Lawrence Kren
Senior Editor

A worker adjusts equipment in a biodiesel plant owned by Renewable Energy Group Inc., Ralston, Iowa. REG's three plants make 72 million gallons of biodiesel annually. Three additional plants under construction will have a capacity of 90 million gallons, and three more with a total capacity of 120 million gallons are in the fundraising stage.

Daimler-Chrysler says its 2007 Jeep Cherokee CRD SUVs will be factory fueled with B5 (5% biodiesel, 95% petroleum diesel). The 3.0 L common-rail turbo diesel (CRD) engine built by Mercedes-Benz uses clean diesel technology that is said to boost fuel economy by about 30% and lower CO2 emissions 20%. A CRD engine also powers the company's Jeep Liberty SUV. On a related note, tractor-maker John Deere says it has switched to B2 for new-equipment fueling.

Most would agree, the days of cheap oil are gone. Burgeoning economies in China and India, instability in oil-producing regions, and refineries running at capacity, exacerbate already tight crude supplies. This confluence of events has forced major oilconsuming nations to take a more serious look at alternative fuels.

In the U.S., ethanol from corn has helped cut dependence on foreign oil. The U.S. in 2004 produced about 3.4 billion gallons of ethanol , equivalent to roughly 2% of annual gasoline consumption. Europe, on the other hand, has seen a decline in gasoline consumption, along with a commensurate rise in demand for diesel fuel. For years, strapped with high fuel prices, Europeans have embraced diesel-powered cars because they use about 40% less fuel than gasoline burners. In fact, some 40% of registered cars there are diesels.

As in the U.S., concern over fuel supplies in Europe has spurred development of renewable fuels, notably biodiesel. The EU25 consumed 22.7 million gallons of biodiesel last year, up sixfold since 1996, according to the German biodiesel trade association, Verband der Deutschen Biokraftstoffindustrie. About 4% of diesel fuel sold in Germany is biodiesel, and that percentage is expected to rise, helped, in part, by tax incentives.

The U.S. is on a significantly steeper trajectory than Europe with respect to biodiesel production,-this despite the fact diesel engines in 2004 powered just 3% of U.S light-duty vehicles. The U.S. last year consumed 75 million gallons of biodiesel, 50 more than in 1999, says the trade association National Biodiesel Board (NBB), Jefferson City, Mo. The industry is on track to make 150 million gallons this year. Production should continue to climb as more plants come on line and dieselpowered cars gain market share, which by some estimates, could reach 12% by 2012.

"Replacing 5% of petroleumbased diesel fuel with biodiesel each year would supplant the crude oil the U. S. buys from Iraq for diesel," says NBB CEO Joe Jobe. That's a start, but a drop in the barrel compared to the roughly 40 billion gallons of diesel fuel the U.S. consumed last year for onroad transportation. Perhaps more compelling arguments for biodiesel fuel are environmental.

Studies show biodiesel is both nontoxic and biodegradable. Compared with petroleum diesel, the burning of biodiesel produces half the carbon monoxide and 78% less net carbon dioxide (CO₂), the gas thought to cause global warming. Lower CO₂ emissions are the result of biodiesel's closed-carbon cycle: CO₂ released into the atmosphere when biodiesel burns is recycled by growing plants, which are later processed into fuel, suggests a study by the Dept. of Energy (DoE) and USDA. The jury is still out on whether biodiesel-fired engines generate more oxides of nitrogen (NO_x). NO_x is a main contributor to smog.

An important factor called energy balance is a way of rating fuels by the amount of energy consumed in their production. A recent report by the USDA found corn ethanol has an energy balance of 1.34. That is, every Btu dedicated to the production of ethanol yields a 34% energy gain. Biodiesel has an energy balance of 3.2, according to a joint USDADoE study. Solar energy collected by the crops from which the fuels are made is said to account for the positive energy balances of ethanol and biodiesel. For comparison, gasoline has an energy balance of 0.805, or a 19.5% net energy loss. For petroleum diesel, that number is 0.83.

Another key metric for rating fuels is volumetric energy content because both engine power and fuel economy scale with it. Pure biodiesel fuel contains about 10% less energy per volume than No. 2 petroleum diesel. Theoretically, burning pure biodiesel should lower power output by the same percentage. However, biodiesel is slightly more viscous than petroleum diesel, which boosts injector efficiency, so the actual loss is about 5 to 7% according to the trade group Engine Manufacturers Assn. (EMA), Chicago.

Biodiesel is typically blended with petroleum diesel to make B2, B5, and B20, which are 2, 5, and 20% biodiesel by volume, respectively. Such blends keep energy content at levels near that of conventional diesel fuel and help offset some of biodiesel's less-desirable qualities.

All diesel fuels thicken or gel at cold temperatures, necessitating the use of special additives to keep them liquid. But biodiesel gels at warmer temperatures than petroleum diesel, which may limit its use at high concentrations in cold climates. Biodiesel is also less chemically stable than petroleum diesel and more prone to microbial growth and oxidation. Biodiesel is a good solvent as well. Cars run exclusively on petroleum diesel may, over time, develop deposits in the fuel system that are subsequently cleaned out when switching to biodiesel, clogging fuel filters and lines in the process. Biodiesel may also degrade and swell certain elastomer seals, gaskets, and hoses, as well as foul piston rings and coke up injectors.

For all these reasons, the EMA and makers of diesel-fuel-injection equipment, including Bosch, Delphi, Denso, and Stanadyne, suggest running no more than 5% biodiesel blends (B5) in modern diesel engines, provided the B100 used in the blend meets established specifications, such as ASTM D 6751.

Meanwhile, a growing number of diesel car and light-truck owners are ignoring the warnings of potential problems with higher-percentage biodiesel blends and voided manufacturer warranties. Many routinely run B20 — even B99 and B100 — in their newer diesel vehicles without issue, according to biodiesel Web sites such as Biodiesel & SVO Forums (biodiesel.infopop.cc/ eve/forums). Some claim engines run better on pure biodiesel and blends than on straight diesel fuel. Increasing demand for B20 has prompted the EMA, NBB, and the American Society of Testing and Materials (ASTM) to hammer out specifications for the fuel's production and testing. An ASTM stamp of approval for B20 is seen as an important step toward widespread adoption of the blend. B20 is now available at about 600 pumps nationwide, according to the NBB.

MAKE CONTACT
Engine Manufacturers Assn., enginemanufacturers.org
Greasecar Vegetable Fuel Systems, greasecar.com
National Biodiesel Board, biodiesel.org
Renewable Energy Group Inc., www.renewableenergygroup.com
U.S. Dept. of Energy, Alternative Fuels Data Center, eere.energy.gov/afdc/altfuel/biodiesel.html