Chemistry
Production of Ethanol
Ethanol is produced through the fermentation of sugars by yeast, resulting in the conversion of glucose into ethanol and carbon dioxide. This process can also be achieved through the hydration of ethylene, a byproduct of petroleum refining. Ethanol is commonly used as a biofuel and as a key ingredient in alcoholic beverages.
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11 Key excerpts on "Production of Ethanol"
eBook - ePub- Jay Cheng(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
7Biological Process for Ethanol Production
Jay J. Cheng North Carolina State UniversityCONTENTS
7.1 History of Alcohol Fermentation and Ethanol as Fuel 7.2 Bioethanol Production Process 7.3 Saccharification and Hydrolysis for Fermentable Sugar Production 7.3.1 Saccharification of Starch 7.3.1.1 Starch 7.3.1.2 Liquefaction 7.3.1.3 Saccharification 7.3.2 Hydrolysis of Lignocellulose 7.3.2.1 Lignocellulose 7.3.2.2 Pretreatment 7.3.2.3 Enzymatic Hydrolysis 7.4 Fermentation Process 7.4.1 Enzymatic Reactions in Fermentation 7.4.1.1 EMP pathway 7.4.1.2 Other Products 7.4.2 Yeast Microbiology 7.4.2.1 Yeast Morphology 7.4.2.2 Yeast Cell Structure 7.4.2.3 Yeast Propagation 7.4.3 Fermenters 7.5 Ethanol Purification 7.5.1 Fractionation 7.5.1.1 Phase Equilibrium 7.5.1.2 Fractionation to Separate Ethanol from Water 7.5.2 Dehydration 7.5.2.1 Molecular Sieve Adsorption 7.5.2.2 Dry Corn Powder Adsorption7.5.2.3 Supercritical CO2 Extraction7.6 Byproducts 7.6.1 Distiller’s Dried Grains with Solubles (DDGS) 7.6.2 Carbon Dioxide 7.6.3 Other Byproducts 7.7 Examples 7.8 Problems ReferencesTABLE 7.1 Basic Properties of EthanolEthanol is also called ethyl alcohol. Pure ethanol is a colorless, volatile, flammable liquid. It is also a major component in alcoholic beverages such as liquor, wine, and beer. Ethanol is volatile and the mixture of ethanol vapor with air can be explosive when the volume fraction of ethanol vapor is in the range of 3.3%–19%. Liquid ethanol can be dissolved in water at any ethanol:water ratios. Ethanol is a constitutional isomer of dimethyl ether (CH3 –O–CH3 ) and often abbreviated as EtOH with Et representing C2 H5 –. The basic properties of pure ethanol are listed in Table 7.1
eBook - PDFEnergy From Alcohol
The Brazilian Experience
- Harry Rothman, Rod Greenshields, Callé Francisco Rosillo(Authors)
- 2014(Publication Date)
- The University Press of Kentucky(Publisher)
4 THE ETHANOL CHEMICAL INDUSTRY 4.1 The Ethanol Alternative Petroleum and coal have a dual industrial function, as sources of energy and feedstocks for the chemical industry. Ethanol is a rare alternative capable of fulfilling both these functions, although there are still many problems preventing this potential being realized on a large scale. For example, though alcohol fermentation is a well-understood process it remains a wasteful one. For every ton of alcohol produced 2 tons of sugar are required, a consequence of the chemistry rather than poor process efficiency alone. Thus, the cost of the substrate is of overwhelming importance. Ethanol is, none the less, presently being commercially exploited as a dual-purpose feed, although it has not as yet been proved to be financially advantageous over present oil prices. Several other possible competitive ethanol-derived chemical pro-ducts exist. Although few are commercially and economically feasible, a tremendous variety of derivatives are technically possible from an ethanol base, as can be seen from Figs. 4.1, 4.2 and 4.3. Brazil is regarded as the country most likely, in present circumstances, to make commercial use of such potential. The general production of chemicals from biomass is carried out in four stages: cultivation; fermentation; synthesis; and product preparation. All four stages must be evaluated together and not separately as is often the case. The most obvious problems arising in this combined complex are the on-stream factor and energy interaction. Sugar beet factories, for example, usually operate for a 'campaign' of 100 days per year to meet harvesting periods and cane mills from between 120-280 days per year. The capital intensive petro-chemical industry invests in plant systems designed to operate
