How is biodiesel made?

Vegetable oil or animal fat is combined with alcohol, either methanol or ethanol, in the presence of a catalyst, generally sodium or potassium hydroxide. The catalyst typically is recovered for re-use. Most biodiesel today derives from soy oil and used cooking oil from restaurants (yellow grease). Other vegetable oils, including rapeseed, mustard, canola and sunflower, make good biodiesel feedstock, as do animal fats.

A number of folks are also successfully making and using biodiesel on a small-scale basis. While the National Biodiesel Board does not recommend the practice, citing concerns over quality control and handling of toxic materials, there are many advocates of homegrown fuels in the biodiesel community.

How does performance compare to petrodiesel?

Biodiesel runs all diesel engines, and can be blended in any proportion with petrodiesel. The most commonly used blends are 5% (B5) and 20% (B20) biodiesel, while some fleets are successfully running on pure biodiesel (B100).

Blends of B20 and below have virtually the same fuel economy and power as petrodiesel, and require no engine modifications. Numerous independent studies show biodiesel has excellent lubricating qualities that reduce wear and tear. Some fleet owners report decreased idle vibration and quieter operation. Most engine manufacturers have stated that B20 which meets their specifications will not void warranties, and some have approved B100. Fuel should conform to ASTM (American Society of Testing and Materials) specifications to ensure good quality.

Engines made before 1993 should have rubber seals, gaskets and hoses in the fuel system replaced before using blends above 35%. Biodiesel is a mild solvent that will clean petrodiesel crud out of tanks and engines even at lower blends, so fuel filter changes may be necessary during initial use. B100 contains 10-12% less energy than an equal weight of petrodiesel but is denser in the tank, so the reduction in mileage and peak power is only 3-7%.

Are there special handling considerations?

Biodiesel burns at around 300° F, compared to 125° F for petrodiesel, so it is very safe to use, handle and store. It biodegrades four times faster than petrodiesel, about the same rate as dextrose, making it especially attractive for use in boats. With only one-tenth the toxicity of table salt, biodiesel is less irritating to skin than a 4% soap and water solution. Mechanics report it does not cause the cracked skin that petrodiesel does.

During winter months, biodiesel should be treated like common No. 2 diesel, blending it with No. 1 diesel or using engine heaters to maintain viscosity. B20 used in temperatures well below 0° F should cause no difficulties. Depending on the oil source, B100 may require additives or fuel system heating to prevent gelling. Rapeseed and canola-based fuels gel at lower temperatures than those derived from waste oil, and have been used at Yellowstone National Park since 1995 without troubles.

How significant are the environmental benefits?

Petrodiesel trucks and buses constitute 6% of miles driven but emit 20% of particulate pollution. These tiny toxin-laden particles are considered a probable cancer causer, and are a major contributor to smog. Biodiesel use substantially reduces the emission of particulates, as well as unburned hydrocarbons and carbon monoxide. Biodiesel also yields 3.24 times the energy required to produce it, making it more energy efficient than any other liquid fuel.

Biodiesel emits virtually no sulfur dioxide, a pollutant which causes acid rain and burns lungs, throats and eyes. Without the sulfurous bite of petrodiesel, many say burning biodiesel smells like popcorn. Biodiesel from some feedstocks may produce slightly higher levels of nitrogen oxides, the building blocks for ozone, but other pollution reductions still diminish the overall ozone potential by up to 50%.

New ultra-low sulfur diesel, mandated by the US Environmental Protection Agency to be phased into production starting in 2006, provides another opportunity to expand biodiesel use. A modest B2 (2%) biodiesel blend can restore the lubricity lost when sulfur is removed.

What does the future hold for biodiesel?

The National Renewable Energy Lab estimates feedstocks sufficient to supply 3.4% of US diesel demand now exist, and that mustard oil alone could eventually supply the equivalent of 18% of current US diesel consumption. Expanded mustard production would also generate an organic soil fumigant that could take 10% of the US pesticide market.

An Iowa study found that using B20 in state fleets would cost an added $500,000 annually, but if that spurred creation of a biodiesel plant capable of producing 5 mgy the added tax revenues would more than make up the cost. A University of Missouri study estimated that a region producing 100 mgy would add $8.34 million to annual personal income. And a study conducted by AUS Consultants found that 4% renewable fuel use by 2016 could boost the US economy by $300 billion and create as many as 300,000 new jobs.

Biodiesel is still a small contributor to the overall market for domestic transportation diesel fuel. Future growth could be substantial, but is difficult to quantify in part because biodiesel’s success in the marketplace is so recent. Most biodiesel users are fleets, but growth in demand by individual users has spawned several publicly accessible fueling stations nationwide. Any cost differential with petrodiesel is expected to narrow in coming years as the biodiesel industry scales up, technologies improve and petrodiesel prices rise.