Hard to believe, but true: there are plenty of people out there who want to see the end of the diesel engine. Like, right now. What are they thinking? Thankfully, the most passionate amongst them live and lobby mostly in California, but that doesn’t mean you can discount them as former-hippie tree-huggers out on the fringe of civilization. In fact, in that smog-ridden state, they’re mainstream. And they have friends in Washington.

The South Coast Air Quality Management District, which sets environmental policy affecting millions of vehicles in Southern California, proposed new rules last year that would have forced public and private fleets to switch from diesel to alternate fuels almost right away. But a couple of months later the agency bowed to intense lobbying by diesel advocates and accepted an amendment: they’d reconsider the diesel ban if so-called “green diesels”-using ultra-low-sulphur fuel and aftertreatment devices-were certified to be as clean as natural-gas engines.

The diesel escaped a bullet there, at least temporarily, but we still get a view into the future, Canada included. With the exceptions of British Columbia’s Lower Mainland and Saint John, N.B., maybe Toronto as well, Canada doesn’t have the same pressing environmental problem seen in California.

But there is worry, as a nation, about greenhouse gases and global warming. So the often arbitrary rule-making we see within U.S. environmental bureaucracies, not just in California, will eventually migrate north.

It’s almost certain that Canadian trucks heading south will have to comply with American rules anyway. For that matter, engine makers aren’t likely to produce a specifically Canadian spec. The bottom line is that American rules are in many cases our rules, too, like it or not.

As things stand now, the new Southern California regs require government-owned fleets and private fleets with government contracts to choose alternate-fuel vehicles when they buy or replace trucks. The rules take effect July 1, 2001 for larger carriers, including public and private garbage haulers.

Diesel makers are working hard to get their engines certified so that fleets will have the option of sticking with diesel next July. But they might not have enough time, and they’ll have a fight on their hands anyway. The California Air Resources Board has been tough on emissions for years, but the U.S. Environmental Protection Agency isn’t much different. Both of them, without scientific proof of any satisfying sort, have labelled diesel-fuel emissions a cancer risk and are actively promoting natural gas. CARB actually seems convinced that diesels can’t be made free of cancer-causing particulate emissions.

This flies in the face of recent engine-development history-not to mention logic.

Harvard University’s Center for Risk Analysis has looked at this issue and says that very fine particles in natural-gas emissions could actually penetrate deeper into the human respiratory tract and may be more carcinogenic than diesels. Ironically, the Harvard study also revealed that using natural gas instead of diesel may lead to a 5% to 10% increase in greenhouse gas emissions due to the potency of methane as a greenhouse gas.

When natural-gas engines are fueled, methane escapes into the atmosphere. That’s bad news, because it’s about 20 times more potent as a greenhouse gas than carbon dioxide.

CARB and EPA overlook other factors as well, like the fact that current diesels are far cleaner than diesels built just five years ago and will be even more so in 2002.

With cleaner fuel, and there are several examples around, emissions could drop even lower. Engine makers, led by International Truck & Engine, are busy developing “ultraclean” diesels to be ready for the next round of EPA emissions limits in 2007. International has medium-duty demonstration vehicles on the road now with “green” diesels that run on a special ultra-low-sulfur fuel. They also have special catalytic converters that “scrub” virtually all particulates from the exhaust.

International says it could be building these camless diesel engines now-at an incremental cost far lower than a natural-gas powered engine-but the fuel’s not available. Even the diesel fuel sold in California today, cleanest on the continent, still contains 120 to 500 parts per million (ppm) of sulphur.

The green diesel needs fuel at just 15 ppm sulphur, which is part of the EPA proposal for 2007 emissions limits. Refiners can do it if there’s a demand, but the price would be high without substantial sales volumes.

Combining the advantages of the engine’s digital air and fuel management with exhaust-gas aftertreatment via a regenerative trap gives diesel a clear advantage in emissions performance over other currently available low-emission technologies, says International.

Mack Trucks has started running a special low-emissions Vision tractor in its own parts-distribution fleet. It uses selective catalytic reduction (SCR) technology that cuts nitrous-oxides emissions by up to 70% and particulates by 25%, with no sacrifice to fuel economy. Being developed jointly by Mack and Siemens, the system meters a low-cost liquid urea solution into the exhaust stream prior to its entering a catalyst. The urea then breaks down and reacts with NOx to produce harmless nitrogen and water.

Compressed natural gas (CNG) and liquefied natural gas (LNG) have been held out by some as the low-emissions fuel that will be necessary to meet 2007 EPA inner-city requirements, but International says this new diesel technology can beat CNG “hands down” in terms of particulates and other emissions.

More compelling still, at least in a truck buyer’s eyes, is the lower price tag of the green diesel engine compared to a CNG conversion. And that’s not to mention avoiding the huge cost of the infrastructure required by natural gas.

Other engine makers are working on different solutions, of course. In the short term, they all continue to engineer their powerplants to meet a 2002 deadline for particulate reductions imposed by the EPA.

So far there are no changes to that looming date, which arose from the $1-billion US settlement between the EPA and diesel manufacturers over a breakdown in the emissions testing process. Part of the agreement requires six manufacturers-Caterpillar, Cummins, Detroit Diesel, Mack, International, and Volvo-to take extra steps to meet the 2002 emissions requirements and to speed up their compliance with emission rules. In August, the agency drafted a regulation that gives heavy-duty diesel engine manufacturers more time to comply with emission testing requirements. Engine makers have until the 2007 model year to start using the new emission testing procedures-a change from the 2004 deadline EPA proposed earlier. The agency said it expects to follow this rule with another by the end of the year that requires both cleaner engines and cleaner diesel fuel-and will cut pollution by an additional 90%.

But for now, there will be no revisions to the deadlines or emission targets. Manufacturers have been talking with the EPA about ways to adjust the compliance schedule. The engine builders are encountering technical difficulty making some higher horsepower engines meet the emission requirement.

As engine makers press for accommodations, EPA is under pressure from others who want the 2002 emissions deadline to be enforced no matter what.

EPA’s decision to extend the deadline for testing procedures triggered an attack from the Clean Air Trust. The environmental watchdog awarded its clean air “Villain of the Month” award to the six engine companies, saying they are trying to wiggle out of the consent decree by asking for more time to meet the stricter standards.

Despite their best efforts, it seems the engine makers are easy targets. But as long as manufacturers continue to build diesel engines that burn cleaner without seriously compromising fuel economy, diesels will power the trucks that deliver the plaques and trophies awarded by the likes of the Clean Air Trust.