eBook - PDF- Walter Koch(Author)
- 2023(Publication Date)
- Wiley-VCH(Publisher)
2.2 Production of Ethanol Ethanol is mainly produced via fermentation. As carbon and energy source predominantly corn in the US, wheat and corn in Europe and sugarcane in Brazil is used which reflects regional agricultural preferences. The feed is hydrolyzed to the monosaccharide level and then fermented with customized yeast strains typically of Saccharomyces cerevisiae family. Most of the ethanol fermentation plants do not source glucose or sucrose in the market, as usual for the standard non-ethanol fermentation plant, though are backward-integrated and source the grain or respective carbohydrate externally and pursue the digestion of the polysaccharide into the monosaccharide in their own plant. The obtained by-products are independently sold in the market. The backward integration into the feedstock provides a cost advantage. These activities covering the hydrolysis of cellulose and the fermentation part are sub- sumed under the header first-generation ethanol technology. In parallel, alternative raw material sources are accessed. Lignocellulosic biomass like corn stover or wheat straw is applied as fermentation feed. The endeavor to employ lignocellulosic biomass is driven by several reasons: Besides economic and political competition on the use of agricultural acreage either for “food or fuel,” the more sustainable use of lignocellulosic biomass for the production of chemicals opposed to the traditional burning of biomass for heat generation also a reduction of production cost is envisaged. Last, but not least, ethanol is produced based on industrial off-gas consisting of primarily CO, CO 2 , and H 2 . This developing tech- nology has for the first time been implemented by Lanzatech in China (Shougang). The technology applies acetogenic bacteria like Clostridium autoethanogenum and allows effi- cient conversion of industrial waste streams (Heijstra et al. 2017). The chemical Production of Ethanol is minor and can be neglected.
eBook - PDF- Harold Schobert(Author)
- 2013(Publication Date)
- Cambridge University Press(Publisher)
4 Ethanol 4.1 Fermentation chemistry Fermentation represents the first or second chemical process to be exploited deliber- ately by humankind. The other contender is combustion, i.e. controlled use of fire. Fermentation of sugars, particularly glucose, produces ethanol. Ethanol was probably the first organic chemical to be produced on a large scale. Ethanol’s importance in fuel chemistry lies in its use as a liquid transportation fuel, either blended with, or as a replacement for, gasoline. Fermentation begins with enzyme-catalyzed hydrolysis of a polysaccharide to glu- cose. Starches tend to be easier to hydrolyze than cellulose. Consequently, starches are, at present, the preferred feedstock for ethanol production. As mentioned in Chapter 3, humans can digest starches but not cellulose. Therefore, the possible diversion of large quantities of starch into ethanol production has significant ramifications, which are discussed later in this chapter. Glucose becomes phosphorylated by enzyme-catalyzed reaction with ATP, produ- cing a-glucose-6-phosphate: O CH 2 OH HO HO OH OH + ATP O HO HO OH OH + ADP CH 2 OPO 3 In many biochemical processes a thermodynamically unfavorable reaction can proceed by combining it with at least one additional reaction that is favored, provided that the net change in DG for the two (or more) combined reactions is negative. The reaction of glucose with HOPO 3 2 is not, by itself, favorable. But the reaction of glucose with ATP to form a-glucose 6-phosphate and ADP has a net DG that is negative. The utility, and great importance, of ATP in biochemical processes stems from its ability to drive reactions that would otherwise be unfavorable, such as the phosphorylation of glucose. a-Glucose 6-phosphate isomerizes to fructose 6-phosphate, converting an aldohexose to a ketohexose. Isomerization relies on keto-enol tautomerism; the exact reverse of this isomerization was presented in Chapter 3.
