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Costlier and Cleaner
Lower exhaust emissions mean more changes to engines and fuel.
By Tom Berg
More changes in diesel engines and fuel will come in the next several years as the federal Environmental Protection Agency prepares to further tighten its rules for exhaust emissions. Last autumn, the EPA announced its intent to require cleaner exhaust for 2002 and 2007.
Rules for 2002 will push diesel development toward exhaust-gas recirculation (EGR), while many 2007 diesels will use "after-treatment" devices similar to catalytic converters. The devices will need very low-sulfur fuel to work without becoming clogged, so EPA and the California Air Resources Board (CARB) are preparing rules requiring fuel cleansed of most sulfur.
The new equipment and cleaner fuel will mean still higher prices at the pump and at truck dealers, as all costs will have to be passed on to users. The new fuel will probably cost up to 15 cents a gallon for extra refining. Engine equipment will add $400 to $800 per vehicle, depending on which agency's estimates are cited.
The 2002 limits were originally scheduled for 2004, but last year's consent decree between EPA and diesel builders will put the '04 limits into effect two years sooner, according to industry sources. The consent decree also requires builders to change certification tests to measure exhaust under a wide range of operating conditions.
That controversial decree forced builders to tighten exhaust emissions on their '99 engines. They also paid hundreds of millions of dollars in fines for supposedly tampering with electronic engine controls to let them emit higher pollutants at highway speeds. Builders denied the charges, but buckled under when EPA threatened to shut them down while arguing the case in court.
Until now, builders have used electronic controls, retarded ignition timing and other refinements to meet emissions rules. But they will need exhaust-gas recirculation, or EGR, to meet 2002 limits. Through special plumbing, EGR siphons a small amount of gas, cleans and cools it, then sends it back to the cylinders for mixing with fresh air and fuel. This helps lower oxides of nitrogen, or NOx, in the exhaust that goes out the stack.
But EGR will raise operating temperatures and introduce more acids to crankcase oil. So more effective cooling systems and a new category of engine oil will be needed. Also in store for many 2002 diesels are high-pressure "common rail" fuel injection and/or variable geometry turbochargers.
The 2007 heavy-duty diesels will need fuel that's almost entirely free of sulfur, which will allow use of after-treatment devices, builders have said. Both EPA and CARB are preparing rules that would mandate very low-sulfur fuel by 2007.
The 2007 catalytic converters will be similar to those long used on gasoline-fueled cars and some medium-duty diesels. Some diesels may get soot traps. All of this would add weight, consume chassis space and cost money, builders say.
EPA's announcement on Oct. 4 formalizes goals for reduction of emissions originally set for 2004 engines. But the announcement was expected because it's part of the agency's rule-making process.
EPA will probably formally propose its 2002 rules early next year and finalize them late in the year. While most general press coverage focuses on light-duty diesels and gasoline engines in large pickups and sport-utility diesels, the trucking industry is more concerned with the rules' effects on medium- and heavy-duty diesels.
Meanwhile, CARB is considering a rule that would require manufacturers to cut particulates by 90% and nitrogen oxides by 75% by 2007. Today, a new diesel truck puts out an average of 4 grams of nitrogen oxides (NOx) and 0.10 of a gram of particulates per brake horsepower hour.
Under EPA's standards for 2002, the combined NOx and hydrocarbon allowed will drop to 2.4 grams. California's rules would be 0.5 of a gram or less for NOx, and 0.01 for particulates in 2007. EPA plans to change national truck standards to the same levels as California's proposals.
Initial testing of very low-sulfur fuel by one California refiner resulted in as much as a 15% reduction in particulates and a 5% reduction in NOx, with no apparent loss in fuel economy compared with today's diesel fuel.
The increase in cost for the new formulation is estimated at between 5 and 15 cents more per gallon than current diesel prices.
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