Biodiesel is an alternative fuel that can be used in standard diesel-powered vehicles without the need to make any modifications to the engine. Unlike regular petroleum-based diesel fuel, it can be refined from any fat or vegetable oil. In America, biodiesel is produced primarily from domestically grown soybeans. This gives the fuel several advantages. First, the fuel source is renewable. Second, when consumed in a vehicle, it's much better for the environment, because it doesn't release as much black soot and carbon dioxide, a "greenhouse" gas which can contribute to global warming.
To determine just how effective an alternative fuel really is, scientists consider a fuel's so-called energy balance. The energy balance takes account of how much energy is consumed to actually make a fuel like biodiesel. For example, let's say it takes a total of three units of energy to harvest a crop, and one more unit of energy to convert the crop into useable auto fuel, for a total of four energy units. If we were able to invest those four units of energy and produce a fuel that can do six energy units worth of work in the end, then that fuel would have a positive energy balance.
David Pimental, a professor of ecology and agricultural sciences at Cornell University in New York, has studied several alternative energy sources, and gives biodiesel a good rating. "It turns out that with soybean oil, energetically (in terms of energy), you get a positive return. In other words, you get about a gallon and a half (5.7 liters) for every gallon (3.8 liters) of oil that you invest in that. So it is positive in that sense. However, the cost is significant," he says. "The data that I have indicate that it costs you about a one dollar and eighty cents per gallon (per 3.8 liters). That's for production and it's not distribution and so forth. So that is a significant price."
David Pimental is not as fond of a similar alternative fuel called ethanol, which is refined in the United States from corn, or maize, and other crop residues. For the past twenty years, Mr. Pimental has argued that ethanol suffers from a very poor energy balance, meaning it yields less energy as a fuel than is spent harvesting and producing it.
While most scientists are in agreement that biodiesel is generally a good energy investment, there may be another obstacle to its widespread adoption: the negative perceptions Americans have about diesel engines. John Farrel at the U.S. Department of Energy says that those perceptions are driven largely by aesthetic and environmental concerns. "In the early 70's in the U.S., Detroit came out with a number of diesel engines that were really not all that great," he says. "I think that there are a number of people who still associate diesel with the early 70's and those vehicles. I think the other issue is you've got a lot of old diesels running around the U.S., particularly in school buses. Because of the nature of the engine, when you take off, you see a big cloud of smoke and people associate that with diesel and nothing else."
But Mr Farrell believes that this negative perception is gradually improving. European car companies like Volkswagen are demonstrating that diesel cars can be more fuel-efficient and run cleaner at the same time. And studies have shown that biodiesel fuel can help reduce the clouds of black smoke emitted by many older diesel vehicles.
Use of biodiesel is growing in America, not just in privately-owned vehicles, but also in government and company-operated automobiles. Many government bus fleets and industrial vehicles now use a mix of diesel and biodiesel fuels. Such use complies with Congressional laws that set guidelines for cleaner air and increased use of alternative fuels. Biodiesel is a little more expensive at the gas pump than standard diesel. However, bus fleet owners don't have to purchase any new or specialized equipment to use biodiesel.
The trend toward increased use of biodiesel could be a boon for American soybean farmers, by increasing the value of soybean oil. A study completed in 2001 by the U.S. Department of Agriculture stated that biodiesel could increase the value of soybeans by an average of 17 cents annually through 2010. The study estimates that could result in a $5.2 billion boost to the U.S. farm economy over 10 years.