Ethyl Alcohol Production

Introduction

Ethanol is produced by fermenting plant carbohydrates with yeast. Plant carbohydrates include soluble sugars such as sucrose from sugarcane, storage carbohydrates such as starch from grains and tubers, and structural carbohydrates which make up the plant cell wall of grasses and wood, such as cellulose, hemicellulose, and pectin. The principal carbohydrates contained in lignocellulose resources are the structural carbohydrates. These carbohydrates, along with proteins and lignin, form the complex matrix of plant cell walls that give plants structural stability and protection from the environment.

Ethanol production processes vary by type of feedstock. Production from corn primarily uses the Dry Grind Process or, to a lesser extent, the more capital intensive Wet Milling Process, which produces a greater variety of marketable co-products. Production of ethanol from sugarcane juice or molasses uses technologies similar to those used to produce ethanol from corn.

Production of ethanol from cellulosic biomass such as crop residues, grasses or wood involves intensive pretreatment to break down the biomass (hydrolysis) into fermentable sugars. A number of pretreatment approaches are currently under evaluation. However, scaling pretreatment processes to commercial sizes and the associated reactor design issues so far remain a major barrier to the commercial production of fuel ethanol from lignocellulosic biomass.

On a mass basis, one kilogram of glucose will theoretically produce 0.51 kilogram of ethanol and 0.49 kilogram of carbon dioxide. However, the glucose consumed to generate additional yeast cells does not result in the production of ethanol. Most industrial fermentation processes therefore operate at 90 to 95% of the theoretical yield.

Raw Materials

The three basic types of feedstock  used in Ethanol Production are:

a.       SACCHARINE (sugar containing) materials in which the carbohydrate (the actual substance from which the alcohol is made) is present in the form of simple, directly fermentable six and twelve carbon sugar molecules such as glucose, fructose, and maltose. Such materials include sugar cane, sugar beets, fruit (fresh or dried), citrus molasses, cane sorghum, whey and skim milk.

b.      STARCHY MATERIALS that contain more complex carbohydrates such as starch and insulin that can be broken down into the simpler six and twelve carbon sugars by hydrolysis with acid or by the action of enzymes in a process called malting. Such materials include corn, grain sorghum, barley, wheat, potatoes, sweet potatoes, Jerusalem artichokes, cacti, manioc, arrowroot, and so on.

c.       CELLULOSE MATERIALS such as wood, wood waste, paper, straw, corn stalks, corn cobs, cotton, etc., which contain material that can be hydrolyzed with acid, enzymes or otherwise converted into fermentable sugars called glucose.

Production of Ethanol in Dry - Milling Process

Grain Preparation

Preparation of the corn grain involves cleaning and conditioning steps, as well as generating an aqueous solution high in simple sugars. Generally, enough grain is stored on site in bins to meet facility needs for 8-12 days of operation (Kwiatkowski, 2006). Broken corn kernels and foreign materials (metal, dirt, cobs, etc.) are removed by blowers and screens. The cleaned corn is then ground in hammer mills fitted with screens with openings ranging between 3.2 and 4.8 mm in diameter, which provides grain particles of a more uniform size: more than 90% of the ground corn, by weight, has a diameter between 0.5 to 2 mm (Rausch, 2005). Grinding serves to break the tough outer coating of the corn kernel and increases the surface area of exposed starch.

Liquefaction involves combining the ground corn with process water to form a slurry which is approximately 30% solids by weight (Kwiatkowski, 2006). Ammonia and lime are added at this step to adjust the pH of the slurry to 6.5. The ammonia, which contains nitrogen, also serves as a nutrient for the yeast in the subsequent fermentation step. The slurry is heated to 88°C by direct steam injection using a “jet-cooker”. A thermostable enzyme (alpha-amylase) is added to cleave the starch molecules at random points along the middle of the polymer chain and to break the starch into smaller water soluble fragments called dextrins. After approximately one hour, the output from the first step of liquefaction is combined with “backset”, which is recycled water from the end of the ethanol distillation process. The backset accounts for approximately 15% of the final volume of the corn mash (McAloon, 2000). Critical nutrients for the yeast are also carried in the backset. As the liquefied slurry is cooled to 60°C, the heat is recovered and used to heat new, incoming slurry going to the jet-cooker (Kwiatkowski, 2006). A new enzyme technology developed by Genencor allows for the rapid hydrolysis of granular starch and eliminates the need for gelatination of the starch slurry by jet-cooking, thus significantly lowering the energy requirements for ethanol production from corn (Shetty, 2005).

Following liquefaction, sulfuric acid is added to the slurry to lower the pH to 4.5. An additional enzyme, glucoamylase (also called beta-amylase) is added to break the starch and dextrins into glucose via a stepwise hydrolysis of glucose from the end of the molecules. The slurry is held at 60°C for 5-6 hours as the glucoamylase hydrolyzes the dextrins to fermentable glucose (Schenck, 2002). Most of the dextrins are converted to glucose during this step, however the glucoamylase remains active throughout the fermentation step and will continue to hydrolyze any residual dextrins during fermentation. After saccharification, the slurry (now called mash) is cooled to 32°C with the heat recovered and transferred to other process streams. The cooled mash then enters the fermentation tanks. A popular alternative to mash-presaccharification is to add glucoamylase during the filling of the fermentor and to saccharify and ferment the starch simultaneously (SSF, Simultaneous Saccharification and Fermentation). An additional advantage to this approach is that reversion reactions (re-polymerization of glucose) are much less likely to occur (Power, 2003).

Sugar Fermentation

Fermentation uses microorganisms (the yeast Saccharomyces cerevisiae, which is also used for brewing beer and baking bread) to convert sugars to ethanol, and results in the production of ethanol and carbon dioxide, as well as additional yeast cells (from cell division) and heat. One molecule of glucose yields 2 molecules of ethanol and 2 molecules of carbon dioxide.

On a mass basis, one kilogram of glucose will theoretically produce 0.51 kilogram of ethanol and 0.49 kilogram of carbon dioxide. However, glucose consumed to generate additional yeast cells (cell mass) does not result in the production of ethanol. Most industrial fermentation processes operate at 90 to 95% of the theoretical yield.

In the fermentation step, yeast grown in seed tanks is added to the corn mash to ferment the simple sugars (glucose) to ethanol.  The other components of the corn kernel (protein, oil, etc.) remain largely unchanged during the fermentation process, though the corn oil helps to prevent foaming during the fermentation.

In most dry-grind ethanol plants, the fermentation process occurs in batches. A fermentation tank is filled and ferments completely before being drained and refilled with a new batch. The up-stream processes (grinding, liquefaction, and saccharification) and downstream processes (distillation and recovery) occur continuously. Thus, dry-grind facilities using batch processing usually have three or more fermentors, with one fermentor filling, one fermenting (for approximately 46-68 hours), and one emptying and resetting for the next batch all at the same time. While the exact size of each fermentor varies between plant designs, common fermentor sizes range between 300,000-500,000 gallons (1-2 million liters) each (Kwiatkowski, 2006). A major advantage of batch fermernations is that there are fewer opportunities for contamination, provided they are properly sanitized between runs. Bacteria, especially species of Lactobacillus, can infect yeast fermentations and produce organic acids that lower ethanol yields and interfere with the Saccharomyces (Graves, 2006).

While batch fermentation is more common in dry-grind facilities, continuous fermentation processes are used in some facilities. In this process, fermentation occurs through a series of cascading tanks where the liquid continuously flows through the process. New fermentation media is continuously added at the front end and fermented product is continuously removed from the back end. While continuous fermentation has greater reactor productivity because it is continuously operating with high yeast loads, much more care needs to be exercised to prevent contamination (Bayrock, 2001).

In addition to ethanol, carbon dioxide is also produced during fermentation. Usually, the carbon dioxide is not recovered as a sellable product. If recovered, this carbon dioxide can be cleaned, compressed and sold for carbonation of soft drinks or frozen into dry-ice for cold product storage and transportation. If the carbon dioxide is not recovered, it passes through a water scrubber to remove evaporated ethanol and other volatile organic compounds (VOCs) carried in the gas. The water from the scrubber, containing the recovered ethanol, is sent to the distillation system. The cleaned carbon dioxide is vented to the atmosphere.

