Biobutanol: a Green Energy Fuel

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1 14 Biobutanol: a Green Energy Fuel Haruna Ibrahim 1* and Oluwole Joshua Okunola 2 1&2 National Research Institute for Chemical Technology, Zaria-Nigeria Abstract: The increasing cost of petroleum products, its nonsustainability, political crisis at source locations, couple with environmental hazard, renew interest is now focusing on renewable, sustainable and environmental benign fuels as alternatives. The greatest area that brings about the rise in price of fossil fuels is the transportation sector that use gasoline and diesel. While ethanol has been identified for fuel additive in internal combustion engines, butanol could be a better alternative as its properties are closer to that of gasoline than that of ethanol. However, the commercial fermentation production of biobutanol has not been encouraged due its energy intensive which makes it more expensive than petroleum production process. But recently bioengineering technology is discovering new production and separation techniques that have shown a promising and attractive process for biobutanol fermentation production. Keywords biobuthanol, history, modern technique, production 1. INTRODUCTION The increasing cost of petroleum products, its nonsustainability, political crisis at source locations, couple with environmental hazard, renew interest is now focusing on renewable, sustainable and environmental benign fuels as alternatives. Biobutanol or biobased butanol is also called biogasoline is a second generation alcoholic fuel with very high energy density [1] and low volatility. It is a colourless and flammable alcohol widely used in industry as solvents [2]. The renew interest research on biobutanol production arouses due to its quality as biofuels that supersede that of ethanol. It has an established history a chemical and solvent particularly for use in paints, coatings, printing inks, adhesives, sealants, textiles and plastics [3]. It is a biofuel that has the tendency to replace ethanol because of its numerous advantages over ethanol. These advantages include; low volatility, high energy density, eases separation from water mixture. Biobutanol can be used in internal combustion engines as blend, additive or wholly. This might be due to its closeness in chemical similarity to petroleum gasoline. The production and consumption of biobutanol is expected to reduce the consumption of oil and natural gas by automobile industry [2] and also reduce emission of greenhouse gases that are harmful to environment. 1.1 Isomers of Butanol Butanol has four isomers with slightly different properties. They are; 1. n-butanol or butan-1-ol (CH 3 CH 2 CH 2 CH 2 OH), is colourless, odouless and flammable liquid with banana smell. It is found useful as solvent in paints, coatings and varnishes, in plasticizers, in textiles as swelling agent for coated fabrics, in cosmetics as makeup, nail care, and shaving, in drugs as antibiotics, hormones and vitamins and as fuel in gasoline additive and brake fluid. 2. iso-butanol or 2-methyl propan-1-ol (OHCH 2 (CH 3 ) 2 CCH 3 ), is a colourless liquid with characteristic sweet smell immiscible in water but miscible in most organic solvents. It is found useful as solvent for coatings and adhesives, manufacturing other chemicals, as dispersing agent for cleaning and floor polishing, as flavor and fragrance and in pharmaceuticals as pesticides and gasoline additive. 3. Sec-butanol or butan-2-ol (CH 3 (OH)CHCH 2 CH 3 ), is a colourless, flammable liquid, slightly miscible in water but miscible in organic solvents. It is found useful as solvent, domestic cleaning in paints remover and as perfumes and flavours. 4. Tert-butanol or 2-methyl propan-2-ol (CH 3 (CH 3 ) 2 OH), is a clear liquid with characteristic camphor smell very miscible in water and ethanol and forms solid at 25 0 C. It is used in denature ethanol, as paint removal, octane booster in gasoline and for synthesis of other chemicals. Table 1 below summarizes the physical properties of the four isomers of butanol as claimed by Machada [4].

