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Clean Diesel Fuel?

By Andrea Lyn Van Benschoten, Web Editor, Manufacturing.netHigh gasoline prices, coupled with a mandate to reduce dependence on foreign oil, have sparked a new interest in alternative fuels. But is diesel really an alternative fuel? And is it really that clean?

High gasoline prices and the President’s challenge to reduce dependence on foreign oil have sparked a new interest in alternative fuels. But is diesel really an alternative fuel? And is it really that clean?
What is Clean Diesel?
Diesel is a petroleum-based fuel with a high energy content, which helps it go further per gallon than other fuels. However, traditional diesel fuel can be very dirty. A new generation of diesel technology is being adopted which is much cleaner than its original counterpart.
What makes diesel fuel dirty is its sulfur content, which clogs exhaust-control devices in diesel-based engines. Recently developed ultra-low sulfur diesel (ULSD) fuel removes a large majority of the sulfur, allowing the fuel to burn more efficiently than its dirty predecessor.
According to Steve Ciatta, Ph.D., Engine Research Scientist at the Argonne National Laboratory, the challenge for diesel engines is how they handle oxides of nitrogen (NOx) and particulate matter.
“Diesel vehicles are not what you remember at all,” Ciatta said. “Carbon dioxide (CO2) and fuel efficiency are very good with diesel technology.”
Spreading the Word
The Diesel Technology Forum and its Executive Director, Allen Schaeffer, are also working to spread the word about clean diesel.
“Diesel today has more possibility than previously,” Schaeffer said. “In the next two years, the U.S. will have the cleanest diesel fuel in the world.”
In October of 2006, the Environmental Protection Agency, (EPA) began requiring most diesel fuel used in the U.S. to have sulfur levels that do not exceed 15 parts-per-million (ppm), which represents approximately a 95 percent reduction from previous levels. On average, the new standards will result in a 77 percent reduction in NOx emissions and an 88 percent reduction in particulate emissions.
On average, diesel engines provide 20 – 40 percent better fuel economy and offer more torque at lower rpm compared to gas-powered engines.
“The diesel engine is the most efficient engine out there,” Schaeffer said. “Just like the hybrid, it needs some jump-starting. People are more aware of the technology since the President’s State of the Union address.”
EPA Standards
EPA’s multi-tier regulatory program places responsibility for meeting the new regulations on engine manufacturers. The primary focus is on the reduction of NOx since it contributes the most to ozone depletion.

In 1998, the EPA adopted more stringent emission standards for NOx, unburned hydrocarbons, carbon monoxide, and particulate matter from new non-road mobile diesel engines. This included the first set of standards for non-road mobile diesel engines producing less than 50 horsepower.
Stricter Tier Two emission standards were phased in from 2001 to 2006 for all engine sizes and Tier Three standards for engines from 50 to 750 horsepower are being implemented from 2005/2006 through 2008.  Tier Four will phase in from 2008 and will continue through 2015.
Another concern of the EPA, according to Ciatta, is the maintenance perspective of diesel engines. If the new diesel engines require additional maintenance by consumers, the fuel-efficiency—and subsequently ozone-saving measures—will not be as effective as they could be.
“The EPA doesn’t want to leave this maintenance in the hands of consumers,” Ciatta said.
ACERT: A Long-Term Solution
One company that has put significant R&D time and money into diesel technology, according to Ciatta, is Caterpillar Inc.
“Caterpillar is head and shoulders above everyone else,” Ciatta said. “They want to be industry leaders and they invest in R&D to stay industry leaders.”
Caterpillar’s ACERT diesel technology focuses on air management and electronic control modules which manage fuel delivery. This combination of technology provides the NOx and emissions control the EPA is requiring. This technology can also be adjusted according to the size of the engine in use.
The key to ACERT is the intake of only cool air into the engine. As a result, combustion temperatures are controlled by multiple injections of fuel.
“ACERT Technology is the result of a stringent new product introduction and testing process and years of investment in numerous technologies,” Mark W. Craig, Division Manager, Caterpillar Global Engine Development, said. “It affords customers the ability to meet emissions standards today and in the future, without sacrificing the durability, reliability and fuel economy they require.”
The system currently meets EPA Tier Two and Tier Three standards, and has a plan for compliance for Tier Four/EU Stage IIIB emission levels.
For more information on the Clean Air Act, click here.