Heat is generated during fermentation: approximately 12000 kJ per kilogram of ethanol; 516 BTU per pound (Kwiatkowski, 2006). This heat must be continuously removed from the fermentors and is accomplished either by passing water through a cooling coil contained within the fermentor, or by continuously pumping the fermenting mash through a large heat exchanger where the heat is transferred to cooling water before the mash is returned to the fermentor. Failure to remove the heat causes a rise in temperature sufficient to kill the yeast. The optimal temperature for ethanol fermentation is between 27 and 32°C.

After the fermentation is nearly complete, the fermented corn mash (now called beer) produced in individual batches is emptied from the fermentor into a beer well where it is stored enabling a continuous stream to be supplied to the ethanol recovery system. The beer contains 8-10% ethanol by weight.

Ethanol Recovery

Separation and recovery of the ethanol is accomplished through a continuous process involving several steps (figure 4). In the first step, the beer is processed through a beer column where steam is used to strip off almost all of the ethanol, along with some water, from the slurry. The ethanol and water vapor exit the top of the beer column and the whole stillage (containing less than 0.1% ethanol by weight) exits from the bottom. The overhead vapor flows to a rectifier column where the ethanol is concentrated from 45% to 91% through fractional distillation. The bottoms from the rectifier pass through a stripping column to remove residual ethanol.  Liquid exiting the bottom of the stripper has less than 0.1% ethanol by weight, and is recycled as process water for slurrying the ground corn.  The overhead vapor from the rectifier (91% ethanol by weight) is superheated and passes through molecular sieves. The final product from the molecular sieve system is ethanol vapor that is at least 99.6% pure. This vapor is condensed and mixed with a denaturant (e.g. gasoline) to render it as non-potable fuel ethanol. Generally, 8 to 12 days worth of denatured fuel ethanol production is stored on site (Kwiatkowski, 2006).

All industrial fuel ethanol production uses continuous-feed distillation column systems. Distillation is a common chemical separation method that is based upon differences in volatility (Wankat, 1988). If a mixture of ethanol and water are placed in a container at a given temperature and pressure, after time, the mixture will reach equilibrium. At equilibrium, some of the ethanol will be a vapor in the gas above the liquid and some will be in the liquid phase. Similarly, some of the water will be in the vapor phase and some will be in the liquid phase. Because ethanol is more volatile than water (boils at a lower temperature), the ratio of ethanol to water in the vapor phase is greater than the ratio of ethanol to water in the liquid phase. This characteristic allows for the separation of the ethanol from the water.

Through subsequent vaporization of the mixture, condensation, re-vaporization, and re-condensation, the mixture becomes higher and higher in ethanol content because the vapor at each vaporization step has higher ethanol concentration than the liquid from which it was vaporized. Thus, multiple fractionation steps can be used to purify ethanol from water. However, the basic principle by which this occurs - difference in boiling points between water and ethanol - ceases to exist when the mixture is 95.6 wt% ethanol (4.4% water). At this point (the azeotrope), the ethanol and water both vaporize to the same degree and cannot be further fractionated by distillation. Either a third solvent can be introduced to break the azeotrope (e.g. beneze) or an alternate seperation method can be used such as absorption of water using molecular sieves.

Molecular sieves used to dry ethanol are crystalline metal zeolites (aluminosilicates) with a 3-dimensional porous structure of silica and alumina tetrahedra. Zeolites strongly and preferentially adsorb water from vapor/gas mixtures. The adsorbed water can be removed by increasing the temperature of the zeolite and passing dry gas over the particles, thus allowing this rather expensive desiccant (~$10/lb) to be reused (Al-Asheh, 2004).

While this drying property was discovered with naturally occurring zeolites, commercial molecular sieves are synthetically produced to have highly uniform pores within a tight size distribution. Industrial molecular sieve drying systems consist of multiple columns each filled with a bed of uniform sized zeolite sieves. The ethanol/water vapor mixture leaving the fractional distillation system is super-heated and forced through the molecular sieve bed. The water vapor is selectively adsorbed to the particles while ethanol passes through the column, where it is recovered and condensed to liquid at high purity. After the capacity of the zeolites to adsorb water from the ethanol vapor is reached, feed vapor is stopped and the flow through the column is reversed. Dry gas (usually CO2 produced by the fermentation process) passes over the zeolites while the system is placed under a slight vacuum to drive the desorption of the water from the solid particles. The water vapor and residual ethanol vapor exiting the column is condensed and returned to the stripper in the distillation system to re-vaporize the residual ethanol which improves the overall efficiency of ethanol recovery by the plant (Ladisch, 1979).

To achieve continuous processing, molecular sieve dehydration systems consist of pairs of beds. As the first bed in the pair processes wet ethanol, a second molecular sieve bed undergoes regeneration to remove the adsorbed water. When the capacity of the first column to remove water is filled, the duties of the columns are switched so that the wet column begins regeneration and the fresh column continues to process wet ethanol vapor.

An alternative to zeolite molecular sieves is using ground corn (corn grits) in a packed bed, similar in design to conventional molecular sieve beds (Chang, 2006; Neuman, 1986; Westgate, 1992). In this system, currently in commercial use by Archer Daniel Midlands, water is selectively adsorbed to corn starch from a water-ethanol vapor mixture (Beery, 1998; Beery, 2001; Ladisch, 1979). Similar in design to the zeolite molecular sieve beds, the corn grit system operates in pairs of beds with one drying ethanol vapor while the other(s) are undergoing regeneration to remove the adsorbed water. The major advantages of the bio-based adsorbents that they are easily available, less expensive than molecular sieves, mechanically stable, and easily disposable (Ladisch, 1997).

Industrial fractional distillation to produce fuel ethanol is one of the major energy inputs for the production of fuel ethanol. Process improvements that capture and recycle energy from the process have greatly reduced the cost (Gulati, 1996; Ladisch, 1979).

Co-product production and handling

The principal co-product from ethanol production using the dry-grind process is distiller’s dried grains and solubles (DDGS). The whole stillage leaving the bottom of the beer column contains approximately 15% solids. Centrifugation of the whole stillage removes approximately 83% of the water and results in wet distillers grains (also called wet cake) which is 35 to 40% solids (figure 3). The liquid stream, called thin stillage, is partially recycled as backset to the second stage of the liquefaction process. The remaining thin stillage passes to a surge tank which supplies a steady feed to the evaporators, where it is concentrated.

Thin stillage passes through a multiple effect evaporator which removes a significant amount of the water as steam, which is used to vaporize the ethanol during the recovery process (in the reflux of the rectifier). The steam, now condensed to liquid, is mixed with other condensates and added to the ground corn at the beginning of the grain preparation phase. The concentrated product of the evaporators is a syrup containing 55% solids by weight (McAloon, 2000) which is mixed with wet distillers grains and sent to a large rotary drum dryer where the mixture is dried from 64 to 9-10% moisture to form the DDGS. The hot gas from the dryers is processed prior to venting to the atmosphere to remove volatile organic compounds (VOCs) released during drying. Thermal oxidation is commonly used to convert VOCs to carbon dioxide and water (Vij, 2003).

Distillers dried grains and solubles are currently used as livestock feed as they contain relatively high quantities of protein (table 2). They have long been used in cattle feed rations at rates up to 40% (Ham, 1994; Peter, 2000), but not as widely used in feed rations for non-ruminants (swine and poultry). Recommended inclusion rates (based on amino acid content) for swine are up to 20% of the ration (Whitney, 2006), but are less than 10% for laying hens (Lumpkins, 2005). As fuel ethanol production from corn dry-grind technology continues to increase, efficient use and capturing the value of the co-products becomes increasingly important (Rausch, 2006; Belyea, 2004).

Production of Ethanol using Wet Milling Process

Producing fuel ethanol from grains using the wet mill process involves four major steps-preparation of the grain, fermentation of the sugars, recovery of the ethanol, and handling of the co products. The principal differences between the ethanol dry-grind process and the ethanol wet mill process are the grain preparation steps and the numbers and types of co-products recovered. Once the starch has been recovered the process of converting it to fuel ethanol and recovering the ethanol is similar in both wet mill and dry-grind facilities. But, the wet mill process is designed to fully fractionate the grain so that the major constituents (carbohydrates, lipids, and protein) can be efficiently recovered and purified for the production of value-added products (figure 3).

