Innovations for diesel vehicles stalled

By Russell Clemings / The Fresno Bee

Southern California entrepreneur Phil Roberts thinks he has a solution for the San Joaquin Valley's air pollution. His company has a device that he says can clean up any diesel vehicle's exhaust. It works something like a catalytic converter on a gasoline engine. [See an animation of the device]

Roberts says tests show the device can cut emissions of two major pollutants by 90% or more. But you won't find it in the new ozone plan that the San Joaquin Valley Air Pollution Control District approved earlier this year.

One reason: Until state regulators finish reviewing how well it performs, they won't approve the device's use. And until that happens, the district can't claim credit for any resulting cuts in emissions.

Such is the state of air pollution regulation. Having promise isn't enough to bring an innovation to bear on the nation's stubbornest smog. Approval from higher levels of government is also needed.

In fact, reducing smog is not even the district's only goal. Its officials say they serve another master as well -- a web of federal and state laws that sometimes ties their hands.

In the case of the ozone plan, the Clean Air Act requires the district to explain what steps it will take to clean the air. Those steps generally have to be approved in advance by higher levels of government.

If the cleanup measures aren't approved, the plan won't be approved. If the plan is not approved, the district is not complying with federal law.

And if the district is out of compliance, federal highway funds can dry up. Businesses can face higher fees for new or expanded facilities.

All that is true. But critics say the air district should do more to challenge the roadblocks that prevent it from embracing new ideas such as the device Roberts has come up with.

That device uses a method called selective catalytic reduction, or SCR. It reduces emissions of nitrogen oxides, or NOx, one of ozone's main building blocks.

SCR is not a new technology. It is already widely used on stationary diesel engines, such as large industrial boilers and gas turbines.But it has been used only recently on cars and trucks. From a regulatory point of view, new means uncertain -- and unacceptable.

"We couldn't take credit for a widespread application of SCR retrofits for the simple fact that there is none certified at this point," said Scott Nester, the air district's planning director. "There is not a system out there that's available that we could even point to, to take credit for in this plan."

Roberts thinks that shouldn't matter.

His device uses a special type of catalytic converter and a chemical reductant, such as urea or ammonia. The reductant is injected into the exhaust before it reaches the catalyst, which consists of a metal that sets off a chemical reaction.

The process converts smog-forming nitrogen oxides, or NOx, into water vapor and nitrogen, a safe and common atmospheric gas.

The chemistry is fairly straightforward. But it is a challenge to fit the device on a vehicle engine.

Mobile engines speed up and slow down as power demand varies. When that happens, the amount of reductant injected into the exhaust needs to change as well.

That's a tricky technical issue that previous generations of pollution controls for diesel engines have been hard-pressed to overcome. Roberts said his firm has perfected a way to measure NOx levels in the exhaust and fine-tune the reductant to match.

It works something like a gasoline engine's oxygen sensor. That device makes constant adjustments to the engine's air-fuel mixture to reduce emissions.

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