Does anyone know of a good website on ethanol production?

Question

I am curious as to how much raw material is needed to produce a gallon of ethanol. Corn vs. sugarcane and other materials that might be used to produce ethanol. Also what the cost of production might be.

Answer 1

HOW IS ETHANOL MADE?

The majority of the ethanol in the U.S. 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. Most of the ethanol in the U.S. is made using the dry mill method. 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, 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% 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% 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 gasoline (2-5%). 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.

View Ethanol Today magazine's "Technical Connections" series on the steps of the ethanol production process.



http://www.nwicc.com/pages/continuing/business/ethanolcurriculum.html
http://www.ethanol.org/pdfs/EthanolCurriculum.pdf
http://www.ethanol.org/documents/QuestionsandAnswersonEthanol.pdf
http://en.wikipedia.org/wiki/Ethanol_fuel
http://ethanol.org/ethanolresearch.html

Answer 2

I will not clutter this answer with a huge list of steps. The first link is a very nice easy to understand and yet thorough introduction into ethanol production. This particular article focuses on the current production method based on corn and particularly the first few steps will be different for celulosic feedstocks.

The second and third links are to a summary and the actual study that looks at the energy efficiency of producing ethanol in various ways. The authors reviewed a number of prior studies and was able to reconcile differences and correct methodologies thereby being able to demonstrate that ethanol production is indeed a net producer of energy.

The final link is very interesting. It is an article about the US Department of Energy's Roadmap for Development of Cellulosic Ethanol Production. One interesting aspect of this is that the DOE road map indicates that cellulosic ethanol will not consume any of the food supply.

Answer 3

Ethanol can be produced in different ways, using a variety of feedstocks. [1] Brazil uses sugarcane as primary feedstock, but a large variety of feedstocks are possible. For information on Brazil's method of ethanol production, see ethanol fuel in Brazil.

Crops with higher yields of energy, such as switchgrass and sugar cane, are more effective in producing ethanol than corn[citation needed]. Ethanol can also be produced from sweet sorghum, a dryland crop that uses much less water than sugarcane and produces food, and fodder in addition to fuel. [2] [3]

Basic steps for dry mill production of ethanol are: refining into starch, liquification and saccharification (hydrolysis of starch into glucose), fermentation, distillation, dehydration, and denaturing (optional). Carbon dioxide, a potentially harmful greenhouse gas, is emitted during fermentation. However, the net effect is more than offset by the uptake of carbon gases by the plants grown to produce ethanol. [4] The net result of using ethanol as a fuel is to reduce green house gases. [5] [6]

Ethanol produced by fermentation results in a solution of ethanol in water. During ethanol fermentation, glucose is evolved into ethanol and carbon dioxide. The equation is:

C6H12O6 → 2 CH3CH2OH + 2 CO2

For the ethanol to be usable as a fuel, water must be removed. The oldest method is distillation, but the purity is limited to 95-96 % due to the formation of a low-boiling water-ethanol azeotrope. The 96% ethanol, 4% water mixture may be used as a fuel, and it's called hydrated ethyl alcohol fuel (álcool etílico hidratado combustível, or AEHC in Portuguese). In 2002, almost 5 billion liters (1,3 billion gallons) of hydrated ethyl alcohol fuel were produced in Brazil, to be used in ethanol powered vehicles.

It is not possible to obtain ethanol of purity > 96 % by distilling any more dilute solution. For blending with gasoline, purities of 99.5 to 99.9% are required, depending on temperature, to avoid separation. Currently, the most widely used purification method is a physical adsorption process using molecular sieves.

In the past, when farmers distilled their own ethanol, they sometimes used radiators as part of the still. The radiators often contained lead, which would get into the ethanol. Lead entered the air during the burning of contaminated fuel, possibly leading to neural damage. However this was a relatively minor source of lead since at the time tetraethyl lead was used as a mainstream gasoline additive. Today, ethanol for fuel use is produced almost exclusively from purpose-built plants, avoiding any lead presence.

Biotechnology can help to improve the energetic productions of bioethanol.

Answer 4

the main products today are fuel and also food additives.