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  Biofuels in Kentucky
Biosystems and Agricultural Engineering
University of Kentucky


Frequently Asked Questions


General FAQs

Biodiesel FAQs

Ethanol FAQs


General Biofuel Questions

Will biofuels production affect the nation’s food supply?

The great bulk of U.S. ethanol is made from field corn, the United States’ largest agricultural crop (sweet corn for direct human consumption is a minor crop) and one that typically has enough surplus to require price supports. Most field corn is used for animal feed, a lesser amount for food processing. The 7% currently used for ethanol production has little or no impact on the nation’s food supply. Ethanol production is credited with modestly increasing corn prices—which is of course welcome by the agricultural community and saves the government money by reducing price support payments—but has minimal impact on consumer food prices.

U.S. biodiesel production is based mostly upon soybean oil and recycled restaurant cooking oil. Currently both are available in surplus and biodiesel production uses a minor amount of each. Although soybean oil is used for cooking oil and various food products, it is also used in a wide range of industrial products. Its use for biodiesel has little impact on food supply.

Is the United States the leader in biofuels use?

The United States is second to Brazil, which produces ethanol from the sugar in sugar cane, in both production and use of fuel ethanol. In both production and use of biodiesel, the United States is second to Europe, which makes biodiesel from rapeseed oil.


Biodiesel Questions

What is biodiesel?

Biodiesel is a renewable fuel for diesel engines.  Biodiesel, defined by ASTM International D6751  consists of long-chain fatty acid alkyl esters and is made from renewable vegetable oils, recycled cooking oils, or animal fats.  It can be used at full strength, but is typically blended with petroleum diesel.  A blend of 2% biodiesel and 98% diesel is referred to as B2.  Other typical blends include B5, B10, and B20; pure biodiesel is sometimes referred to as B100. 

Why should I consider using biodiesel?

Biodiesel is a renewable, biodegradable, cleaner burning alternative to petroleum fuels.  It has a slightly higher cetane rating which can promote easier cold starting and lower idle noise.  With tax incentives and rising petroleum prices, biodiesel is becoming more economically competitive.

Is all biodiesel the same?

Because biodiesel can be made from a number of different raw materials and with a number of different processes, there can be some subtle variations in chemical and physical properties.  ASTM has established standards for testing diesel fuels to insure some uniformity in performance.  In most applications, if the biodiesel conforms to ASTM standards it can be used in the same equipment as other diesel fuels.  Verify with your supplier that the biodiesel conforms to ASTM standards.

Will I have to modify anything mechanically in my engine to use biodiesel?   

Not if you are using blends of B20 or less.  The specifications for biodiesel have been established so that it can be used in any diesel engine.  Some modifications may be desirable with higher biodiesel concentrations.  Consult your equipment manufacturer before using higher biodiesel blends.

Will biodiesel hurt the mechanical parts of my engine?

No.  In fact biodiesel can be good for an engine for two reasons.  First, biodiesel has more lubricating properties than petroleum diesel.  Loss of lubricity is one of the drawbacks of newer low sulphur diesel fuels.  Adding just 1% biodiesel increases the lubricity to an acceptable level, so any biodiesel blend will have the required lubricity without sulfur or other additives.  The second advantage is that biodiesel will actually help clean the fuel system.  Because it is a good solvent, it can remove deposits and buildup from tanks, lines, pumps and other fuel system components.  Be aware, though, that since it is such a good solvent, it has the potential to damage certain paints and finishes, so always clean up spills immediately.

Will biodiesel hurt seals and other components?

Biodiesel blends higher than B20 can cause problems with natural rubber engine components, such as seals and hoses.  Biodiesel will degrade rubber, so any seals or hoses in the fuel system that are made of rubber will be susceptible to damage.  Biodiesel blends of B20 or below should not cause problems with rubber components, but users should periodically check rubber components when using any biodiesel blend to make sure they are not degrading or getting hard.  As the use of biodiesel increases, most equipment manufacturers are increasing the use Viton-based materials in seals and hoses.  Viton is a synthetic rubber substitute that will not be damaged by biodiesel.

Some manufacturers do caution users about potential problems with the lubricating oil in an engine.  If biodiesel gets mixed with the lubricating oil, it can react with the oils to create “sludge” that might accumulate in the sump or in oil passages.  Check manufacturer recommendations about oil change frequency as some suggest changing oil more often when using biodiesel.

Will biodiesel cause fuel filter problems?

The most common fuel filter problems occur when switching older machinery from petroleum diesel to biodiesel.  Petroleum diesel has a tendency to leave paraffin-based buildup on the insides of tanks and other fuel system components.  Biodiesel will loosen this buildup, which will be trapped in the fuel filter.  Users can expect to replace fuel filters several times after switching older equipment to biodiesel.  After the fuel system gets cleaned out, filter usage should return to normal.