Grain preparation
The upstream processing steps of corn (steeping and fractionation) are common to all wet mills. Steeping, the first step in the wet milling process, is what differentiates this process from dry milling (for cereal processing) and dry-grinding (for ethanol production) processes. In the steeping process, the corn kernels are soaked in water acidified with sulfur dioxide (SO2), typically for 22-50 hours at 52°C (125°F). Steeping softens the kernels by thoroughly wetting the grain and increaseing the moisture content from 15% to 45%. The sulfur dioxide (typically at 0.12 - 0.20% of the water) and possibly lactic acid produced by bacteria in the mix, break down the protein-starch matrix contained in the endosperm (figure 4) of the grain, which aids in the separation of the starch from the protein and other components of the grain. Source: May, 1987. The corn kernel is further fractionated by first coarse grinding the grain followed by several separation steps. The coarse grinding mill consists of a stationary disk and a rotating disk, each with knobs that break up the kernels. They are adjusted so that few kernels exit without being broken while the seed germ remains undamaged (May, 1987). Following coarse grinding, the oil-rich germ is separated from the slurry based on differences in densities. Hydrocyclones are used to separate solids from a liquid slurry using centrifugal force. The slurry is fed tangentially at the top of a cylindrical entry section. The germ floats to the top and exits through a large opening located on the cylinder. Water and any remaining slurry exit through a smaller opening at the apex of a cone located at the bottom of the cylinder. The separated germ is dewatered and dried before removal of the corn oil by solvent extraction. The material leaving the bottom of the cyclone passes through a wedge-wire screen to separate the hull and the fiber from the starch and protein (i.e., gluten). Approximately 30-40% of the starch is recovered in this step (May, 1987). The recovered fiber, containing attached starch, is next milled using either an entoleter or a disk mill. An entoleter mill forces the fiber against pins at high speed to shear the starch from the fiber. Disk mills, similar to the coarse mill, have knobs or grooves that remove the starch from the fiber. Both milling processes are adjusted to maximize starch seperation from the fiber, while keeping the fiber intract. The starch is separated a second time by passing it through a screen sized to prohibit passage of the fiber. The processed fiber is then pressed to remove water (to 40-60% moisture), mixed with evaporated stillage, and dried to produce corn gluten feed. Corn gluten feed contains less protein and has a lower energy content than distiller’s dried grains and solubles produced in the dry-grind process. The starch/protein slurry that is fractionated from the fiber is further processed to separate the starch and the protein. Gluten (the protein) is lower in density than starch (1.06 specific gravity compared with 1.6 specific gravity for starch) permitting efficient separation by centrifugation or hydrocyclones (May, 1987). The fractionated protein is dewatered and dried to produce corn gluten meal which is used as livestock feed. The remaining starch contains 3-5% protein and may be further purified depending on the final use of the starch. For fuel ethanol production, this primary starch slurry usually undergoes liquefaction and saccharifaction processes similar to those used in the ethanol dry-grind process. Liquefaction involves adding ammonia and lime to the starch slurry to adjust the pH to 6.5. The ammonia, which contains nitrogen, also serves as a nutrient for the yeast in the subsequent fermentation step. The slurry is heated to 88°C by direct steam injection using a “jet-cooker”. A thermostable enzyme (alpha-amylase) is added to cleave the starch molecules at random points along the middle of the polymer chain and to break the starch into smaller water soluble fragments called dextrins. After approximately one hour, the output from the first step of liquefaction is combined with “backset”, which is recycled water from the end of the ethanol distillation process. The backset accounts for approximately 15% of the final volume of the corn mash (McAloon, 2000). Critical nutrients for the yeast are also carried in the backset. As the liquefied slurry is cooled to 60°C, the heat is recovered and used to heat new, incoming slurry going to the jet-cooker (Kwiatkowski, 2006). A new enzyme technology developed by Genencor allows for the rapid hydrolysis of granular starch and eliminates the need for gelatination of the starch slurry by jet-cooking, thus significantly lowering the energy requirements for ethanol production from corn (Shetty, 2005). Following liquefaction, sulfuric acid is added to the slurry to lower the pH to 4.5. An additional enzyme, glucoamylase (also called beta-amylase) is added to break down the starch and dextrins into glucose via a stepwise hydrolysis of glucose from the end of the molecules. The slurry is held at 60°C for 5-6 hours as the glucoamylase hydrolyzes the dextrins to glucose (Schenck, 2002). Most of the dextrins are converted to glucose during this step, however the glucoamylase remains active throughout the fermentation step and will continue to hydrolyze any residual dextrins during fermentation. After saccharification, the slurry (now called mash) is cooled to 32°C with the heat transferred to other process streams. The cooled mash then enters the fermentation tanks. A popular alternative to mash-presaccharification is to add the glucoamylase during the filling of the fermentor and to saccharify and ferment the starch simultaneously (SSF, Simultaneous Saccharification and Fermentation). An additional advantage to this approach is that reversion reactions (re-polymerization of glucose) are much less likely to occur (Power, 2003)

Sugar fermentation
Fermentation uses microorganisms (the yeast Saccharomyces cerevisiae, which is also used for brewing beer and baking bread) to convert sugars to ethanol and results in the production of ethanol and carbon dioxide, as well as additional yeast cells (from cell division) and heat. On a mass basis, one kilogram of glucose will theoretically produce 0.51 kilogram of ethanol and 0.49 kilogram of carbon dioxide. However, glucose consumed to generate additional yeast cells (cell mass) does not result in the production of ethanol. Most industrial fermentation processes operate at 90 to 95% of the theoretical yield. The fermentation of the saccharified starch in a wet mill is similar to the process used in dry-grind facilities with the only major differences being the presences of fewer insoluble solids in the fermentation liquid (due to the removal of the fiber and germ), and the use of steep water. The liquid used in the steeping process contains a significant amount of protein and micronutrients from the corn (Rausch, Thompson, Belyea, & Tumbleson, 2003) and is sometimes sold in a condensed form as a complex nitrogen/nutrient source for industrial fermentations (Kapen, 1996). For fuel ethanol production, the steep water is typically added to the saccharified starch to dilute it to the desired concentration (16 - 22 wt% sugar) before adding the yeast. The yeast, which is grown in seed tanks, is added to the saccharified starch to ferment the simple sugars (glucose) to ethanol. Fermentation processes involve either batch or continuous processing methods. In a batch process, a fermentation tank is filled and ferments completely before being drained and refilled with a new batch. The up-stream processes (grain preparation and separation, liquefaction, and saccharification) and downstream processes (distillation and recovery) occur continuously. Facilities using batch processing usually have three or more fermentors, with one or more fermentor filling, one or more fermenting (for approximately 46-68 hours), and one or more emptying and resetting for the next batch operating at the same time. While the exact size of each fermentor varies between plant designs, common fermentor sizes range between 300,000-500,000 gallons (1-2 million liters) each (Kwiatkowski, 2006). A major advantage of batch fermernations is that there are fewer opportunities for contamination, provided they properly santized between runs. Bacteria, especially species of Lactobacillus, can infect yeast fermentations and produce organic acids that lower ethanol yields and interfere with the Saccharomyces (Graves, 2006). Continuous fermentation processes involve a series of cascading tanks where the liquid continuously flows through the process. New fermentation media is continuously added at the front end and fermented product is continuously removed from the back end. While continuous fermentation has greater reactor productivity because it is continuously operating with high yeast loads, much more care needs to be exercised to prevent contamination (Bayrock, 2001). In addition to ethanol, carbon dioxide is also produced during fermentation. Carbon dioxide can be captured, cleaned, compressed and sold for carbonation of soft drinks or frozen into dry-ice for cold product storage and transportation. If the carbon dioxide is not recovered, it passes through a water scrubber to remove evaporated ethanol and other volatile organic compounds (VOCs) carried in the gas. The water from the scrubber, containing the recovered ethanol, is sent to the distillation system. The cleaned carbon dioxide is vented to the atmosphere. Heat is generated during fermentation (approximately 12000 kJ per kilogram of ethanol; 516 BTU per pound) (Kwiatkowski, 2006). This heat must be continuously removed from the fermentors and is accomplished either by passing water through a cooling coil contained within the fermentor, or by continuously pumping the fermenting mash through a large heat exchanger where the heat is transferred to cooling water before the mash is returned to the fermentor. Failure to remove the heat causes a rise in temperature sufficient to kill the yeast. The optimal temperature for ethanol fermentation is between 27 and 32°C. After the fermentation is nearly complete, the fermented corn mash (now called beer) is emptied from the fermentor into a beer well where it is stored enabling a continuous stream to be supplied to the ethanol recovery system. The beer contains 8-10% ethanol by weight.

