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Biodiesel is becoming widely available in most parts of the U.S. and can be substituted for petroleum-based diesel fuel (“petro diesel”) in virtually any standard unmodified diesel engine. Biodiesel offers many advantages over petroleum-based diesel:
It is made from domestically produced and renewable agricultural products, mainly vegetable oil or animal fat.
• It is essentially non-toxic and biodegradable.
• It has a high flash point (over 300ºF) and is difficult to light on fire with a match.
• It reduces emissions of many toxic air pollutants.
• It functions as an excellent fuel lubricant and performs similarly to low-sulfur diesel with regards to power, torque, and fuel consumption.
• It can greatly reduce carbon emissions.
Biodiesel is a very different substance from ethanol. Ethanol (or grain alcohol), the familiar alcohol found in alcoholic beverages, is commonly blended with gasoline (not diesel fuel) and is made by fermenting grains or other plants that contain sugar. Fermentation is a biological process accomplished by yeasts and bacteria.
Biodiesel is also very different from raw or “straight” vegetable oil (SVO). Almost any vegetable oil will combust, to one degree or another, in a diesel engine. So it’s possible to run most diesel engines on SVO. But this is a somewhat risky process, mainly since raw vegetable oil is too thick and viscous to run well in diesel engines.
The U.S. Department of Energy, among many other organizations, cautions that SVO can reduce engine life and should not be considered a fuel for long-term use.(2) The use of SVO has been shown to cause piston ring sticking, injector and combustion chamber deposits, fuel system deposits, reduced power, reduced fuel economy, and increased exhaust emissions. Any of these conditions can reduce engine life, increase maintenance costs, or cause engine failure. Modern diesel engines are also equipped with catalytic converters, or filter traps, that are not designed to handle SVO.
Despite the very real risk of engine damage, SVO has certain advantages that may make it worth considering for some farming situations and equipment, especially in older engines. Using SVO is in some ways simpler than making your own biodiesel. Making biodiesel generally requires you to use methanol, a toxic chemical, and to dispose of glycerin, a waste product. By contrast, SVO is generally only filtered before use, and there are few if any waste products to deal with.
Biodiesel Blends
Biodiesel in its pure (100 percent) form is known as neat biodiesel or B100. It can be readily blended with petroleum diesel in any proportion. A B20 blend, for example, is 20 percent by volume biodiesel and 80 percent petro diesel.
Different blends serve different purposes. Small amounts of biodiesel (B1-B2) add lubrication to low-sulfur fuels. Blends in the B20 to B50 range provide significant environmental benefits with a low increase in cost to consumers. Blending also reduces the likelihood of the solvency, material incompatibility, or cold weather problems discussed below.
The simplest method is splash blending. Biodiesel should always be poured on top of petroleum diesel, since it is slightly heavier. The two fuels will mix fairly well as the biodiesel gradually sinks through the lighter petro diesel. Some form of agitation is needed, though, to achieve highly uniform fuel. Random samples of splash blended fuel being marketed as B20 have been found to contain actual biodiesel content ranging from B2 to B90.