eBook - ePub- John Love, John A. Bryant, John Love, John A. Bryant(Authors)
- 2017(Publication Date)
- Wiley-Blackwell(Publisher)
5 Ethanol Production from Renewable Lignocellulosic Biomass Leah M. Brown, Gary M. Hawkins and Joy Doran‐Peterson University of Georgia, Athens, USA Summary Ethanol was first used as a motor fuel over 100 years ago but fell out of favour as the oil industry expanded. However, interest in ethanol as a fuel has increased greatly in the past 30 years for economic and political reasons and because of the desirability of decreasing the use of fossil fuels in order to reduce the extent of climate change. To date, most fuel ethanol comes from fermentation of sucrose from sugar cane and other sugar crops and from the carbohydrates of cereal grains, especially corn (maize). However, the latter raises concerns that crops that can be used for animal or human nutrition are being used to make fuel. Other sources of fuel ethanol are therefore being sought, including waste plant biomass left over after harvest and biomass grown specifically as a biofuel. However, the sugars in waste biomass are locked up in complex molecules. The plant material needs biological and physio‐chemical pre‐treatment to release the sugars. Furthermore, several of these sugars are not amenable to fermentation by conventional yeasts. The use of other microbial species, in some cases genetically modified, is required to ferment these sugars. In spite of these problems, there is very active interest in Production of Ethanol from plant biomass, and biomass refineries have been opened in the USA, Brazil and several countries in the EU. 5.1 Brief History of Fuel‐Ethanol Production Ethanol is a high‐octane motor fuel produced from the sugars, starches and cellulose found in plant materials. This biodegradable fuel has been in use for over a century, since the Model T Ford was launched in 1906 (Figure 5.1 a). Henry Ford recognised some of the desirable qualities of ethanol, particularly that it came from renewable biological materials and was relatively easy to produce
eBook - PDFCatalysis
Volume 22
- James J Spivey, K M Dooley(Authors)
- 2010(Publication Date)
- Royal Society of Chemistry(Publisher)
It should be noted that that fer-mentation is not a ‘‘green’’ process since one C6 unit of sugar gives only two moles of ethanol, two carbons being lost as CO 2 . Brazil and United States produce large quantities of bioethanol from sugar cane and corn respect-ively. In the European Union, where France and Spain are the largest producers, the ethanol production is more modest and comes from the fermentation of sugar beet or wheat in a large part. As ethanol is produced from biomass, its environmental performances in terms of greenhouse gas (GHG) emissions and energy saving are strongly related to the raw material. As an example, depending on the crop, the ethanol yield could vary dras-tically. Table 21 gives a comparison of the performances obtained in terms of ethanol yields from main ‘‘first generation’’ feedstocks. Catalysis , 2010, 22 , 1–55 | 37 These data corresponding to the cultivation efficiency have a direct im-pact on the climate benefits. Other factors influence the GHG emissions : (i) the fuel and fertilizer used in the ethanol plant; (ii) the efficiency with which by-product are dealt with; (iii) the type of land for cultivation. 218 According to the raw material, to the agricultural yield and to the transformation process efficiency, the energy balance (energy used/energy produced) has been shown to vary from 0.3 to 1.6 when bioethanol is used as biofuel. 217 Because of the existence of the high diversity of ways to produce ethanol, the divergences about the method to be used for calculating the level of GHG saving cannot be avoided. Different studies can bring to entirely opposite conclusions. For Searchinger et al. who assume that a production of biofuel requires new cultivation of cropland by ‘‘displacement effect’’, the production of bioethanol is considered as a threat for the environment. 219 From other authors it seems clear that, under most production scenari, the net greenhouse gas effect of bioethanol is positive.