Ethanol Recovery
Separation and recovery of the ethanol is accomplished through a continuous process involving several steps (figure 5). In the first step, the beer is processed through a beer column where steam is used to strip off almost all of the ethanol, along with some water, from the slurry. The ethanol and water vapor exit the top of the beer column and the whole stillage (containing less than 0.1% ethanol by weight) exits from the bottom. The overhead vapor flows to a rectifier column where the ethanol is concentrated from 45% to 91% through fractional distillation. The bottoms from the rectifier pass through a stripping column to remove residual ethanol.  Liquid exiting the bottom of the stripper has less than 0.1% ethanol by weight, and is recycled as process water for slurrying the ground corn.  The overhead vapor from the rectifier (91% ethanol by weight) is superheated and passes through molecular sieves. The final product from the molecular sieve system is ethanol vapor that is at least 99.6% pure. This vapor is condensed and mixed with a denaturant (e.g. gasoline) to render it as non-potable fuel ethanol. Generally, 8 to 12 days worth of denatured fuel ethanol production is stored on site (Kwiatkowski, 2006). All industrial fuel ethanol production uses continuous-feed distillation column systems. Distillation is a common chemical separation method that is based upon differences in volatility (Wankat, 1988). If a mixture of ethanol and water are placed in a container at a given temperature and pressure, after time the mixture will reach equilibrium. At equilibrium, some of the ethanol will be a vapor in the gas above the liquid and some will be in the liquid phase. Similarly, some of the water will be in the vapor phase and some will be in the liquid phase. Because ethanol is more volatile than water (boils at a lower temperature), the ratio of ethanol to water in the vapor phase is greater than the ratio of ethanol to water in the liquid phase. This characteristic allows for the separation of the ethanol from the water. Through subsequent vaporization of the mixture, condensation, re-vaporization, and re-condensation the mixture becomes higher and higher in ethanol content because the vapor at each vaporization step has higher ethanol concentration than the liquid from which it was vaporized. Thus, multiple fractionation steps can be used to purify ethanol from water. However, the basic principle by which this occurs - difference in boiling points between water and ethanol - ceases to exist when the mixture is 95.6 wt% ethanol (4.4% water). At this point (the azeotrope), the ethanol and water both vaporize to the same degree and cannot be further fractionated by distillation. Either a third solvent can be introduced to break the azeotrope (e.g. beneze) or an alternate seperation method can be used such as adsorption of water using molecular sieves. Molecular sieves for drying ethanol are crystalline metal zeolites (aluminosilicates) with a 3-dimensional porous structure of silica and alumina tetrahedra. Zeolites strongly and preferentially adsorb water from vapor/gas mixtures. The adsorbed water can be removed by increasing the temperature of the zeolite and passing dry gas over the particles, thus allowing this rather expensive desiccant (~$10/lb) to be reused (Al-Asheh, 2004). While this drying property was discovered with naturally occurring zeolites, commercial molecular sieves are synthetically produced to have highly uniform pores within a tight size distribution. Industrial molecular sieve drying systems consist of multiple columns each filled with a bed of uniform sized zeolite sieves. The ethanol/water vapor mixture leaving the fractional distillation system is super-heated and forced through the molecular sieve bed. The water vapor is selectively adsorbed to the particles while ethanol passes through the column, where it is recovered and condensed to liquid at high purity. After the capacity of the zeolites to adsorb water from the ethanol vapor is reached, feed vapor is stopped and the flow through the column is reversed. Dry gas (usually CO2 produced by the fermentation process) passes over the zeolites while the system is placed under a slight vacuum to drive the desorption of the water from the solid particles.  The water vapor and residual ethanol vapor exiting the column is condensed and returned to the stripper in the distillation system to re-vaporize the residual ethanol which improves the overall efficiency of ethanol recovery by the plant (Ladisch, 1979). To achieve continuous processing, molecular sieve dehydration systems consist of pairs of beds. As the first bed in the pair processes wet ethanol, a second molecular sieve bed undergoes regeneration to remove the adsorbed water. When the capacity of the first column to remove water is filled, the duties of the columns are switched so that the wet column begins regeneration and the fresh column continues to process wet ethanol vapor. An alternative to zeolite molecular sieves is using ground corn (corn grits) in a packed bed, similar in design to conventional molecular sieve beds (Chang, 2006; Neuman, 1986; Westgate, 1992). In this system, currently in commercial use by Archer Daniel Midlands, water is selectively adsorbed to corn starch from a water-ethanol vapor mixture (Beery, 1998; Beery, 2001; Ladisch, 1979). Similar in design to the zeolite molecular sieve beds, the corn grit system operates in pairs of beds with one drying ethanol vapor while the other(s) are undergoing regeneration to remove the adsorbed water. The major advantages of the bio-based adsorbents are that they are readily available, less expensive than molecular sieves, mechanically stable, and easily disposed (Ladisch, 1997). Industrial fractional distillation to produce fuel ethanol is one of the major energy inputs for the production of fuel ethanol.  Process improvements that capture and recycle energy from the process has greatly reduced the cost of this step (Gulati, 1996; Ladisch, 1979).

Co-product production and handling The wet milling of corn produces ethanol and three co-products-germ, corn gluten meal, and corn gluten feed. The germ, which is separated from the other kernel constituents after the coarse grind, contains most of the oil contained in the grain. It can be processed to extract the oil, which can then be further refined into food-grade corn oil. This may be done in the same facility as the ethanol plant or sold to a secondary processor. Corn gluten meal is the protein rich (about 60%) product separated from the gluten-starch slurry and sold as a high-protein animal feed (Ham, 1994). The residual corn fiber separated from the starch-gluten slurry after the second milling step is mixed with evaporated light stillage and dried to produce corn gluten feed, a medium-grade protein product (20-26% of dry matter), which is also used as animal feed (Loe, 2006). Corn gluten feed is similar in fiber content, lower in protein content, and much lower in oil content compared to Distiller’s Dried Grains and Solubles (DDGS) produced in the corn ethanol dry grind process (Ham, 1994). Approximately 2.5 gallons of ethanol, 16.4 pounds of carbon dioxide, 2.1 pounds of oil, 2.6 pounds (dry mass) of corn gluten meal, and 11.2 pounds (dry mass) of corn gluten feed are produced per bushel of corn using the wet milling process (May, 1987).

Production of Ethanol using Cellulose Resources

Feedstock preparation

The stability and chemical complexity of cellulose increase the difficulty of breaking it down into glucose, a situation frequently referred to as the recalcintrance of cellulose. A number of pretreatment approaches are being explored to overcome this problem. Pretreatment is the general term used to describe the processing steps preceding hydrolysis of cellulose and hemicellulose into fermentable sugars. The goal of any pretreatment technology is to alter or remove structural and compositional factors present in plant biomass that hinder the breakdown (hydrolysis) of cell wall polysaccharides (polymers of simple sugars) into the fermentable simple sugars (Mosier, 2005a, 2005b; Grohmann, 1984; Lynd, 1999; McMillan, 1994). Pretreatment methods often involve harsh conditions and non-selectively hydrolyze the polysaccharides in the plant material. Sugars that are produced during pretreatment are also subject to further degradation to form compounds that act as inhibitors to the subsequent fermentation process (Klinke, 2004; Olsson, 1996; Palmqvist, 2000; Taherzadeh, 1997).

Pretreatment methods are usually either physical or chemical, although some approaches incorporate both (Hsu, 1996; McMillan, 1994). Chemical approaches use acids or bases to promote the hydrolysis of cellulose by removing the hemicellulose and/or lignin during pretreatment. The most commonly used acids and bases are sulfuric acid (H₂SO₄), sodium hydroxide (NaOH) or ammonia. Other chemicals used include cellulose solvents such as alkaline H₂O₂, ozone, organosolv (Lewis acids, FeCl₃, and Al₂SO₄ in aqueous alcohol), glycerol, dioxane, phenol, or ethylene glycol, which disrupt the cellulose structure and promote hydrolysis (Wood, 1988).

Dilute sulfuric acid is commonly used as a pretreatment method, but increases cost, due to the need for reactors constructed of expensive steel materials, and results in the formation of unwanted salts that require neutralizing agents (Hinman, 1992; Lynd, 1996; Lynd, 1999;  Thompson, 1979). Liquid hot water pretreatment with pH control effectively dissolves hemicellulose and lignin, while minimizing degradation of monosaccharides without the need for costly and potentially dangerous pretreatments and neutralizing agents (Kim, 2005; Weil, 1998). Other pretreatment methods include steam explosion (Abatzoglou, 1992; Heitz, 1991; Ramos, 1992), ammonia fiber expansion (AFEX) (Gollapalli, 2002; Teymouri, 2005; Wang, 1998), and other chemical solvents (Hsu, 1996; McMillan, 1994). Few of these pretreatment processes have been fully commercialized or tested at industrial scales (Mosier, 2005a, 2005b). Scaling pretreatment processes to commercial sizes and the associated reactor design issues remains a major barrier to the commercial production of fuel ethanol from lignocellulosic biomass (Lynd, 1999; Mosier, 2005a, 2005b). A summary and evaluation of a number of pretreatment processes can be found in Lynd (1999), Mosier (2005a, 2005b), and Kim (2005).

