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July 2002
Bus running on soybean biodiesel. Photo: U.S. Department of Energy.
Diesel is the fuel for many vehicles. Diesel engines are a type of internal combustion engine in which heat caused by air compression ignites the fuel. At the instant fuel is injected into a diesel engine’s combustion chambers, the air inside is hot enough to ignite the fuel on contact. Diesel engines therefore do not need spark plugs, which are required to ignite the air-fuel mixture in gasoline engines. Diesel engines burn a petroleum product similar to kerosene, jet fuel, and home heating oil. A major disadvantage of the diesel engine is the production of sooty, smelly, black smoke.
The many advantages of biodiesel fuel
With gas prices soaring and our fossil fuel supply diminishing, most people would agree that we need to find a cheaper way to fuel our economy. Biodiesel can be a viable alternative to petroleum diesel fuel because it is:
- made from renewable oils
- biodegradable
- free of sulfur and aromatics
- cleaner for the environment
In the past decade, biodiesel has been gaining worldwide popularity as an alternative energy source because of its many benefits.
- Biodiesel is made from renewable fats and oils, such as vegetable and canola oil, by a simple refining process.7
- One of the main commodity sources for biodiesel is soybeans, a major crop produced in many parts of the world. It is grown in 30 states in America, yielding 75.39 million metric tons in 2000.1
- The by-product glycerin can be used as well, in products such as toothpaste, cough syrup, and plastic.5
In addition to easily-available sources, biodiesel has other major advantages:
“It can be used in existing engines and fuel injection equipment without negative impacts to operating performance.”2
It can replace or blend with petroleum diesel with little or no engine modifications.
Blended at a 20% rate with petroleum diesel, it has lower wear than traditional fuel and shows improved lubricity. In fact, it is the only alternative fuel “that can actually extend engine life because of its superior lubricating properties.”2
Biodiesel stays blended with petroleum diesel, making it possible to store and dispense wherever diesel fuel is now stored or sold.2
It degrades about four times faster then petroleum diesel fuel.
Operationally, biodiesel has a higher flashpoint (the temperature at which diesel fuel ignites), making it a more versatile fuel than conventional diesel where safety is concerned. Due to lower volatility (tendency to vaporize) and a higher flashpoint, it is less likely to catch fire during an accident.9
According to university tests, biodiesel is a viable option for niche markets, such as urban bus fleets and the marine industry, including “recreational boats; inland commercial and ocean-going commercial ships; research vessels;”3 and coast guard fleets. For example, recreational boats consume 95 million gallons of diesel fuel annually9 and, overall, the marine industry accounts for 10% of the petroleum diesel fuel market in the United States.
Good for the environment
“Pure biodiesel is biodegradable, non-toxic, and essentially free of sulfur and aromatics.”3 The use of biodiesel and biodiesel blends results in:
- a less offensive exhaust odor, which can be a real benefit in confined spaces or large urban areas
- no eye irritation, since biodiesel is oxygenated, resulting in engine combustion that is more complete than petroleum
- a reduction of pollutants, such as carbon dioxide, which in turn helps to prevent depletion of the ozone layer and acid rain
Conventional diesel causes a lot of pollution in the form of hydrocarbons (family of organic compounds composed entirely of carbon and hydrogen) and sulfur emissions (a problem with most fossil fuels).8 “There is strong environmental pressure to eliminate or at least greatly reduce these emissions, especially in areas of environmental sensitivity such as lakes and inland waterways and inner city areas.”
- Emission of chemicals into the atmosphere depletes the ozone layer.
- The pH level of many freshwater lakes in America has been altered so dramatically by acid rain that entire fish populations have been destroyed.
- Sulfur dioxide emissions and sulfuric acid, even from long distances, can also damage limestone and marble.
By contrast, biodiesel reduces the major greenhouse gas components in the atmosphere, carbon monoxide, hazardous diesel particulate, and life cycle carbon dioxide emissions — all of which are damaging to the environment.2 Biodiesel’s cleaner emissions and favorable odor are clearly an improvement over petroleum diesel.
Cost and performance
The cost of biodiesel depends on the market price for oils. Biodiesel blended at a 20% level with petroleum diesel costs 15-30 cents per gallon more than petroleum diesel alone. However, given the other advantages of biodiesel, it is a still an option to diesel, especially “in certain niche markets that require a cleaner-burning, biodegradable fuel.”6 Costs could decrease if, for example, more agricultural land was used to grow and use crops for biodiesel ingredients.
More than 100 biodiesel demonstrations, including 1,000,000 mile tests and more than thirty 50,000 mile tests, have logged more than 30 million road miles with biodiesel blends. In these tests, performance, fuel mileage, drivability, start-up, power, range, and cold weather performance characteristics of blends were similar to petroleum diesel.10
Biodiesel still has some obstacles to overcome in addition to its high cost. “Because of its unsaturated fatty compounds, vegetable oil reacts with oxygen more easily than diesel does, and so its properties can change. Biodiesel can also leave more gummy deposits in engines than regular diesel does.”4 However, it is a worthwhile investment for nations to help biodiesel research. Biodiesel may be one major solution to ensuring future fuel supplies that are environmentally friendly.
© 2002, American Institute of Biological Sciences. Educators have permission to reprint articles for classroom use; other users, please contact editor@actionbioscience.org for reprint permission. See reprint policy.
