Not long ago, biodiesel was a pretty exotic substance, often home-brewed and reputed to make the exhaust from the cars that used it smell like French fries. But biodiesel production has grown from a meager 25 million gallons in 2005 to almost 1.7 billion gallons in 2013. Biodiesel is now blended at a rate of 5 percent or less into almost every gallon of diesel fuel sold in the U.S., and its use is expected to climb.
A biodegradable alternative fuel, biodiesel is made from renewable resources. The primary U.S. source is soybean oil, though biodiesel also can be made from "yellow grease" (essentially used restaurant cooking oil) and other oily sources such as algae, canola and animal tallow.
To Use Biodiesel You Need a Diesel Vehicle
Though they have long been the de facto standard in Europe, diesel-powered passenger vehicles represented just 1 percent of U.S. passenger vehicle sales in 2012, according to Edmunds.com data. Part of this disparity is due to Americans' memories of the rattling engines, belching tailpipes and cold starts of '70s-era diesel vehicles.
But thanks to the Environmental Protection Agency's National Clean Diesel Campaign, technologically advanced diesels are now being produced to meet new, strict emissions standards and eliminate those headaches.
The U.S. passenger car market now includes diesels from Audi, BMW, Chevrolet, Jeep, Mercedes, Porsche and Volkswagen — a total of 23 different models versus the paltry nine available in 2008. Additionally, Chrysler is planning to introduce a light-duty Ram 1500 diesel pickup in late 2013, and there have been rumors of diesel options for General Motors Corporation's compact Chevrolet and GMC pickups. As these vehicles hit the market, there is increased demand for diesel fuel — and biodiesel.
Today's diesel engines provide 20-40 percent better fuel economy and offer more torque at lower rpm than their gasoline counterparts. Using biodiesel fuel in these vehicles offers additional advantages over petroleum diesel: Its production is more environmentally friendly, it helps further reduce emissions and it decreases American dependence on foreign oil, all without requiring any vehicle modifications.
Today, thousands of major fleets use biodiesel, including all four branches of the United States military, NASA and state, city and private fleets. Biodiesel is also frequently used to run boats as well as farm, construction and manufacturing equipment.
Biodiesel is seldom used in its pure form. Instead, it is typically blended with petroleum diesel and designated by the percentage of biodiesel in the mix. For example, B5 is comprised of 5 percent biodiesel and 95 percent petroleum diesel. There is some biodiesel in almost all "regular" diesel sold in the U.S., at blends of up to B5. After that, B20, which is a blend of 20 percent biodiesel and 80 percent petroleum diesel, is used in many fleet and commercial vehicles and is the blend most often sold.
Better for the Environment — Mostly
There are numerous environmental benefits to using biodiesel, even in a blended form, although some are dependent on how the fuel is produced. Biodiesel is nontoxic and biodegradable, and it is nearly free of sulfur and carcinogenic benzene, which are two of the components of petroleum diesel that the EPA and state emissions boards regulate due to environmental and health concerns.
Using a biodiesel blend of B20 has been shown to reduce the output of certain emissions compared to using petroleum diesel. EPA research on heavy-duty diesel engines shows a 20 percent drop in total unburned hydrocarbons, an 11 percent decline in carbon monoxide and a 10 percent decrease in particulate matter when regulated B20 biodiesel is used.
This same study also indicates that NOx emissions rise by 2 percent when using B20 biodiesel and that fuel economy is expected to decrease by 1-2 percent. But tests by the National Renewable Energy Laboratory (NREL) showed that one major producer, Blue Sun Biodiesel offers a B20 blend that can actually reduce NOx by 4 percent. Blue Sun also claims that its clients, which are mostly commercial and government fleets, report fuel savings of up to 7 percent with the company's B20 blend.
Thanks to engine improvements, many of today's new diesel-powered passenger vehicles already have significantly reduced unburned hydrocarbons and carbon monoxide using petroleum diesel. Particulate matter emissions have been reduced to gasoline-engine levels since 2006, thanks to the new emissions standards that require the availability of low-sulfur diesel and mandate that automakers add particulate matter traps and NOx reduction systems to their vehicles.
What Biodiesel Costs
The cost of producing biodiesel is similar to or slightly higher than the production price of petroleum diesel, according to the National Biodiesel Board. Favorable federal policy, however, has provided various incentives that have helped keep the market price competitive.
The federal low-sulfur diesel fuel standards that went into effect in 2006 also have given biodiesel a boost. The standards state that biodiesel may be used in low percentages in all diesel fuel or as a fuel additive to increase the lubricity of petroleum diesel. The National Renewable Energy Laboratory, the Department of Energy's premier laboratory for renewable energy research and development, estimates that biodiesel could one day replace 10 percent of the petroleum diesel we use today. That's an amount that biodiesel advocates find encouraging.
"That may not seem like a lot, but 10 percent of the on-road diesel fuel this country uses would be 380 million gallons a year," says Joe Jobe, executive director of the biodiesel board. The biodiesel industry's shorter-term goal is "5 by 15," or for biodiesel to make up 5 percent of the diesel fuel market by 2015.
"If we could meet just 5 percent of our nation's diesel fuel needs, that would be the equivalent of the amount of diesel we make today from oil that we import from Iraq," Jobe says. "So it is quite significant."
Is Biodiesel Safe for Cars?