Following pretreatment, plant cell wall polysaccharides are more susceptible to chemical or enzymatic hydrolysis that breaks them into monomeric (single) sugars (saccharification) that can be fermented into ethanol (Lynd, 1999). Depending on the type and effectiveness of the pretreatment method, hydrolysis takes 24-48 hours to complete (Lin, 2006; Olsson, 1996). In an effort to reduce the overall time needed to produce ethanol, the hydrolysis and fermentation processes are being combined, rather than conducted sequentially, in a process called simultaneous saccharification and fermentation (SSF) (Lynd, 1999). In SSF, the fermenting microorganism (e.g., yeast) and enzymes that hydrolyze the polysaccharides are added at the same time so that the sugars are fermented as soon as they are available in a just-in-time process. SSF reduces ethanol production time and reduces the amount of enzyme used when a separate hydrolysis step is conducted, due to the formation of fewer compounds that inhibit ethanol production (Lin, 2006).

Fermentation of sugars

Fermentation involves microorganisms which consume sugars as a food source. Ethanol fermentation results in four major products: additional yeast cells (cell division), ethanol, carbon dioxide, and heat. One molecule of glucose will yield, stoichiometrically, 2 molecules of ethanol plus 2 molecules of carbon dioxide (Figure 3). On a mass basis, one kilogram of glucose will theoretically produce 0.51 kilogram of ethanol and 0.49 kilogram of carbon dioxide. However, glucose consumed to generate additional yeast cells (cell mass) does not result in the production of ethanol. Most industrial fermentation processes operate at 90-95% of the theoretical yield of ethanol from glucose fed to the yeast.

The fermentation process for producing fuel ethanol from cellulose is similar to that from corn grain. The fermentation media contains insoluble solids from the plant biomass, yeast, and soluble products from the pretreatment and saccharification steps. Hexoses (the six carbon sugars glucose and galactose) produced by hydrolysis of cellulose and hemicellulose can be fermented to ethanol using existing industrial strains of Saccharomyces cerevisiae.

The major difference between using cellulosic feedstocks and starch feedstocks lies in the existence of relatively large amounts of pentose sugars (five carbon sugars such as xylose and arabinose) contained in the hemicellulose. These sugars also need to be fermented to make the overall process economically feasible (Eggeman, 2005; Nagle, 1999). Existing strains of S. cerevisiae cannot directly ferment xylose, but can ferment xylulose through the pentose phosphate pathway (figure 4). Other yeasts and bacteria can ferment xylose or xylitol; efforts utilizing the tools of biotechnology are underway to develop industrial microorganisms capable of efficiently converting xylose to ethanol. A number of approaches are being explored.

Ethanol recovery

The recovery of ethanol produced in cellulosic processes is expected to use technology similar to that used in corn ethanol or sugar cane ethanol facilities. These technologies include repeated distillation (vaporization) and condensation of the ethanol-water mixtures produced during fermentation until the azeotrope point is reached (the point at which the difference between the boiling points of water and ethanol ceases to exist, which occurs when the mixture is 95.6% ethanol and 4.4% water by weight). At this point, the ethanol and water both vaporize to the same extent and cannot be further fractionated by distillation and final purification will by performed by the use of molecular sieves (zeolites which adsorb water from a vapor/gas mixture) (Al-Asheh, 2004; Kwiatkowski, 2006; Ladisch, 1979; Wankat, 1988).

Co-product production and handling

Unlike processes that produce ethanol from corn, the residual solid material produced in lignocellulose processes has little value as an animal feed as it is high in lignin while low in fiber and protein (McAloon, 2000). The material can be used to produce heat, steam, and electricity needed to run the ethanol facility, with the excess electricity sold to the electrical grid (Nagle, 1999).

Production of Ethanol using Sucrose Resources

Ethanol is produced by fermenting plant carbohydrates with yeast. Plant carbohydrates are grouped as soluble sugars (such as sucrose from sugarcane), storage carbohydrates (such as starch from grains and tubers), and structural carbohydrates which make up the plant cell wall (such as cellulose, hemicellulose, and pectin). Sucrose, commonly called table sugar, is composed of two simple sugars (fructose and glucose). It is the main sugar extracted from sugar cane and sugar beets, and is highly soluble in water. Industrial strains of yeast such as Saccharomyces can be used to hydrolyze sucrose into fructose and glucose, and ferment the sugars into ethanol. Ethanol production from sucrose predominates in tropical regions with sugar cane production, such as Brazil, which produced 4.2 billion gallons (15 billion liters) of fuel ethanol in 2004 (Barros, 2005).

Sugar is produced by first squeezing the juice out of the stems. The raw juice is clarified, impurities and solids removed, and thickened, followed by a series of crystallization steps to produce sugar crystals, which are removed. The remaining syrup is molasses. Approximately 3 gallons of molasses are produced for every 100 pounds of raw sugar produced (Shapouri, 2006). Fermentation of sucrose from sugar cane can be conducted using the juice directly obtained from squeezing the sugar cane stalks, or from the molasses. Most ethanol plants in Brazil produce ethanol from molasses, typically molasses A, which has had the sugar removed by a single crystallization step. The ethanol concentration in the fermented molasses is about 9% v/v (7% w/w). As sugarcane molasses is naturally low in free nitrogen, urea is typically added as a nitrogen source to insure proper yeast performance. Depending upon the quality of the molasses, other nutrients such as phosphorous, biotin, pantothenic acid, and inositol may also be added (Piggot, 2003). From each gallon of sugar cane molasses, 0.41 gallons of ethanol can be produced. If the raw sugar and molasses in sugar cane is used to produce ethanol, 19.6 gallons of ethanol can be produced per ton of harvested sugar cane (Shapouri, 2006).

The major processes involved in the production of ethanol from cane molasses are:

a. Fermentation of the sugar in the raw materials into alcohol and Carbon dioxide and;

b. Concentrations and purification of the aqueous alcohol by distillation

Fermentation of Sugar

Starts with the gradual propagation of pure yeast in the laboratory, which is done by growing the yeast in the sugar solution that takes about 24 hrs. The yeast is then transferred into a bigger cultivator until the yeast in sufficient quantity is produced in the pre-fermenter. Ample air is used in all the yeast cultivation stages to speed up this yeast growing cycle.

When the yeast is fully matured in the pre-fermenter, it is transferred to the first fermenter, which is previously cleansed. Diluted molasses from the continuous molasses mixer are mixed together with the yeast and fermentation commences as shown by the evolution of carbon dioxide. During the process, heat is evolved and it is being cooled down by recirculating the fermented liquor or “beer” into plate heat exchangers. This process of cooling lasts for about 16 to 24 hours.

After fermentation is complete, the “beer” that contains about 8% alcohol by volume is immediately transferred to the beer receiving tank ready for distillation.  This is done to allow the early cleaning of the fermenter to be ready for distillation.

Distillation

The beer from the receiving tank is pumped to the beer still column via a heating system:

a. Beer is first pre-heated by heat from hot spent wastewater to save on the usage of  steam, and;

b. The hot spent wastewater (slops) originally at 105°C is cooled to around 50°C before it   is introduced into the slops biological digester

The purpose of the beer still is to recover all the alcohol from the beer including all the volatile components of the beer. The hot crude alcohol vapor is partially condensed and the resulting condensate is again pumped to the midpoint of the purifying column. The purpose of the Purifying column is to separate alcohol from the other volatile component of the crude alcohol by virtue of the addition of hot pure water at the top of the column. Due to the interaction of the ascending hot water in the column, the volatile component of the ascending vapor separates from the alcohol.

The bottom product of the purifying column is fed to the rectifying column for final concentration and purification.

The rectifying column contains numerous rectification trays that cause the gradual increase in ethanol concentration by virtue of the difference in temperature.

Therefore, the bottom product of the rectifying column is almost pure water and the overhead product of the column, which is the more volatile compound, is high-grade ethyl alcohol.

