Ethanol Facts

Primary Uses of Ethanol

Ethanol is primarily used as a gasoline fuel additive to lower the lifecycle emissions of greenhouse gases. The lifecycle emissions from the production and combustion of ethanol are significantly lower than the lifecycle emissions from the production and combustion of gasoline. Ethanol “lifestyle emissions” are the greenhouse gas emissions resulting from the production of feedstock (typically wheat or corn), the conversion of the feedstock to ethanol, and the combustion of ethanol. Ethanol has also gained wide acceptance as a replacement for the fuel additive methyl tertiary butyl ether (MTBE), which as been banned in certain jurisdictions due to concerns regarding its impact on the environment. As a gasoline blendstock, ethanol functions as an octane enhancer, a clean air additive and a fuel extender.

Greenhouse Gas Emissions Reduction – When ethanol is produced from renewable feedstocks such as wheat and corn, the greenhouse gas emissions are reduced on a full lifecycle basis. The use of renewable fuels such as ethanol in place of fossil fuels represents one of the most effective means of reducing greenhouse gas emissions in the transportation sector.

Octane Enhancer – Pure ethanol possesses an average octane rating of 113 (compared to regular unleaded gasoline’s average octane rating of 87), enabling refiners to conform lower octane blendstock to gasoline standards, while also expanding the volume of fuel produced. In addition, ethanol is commonly added to finished regular grade gasoline at the wholesale terminal as a means of producing higher octane mid-grade and premium gasoline. Ethanol represents one of the few commercially viable sources of octane available to refiners.

Clean Air Additive – A clean air additive is a substance that, when added to gasoline, reduced tailpipe emissions and improves air quality characteristics. Ethanol contains 35% oxygen, approximately twice that of MTBE, a historically used oxygenate. The additional oxygen found in ethanol results in more compete combustion of the fuel in the engine cylinder, which reduces tailpipe emissions by as much as 30%. Ethanol, which is non-toxic, water soluble and biodegradable, replaces some of the harmful gasoline components, including benzene.

Fuel Extender – Ethanol extends the volume of gasoline by the amount of ethanol blended with conventional gasoline, thereby reducing dependence on foreign crude oil and refined products. Furthermore, ethanol is easily added to gasoline after the refining process, reducing the need for large, capital intensive capacity expansion projects at refineries.

Ethanol Production Process

In North America, fuel ethanol is currently produced mostly from starch containing crops such as wheat, corn and milo. Several plants use a waste sugar stream from another industrial plant such as a sulphite pulp mill, a brewery, cheese factories, potato processors and other food processing plants. However, the dominant feedstock is corn. The basic process involved the enzymatic hydrolysis of starch to sugars and the fermentation of the sugars to ethanol via yeast. The weak ethanol solution known as beer is then distilled and dried to produce anhydrous ethanol, which is suitable for blending with gasoline. There are a number of process variations that are employed, such as dry or wet milling and batch or continuous fermentation.

Most new ethanol plants being considered are dry mill ethanol plants because these plants have lower capital costs and produce fewer co-products.

The major steps in the dry milling process are summarized below.

• Grain Unloading . Trucks deliver wheat to the plant directly from farms or from grain elevators.

• Milling. The wheat will pass through a grain milling system which mills the wheat into a fine powder called “meal”. A cyclone or baghouse dust collector eliminates grain dust during milling.

- Liquefaction.. The meal is mixed with water and the enzyme alpha-amylase. This mixtures then passes through cookers, where the starch is liquefied. Heat is supplied at this stage of the process to enable liquefaction.

- Saccharification. The mash from the cookers is cooled and the secondary enzyme gluco-amylase is added to convert the liquefied starch into fermentable sugars. This process is called “saccharification”.

- Fermentation. Yeast is added to the mash to ferment the sugars into ethanol and carbon dioxide.

- Distillation. The fermented mash, called “beer”, contains approximately 12.5% ethanol by volume and the non-fermented solids from the wheat and the yeast cells. The beer mash is pumped into a continuous flow, multi-column distillation system where the ethanol is separated from the solids and water. The ethanol leaves the top of the final column at approximately 95% strength and the residual mash, called stillage, is recovered from the base of the column and is transferred to the by-product processing area.

- Dehydration. The ethanol then passes through a dehydration system where the remaining water is removed. The alcohol product at this stage is called “anhydrous ethanol”.

- By-Product Recovery. Evaporators and gas fired ring dryers are used to remove the water from the stillage and produce the dried distillers grains.

- Ethanol Storage. The ethanol will be stored in carbon steel tanks. The tanks will be sized to contain 10 to 15 days of production storage. The ethanol will then be blended with a 1 to 5 percent mix of gasoline.

- Ethanol and Dried Distillers Grains Load-out. Trucks and railcars will move the ethanol to the gasoline terminals. Trucks and railcars will also be used to deliver the dried distillers grains to customers. The load-out facility will be equipped with “dustless spouts” to load trucks and hopper cars.