As "clean diesels" continue appearing in the U.S. automotive market, you may hear a lot more about using biodiesel. But is it safe for cars?
One of the most challenging issues concerning biodiesel fuel has been its quality and the long-term effects of using it in a diesel-powered vehicle. To help address these concerns, the National Biodiesel Board worked with regulators, auto and engine manufacturers and the biodiesel industry to create national standards for pure biodiesel (B100) and biodiesel blends, most commonly B2, B5 and B20.
Biodiesel standards are stringent, but adherence is voluntary and not all biodiesel producers meet them, which means the consumer can encounter quality issues. Inconsistent quality among producers is an issue that concerns the biodiesel industry, automakers, engine suppliers and consumers.
Issues With 100 Percent Biodiesel
When fueling stations deal with pure biodiesel rather than petroleum-biodiesel blends, they must treat it a bit differently from other fuels. Because pure biodiesel is made with vegetable-based products, storage temperature it is more critical than with petroleum diesel. If biodiesel sits in a warm storage tank for too long, it can grow mold, and if it is stored at too cold a temperature, it will thicken and could be difficult to dispense.
While these problems can also occur after the biodiesel has been pumped into a vehicle, it is more important for diesel vehicle owners to watch for signs of clogs in fuel filters and systems — particularly when biodiesel is first introduced to a vehicle's fuel system and especially if the owner is using pure biodiesel. All biodiesel acts as a solvent, meaning it can loosen deposits that are stuck in fuel lines and in the fuel tank, which can then clog fuel filters, injectors and other parts of the fuel system. Experts say that this is a greater issue when pure biodiesel is used with older diesel vehicles. Higher mileage generally means greater deposits. It's also an issue with vehicles using the newest high-pressure fuel-injection technology.
Because these issues relate mainly to pure biodiesel, it might seem that the risks would be significantly less or perhaps even negligible with low-biodiesel blends.
This isn't the case, however, as the risk depends largely on the quality of the biodiesel produced. The Worldwide Fuel Charter, a list of fuel requirements endorsed by auto and engine manufacturers, only recommends the use of biodiesel blends of up to 5 percent in the United States.
"While the quality of various biodiesel blends has improved in recent years, the lack of industry quality standards for biodiesel remains a concern for us," says Darryll Harrison, a spokesman for Volkswagen of America. Volkswagen is the leading seller of diesel-fueled passenger vehicles in the U.S.
"We do believe that there is a future for advanced biodiesel and renewable diesel fuels as quality improves and the technology continues to advance," says Harrison. "In fact, our research into the next generation of clean diesel continues to ramp up as partnerships with renewable diesel innovators like Solazyme and Amryis have helped VW to better understand the impacts advanced biodiesel blends have on existing TDI Clean Diesel technology."
Still, VW is in the majority when it comes to warranty coverage of issues due to fuel use in its diesels. No automaker recommends the use of biodiesel in quantities higher than B5 for passenger vehicles in the U.S. — with one notable exception: The General Motors warranty covers use of biodiesel blends of up to B20 in the new diesel-powered 2014 Chevrolet Cruze TD.
Chrysler, Ford and GM do allow the use of B20 in some heavy-duty vans and in their heavy-duty pickups. For Ford and GM, however, that only applies to model-year 2011 and newer vehicles.
A Word About Homemade Biodiesel
There are numerous advocates of making biodiesel at home, usually from used or new cooking oil, and it's easy to find both suppliers of "home brew" biodiesel kits and instructions on the Internet. But the consensus among the major automakers is that it is not yet a good idea to use 100 percent biodiesel. As with the products from major corporate producers, the homemade stuff's quality is all over the map.
Biodiesel quality is still "too inconsistent for us to have any confidence in the behavior of anything with a higher proportion biodiesel" than B5, says Dave Coleman, vehicle testing director at Mazda R&D North America.
Mazda plans to launch a diesel version of its Mazda 6 sedan in the U.S. in the first half of 2014 and won't warranty the engine or fuel system against damage if anything greater than B5 is used.
"We could test with one kind of B20, decide everything was OK, and then our customers could pump in a completely different kind of B20 that behaves differently," Coleman says, explaining the company's concern.
Among other issues, according to the Worldwide Fuel Charter, 100 percent biodiesel and high-concentration biodiesel blend fuels have "demonstrated an increase in NOx emissions levels."
Biodiesel, especially in high concentrations also "may negatively impact" natural and synthetic rubber seals in fuel systems and can oxidize parts made with alloys such as brass, copper, lead or zinc, causing sediment to build up in the fuel system. That can lead to plugged fuel filters as well as damaged fuel system components, according to the charter's biodiesel section.
Benefits Outweigh Potential Problems
While most motorists who drive diesel passenger vehicles aren't even aware that the fuel they buy usually has up to 5 percent biodiesel content, fleet operators actively seek out the non-petroleum fuel, often running their diesel-powered vehicles on B20.
That's because biodiesel's lower emissions and the national drive to reduce petroleum use has made biodiesel a favored fuel with the federal government. By using high levels of biodiesel, fleets can gain credits that help satisfy federal requirements for the purchase of alternative-fuel vehicles.
It has been demand from business and public fleets (including school buses, refuse trucks and street sweepers) that has provided a growing market for biodiesel producers. That growth will continue to make biodiesel available to consumers as more and more diesel passenger vehicles enter the market.