2 15 Table 1: Physical properties of isomers of butanol [4] Property n-butanol Iso-butanol Sec-butanol Tert-butanol 20 0 C (g/cm 3 ) Boiling point ( 0 C) Water solubility (g/100ml) Miscible Flash point ( 0 C) Octane Number HISTORY Of BIOBUTANOL The use of butanol as biofuel started 2005 when David Ramey toured the United States in a 13-year old buick fueled by butanol [5]. It was found to have 9% higher consumption but lower emissions of carbon mono oxide, hydrocarbons and nitrogen oxides (NO x ). It was reported that, biobutanol production via anaerobic fermentation has been observed since 1861, when it was witnessed by Pasteur [6]. During the anaerobic bacteria fermentation process, butanol is a single product among many. In 1905, Schardinger produced acetone by similar process. Kaminiski et al [2] claimed that the interest in biobutanol in 20 th century was as a result of inadequate level of supply of natural rubber that resulted increase in its market price. Butanol was the raw material for production of butadiene being a raw material for synthetic rubber production. The production of butanol via Acetone, Butanol and Ethanol (ABE) was first commercialized in the 1910s in the United Kingdom for the production of acetone which was the solvent needed for the production of cordite [7]. ABE fermentation was second to ethanol fermentation by yeast in its scale of production and is one of the largest biotechnological process ever emerged [8]. At the beginning of the 20th century, interest in biobutanol synthesis had risen due to butanol s involvement in the solution for material shortage of natural rubber. Natural rubber was out of stock and efforts were taken to make synthetic rubber from butadiene which could be synthesized from butanol. This discovery stimulated great interests in the fermentation production of biobutanol process. According to Jones [9], the industrial production of butanol by Clostridium spp. of Acetone-Butanol-Ethanol (ABE) fermentation process flourished during the first half of 20th century and continued into second half of the century until the availability of cheap crude oil made petrochemical synthesis more economically competitive. Ibrahim [10] claimed that the ABE production of biobutanol by fermentation was discovered by Russian Chemist Chaim Weizman at Manchester University, in He isolated a bacterium later known as Clostrium Acetobutylicum which he used to ferment starch into Acetone, Butanol and Ethanol. Acetone was in high demand then during the First World War for the production of cordite, cartridges and propellant. Another report [6], claimed that between 1912 and 1914 Chaim Weizmann performed one of his first microorganism screenings to study microbiology in hopes to better understand the fermentation process. During the World War 1, the need for production of the smokeless gun powder in large quantities as cannot be imported let British to seek for the assistance of Weizmann to design a system to increase acetone production by fermentation. Acetone was used to produce smokeless gun powder, or cordite. The British Army later adopted and implemented it at the loyal Naval Cordite Factory. Industrial fermentation of starchy raw materials as feedstock using Clostridium acetobutylicum as bacteria fermentation agent was first commercialized in 1914 [4]. When the U.S joined the war, Britain and U.S started a joint project for production of acetone. At the end of the World War 1, large stockpiles of butanol a by-product of acetone had built up [5]. The stockpiles of the butanol were employed by E.I. du pont de Nemours and co which used the butanol as solvent for cellulose lacquer, which was a quick-drying automobile finish [4&5]. It was reported [5] that Weizmann demanded for a home for Jews in the Palestine as a reward from Great Britain which lead to the Balfour declaration of 1917 which formed the foundation of the State of Israel. Weizmann became the first president after the establishment of the state of Israel. After the expiration of Weizmann s patent in 1936, the anaerobic fermentation plants were left opened for production of acetone and butanol. It was reported [6] that every company had its own patent microorganism, which was able to produce acetone and butanol in large amounts from molasses. Later again during the Second World War, acetone was needed for munitions, this spike off production of acetone and butanol [6]. Great Britain had to import molasses and U.S. used corn mash to produce acetone. It was reported that, India, Australia, South Africa and

3 16 Japan joined in the production of acetone. After the Second World War in 1960 s, fermentation process of butanol production gave way to petrochemical process, because the later process was much easier and cheaper. Most of the plants in Western countries were closed because of rising substrate prices and competition by the growing petrochemical industry [5]. Besides, the price of molasses had increased, hence the fermentation process for acetone and butanol production became inefficient and not economical. Kopke et al [5] reported that, ABE fermentation was only continued in countries that were cut off from international supplies for political or monetary reasons; the South African apartheid regime ran a plant in Germiston with a capacity of 1,080 m³ until The former USSR operated at least eight plants, some of them up to the late 1980s. Continuous fermentations with lignocellulose hydrolates as substrate and working volumes of more than 2,000 m³ were carried out. During the 1960s and 1970s more than 100,000 tons of butanol per year was produced. China also developed the continuous fermentation process and about 30 plants produced an annual amount of 170,000 tons of solvents at its peak in the 1980s. Afterwards the production decreased successively and the last plant was closed in WHY THE QUEST FOR BIOBUTANOL Butanol is a high quality liquid fuel and a widely used industrial chemical [10]. Biobutanol suits internal combustion engine more than bioethanol and