RICHARD MICHAEL PRUITT/DMN Sylvester Crabb fills his streets department truck with the TxLED formulation of diesel. The city's use of the new blend will cut regional nitrous oxide emissions 7 percent.

That might not seem like much, but it's 7 fewer tons of nitrogen oxides going into the Dallas-Fort Worth atmosphere every day. That's equivalent to the nitrogen oxides emitted by the Ash Grove cement plant in Midlothian on any given day. Or it's like shutting off all diesel trucks and equipment for three work weeks a year.

The law doesn't require the use of Texas Low Emission Diesel, or TxLED, until Oct. 1. But Ramiro Lopez, who oversees the city's equipment and buildings, jumped to use the cleaner fuel more than two months early.

"You don't want to wait till the 11th hour, when the law starts in at midnight. I said, 'We might as well start early,' " he recalled.

TxLED is now being pumped into city garbage trucks, backhoes, fire engines and other vehicles. As of Jan. 1, it will be available to motorists at the retail level.

And low-sulfur gasoline blends known as Tier II being introduced next year are designed to further reduce smog. David Jodray, principal transportation planner at the North Central Texas Council of Governments, said Tier II is expected to reduce regional emissions of nitrogen oxides by 20 percent in 2007 and 60 percent by 2030.

Gregg Cooke, a former regional EPA administrator who is now a consultant to county governments in the region – and who also acted as a consultant for Oryxe Energy International on developing the new blend – said these low-key, nearly invisible regulations on diesel and gasoline can do as much to clean the air in Dallas-Fort Worth as more visible targets.

"Everybody gets wrapped around things with the cement kilns, but that's not the only thing going," he said. "You can see [the kilns], but this other thing is regulatory and so much harder to understand."

While Mr. Cooke has no doubt the new diesel and gasoline standards will help Dallas-Fort Worth attain clean-air status, the region won't do so by the required date of 2010 without efforts on many other fronts.

"People can't get into the idea there's just one cause," he said. "It's not just going to be cement kilns; it's not just going to be railroads. We have to look under every rock for every cause."

Mr. Lopez is looking under those rocks in Dallas.

Before a year ago, he had the city's heavy equipment fleet and trucks running on a blend that was 20 percent biodiesel, a fuel made from soybeans. But because biodiesel's nitrogen oxide emissions do not meet the new low-emission standards, he switched. When he saw that the Oryxe blend was going to enter the market, he had his supplier get 1.6 million gallons. It was cheaper than last year's diesel, saving $128,000.

"We're stewards of the environment," he said, "but we're also stewards of the taxpayers' dollars."

He also is hoping to be the first to buy the best of both worlds, a biodiesel-TxLED blend, when it becomes available.

In fact, Mr. Lopez says he gets a kick out of the fact that most people don't see Dallas as a leader in environmental efforts.

"We don't do it with a lot of hoopla," he said. "I just try to keep up with what's out there, the latest fuels, the latest vehicles. I find it exciting. Maybe I need to get a life, but it always catches my attention. Dallas is a leader, even though people don't see us like that. Other cities call us all the time."