- Kenneth Williamson, Katherine Masters(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
Fermentation Glucose S 2C 2 H 5 OH 1 2CO 2 Pasteur’s contribution Despite hundreds of millions of dollars spent each year on research on cellulosic ethanol, it is still far from competitive commercially. The use of ethanol to replace fossil fuels will only mitigate the greenhouse gas problem. It cannot possibly reduce it. Consider the entire world being planted with sugar cane. Growing the cane removes carbon dioxide from the air, but subsequent fermentation and combustion releases exactly the same quantity of carbon dioxide that was used to grow it. Overall, heat has been produced from light in a controlled and convenient manner through ethanol, but the carbon footprint from this activity remains in stasis, without a reduction. The future of ethanol as an automobile fuel is undergoing rapid change. The recent very low cost of petroleum due to fracking, the loss of subsidies, tariffs and tax incentives for corn ethanol, the recent exploitation of offshore oil by Brazil, and the increased cost of food due to diversion of corn from animal feed to ethanol all contribute to the uncertain future of ethanol in our fuel tanks. It takes 1.5 gal of ethanol to produce the same energy as 1.0 gal of gasoline. Copyright 2017 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 735 Chapter 65 ■ Biosynthesis of Ethanol and Enzymatic Reactions as the action of a living organism, but because the conversion of glucose to ethanol and carbon dioxide is a balanced equation, other chemists thought a chemical was responsible and disputed his findings.
- C.A. Cardona, O.J. Sanchez, L.F. Gutierrez(Authors)
- 2009(Publication Date)
- CRC Press(Publisher)
10.2.3 O THER M ETHODOLOGIES FOR THE E NVIRONMENTAL A NALYSIS OF B IOETHANOL P RODUCTION An integral study was carried out in Brazil regarding the ecological, economic, and social aspects of fuel ethanol production including the agricultural and indus-trial steps. Three ethanol production plants were analyzed and the results were quantified through the environmental efficiency of each process. According to the analysis performed, none of the three plants achieved the highest level estab-lished for environmental efficiency (Borrero et al., 2003). Prakash et al. (1998), in turn, proposed an indicator called figure of merit , which is expressed as the ratio between the net energy yield of a fuel (the difference between the gross energy produced during its combustion and the energy needed to produce it) and the CO 2 emissions produced by that fuel. Using this figure, it was concluded that for anhy-drous ethanol production from cane molasses in India the net energy yield is about 2% the potential of ethanol as a gasoline substitute in road transport has been estimated to be as high as 28%. A similar indicator based on the figure of merit has been proposed by Hu et al. (2004a) as well. Lynd and Wang (2004) developed a methodology for evaluating fossil fuel displacement for biological processing of biomass in the absence of product-specific information other than the product yield and whether fermentation is aerobic or anaerobic. With the help of this meth-odology, the authors answer affirmatively the question: Are there biomass-based processes and products with fossil fuel displacement sufficiently large that they could play a substantial role in a society supported by sustainable resources? Another methodology that has been used to measure the environmental fea-sibility and sustainability of bioethanol production processes over a long term is the so-called emergy analysis (see Chapter 2, Section 2.2.5).
eBook - PDFPolysaccharides
Structural Diversity and Functional Versatility, Second Edition
- Severian Dumitriu(Author)
- 2004(Publication Date)
- CRC Press(Publisher)
42 Bioethanol Production from Lignocellulosic Material Lisbeth Olsson, Henning Jørgensen, * Kristian B. R. Krogh, and Christophe Roca y Center for Microbial Biotechnology BioCentrum-DTU, kgs. Lyngby, Denmark I. INTRODUCTION Presently, bioethanol production receives tremendous at-tention, as bioethanol used as fuel in the transportation sector is sustainable and carbon dioxide neutral in contrast to fossil fuels. Furthermore, being produced from ligno-cellulosic material, it can represent a domestic energy source that is renewable. Bioethanol production is getting close to commercialization and presently large resources are put into solving the bottlenecks in the process. The use of ethanol is forecasted to grow rapidly in the coming years, and the first plant producing fuel ethanol from lignocellu-losic material is expected to be running in the near future. This chapter describes and evaluates the process for fuel ethanol production. The raw material, hydrolysis, and fermentation are described in detail, and different possibil-ities to perform these process steps in various process designs are discussed. The bottlenecks for the process and possible improvements in the future are assessed. A. Ethanol and Oil as Transportation Fuels: History and Interests Just before 1900, Henry Ford built his first vehicle, the quadricycle, which used ethanol as fuel. He also produced the Model T using ethanol as fuel. At this time, gasoline emerged as a more favorable transportation fuel, and the interest for ethanol decreased. This view has been domi-nant until the oil price suddenly escalated in 1973, and again in 1979. These oil crises demonstrated the world’s dependence on oil, and they were the onset for intensified search for alternative energy sources. One alternative to oil has been ethanol, produced from lignocellulosic material— also named bioethanol [1].
