Clean diesels: Are they or aren’t they … ‘clean’?

Not to digress too much, but hanging out by the railroad tracks as a kid (off to the side and at a safe viewing distance, to be sure), you learn pretty quickly some of the characteristics and practices of the industry, such as control-signal-aspect indication (what each signal display color and/or position means – which could come in quite handy as far as determining when the next train is likely to show up). Coupled with this, there is the familiarization regarding the sights, sounds and smells the big diesel locomotives produced and by smells I mean the smell of diesel exhaust, part and parcel of railway diesel-engine operation.

Meanwhile, in the automotive realm? Well, where the diesel engine is concerned, it is little different or, it was, anyway.

As it relates, back on June 22, 2013 in “Diesel: It isn’t just for trucks, buses and locomotives anymore,” quoted was Diesel Technology Forum Executive Director Allen R. Schaeffer who in “Are hybrids the best ‘green’ bet for motorists? No: New diesels go further on a tank, are greener,” stressed, “Gone are the clatter and smoke, and wheezy slow performance. They’ve been replaced with clean, quiet and fun to drive cars.”

Two Cycle Diesel engine with Roots blower
Two Cycle Diesel engine with Roots blower

I wouldn’t know about the fun-to-drive part. But, diesels being smoke-less?! Let’s just say I have my doubts. They do pollute; I know that. As for how much pollution and what pollutants are emitted from such, that is the question. Furthermore, the last sentence in the paragraph above, that is, except for the “quiet and fun to drive” part, appears to be somewhat at odds with the information presented two paragraphs below.

So, check it out.

The International Council on Clean Transportation (ICCT) press release: “New ICCT study shows real-world exhaust emissions from modern diesel cars seven times higher than EU, US regulatory limits,” of Oct. 11, 2014 is quite telling.

The ICCT declared in no uncertain terms, “On-road nitrogen oxides emission levels of modern diesel cars are on average about seven times higher than the limit set by the Euro 6 emission standard, which went into effect September 2014. This is the key finding from a new report published today in Berlin by the International Council on Clean Transportation (ICCT), an independent research organization.”

Wait, there is more.

“The study, which is the most comprehensive report on the real-world behavior of the latest generation of diesel cars published to date, found remarkable differences among individual vehicle models, indicating that technologies for real-world clean diesels already exist but are not being employed consistently by different vehicle manufacturers,” the ICCT went on to state. “The findings come at a time when the European Commission is preparing to propose an improved car emissions testing procedure, including on-road measurement, that could take effect in 2017.”

According to the research organization, in the EU, around half of new cars, are diesel-powered.

Added the ICCT: “The European Commission is currently preparing to require on-road testing as part of the passenger car type-approval process in the EU. According to these plans, vehicle manufacturers from 2017 would have to test new vehicles not only under laboratory conditions but also on the road, using PEMS [Portable Emissions Measurement Systems] equipment. Technical experts from the EU member states will meet in Brussels on October 15 to discuss further steps and whether the new regulation can be approved at the end of 2014, as originally planned.”

It is my belief in speaking to Europe’s relatively high passenger diesel car numbers, the notion that the diesel cars in question emit lower levels of carbon dioxide (CO2) and for that reason, in an effort to try to limit CO2 and other greenhouse gases from motor vehicles, there was a concerted effort advanced to promote increased reliance on diesel as applied to automotive engine propulsion.

Now, as to whether or not clean diesels are, in fact, “clean,” on this I believe the jury is still out.

Image above: Pearson Scott Foresman

– Alan Kandel

1 thought on “Clean diesels: Are they or aren’t they … ‘clean’?”

  1. This report is based on European vehicles and their test cycles and emissions standards which are not the same as in the U.S.

    And there is no secret about the European decision over a decade ago to favor CO2 emissions reductions through tax policies that made gasoline about $1 USD higher than diesel. As the more fuel efficient powerplant, diesels took off in popularity for practical reasons. And they make up more than 50 percent of all new vehicle sales in the EU.

    In the US (where diesel passenger cars have been around since the 1970’s)- no such fuel tax policy was ever in place, and diesel car market share is only about 1 percent. EPA established a level playing field- forcing diesels to meet the same low emissions standards as gasoline beginning in 2007. Now we can see a time where clean diesels in the US might approach 10 percent market share by 2020 because of EPA’s increasing fuel economy requirements.

    As we know from recent experience in the U.S. with a number of manufacturers forced to re-state fuel economy values, aligning vehicle test and certification requirements with real world driving conditions is not a perfect system.

    In the U.S., EPA has established the test procedures and protocols and manufacturers are meeting those. If those standards or test procedures were a concern, (as noted in the ICCT study) then we’re sure manufacturers would work with EPA to address those concerns. We suspect this is playing out in Europe today.

    We also think everyone would benefit from understanding more about how other fuels perform in real-world driving – i.e gasoline vehicles, propane and others, and not just diesel. The study chose not to look at that question- which is interesting since half the cars in Europe are gasoline.

    This report raises a vehicle emissions testing issue that is specific to vehicles in Europe and really doesn’t apply here in the U.S. That’s because the U.S. system requires both pre-production certification testing and post-production testing of in-use emissions.

    Also, the test procedures used in the U.S. include emissions that occur while driving and when the vehicle’s emission control system is “regenerating” its particulate filter and any NOx trap.

    Clean Diesel? We think so.. thanks to a new generation of vehicle emission controls (particulate traps plus catalytic converters), coupled with today’s ultra-low sulfur diesel fuels, today’s light-duty diesels meet strict air pollution standards in all 50 states while still achieving great fuel efficiency- 30 percent better than comparable gasoline.

    More at

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