inter- mediates, oil from the lipids that is transesterified with ethanol producing biodiesel (Fatty acid ethyl ester, FAEE), while the glycerol, byproduct of the transesterification reaction, reacts with isobutene producing glycerol ethers which are diesel substitutes. Since isobutene and bioethanol are produced from the starchy biomass within the algae, the composition of the algae may need to be adjusted so that we can self-sufficiently produce the intermediates that are needed for the production of biodiesel and glycerol ethers avoiding the need for fossil based raw materials. Thus, in this paper, we present the conceptual design of an integrated biorefinery from algae, which produces diesel substitutes, biodiesel (FAEE), and glycerol ethers, but which can also produce isobutene and ethanol, for internal use. We use a hybrid approach employing modular process simulators such as CHEMCAD coupled with equation based software, MATLAB. After the rigorous simulation, we design a heat exchanger network and perform an economic evaluation of the operation of such facility. The paper is organized as follows. Section 2 presents the description of the different sections of the process and the main operating conditions and constraints. Section 3 describes the modeling approach using CHEMCAD and MATLAB. Section 4 presents results from the material and energy balances, water consumption, and the economic evaluation. Finally, in section 5, we draw some conclusions. 2. OVERALL PROCESS DESCRIPTION As seen in Figure 1, we divide the process in five sections: algae oil production, ethanol production from starch, isobutene production from starch, biodiesel production from oil, and finally high glycerol ethers (di- and tri-tert-butyl glycerol: DTBG + TTBG = hTBG) production from glycerol. Received: June 5, 2014 Revised: August 13, 2014 Accepted: August 13, 2014 Article pubs.acs.org/IECR © XXXX American Chemical Society A dx.doi.org/10.1021/ie5022738 | Ind. Eng. Chem. Res. XXXX, XXX, XXX-XXX