Biodiesel is an alternative to petroleum-based diesel fuel made from renewable resources like vegetable oils, animal fats, or algae. It has very similar combustion properties to petroleum diesel, and can replace it in current uses. However, it’s most often used as an additive to petroleum diesel, improving the low lubricity of pure ultra low sulfur petrodiesel fuel. It is one of the most realistic candidates to replace fossil fuels as the world’s primary transportation energy source, because it’s a renewable fuel that can replace petrodiesel in current engines and can be transported and sold using today’s infrastructure. A growing number of fuel stations are making biodiesel available to consumers, and a growing number of large transportation fleets use some proportion of biodiesel in their fuel.
Biodiesel is non-flammable, and in contrast to petroleum diesel it is non-explosive, with a flash point of 150°C for biodiesel as compared to 64°C for petrodiesel. Unlike petrodiesel, it is biodegradable and non-toxic, and it significantly reduces toxic and other emissions when burned as a fuel. Chemically, it is a fuel comprised of a mix of mono-alkyl esters of long chain fatty acids. The most common form uses methanol to produce methyl esters, though ethanol can be used to produce an ethyl ester biodiesel. A lipid transesterification production process is used to convert the base oil to the desired esters and remove free fatty acids. A byproduct of the process is the production of glycerol.
Currently, biodiesel is more expensive to produce than petroleum diesel, which appears to be the primary factor keeping it from being in more widespread use. Current worldwide production of vegetable oil and animal fat is not enough to replace liquid fossil fuel use. Some environmental groups, notably NRDC object to the vast amount of farming and the resulting over-fertilization, pesticide use, and land use conversion that would be needed to produce the additional vegetable oil.
Transesterification of a vegetable oil was conducted as early as 1853, by scientists E. Duffy and J. Patrick, many years before the first diesel engine became functional.
Rudolf Diesel’s diesel engine, a single 10 ft (3 m) iron cylinder with a flywheel at its base, ran on its own power for the first time in Augsburg, Germany on August 10, 1893. Diesel later demonstrated his engine at the World Fair in Paris, France in 1900. This engine stood as an example of Diesel’s vision because it was powered by peanut oil—a biofuel. He believed that the utilization of a biomass fuel was the real future of his engine. In a 1912 speech, Rudolf Diesel said, “the use of vegetable oils for engine fuels may seem insignificant today, but such oils may become, in the course of time, as important as petroleum and the coal-tar products of the present time.”
During the 1920s, diesel engine manufacturers altered their engines to utilize the lower viscosity of the fossil fuel (petrodiesel) rather than vegetable oil, a biomass fuel. The petroleum industries were able to make inroads in fuel markets because their fuel was much cheaper to produce than the biomass alternatives. The result was, for many years, a near elimination of the biomass fuel production infrastructure. Only recently have environmental impact concerns and a decreasing cost differential made biomass fuels such as biodiesel a growing alternative.
In the 1990s, France launched the local production of biodiesel fuel (known locally as diester) obtained by the transesterification of rapeseed oil. It is mixed to the proportion of 5% into regular diesel fuel, and to the proportion of 30% into the diesel fuel used by some captive fleets (public transportation). Renault, Peugeot and other manufacturers have certified truck engines for use with up to this partial biodiesel. Experiments with 50% biodiesel are underway.
Many environmentalists and farmers have turned to making their own home brew biodiesel by using either their excess crops or used oil from restaurants, not only are they helping the environment they are also saving money