eBook - PDFBiofuels
Biotechnology, Chemistry, and Sustainable Development
- David M. Mousdale(Author)
- 2008(Publication Date)
- CRC Press(Publisher)
(Data from Sikyta. 254 ) Biochemical Engineering and Bioprocess Management for Fuel Ethanol 195 process efficiencies and energy cycling with the development of low-energy hydrous ethanol distillation plants with 50% lower steam-generating requirements. 252 The economics of downstream processing are markedly affected by the concen-tration of ethanol in the fermented broth; for example, the steam required to produce an ethanol from a 10% v/v solution of ethanol is only 58% of that required for a more dilute (5% v/v) starting point, and pushing the ethanol concentration in the fermenta-tion to 15% v/v reduces the required steam to approximately half that required for low conversion broth feeds. 253 4.6.2 C ONTINUOUS E THANOL R ECOVERY FROM F ERMENTORS Partly as another explored route for process cost reduction but also as a means to avoid the accumulation of ethanol concentrations inhibitory to cell growth or toxic to cellular biochemistry, technologies to remove ethanol in situ, that is, during the course of the fermentation, have proved intermittently popular. 254 Seven different modes of separation have been demonstrated in small-scale fermentors: A volatile product such as ethanol can be separated from a fermentation broth under vacuum even at a normal operating temperature; a system with partial medium removal and cell recycling was devised to minimize the accumula-tion of nonvolatile products inhibitory to yeast growth and productivity. 152 If the fermentor is operated normally but the culture liquid is circulated through a vacuum chamber, the ethanol formed can be removed on a con-tinuous basis; this arrangement avoids the need to supply O 2 to vessels maintained under vacuum. 255 Solvent extraction with a long chain alcohol ( n -decanol) with immobilized cells of S. cerevisiae ; up to 409 g/l of glucose (from glucose syrup) could be metabolized at 35°C.
eBook - PDF- Jamal Manassah(Author)
- 2014(Publication Date)
- Academic Press(Publisher)
ETHANOL FROM BIOMASS GEORGE F. HUFF Gulf Oil Science and Technology ABSTRACT Biomass represents stored solar energy. The light energy of the sun is converted by green plants into chemical, energy which is stored in chemical compounds such as starch and cellulose. Both materials can be used as raw materials for the pro-duction of ethanol which can be used as gasoline additive, for improving the octane number, or even as a gasoline replacement. The fermentation of starch as contained in grains, such as, maize and wheat, is well known and is widely practiced. This paper defines the fermentation of cellulose, a much more abundant material found in municipal and agricultural wastes, but which is not yet utilized in com-mercial processes. However, research to date indicates that commercialization will be achieved within the next few years. Economic projections for the commercialization of this process are presented. Preliminary results suggest that ethanol produced from cellulose will be price-competitive with non-subsidized gasoline. ALTERNATIVE ENERGY SOURCES 331 332 GEORGE F. HUFF INTRODUCTION The subject of alcohol fuels from biomass is receiving increasing interest world-wide. Alcohol fuels are by no means a complete or even principal solution to the coming shortages in liquid energy, but they can make a contribution to the solution as they take their place beside other alternate liquid fuels. Alternate fuels must be high on the agenda of the scientific and technical community in the closing decades of this century if civilization as we know it is to be preserved, and parts of mankind are not to be doomed to return to savagery. Biomass represents stored solar energy. This form of energy is stored by living plants containing chlorophyll. Green plants receive sunlight and in combination with water, atmospheric carbon dioxide, and soil nutrients convert light energy to chemical energy in a process called photosynthesis.
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