Clean Diesel Not So Clean, Depending on Who You Ask


Turns out modern “clean” diesel engines purporting to be “green” are actually more “black” than they seem.

Oooh, it rhymes.

Anyway, that’s due to a nearly undetectable substance called “black carbon,” which sounds every bit as mysterious and science-y as dark matter.  It’s basically the stuff that’s in soot, but because it’s so hard to measure, black carbon is not factored into carbon dioxide emissions tests.

According to experts even reduced emissions from soot could add up to additional gram of carbon emissions per kilometer (slightly under that per mile). However, many automakers live right on the edge when it comes to emission standards, so if the powers that be ever started testing and measuring black carbon, it could just barely push some models over the limit.

There’s also the issue of climate effects. Climate scientists are saying that black carbon contributes to global warming as well, which is pretty much a given, because almost everything nowadays either contributes to global warming or cancer. Fortunately a Pew Research study indicates that black carbon doesn’t hang around nearly as long as CO2 does, so reducing black carbon emissions could dramatically improve air quality in BC-heavy cities—and the results would be almost instantaneous.

There doesn’t seem to be a huge push to do so in the U.S. Given the relative scarcity of diesel vehicles, that’s somewhat understandable.  Europe, China, and India, however, might be wise to study this issue a little more.

Source: Autobloggreen

About the Author

  • Tyler,
    This issues deserves more than rhyming couplets. Modern, clean diesel cars and trucks feature particulate filters that trap black carbon and other elements, making them actually cleaner at the tailpipe for these pollutants than gas vehicles. See this paper for more details: Those who study this issue at the UN know the big black carbon contributors are forest burning and residential cooking and heating, not new diesel engines.

    • Tyler Massie

      Great read, Michael. That’s a very encouraging report, and if true we might do well to push diesel more in the USA, at least as a stop-gap along the way to electric cars.

      Still, the chart showed 25% of black carbon emissions coming from transportation using diesel engines, so obviously somebody isn’t using these new engines. Industrializing countries like the ones I mentioned are the likely culprits.

  • It looks like this Black carbon will have the equivalent effect of 1% additional CO2 (green house effect) in a a sub 100g/km car like the Polo Blue motion – 70+ mpg Imperial.

    Diesels are good because they are frugal, the combustion process itself is 20% more thermodynamically efficient compared to petrol and the driving characteristics mean that you can use low rev torque which drives further frugality.

    Anyone who tries to market Diesel as “Clean” needs to go back to school.

    50% of the cars in Europe are Diesel because they consume less for the same result. That is what the consumer wants.

    And as a regular visitor to both New York and London I would say the Air quality is about the same .

    I would agree that Delhi is a different proposition regarding air quality but that is because most of the cars are over 25 years old and there is little regulation.

    There are very few Diesel cars in China but the air quality in some cities is terrible.

    I still can’t for the life of me understand the US stance on Diesel. It is ideal for your larger vehicles and slower paced driving.

  • The biggest issue is actually not the combustion process, it’s more about how “clean” is the fuel. Biodiesel is a good answer to meet this requirement.

  • Pingback: Union Pacific Railroad Will Test 25 Emissions Reducing Locomotives - Gas 2()