STATUS

 

The United States last year consumed an estimated 4 billion gallons of ethanol, compared with 140 billion gallons of gasoline.
 

The typical ethanol-to-gasoline blend is 1 to 9, but now the ethanol industry is pushing for more widespread use of an auto fuel called E85, a mixture of 85 percent ethanol and 15 percent gasoline. The fuel is meant for use only in some "flex-fuel" vehicles that are specially built to accommodate regular gasoline or other blends, including the majority-ethanol mixture.

 

Bumps in the Road

 

That concept faces hurdles. First, a small number of cars sold in the United States are flex-fuel vehicles. And of the 180,000 gasoline stations around the country, only an estimated 600 sell E85. Plus, stations charge more for E85 than gasoline, even though it carries cars fewer miles. The National Ethanol Vehicle Coalition lists four E85 stations open to the public in the Washington area.

 

VeraSun is trying to persuade some stations in the Midwest to sell its branded E85 with modest success. A BP station near the Aurora plant sells the fuel and has a video screen on the pump that gives information about E85.

 

Ethanol producers foresee steady increases in production — thrilling corn farmers, who have found a new market for their crops. But the industry expects that in a decade it will max out available corn and grain crops, producing 15 billion gallons of ethanol a year from those sources.

 

The industry is hoping to eventually increase production using a different type of ethanol, called cellulosic ethanol — using plant material and agricultural waste, including wood chips, stalks or the formerly obscure switch grass mentioned in Bush's State of the Union address. Though technology exists to produce cellulosic ethanol, the process is too expensive to be competitive.

 

PROCESS DESCRIPTION

 

The production of ethanol or ethyl alcohol from starch or sugar-based feedstocks is among man's earliest ventures into value-added processing. While the basic steps remain the same, the process has been considerably refined in recent years, leading to a very efficient process. There are two production processes: wet milling and dry milling. The main difference between the two is in the initial treatment of the grain.

Take a video tour (Windows Media Player required) of an Ethanol Plant and learn about the production process from start to finish. (Courtesy of Midwest Grain Processors.)

 

In dry milling, the entire corn kernel or other starchy grain is first ground into flour, which is referred to in the industry as "meal" and processed without separating out the various component parts of the grain. The meal is slurried with water to form a "mash." Enzymes are added to the mash to convert the starch to dextrose, a simple sugar. Ammonia is added for pH control and as a nutrient to the yeast.

The mash is processed in a high-temperature cooker to reduce bacteria levels ahead of fermentation. The mash is cooled and transferred to fermenters where yeast is added and the conversion of sugar to ethanol and carbon dioxide (CO2) begins.

The fermentation process generally takes about 40 to 50 hours. During this part of the process, the mash is agitated and kept cool to facilitate the activity of the yeast. After fermentation, the resulting "beer" is transferred to distillation columns where the ethanol is separated from the remaining "stillage." The ethanol is concentrated to 190 proof using conventional distillation and then is dehydrated to approximately 200 proof in a molecular sieve system.

The anhydrous ethanol is then blended with about 5 percent denaturant (such as natural gasoline) to render it undrinkable and thus not subject to beverage alcohol tax. It is then ready for shipment to gasoline terminals or retailers.

The stillage is sent through a centrifuge that separates the coarse grain from the solubles. The solubles are then concentrated to about 30% solids by evaporation, resulting in Condensed Distillers Solubles (CDS) or "syrup." The coarse grain and the syrup are then dried together to produce dried distillers grains with solubles (DDGS), a high quality, nutritious livestock feed. The CO2 released during fermentation is captured and sold for use in carbonating soft drinks and beverages and the manufacture of dry ice.

The Ethanol Production Process - Wet Milling
In wet milling, the grain is soaked or "steeped" in water and dilute sulfurous acid for 24 to 48 hours. This steeping facilitates the separation of the grain into its many component parts.

After steeping, the corn slurry is processed through a series of grinders to separate the corn germ. The corn oil from the germ is either extracted on-site or sold to crushers who extract the corn oil. The remaining fiber, gluten and starch components are further segregated using centrifugal, screen and hydroclonic separators.

The steeping liquor is concentrated in an evaporator. This concentrated product, heavy steep water, is co-dried with the fiber component and is then sold as corn gluten feed to the livestock industry. Heavy steep water is also sold by itself as a feed ingredient and is used as a component in Ice Ban, an environmentally friendly alternative to salt for removing ice from roads.

The gluten component (protein) is filtered and dried to produce the corn gluten meal co-product. This product is highly sought after as a feed ingredient in poultry broiler operations.

The starch and any remaining water from the mash can then be processed in one of three ways: fermented into ethanol, dried and sold as dried or modified corn starch, or processed into corn syrup. The fermentation process for ethanol is very similar to the dry mill process described above.

 

CELLULOSIC PROCESS

 

While ethanol is typically produced from the starch contained in grains such as corn and grain sorghum, it can also be produced from cellulose. Cellulose is the main component of plant cell walls and is the most common organic compound on earth. It is more difficult to break down cellulose to convert it into usable sugars for ethanol production. Yet, making ethanol from cellulose dramatically expands the types and amount of available material for ethanol production. This includes many materials now regarded as wastes requiring disposal, as well as corn stalks, rice straw and wood chips or "energy crops" of fast-growing trees and grasses.

 

Producing ethanol from cellulose promises to greatly increase the volume of fuel ethanol that can be produced in the U.S. and abroad. A recent report found the land resources in the U.S. are capable of producing a sustainable supply of 1.3 billion tons per year of biomass, and that 1 billion tons of biomass would be sufficient to displace 30 percent or more of the country's present petroleum consumption.

 

Importantly, it offers tremendous opportunities for new jobs and economic growth outside the traditional "grain belt," with production across the country from locally available resources. Cellulose ethanol production will also provide additional greenhouse gas emissions reductions.

 

Currently, Iogen Corporation in Ottawa, Canada produces just over a million gallons annually of cellulose ethanol from wheat, oat and barley straw in their demonstration facility. Several existing ethanol plants in the U.S. are engaged in research and demonstration projects with the U.S. Department of Energy utilizing the existing fiber in their facility that typically goes into the livestock feed coproduct. Enzyme companies including Genencor International and Novozymes have led successful research projects with the Department to significantly reduce enzyme cost and increase enzyme life and durability.

 

With continued advancements in pretreatment technology, fermentation, and collection and storage logistics, the commercial production of cellulose ethanol becomes more economically feasible.

 

Click here to learn more about the production of ethanol.





 The Energy Policy Act of 2005 (H.R. 6), signed into law in August 2005, contains a number of incentives designed to spur cellulosic ethanol production:

The Biorefinery

 

The concept of a biorefinery is modeled after petrochemical refineries, with production of multiple products at a single facility. Existing biorefineries include wet-mill corn processing and pulp and paper mills. As with petrochemical refineries, the vision is that the biorefinery would integrate several conversion processes to produce both transportation fuel (ethanol and biodiesel) and high-value chemicals or products, including ones that would otherwise be made from petroleum. Industrial biorefineries have been identified as the most promising route to the creation of a new domestic biobased industry.