Process simulation of bioethanol production from brown algae Peyman Fasahati*, J. Jay Liu* *Department of Chemical Engineering, Pukyong National University, Busan, Korea (e-mail: fasahati@pknu.ac.kr; jayliu@pknu.ac.kr Abstract: Steady state ethanol production from brown algae (Saccharina japonica) based on 100,000 ton/year dry feed was simulated using Aspen Plus V7.3 software. Different process units including saccharification, fermentation and purification were modeled based on experimental works obtained from literature. Acid thermal hydrolysis using H 2 SO 4 and simultaneous saccharification and fermentation (SSF) were used and modeled in this simulation. Distillation columns along with molecular sieves were used to recover ethanol from the raw fermentation broth to produce 99.5% ethanol. This simulation is the first attempt in literature to evaluate large-scale production of ethanol from macroalgae and allows its economic analysis. Keywords: Bioethanol, Process simulation, Seaweed, Brown algae, Saccharification, Fermentation 1. INTRODUCTION Biofuels are gaining increased public and scientific attention, driven by factors such as oil price spikes, the need for increased energy security, and concern over greenhouse gas emissions from fossil fuels. It can be obtained from renewable sources containing starch, sugar, or cellulose, such as potatoes, corn, corn cobs and stalks, grains, and wood. One of main problems with using crops or woods as feedstock is that they will affect directly crop prices and will result in destruction of forests. Therefore, seaweed or macroalgae as a solution for this problem has been introduced recently. Some of advantages in using seaweed as feedstock include simple cultivation and possible productiveness. It also has easier manufacturing process (No lignin removal) with a higher CO 2 fixation ability. These advantages motivated researchers to report substantial amounts of experimental works showing possibility of production of ethanol from seaweed. But there is no large scale simulations developed yet to examine possibility of industrialization of the process. On the other hand, it is impossible to explore all the important features and variables of such a process via experimental investigations alone. Computer simulation is an invaluable tool for the analysis, design, and economic evaluation of the individual process units, and for comparing and optimizing various process alternatives. Computer simulations naturally cannot replace experimental studies, but are more of a tool used in the planning and evaluation of the experiments. Brown algae as a seaweed is evolutionarily diverse and abundant in the world’s oceans and coastal waters. The seaweed industry has an estimated total annual value of 5.5 to 6 billion US$, with 7.5 to 8 million tons of naturally grown and cultivated seaweed harvested worldwide. Seaweed is mainly used in food products for human consumption, which generates approximately 5 billion US$ per year, with the remainder used for production of extracted hydrocolloids, fertilizers, and animal feed additives (Adams et al., 2009; McHugh et al., 2003). Brown seaweed has a high content of easily degradable carbohydrates, making it a potential substrate for the production of liquid fuels. The carbohydrates of brown seaweed are mainly composed of alginate, laminaran, mannitol, fucoidan and cellulose in small amounts (Horn et al., 2000). Alginate is the major structural component of the brown algal cell wall, and mainly consists of β-D-Mannuronic acid and α- L-Guluronic acid units. In a wide range of industrial applications, alginates are essential compounds as thickening, gelling or stabilizing agents (McHugh, 1987). Laminaran is a linear polysaccharide of β-(1,3)-D-glucose in which the chain terminates with D-mannitol with low levels of branching at β-(1, 6)- glycosidic linkages (Horn et al., 2000; Myklestad S., 1987). Mannitol, a sugar alcohol derived from mannose, is also one of the main sugar components of brown seaweed. Mannitol, produced by photosynthesis, is universally found in brown algae and can account for 20–30% dw(dry weight) in some Laminaria species (Horn et al, 2000). Mannitol exhibits hydrating and antioxidant properties used in numerous cosmetic and pharmaceutical applications (Iwamoto et al, 2005). Mannitol is not readily fermented. It is oxidised to fructose by mannitol dehydrogenase, a reaction that generates NADH. Regeneration of NAD+ requires oxygen (active electron transport chain) or transhydrogenase, which converts NADH to NADPH. Thus, many microorganisms are not able to carry out strictly anaerobic fermentation of mannitol (Van Dijken et al., 1986) Fucoidan, the sulphated polysaccharide containing substantial percentages of l-fucose and sulphate ester groups, are constituents of brown algae (Patankar et al., 1993). In spite of the many studies attempting to determine the fine structure of the fucoidan, only few examples of regularity were found. Linkages, branching, sulphate positions and composition of monosaccharaides are strongly differing, and thus, the relationship between structure and biological activity is not Preprints of the 8th IFAC Symposium on Advanced Control of Chemical Processes The International Federation of Automatic Control Furama Riverfront, Singapore, July 10-13, 2012 © IFAC, 2012. All rights reserved. 597