Ethanol Recovery

Ethanol recovery processes for sugarcane juice or molasses use technologies similar to those used to produce ethanol from corn, thus distillation and molecular sieves are used to purify the ethanol following fermentation of the sucrose (Rosillocalle, 1986). The stillage left after the distillation of ethanol is used as a fertilizer for sugarcane fields.

The fibrous plant material that remains after the juice has been squeezed out of the sugarcane stalk is called bagasse. Approximately 0.3 lb of wet bagasse (about 50% moisture) is produced per 1 lb of wet sugarcane (Shapouri, 2006). Bagasse is rich in cellulose, hemicellulose, and lignin (Okano, 2006; Pandey, 2000; Silva, 2005), but has no food value. In most processing facilities, bagasse is burned to produce the heat and steam used to evaporate the water from the sugar in the crystallization process, and to distill the ethanol. Bagasse is also used to produce the electricity used by the plant with excess electricity sold to the power grid (Bhatt, 2001; Goldemberg, 2004). However, bagasse could be used as a cellulosic biomass resource to produce ethanol, other biofuels, and bioproducts.

References:

Al-Asheh, S.; Banat, F. and Al-Lagtah, N. (2004). Separation of ethanol-water mixtures using molecular sieves and biobased adsorbents. Chemical Engineering Research and Design, 82(A7), 855-864.

American Feed Industry Association. Evaluation of Analytical Methods for Analysis of Dried Distillers Grains with Solubles. (2007).

Bayrock, D. and Ingledew, W. M. (2001). Changes in steady state on introduction of a Lactobacillus contaminant to a continuous culture ethanol fermentation. Journal of Industrial Microbiology and Biotechnology, 27(1), 39-45.

Beery, K. E.; Gulati, M.; Kvam, E. P. and Ladisch, M. R. (1998). Effect of enzyme modification of corn grits on their properties as an adsorbent in a skarstrom pressure swing cycle dryer. Adsorption-Journal of the International Adsorption Society, 4(3-4), 321-335.

Beery, K. E. and Ladisch, M. A. (2001). Chemistry and properties of starch based desiccants. Enzyme and Microbial Technology, 28(7-8), 573-581.

Belyea, R. L.; Rausch, K. D. and Tumbleson, M. E. (2004). Composition of corn and distillers dried grains with solubles from dry grind ethanol processing. Bioresource Technology, 94(3), 293-298.

BeMiller, J. N., and Whistler, R. L. (1996). Carbohydrates. In Food Chemistry (3rd ed., pp. 157-223.). New York, New York: Marcel Deker.

Chang, H.; Yuan, X. G.; Tian, H. and Zeng, A. W. (2006). Experimental investigation and modeling of adsorption of water and ethanol on cornmeal in an ethanol-water binary vapor system. Chemical Engineering and Technology, 29(4), 454-461.

Ganesan, V., Muthukumarappan, K. and Rosentrater, K. A. (2006). Effect of Flow Agent Addition on the Physical Properties of DDG with Varying Moisture Content Soluble Percentages. Paper presented at the 2006 ASABE Annual International Meeting, Portland, OR.

Graves, T.; Narendranath, N. V.; Dawson, K. and Power, R. (2006). Effect of pH and lactic or acetic acid on ethanol productivity by Saccharomyces cerevisiae in corn mash. Journal of Industrial Microbiology and Biotechnology, 33(6), 469-474.

Gulati, M.; Westgate, P. J.; Brewer, M.; Hendrickson, R. and Ladisch, M. R. (1996). Sorptive recovery of dilute ethanol from distillation column bottoms stream. Applied Biochemistry and Biotechnology, 57-8, 103-119.

Ham, G. A.; Stock, R. A.; Klopfenstein, T. J.; Larson, E. M.; Shain,
D. H. and Huffman, R. P. (1994). Wet Corn Distillers by-Products Compared with Dried Corn Distillers Grains with Solubles as a Source of Protein and Energy for Ruminants. Journal of Animal Science, 72(12), 3246-3257.

Heitz, M.; Capekmenard, E.; Koeberle, P. G.; Gagne, J.; Chornet, E.; Overend, R. P. et al. (1991). Fractionation of Populus-Tremuloides at the Pilot-Plant Scale - Optimization of Steam Pretreatment Conditions Using the Stake-Ii Technology. Bioresource Technology, 35(1), 23-32.

Kwiatkowski, J. R.; Mcaloon, A. J.; Taylor, F. and Johnston, D. B. (2006). Modeling the Process and Costs of Fuel Ethanol Production by the Corn Dry-Grind Process. Industrial Crops and Products, 23, 288-296.

Ladisch, M.; Tyner, W.; Mosier, N.; Cotta, M.; Dien, B.; Blaschek, H. et al. (2006). Research challenges and opportunities for cellulose conversion technology in a dry mill pathway. Paper presented at the 28th Symposium on Biotechnology for Fuels and Chemicals, Nashville, TN.

Ladisch, M. R. (1997). Biobased adsorbents for drying of gases. Enzyme and Microbial Technology, 20(3), 162-164.

Ladisch, M. R. and Dyck, K. (1979). Dehydration of Ethanol: New Approach Gives Positive Energy Balance. Science, 205, 898-900.

Lumpkins, B., Batal, A. and Dale, N. (2005). Use of distillers dried grains plus solubles in laying hen diets. Journal of Applied Poultry Research, 14(1), 25-31.

McAloon, A.; Tayor, F.; Yee, W.; Ibsen, K. and Wooley, R. (2000). Determining the Cost of Producing Ethanol from Corn Starch and Lignocellulosic Feedstocks. NREL/TP-580-28893.

MCGA, A. a. (2005). Methods to improve the flowability and pelleting of distillers dried grains with solubles (DDGS) In AURI and Minnesota Corn Growers Distillers Dried Grain Flowability Study Summary.

Mosier, N. S.; Hendrickson, R.; Brewer, M.; Ho, N.; Sedlak, M.; Dreshel, R. et al. (2005). Industrial scale-up of pH-controlled liquid hot water pretreatment of corn fiber for fuel ethanol production. Applied Biochemistry and Biotechnology, 125(2), 77-97.

Neuman, R.; Voloch, M.; Bienkowski, P. and Ladisch, M. R. (1986). Water Sorption Properties of a Polysaccharide Adsorbent. Industrial and Engineering Chemistry Fundamentals, 25, 422-425.

Peter, C. M.; Faulkner, D. B.; Merchen, N. R.; Parrett, D. F.; Nash, T. G. and Dahlquist, J. M. (2000). The effects of corn milling coproducts on growth performance and diet digestibility by beef cattle. Journal of Animal Science, 78(1), 1-6.

Power, R. F. (2003). Enzymatic conversion of starch to fermentable sugars. In Jacques, K. A.; Lyons, T. P. and Kelsall, D. R.  (Eds.), The Alcohol Textbook, 4th Edition (pp. 23-32). Bath, England: Nottingham University Press.

Rausch, K. D. and Belyea, R. L. (2006). The future of coproducts from corn processing. Applied Biochemistry and Biotechnology, 128(1), 47-86.

Rausch, K. D.; Belyea, R. L.; Ellersieck, M. R.; Singh, V.; Johnston, D. B. and Tumbleson, M. E. (2005). Particle size distributions of ground corn and DDGS from dry grind processing. Transactions of the Asae, 48(1), 273-277.

Renewable Fuels Association. 2006. Ethanol Industry Outlook. Renewable Fuels Association.

Schenck, F. W. (2002). Starch hydrolysates - An overview. International Sugar Journal, 104(1238), 82-+.

Shetty, J. K.; Lantero, O. J. and Dunn-Coleman, N. (2005). Technological advances in ethanol production. International Sugar Journal, 107(1283), 605-+.

Vij, A. (2003, November). A Perspective on VOC Control Technology in the Industry. Ethanol Producer Magazine.

Wankat, P. C. (1988). Introduction to Column Distillation. In Equilibrium-Staged Separations. New York, NY: Prentice Hall PTR.

Watson, S. A. (1987). Structure and Composition. In Watson, S. A.  and Ramstad, Paul E. (Ed.), Corn: Chemistry and Technology (pp. 53-82). Minneapolis, MN: American Association of Cereal Chemists.

Westgate, P.; Lee, J. Y. and Ladisch, M. R. (1992). Modeling of Equilibrium Sorption of Water-Vapor on Starch Materials. Transactions of the Asae, 35(1), 213-219.