can be used as a direct replacement for gasoline. It was recently used as a fuel in an unmodified car that was driven across U.S [9]. Butanol is superior to ethanol in almost every way convertible to jet fuel and gasoline, a valuable established chemical and solvent and gate way molecule to a wide range of chemical derivatives [3]. According to kaminiski et al, [2], researches have shown that the use of butanol as fuel additive is better than ethanol because it has high calorific value, 29.2MJ/dm 3, higher melting point, C high boiling point, C high flash point, 36 0 C and high self-ignition at C. Butanol has higher energy density, lower water adsorption, and better blending ability with gasoline than ethanol [12]. Biobutanol is less flammable, less soluble, in water, and less corrosive [11]. Table 2 compares the properties of butanol, ethanol and gasoline. It is expected that production of biobutanol can reduce consumption of oil and natural gas by the automobile industry and reduce emissions of harmful gasses into the atmosphere [2]. Table2: Comparison of fuel properties of butanol and others [2 &5]. Fuels Energy density (MJ/dm 3 ) Mileage (%)] Air-fuel ratio Boiling point ( 0 C) Flash point ( 0 C) Octane Rating Gasoline Ethanol Butanol Its higher flash point makes it safer in the presence of flame than both gasoline and ethanol. Biobutanol has better water tolerance than ethanol and biodiesel makes it easier to separate from water than ethanol. Its low solubility in water reduces its tendency for spill to spread in underground water, transportable in petroleum pipe lines and usable in gasoline blend at any ratio [12]. Also, these properties enable it to be distributed through pipes. Biobuthanol has properties similar to gasoline than ethanol. The drawback that biobutanol has over the gasoline is lower octane rating as shown in table 2 above. This implies that switching from gasoline to biobutanol would result in larger fuel consumption [13]. However, biobutanol has bigger energy content than ethanol because of the larger number of carbon atoms in the molecule (four for biobutanol and two for ethanol). Biobutanol Bioethanol

4 17 The air-fuel ratio of butanol is higher than that of ethanol, which means that it can be run at richer mixtures and therefore produce more power [13]. Butanol can be blended in any ratio with gasoline well ahead of distribution and can be transported by the existing infrastructure the same cannot be achieved with ethanol for the fear of contamination. Butanol can be transported with pipes but ethanol cannot except by tanks through trucks, rail cars and river badges. With low vapour pressure butanol is safer to handle than ethanol. Biobutanol has higher energy density resulting increase in mileage than ethanol [10]. Butanol is stable on long time storage and highly combustible but not explosive [4]. Butanol can be catalytically converted to jet fuel [7]. 4. PRODUCTION OF BIOBUTANOL Biobutanol can be made from a variety of biomass types which include corn, wheat, sugar cane, sugar beet and, in the future, non-food lignocellulosic materials. According to Jones [9], virtually all butanol is produced chemically using either the oxo process from propylene or aldo process from acetaldehyde. However, it can also be produced by fermentation just like ethanol. Biobutanol can be adapted ethanol plants from corn and other grains or sugar cane and from cellulose [3]. It was reported [15] that biobutanol was made via fermentation of biomass from substrates such as corn grain, corn stovers and other feedstocks. Microbes, especially the Clostridium acetobylicum are introduced to the sugars produced from biomass. The sugars are broken into acetone, butanol and ethanol in the ratio 3:6:1 [2]. But unfortunately, a rise in butanol concentration causes butanol to be toxic to the microoganisms, kill them off after a short while. Ezeji et al [16] claimed that anaerobic bacteria; Solventogenic clostridia are capable of secreting numerous enzymes that facilitate the decomposition of polymeric carbohydrate into monomers. These bacteria are capable of converting simple sugars such as glucose, galactose, mannose, xylose etc. into acetone, butanol and ethanol but the toxicity of the butanol kills these microorganisms. Ramney and Yang [8] reported that, ABE fermentation reaction goes through the production of acetic, butyric and propionic acids by Clostridium acetobylicum, then the metabolic shift of the culture produces solvents; acetone, butanol and ethanol. By increasing butyric acid concentration to >2g/l and decreasing the ph <5 are usual require conditions for the induction of metabolic shift from acidogenesis to solventogenesis (conversion from acids to solvents) but this reaction is difficult to control [8]. Genetically modified versions of the Clostridium to improve butanol tolerance and yield technology is being developed in the US, Europe and Asia [15]. This will eliminate the bacteria poisoned challenge faced by biobutanol developers as these bacteria get poisoned by the butanol they produce once its concentration rises above around 6%. A microbiologist in the College of Agricultural, Consumer and Environmental Sciences at the University of Illinois, Hans Blaschek, is working on strains of the soil bacterium Clostridium beijerinckii, which he himself developed 10 years ago at the Illinois laboratory [15]. An alternative non-fermentative method has been established by metabolic engineering of the amino acid biosynthesis pathways, which allows for production of 1-butanol and also iso-butanol [12]. As the raw materials are expensive due to their demand for food, cellulose waste materials are used to process biobutanol. Straw from crops, wood residues, and other sources of plant biomass are investigated that would be more cost effective [16]. 