Clean-Diesel Retrofit Keys: Incentives, Alternatives, Demonstrations, User-Friendly Information Matrix

Diesel Fuel News, Feb 19, 2001 by Jack Peckham

Los Angeles -- Upcoming California Air Resources Board (CARB) rules aim to retrofit nearly every diesel engine in California between 2002-2010 in order to slash "toxic" particulate matter (PM) emissions by 85%, or else hit U.S. EPA's 0.01 grams/brake-horsepower hour PM limit for new heavy-duty diesels in 2006/7.

But what CARB wants, and what technology provides, may only partially match, at least with today's state-of-art.

As for money: Did anybody leave a big wad of cash laying around to pay for this? Well, no. But some creative ideas did emerge.

Key lessons from CARB's "International Diesel Retrofit Advisory Committee" meeting here:

* Applications such as urban buses, school buses or heavy trucks might be easier to retrofit for steep PM cuts, CARB-supervised demonstration programs show. But some engines/applications -- many of the old two-stroke engines, for example -- don't often generate high-enough exhaust temperatures or have the right exhaust chemistry to enable exhaust technologies to hit an 85% cut or 0.01 gram target, engine and catalyst makers have found. So, more tests and demonstration programs aim to find out what -- if anything -- will work, and what won't.

* Certain trap designs might fit just fine on one type of equipment, but not on others. Point: End-users don't want to configure a trap, but rather, get a complete, installed package. So, some PM trap concepts may require re-engineering. But that might be especially tough if a given application market is viewed as "too small" to justify the investment.

* Fuel economy, operating range, maintenance, insurance, refueling infrastructure investment (if any) and possible hazardous waste disposal (from trap cleaning) penalties must be tallied, so that public and private fleets know the true costs. Too-costly retrofits would discourage turnover of old, "dirty" trucks with new, "clean" trucks, California Trucking Association pointed out. Regulations that merely convince in-state operators to move their base of operations just outside California's border, but continue to operate in-state, wouldn't fix environmental problems, either.

* Government fleets ought to set a "green" example for private fleets, but experience shows that some public operators, like Caltrans, have been among the most recalcitrant. "To get Caltrans to reduce emissions on construction sites, we had to threaten lawsuits," Sacramento Air Quality Management District (AQMD's) Tim Taylor said.

"We had to get help from the Governor's office to include pro-active language in contracts, for low-emissions equipment. It's a pitched battle, and local governments can waive these requirements. It increases the cost of doing business, unless you pay 100% of their cost."

* Once new money appears -- bingo -- retrofits happen. "Caltrans got $20 million for retrofits this year," CARB official Tom Cackette pointed out. "And the city of Los Angles passed a resolution to retrofit 50% of their vehicles within 18 months of CARB [PM technology] verification and one year later do the other 50%." The city also plans to tender bids to convert to 100% ultra-low-sulfur diesel (ULSD), he said.

* Surprisingly, some applications that only infrequently generate high exhaust temps, like garbage trucks that spend a lot of time at idle, sometimes work well with PM traps, some tests show. However, trash trucks with more modern engines (post-1992) seem much more adaptable to PM traps than older engines, catalyst experts here said. On the other hand, some types of equipment (even fairly new models) hardly ever hit favorable temperature targets to enable PM traps, some advisory committee members said here.

* Some PM trap applications might work properly only if regenerated "off-line" through plug-in electrical heaters (as in some fork-lift applications), or through frequent replacement/cleaning, or with active hydrocarbon injection (such as the Ceryx system).

* 5,000 ppm Sulfur Fuel: Mission Impossible?

Still, some engines or applications might fail to work properly with any of these "active" regeneration schemes, technology developers concede. Example: The U.S. Navy has a rather large population of old, two-stroke diesel engines that often operate in low-temperature duty cycles. However, more modest emissions reductions still may be achievable via changes to injectors, turbochargers, injection timing changes, and fuel additives, a Navy representative said.

On the other hand, some older Navy technologies still might be retrofittable with catalyzed PM traps, were it not for the very high sulfur (close to 5,000 ppm) Navy fuel, or possibly excessive lube oil consumption on some engines, as Engelhard PM trap expert Kevin Hallstrom pointed out here.

If traps look dubious on some applications, then CARB might be forced to accept "fall-back" requirements for those engines that can't hit the 85% or 0.01 gram PM targets, CARB officials said here. Some "fall-back" technologies might include oxidation catalysts, or special fuels (such as emulsions) that by themselves don't hit 85%/0.01 gram PM targets.