Whitney, M. H.; Shurson, G. C.; Johnston, L. J.; Wulf, D. M. and Shanks, B. C. (2006). Growth performance and carcass characteristics of grower-finisher pigs fed high-quality corn distillers dried grain with solubles originating from a modern Midwestern ethanol plant. Journal of Animal Science, 84(12), 3356-3363.

Wood, T. M. and Saddler, J. N. (1988). Increasing the Availability of Cellulose in Biomass Materials. Methods in Enzymology, 160, 3-11.

Xue, X. D. and Ho, N. W. Y. (1990). Xylulokinase Activity in Various Yeasts Including Saccharomyces-Cerevisiae Containing the Cloned Xylulokinase Gene. Applied Biochemistry and Biotechnology, 24-5, 193-199.

Zaldivar, J., Nielsen, J., and Olsson, L. (2001). Fuel ethanol production from lignocellulose: a challenge for metabolic engineering and process integration. Applied Microbiology and Biotechnology, 56(1-2), 17-34.

Zhang, M., Franden, M. A., Newman, M., McMillan, J., Finkelstein, M., and Picataggio, S. (1995). Promising Ethanologens for Xylose Fermentation - Scientific Note. Applied Biochemistry and Biotechnology, 51-2, 527-536.

Technorati Tags: alcohol, Distillation, Ethanol Production, Fermentation

Bring 1 quart water to boil and add rice; boil for 3 minutes. Meanwhile, chop the dates and mix then with the coconut in a boiler. Strain the rice, adding the water from it to the boiler containing the coconut and chopped dates. Bring to a boil and hold for 15 minutes. Strain the water over the sugar, yeast nutrients and acid blend and stir until dissolved completely. Allow to cool to room temperature, transfer to primary and add activated yeast. Cover and ferment until initially vigorous fermentation subsides, then transfer to secondary and attach an airlock. After 3 months, rack into clean secondary with crushed and dissolved Campden tablet, top up and refit airlock. Wait 3 additional months and rack, top up and refit airlock again. After additional month, stabilize, sweeten if desired and rack into bottles (http://winemaking.jackeller.net).

4. Basi

Basi Wine is a result one year fermentation of freshly extracted sugar cane juice which was boiled, cleared of impurities and placed inside tightly covered burnay jars after mixing with leaves, seed and bark of the samaka tree, which provide the extract with its flavor and color. After fermentation, the mixture had been aged from one to two years before being bottled and sold (http://natureinspired.net/wines.htm)

The Basi Wine, which has a 10-16% alcohol content, is light brown in color and has a sweet and a sour flavor prized as a restorative (http://mis.dost.gov.ph). It is organic because no chemicals had been introduced into the mixture to lengthen its shelf life of between one to two years.

This product is different from rum although basically derived from the same material. The term ruma was derived from the Latin word for sugar, Saccharum. Molasses, the thick black material residue after the sugar cane is processed and all the sugar crystals have been extracted, is the raw material for the production of rum. It contains 50% sugar and 25% water.

Basi Wine production may be traced to Piddig, a town some 16 kilometers away from Ilocos Norte, the northernmost province of the Luzon Island of the Philippines. They had been traditionally producing basi wine since the Spanish times.

5. Mango Wine

Mango or Mangifera indica is the most celebrated tropical fruit because of its lusciousness. The tree is long-lived, sometimes reaching 300 years and still fruiting.

Its fruits vary in form, size, color and quality from nearly round, to oval, to ovoid-oblong to somewhat kidney-shaped ranging in size from 2 ½ to 10 and weighs from a few ounces to 5 lbs. (2.26kgs.). The skin color ranges from light-or-dark-green to clear yellow, yellow-orange, yellow and reddish-pink when fully ripe.

Some have turpentine odor and flavor, while others are richly pleasantly fragrant. The flesh ranges from pale-yellow to deep orange. It is essentially peach-like but much more fibrous; is extremely juicy, with a flavor from very sweet to sub acid to tart.

In the Philippines, the Carabao variety constitutes 66% of the crop while the Pico variety accounts for 26%. These cultivars, apparently of Southeast Asian origin have remained the most commonly grown and exported for many years (http://natureinspired.net).

Mangoes make a fragrant, golden wine as unmistakably unique as dandelion wine. Getting the juice and mixing it with dissolved sugar, tannin and yeast process mango wine. Racking takes more than six months and aging about a year before drinking it chilled or over ice.

6. Duhat Wine

Purple plum, black plum or damson plum, Syzygium cumini or Syzygium jambolanum DC is known in the Philippines as duhat, lomboy or lunaboy. This fruit tree is believed to be of prehistoric introduction in the country where it is widely planted and naturalized (http://natureinspired.net/wines.htm).

Fruiting season is from mid-May to mid-June because dry weather is desirable during its flowering and fruiting periods. The fruit flavor varies from acid to fairly sweet but is usually astringent, sometimes unpalatably so. They may be eaten raw or made into tarts, sauces and jams. If soaked in salt water or pricked and rubbed with a little salt and letting it stand for an hour, the astringent fruits may be improved in palatability.

Medicinally, the fruit is used as an astringent, stomachic, carminative, antiscorbutic and diuretic. Cooked to a thick jam, it is eaten to ally acute diarrhea.

Duhat wine is made by fermenting the juice of the plum in burnay jars from two to three months. Then it is aged for about a year after which, the wine is bottled and sold. The shelf life is estimated to be from one to two years since there are no chemicals added to extend its shelf life.

The resulting wine is somewhat like Port and the distilled liquors. Brandy and jambaya have also been made from the fermented fruit.

7. Cashew Apple Wine

Cashew apple juice may not be acceptable as a soft drink due to its astringent content but it is a good media for alcoholic fermentation because it contains all the nutrients for the growth of yeast. Cashew apple juice contains sugar, protein, acid and large amounts of Vitamin C.

Cashew apple wine has about 4% alcohol but has astringency. It has an exotic flavor much similar to brandy, a distillate of wine, minus the astringency (http://natureinspired.net/wines.htm).

The juice of sound and ripe cashew apples are used in making the wine. The juice is extracted by pulp fermentation wherein cashew apples are inoculated with wine yeast and then allowed to ferment for two to three days until the juice can be pressed easily. Sugar is then added at the rate of one part sugar to five parts juice after which a 10% starter is added.

After the inoculation, the mouth of the fermenting jar is loosely covered with cotton material for two to three days or until vigorous fermentation subsides. Then the mouth of the fermenting jar is covered with a bung to create an anaerobic condition. Fermentation is continued for four weeks or until the release of carbon dioxide stops.

Racking the wine two to three times follows decanting or siphoning of the clear portion of the wine. Finally, it is aged for about a year prior to bottling.

IV. REASONS AND WRONG BELIEFS WHY PEOPLE DRINK ALCOHOLIC BEVERAGES

Other says that, drinking alcoholic beverages symbolizes the status of an individual whether he was a rich person or poor. They also say that alcoholic beverages is a social lubricant, quenches the thirst of a person, relieves tension and lastly it helps to forget their problems temporarily.

Based on a survey conducted to the teenagers who drink alcoholic beverages, they found out that there are many reasons why teenagers drink. Here are the following:

1. Alcoholic beverages help them to easily socialize with another.
2. They found happiness to themselves while drinking.
3. They found self-compliance to themselves.
4. It helps them to forget their problems.
5. It helps them to ignore what other says something about them.
6. It helps them to conquer their fear.
7. It helps them to lessen self –consciousness.
8. It helps them to achieve more freedom
9. It makes their body and mind happy
10. It helps to make celebrations or gatherings become happier.
11. They feel relax when they drink.
12. Drinking alcoholic beverages became a custom especially in celebrating special events or gatherings.
13. Because the powerful influence of media. (e.g. commercials in radios, newspapers and television)

Many people drinking alcoholic beverages because of their different wrong beliefs. Some of the beliefs are the following:

1. Drinking alcoholic beverages makes them become more happy than usual.
2. Anyone can drink beer without the effect of alcohol.
3. A person who do not drink alcohol does not have plenty friends.
4. Neglegance in drinking alcoholic beverage in a celebration is a big uncouth or insult.
5. It is okay to the parents that their children are addict to alcohol rather than a drug addict.
6. Young persons usually do what they see that is why when they see that their older relative is drinking, they are tempted to do it also.

V. THE DIFFERENT EFFECTS OF ALCOHOL

Drinking alcoholic beverages may greatly affect our body, our community and the economy of the country. Here are some of their effects.