Another less common cause of filter problems comes from the use of higher biodiesel blends that have been stored for extended periods of time.  Biodiesel will degrade with age (see storage question below), producing some gums and sediments, which can cause filter plugging.

Will I get as much power from my engine with biodiesel?

Pure biodiesel contains 5-8% less energy per gallon than petroleum diesel.  Blended fuels obviously will have less of an energy loss.  Some literature does indicate that other factors such as more efficient burning and better injection efficiency due to higher viscosities may counteract this energy loss.  In any event, users might notice a slight power loss with biodiesel fuels.

Will I void the manufacturer’s warranty if I use biodiesel?

Warranties vary significantly from manufacturer to manufacturer, but most will not categorically void a warranty if you use biodiesel.  However, most warranties will not cover damage that was caused by the fuel (be it biodiesel or any other fuel) because those damages were not caused by a defect in the machine.  For instance, if you damage a diesel engine by accidentally putting gasoline in the tank, the manufacturer probably will not repair the engine under warranty.  Therefore, it may be more difficult to get warranty coverage for problems that may have been caused by biodiesel.  Furthermore, many manufacturers are reluctant to recommend use of blends higher than B5 in engines.  Check carefully with the individual manufacturer to verify what is covered and/or recommended. 

Can I use biodiesel in cold weather?

Pure biodiesel is more susceptible to cold temperature problems than petroleum diesel, but when blended, this effect is moderated.  A B2 biodiesel blend, for example, has the same cold flow properties as petroleum-based diesel.  However, B20 will have a higher gel point, from 3 to 5 °F higher.  The bottom line is that as with petroleum diesel, you will need to use a kerosene blend or other anti-gelling additive in colder temperatures.  Consult your fuel supplier to make sure you will be protected in your climate.

Is biodiesel more susceptible to water contamination?

Biodiesel is more susceptible to water contamination than petroleum diesel.  The presence of water in biodiesel or any fuel can promote corrosion of fuel system components and growth of microorganisms.  The following are some common sense techniques useful for preventing water contamination in any fuel system.

bullet Make sure all tank caps are in place and in good condition.
bullet Store machinery with tanks full to minimize condensation inside the tank.  Get in the habit of filling the tanks at the end of the day so there is no room for condensation to form when the temperatures cools overnight.
bullet Large temperature swings can promote moisture condensation on the inside of storage tanks.  Underground storage tanks are best at preventing condensation since fuel is kept at a relatively constant temperature, but underground storage introduces many other potential problems such as leakage and liability.  Above ground storage tanks should be insulated (double wall) and shaded if possible to moderate temperature swings thereby reducing the possibility of condensation formation.
bullet Drain a small amount of fuel from the bottom of storage tanks every 6 months to remove any water that might have accumulated in the tank.
bullet Avoid prolonged exposure of fuel to light, which can induce algae growth.  Fiberglass tanks should be painted and/or placed in shaded areas.
bullet If biological growth is a problem, the same products that are used with petroleum diesel can be used in biodiesel to “dry” the fuel and clean up biological contaminants.

How long can I store biodiesel?

Fuel aging and oxidation can lead to heightened acid content, high viscosity and the formation of gums and sediments that clog filters.  It is recommended that biodiesel be stored for no more than six months without an anti-oxidant additive.

Will biodiesel totally replace diesel someday?

There are no specific efforts at this point to make biodiesel a requirement.  Because it is a cleaner burning, renewable fuel source, though, availability and usage will continue to increase.


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Ethanol Questions

What is Ethanol?
Ethanol is a clear, colorless alcohol fuel made by fermenting the sugars found in grains, such as corn, grain sorghum, and wheat.

How does the use of ethanol reduce exhaust emissions?
Since ethanol contains oxygen, it contributes to a cleaner, more efficient burn of the gasoline, which results in lower CO exhaust emissions. Ethanol is a simple chemical which, when burned, does not produce the complex pollutants and aromatics formed by many hydrocarbons and gasoline additives. Source:

Will the use of ethanol void my vehicle warranty?
No. All vehicle manufacturers in the U.S. approve the use of ethanol in vehicles manufactured since 1982 and some recommend ethanol use for environmental reasons. Many manufacturers do recommend against the use of methanol, which is very corrosive and should not be confused with ethanol. Source:

What is E85?
E85, a blend of 85% ethanol and only 15% petroleum, is making a splash in the fuel and automotive industry. E85 is used to power flexible-fuel vehicles or FFVs, which cost the same as gasoline models and can run on any mixture of ethanol and gasoline. With three million FFVs currently on the road in the U.S., many people are surprised to learn that they already own an FFV. Even better news is that E85 often costs 10 to 20 cents less than gasoline. Source:

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Updated: 11.02.05
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