4.1 Advance Techniques in Biobutanol production It has been reported [4] that Clostrida secrete numerous enzymes that can break down polymeric carbohydrates into monomers. This process utilizes inexpensive agricultural residues as fermentation substrates which is capable of reducing the production cost. Ezeji et al, [16] reported that a lot of Engineering attempts have been employed to increase the ABE fermentation yield such as cell recycle and cell immobilize to increase cell density and reactor productivity and using extractive fermentation to minimize product inhibition. Despite all the efforts employed with ABE fermentation has never produced up to 20g/l glucose of butanol concentration [8]. Colorado based company used genetically modified yeast that produces only iso-butanol from glucose. A biofuel based in California used non-modified Clostrium to break down celluloses, hemicelluloses and starch in plants. It was reported [17] that Cobalt s dilute acid hydrolysis pretreatment process, which extracts sugars from ligno-cellulosic biomass, was validated on woody biomass, bagasse and agricultural residues. To convert the cellulose and hemicellulose in lignocellulosic biomass, Cobalt has developed a process that simultaneously extracts and converts the carbohydrates into simple sugars. It was reported [18] that Cobalt production technologies are designed to process a broad range of non -food feedstocks, avoiding the risks associated with reliance on a single crop. Cobalt's technology is based on a bacterial fermentation

5 18 of biomass sugars into butanol. Cobalt's proprietary bacterial strain development technology improves the fermentation performance of a variety of naturally occurring feedstocks. These feedstocks are specifically selected for their ability to utilize all five of the sugars found in plant materials, including the 5-carbon sugars that cannot be fermented by common yeast. This innovative technology makes it possible to utilize a range of residual biomass feedstocks. cobalt technology has improved the resistance of the microorganism to the by-products of biomass conversion. The Cobalt uses continuous bioreactor system which dramatically increases production rate as much as 11-fold over traditional batch fermentation processes [19]. This results in a more capital efficient production process as well as lower input costs, resulting in a more economic process. 4.2 Characterization of Biobutanol Biobutanol properties are more similar to gasoline than bioethanol [11]. Biobutanol does not form azeotropic mixture with water as ethanol does. It tolerates water contamination unlike ethanol and biodiesel indicating that it has less affinity to water than ethanol [4]. Tables 1 and 2 provide the properties of quality butanol. 4.3 Drawbacks Associate with Production of Biobutanol Distillation of biobutanol from the fermentation broth is very energy consuming [11]. As butanol has a higher boiling point than water, process consumes much energy, and therefore it increases the cost of the whole process, especially at low concentration of butanol in the broth. Therefore, currently other methods are used such as adsorption, membrane perstraction, extraction, pervaporation, reverse osmosis or "gas stripping with more emphasis on pervaporation. The adsorption method of removing butanol from broth is done with silicalite which selectively adsorb small alcohol molecules of methanol to pentanol from aqueous solution. This method is not favourably feasible for industrial scale. This follows from the small-capacity of adsorbents for butanol [2]. Another method is the use of membrane reactor which increases the concentration of butanol from 0.39 g/dm 3 /h to 15.8 g/dm 3 /h. Pervaporation, is one of the membrane separation technologies, which has high selectivity and low energy consumption compared to other separation techniques [11]. Pervaporation can be used to separate azeotropic mixtures and other kind of mixtures, which are usually difficult to separate by conventional techniques like distillation [19]. Pervaporation involves the selective transport by diffusion of some components through a membrane. Due to their low vapour pressure and low solubility in water, ionic liquids are solvents for extraction of organic compounds in water. Pervaporation is effective for removal of organic compounds from water and separation of mixtures of two or more organic compounds [13]. According Marszałek et al, [14], another constrain is the use for the fermentation crop products which is not very economical; primarily because of high price due to demand for these crops by food industries. However, by optimizing fermentation productivity, yield, and titer, Cobalt is making biobutanol a viable and economic transportation fuel. Cobalt's distillation process for butanol recovery uses approximately half the energy and half the equipment compared to conventional butanol distillation [16]. In addition Cobalt s technology platform offers a continuous process to efficiently convert diverse non-food feedstocks into biobutanol. 5. CONCLUSION Biobutanol is a green fuel; its use in transport sector will contribute to reduction in environmental degradation associated with the use of fossil fuels. It has all it takes to replace ethanol as fuel additive with gasoline because its physicochemical properties are closer to that of gasoline than ethanol; higher energy density, low solubility in water, less corrosive and lower vapour pressure that makes it less polluting than ethanol. It can be used as direct replacement for gasoline in internal combustion engine. With cobalt advance technology in biobutanol production, the agricultural residues that were known to be wastes are going to be turned to useful raw materials for biobutanol production. The production of biobutanol from agricultural residues will generate employment opportunities and provide economic empowerment to many. REFERENCES 1. Internet (a), (A ccess: 06/10/2013).Biobutanol: Important biofuel and byproduct, Available at: 2. Kamniniski W. Tomcrak E. Gorak A. (2011). Biobutanol-Production and purification Methods. Ecological Chemistry and Engineering. Vol. 18, No 1 Pp31-37

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