A. Effect of Alcohol in our Body

Whenever we drink alcohol, it always go to the esophagus and stomach without digesting. Some alcohol may go to the bloodstreams of the stomach while some may go directly to the small intestine. Alcohol may also travel to our brains and different internal body organs such as liver, heart, kidney, and pancreas. Malnutrition and changing of traits may also occur while drinking alcoholic beverages.

1. Effect of Alcohol in the Nervous System

Nerves scattered around our body and also a part of the brain and the spinal cord is like a telephone wires. It gives and accepts different messages from the different parts of our body. Alcohol makes the cells of our brain to move slowly and it stops to give messages to the different part of our body. Because of the effects of alcohol, a person forgets his attitude that is why he can do what he wants. Also. A drunkard person does not have an ability to make decisions

Whenever a person became drunkard, he felt that he was on cloud nine. He is experiencing euphoria and he cannot control himself. Concentration, memory, discrimination, locomotor skills, and emotion of a drunkard person became less. The effect of alcohol in the nervous system is based on the amount he drunk. (see appendix, figure 5.1)

Whenever a person drink 3 to 4 bottles of beer, he cannot drive safely anymore eventhough he doesn’t look drunked. If a person drink many bottles in one day, his brain will not funtion well. His will do his normal works slowly and he may always feel sleepy.

While the amount of alcohol present in our body became higher and higher, the brain cells become lesser and lesser it is because alcohol poisons the brain cells. Unlike any cells scattered around the body, brain cells never reproduced. That is why those persons who drink alcohol for a very long time may experience different illnesses.

After a person drinks plenty of alcohol, he or she may experience hangovers. Some of the hangovers are, colds, headaches, always thirsty, weak, vomiting, and muscle pains.

2. Effects of Alcohol in the Stomach and Intestine

Because of alcohol, the stomach and the intestines are wounded. That is why, it caused too much heat, vomiting or sometimes vomiting with blood.

3. Effects of Alcohol in the Liver

When alcohol reaches the liver, he first thing liver do is that it makes alcohol became fat. Other fats travels around the body while most of it stayed in the liver. A six glasses of beer everyday can make the fats inside the liver more.

In order to make the fats inside the liver disappear, liver must work twice the normal that is why it became bigger. When the liver became bigger, the person who drinks alcohol may experience tolerance. He needs more bottles of alcohol for him to be drunk.

When a liver goes big, the reactions of the medicines in the body will change. That is why it is dangerous to drink alcoholic beverages while taking up medicines. Whenwever the liver goes bigger and bigger, the cells of the liver are destroyed and also the person may experience alcoholic hepatitis. When the cells of the liver died, it may scar the tissues. It causes the liver to not funtion very well which is called cirrhosis.

4. Effects of Alcohol in the Heart

Drinking alcoholic beverages may affect the performance of our heart. Our heart will not be as more produtive than the usual. A person may feel that he is always tired and experience difficulty in breathing.

5. Effects of Alcohol in the Blood

Because of the effect of alcohol in the liver, the sugar level of the blood become lower, and the fat become higher. Low sugar level of the blood may cause death to a person.

6. Effects of Alcohol in the Kidneys

Alcohol may weaken the performance of the kidneys in releasing waste of our body like urine. That is why some of the drinkers may have a hard time in urinating.

7. Malnutrition

If a person experienced not to eat the needed food of his body, he became malnutritioned. The persons who drink alcoholic bevarages may suffer malnutrition because of the following:

a. Alcoholic beverages are not food. It is true that it gives energy and vitamin B, but it is not enough.

b. The drinkers are not eating their balanced meal completely. They used their time, money, and energy in drinking alcoholic beverages.

c. Alcohol burns the stomach and the intestines. The food that they eat is not used well by the body. When the liver is destroyed because of alcohol, it may not release important vitamins needed by our body.

Malnutrition may weaken our immune defense of our body to the different infection like ulcer and tubercolosis. Malnutrition may also cause too much cough, emotional problems and locomotor skills problems.

8. Traits

Alcohol may affect the traits of a person it is because of the effects of alcohol in the nervous system. The effect of alcohol in the traits is based on the amount of alcohol in the blood. It is based on these different criteria:

a. Amount of alcohol drink.

b. Kind of alcoholic beverages.

c. The size and weight of the drinker.

d. Time of drinking alcohol.

e. The food inside the stomach.

(see appendix, table 5.1)

9. Effects of Alcohol to the Pregnants

The pregnants who drinks at least 2 glasses of alcoholic beverage may affect the baby in their womb like the following:

a. Abortion

b. The baby will be underweight

c. The baby intellectual development may greatly affect

d. Weak coordination

e. Small head

f. Abnormalities of tha face, hands and feet and also to the brain

g. Heart defect

h. The milk supply of the mother will decrease because of alcohol.

B. Effects of Alcohol in the Community

Because drinking alcoholic beverages affect the traits of an individual, the community is also been affected through having quarrels inside the houses, to the friends, work and employment, accidents in the roads and crimes.

1. Quarrels in the House

Too much drink of alcoholic beverages needs to much expense of money. The money that is alloted for the daily needs of the family like, food, clothing, house bills and also the tuition fees of the children was been used in order to buy alcoholic beverages. This is one of the roots why the couple quarrels inside the house.

Because the family lacks financial needs, quarrels will occur. It makes both of the couple unproductive to seek for money for their financial needs. Many families in the slum areas in the Philippines experienced this kind of problem.

2. Quarrels to the Friends

Drinking with friends may lead to quarrel. Sometimes the quarrel will result in stabbing of knife or even death. It happened because of effect of alcohol to the traits of an individual.

3. Quarrels in the Work

A drunkard employee is lazy or experiencing muscular pains because of the effects of alcohol to him. Because of this, the employee is not already interested to go to their office to work. Sometimes, his performance on his work was affected. There is an instance that sometimes he hurt his feelings or the others feeling while working. It is dangerous if the work of the said employee is operating machineries or mixing chemicals in the laboratories.

4. Accidents in the Roads

If a person is drunk, there is an instance that he may drive recklessly. Driving recklessly may cause accidents that may lead to death. In the Philippines, there are car accidents happened because of the irresponsible drivers who drink and drive.

Here are some of the effects of drinking alcoholic beverages while driving:

a. Most of the person who was drunk while driving thinks that they are excellent drivers what is why they are not afraid in driving.

b. Because of the effect of alcohol, a drunkard driver became rude. It may be seen while driving. For example, while in an intersection, a drunkard driver will not give way to the others.

c. Alcohol makes the reaction of the driver to become slowly.

d. A drive that was drunk has a low visibility after he drinks. There is a study that he cannot determine different vehicles and also the color of the stop light wheter it is green, yellow or red.

e. A drunkard driver is not focused on what he is doing.

f. Distinguishing different road signals like the stop light, railroad crossing and many others is very hard to the drunkard driver. Because of this, accident in the roads happened.

5. Crimes

Drinking too much alcoholic beverages is on of the main roots why there was crime happening in our country. Because most of the drunkards thinks that they are the best, other drunkards disagree to them that is why both of them become aggressive and always what to challenge a fight. Some of the drunkards are also been involved in other crimes like, theft, hold- up, murder, and many more.

C. Effects of Alcohol to the Economy of the Country

The strength on the economy of a country will be based on the health and energy of its members. If a country has a citizen who drinks too much alcohol, that country will not achieve good economical status.

The economy will be much affected if there are people who will not work or became lazy to work because of drinking alcoholic beverages. It may cause decrease in the kind and number of productions of a country.

Drinking alcoholic drinks make the economy of the country to move slow because of different crimes, weak family ties, separation of couple nad accidents in the roads. The income of an individual will not be spending to the daily needs of the family but it will be spend to buy alcoholic beverages that are not really important.

VI. CONCLUSION

Drinking alcoholic beverages requires personal decision making. Teenagers will not drink alcoholic beverages not because their parents refused but its is because they knew the different effects of alcohol in their body, their community and the economy of their country.

In personal decision making, he or she should believe in himself or herself. He or she should face his or her different problems in life. We should also remember that we do not need alcoholic beverages to gather more friends. The important thing is that you should develop your good traits to be more pleasing to others.

An industrious person are the ones who will succeed to their careers and never been influenced by alcoholic beverages. And also, those person who can face their problems fearlessly can not easily tempted to drink alcoholic beverages. A person who is responsible and self- discipline can make to achieve unity and make the economy to grow. These person who shows respect and self -discipline are not easily to be drunk.

And always remember that we should be responsible and self-disciplined person because this kind of person can make a good society.

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