Ethanol is a clean-burning, high-octane fuel that is produced from renewable sources. At its most basic, ethanol is grain alcohol, produced from crops such as wheat, barley, potatoes, corn or sugarcane. If domestically produced, ethanol will help reduce Jamaica's dependence upon foreign sources of energy. Last year over 15 per cent of all gasolene in the United States contained ethanol.
Pure ethanol is not generally used as motor fuel; instead, a percentage of ethanol is combined with unleaded gasolene. This is beneficial because the ethanol:
Decreases the fuel's cost
Increases the fuel's octane rating
Decreases gasolene's harmful emissions
Any amount of ethanol can be combined with gasolene, but the most common blends are:
E10 - 10 per cent ethanol and 90 per cent unleaded gasolene
E10 is approved for use in any make or model of vehicle sold in the U.S. Many automakers recommend its use because of its high performance, clean-burning characteristics. In 2004, about one-third of America's gasolene was blended with ethanol, most in this 10 per cent variety.
E85 - 85 per cent ethanol and 15 per cent unleaded gasolene
E85 is an alternative fuel for use in flexible fuel vehicles (FFVs). There are currently more than four million FFVs operating in the United States today, and automakers are rolling out more each year. In conjunction with more flexible fuel vehicles, more E85 pumps are being installed across the U.S. When E85 is not available, these FFVs can operate on straight gasolene or any ethanol blend up to 85 per cent.
It is important to note that it does not take a 'special' vehicle to run on ethanol. All vehicles can use E10 with no modifications to the engine. E85 is for use in a flexible fuel vehicle, so some people confuse ethanol with the blend of 85 per cent ethanol and 15 per cent gasolene.
HOW IS ETHANOL MADE?
Most of the ethanol in the United States is made from corn, but it can also be produced from other feedstocks such as grain sorghum, wheat, barley, or potatoes. Brazil, the world's largest ethanol producer, makes the fuel from sugarcane.
Ethanol can be made by a dry mill process or a wet mill process. In the dry mill process, the starch portion of the corn is fermented into sugar then distilled into alcohol.
The major steps in the dry mill process are:
1. Milling. The feedstock passes through a hammer mill which grinds it into a fine powder called meal.
2. Liquefaction. The meal is mixed with water and alpha-amylase, and then passed through cookers where the starch is liquefied. Heat is applied at this stage to enable liquefaction. Cookers with a high temperature stage (120-150 degrees Celsius) and a lower temperature holding period (95 degrees Celsius) are used. High temperatures reduce bacteria levels in the mash.
3. Saccharification. The mash from the cookers is cooled and the secondary enzyme (gluco-amylase) is added to convert the liquefied starch to fermentable sugars (dextrose).
4. Fermentation. Yeast is added to the mash to ferment the sugars to ethanol and carbon dioxide. Using a continuous process, the fermenting mash is allowed to flow through several fermenters until it is fully fermented and leaves the final tank. In a batch process, the mash stays in one fermenter for about 48 hours before the distillation process is started.
5. Distillation. The fermented mash, now called beer, contains about 10 per cent alcohol plus all the non-fermentable solids from the corn and yeast cells. The mash is pumped to the continuous flow, multi-column distillation system where the alcohol is removed from the solids and the water. The alcohol leaves the top of the final column at about 96 per cent strength, and the residue mash, called stillage, is transferred from the base of the column to the co-product processing area.
6. Dehydration. The alcohol from the top of the column passes through a dehydration system where the remaining water will be removed. Most ethanol plants use a molecular sieve to capture the last bit of water in the ethanol. The alcohol product at this stage is called anhydrous ethanol (pure, without water) and is approximately 200 proof.
7. Denaturing. Ethanol that will be used for fuel must be denatured, or made unfit for human consumption, with a small amount of gasolene (two to five per cent). This is done at the ethanol plant.
8. Co-Products. There are two main co-products created in the production of ethanol: distillers grain and carbon dioxide. Distillers grain used wet or dry, is a highly nutritious livestock feed. Carbon dioxide is given off in great quantities during fermentation and many ethanol plants collect, compress, and sell it for use in other industries.
BENEFITS OF ETHANOL USE
Using ethanol-blended fuel is one of the easiest ways we can help reduce air pollution and our dependence on imported oil. There is a significant reduction in both carbon monoxide and hydrocarbon tailpipe emissions when ethanol is used.
Ethanol contains oxygen, which helps gasolene burn cleaner and more efficiently. When used in vehicles, ethanol reduces all types of emissions including carbon dioxide - a major contributor to global warming.
QUESTION OF THE DAY
Would you use ethanol-blended gas in your car?
Email responses to mias@uwimona.edu.jm
