The entire "clean diesel" brand has come under new scrutiny in the wake of the Volkswagen emissions scandal, as reporters in search of a good story have begun to dig into the environmentally-friendly claims of other automakers.
So far there are no allegations of criminal behavior -- Volkswagen stands alone in that regard -- but a recent article in the Guardian reveals that other manufacturers have been dancing around diesel emissions standards without running afoul of the law.
These aren't nuisance emissions, either. Diesel engines are valued for their lower carbon dioxide emissions as well as fuel efficiency and power, but there's a tradeoff. Diesel engines emit nitrogen oxides (NOx), toxic airborne pollutants that contribute to asthma and other serious health conditions.
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The trouble starts when the rubber hits the road. Last week, the Guardian reported on vehicle emissions tests in European models undertaken by the aptly named vehicle data service company Emissions Analytics. Instead of using the standard European Union (EU) test, the company conducted its own analysis using real-world driving conditions.
The findings revealed a significant increase in NOx emissions across numerous brands compared to the tests required by law, including Renault, Nissan, Hyundai, Citroen, Fiat, Volvo and Jeep.
None of the cars reached the dizzying height of non-compliance that Volkswagen achieved, in which actual emissions reached up to 40 times higher than U.S. standards. However, in terms of meeting the vital public health goal of reducing NOx emissions, the difference uncovered by Emissions Analytics is significant, typically ranging from three to six times the European Union limit. The average is around four times higher.
There were also several outliers not named by the Guardian, in which the vehicles emitted between 15 and 20 times the legal limit on the road compared to the lab.
According to the report, each car had passed the European Union's required in-lab tests, leading to the conclusion that the diesel systems were engineered specifically to pass the tests first, with on-road emissions a secondary consideration.
BBC also hooked up with Emissions Analytics for a smaller survey involving only two models and found similar results: NOx emissions for both of the cars were about four or five times higher on the road.
This is not a new problem, by the way. Last year, the environmental umbrella organization Transport and Environment noted that diesel cars in the European Union routinely operate with higher NOx emissions on the road, putting the average at about three to four times higher.
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In response to the Guardian, some automakers have argued the fault is in the required test -- it's not designed to reflect hills, turns, traffic and other real driving conditions.
That is true as far as meeting the requirements of the law goes, but it certainly won't help manufacturers make the "clean diesel" pitch moving forward.
The diesel market has been helped along by a classic case of greenwashing, in which lower carbon dioxide emissions and higher fuel efficiency are supposed to make diesel cars a "green" choice.
Now that the rug has been pulled out from that marketing angle, EU automakers are becoming more serious about collaborating on stepped-up standards, though apparently significant action will not be forthcoming until 2019 at the earliest.
Meanwhile here in the U.S., the Environmental Protection Agency has already put manufacturers on notice that some big changes for vehicle emissions tests are in the works. In an Oct. 7 blog post, EPA director of transportation and air quality, Christopher Grundler, outlined the steps that the agency is taking -- first noting that Volkswagen's Clean Air Act violations threaten "public health and the credibility of the industry."
In addition to a thorough investigation of Volkswagen, Grundler stated that EPA will "take the appropriate steps to ensure that this never happens again," including new tests to detect defeat devices.
Interestingly, prior to the Volkswagen scandal, diesel cars were not a particular focus of EPA enforcement. According to Grundler, in the U.S. cars and other light-duty diesel vehicles account for only about 0.10 percent of NOx emissions related to on-road activity. The main focus has been on trucks, which account for about 40 percent.
However, when you get down to the local level, diesel cars can play a make-or-break role in lowering NOx emissions.
EPA is rightfully proud of its role in driving clean air progress since its founding in 1970 -- Grundler notes a 70 percent reduction in air pollution overall while the U.S. economy has tripled -- and it appears that the agency is determined not to let NOx emissions from diesel cars slip through the cracks.
Image (screenshot): via U.S. Environmental Protection Agency.
Tina writes frequently for TriplePundit and other websites, with a focus on military, government and corporate sustainability, clean tech research and emerging energy technologies. She is a former Deputy Director of Public Affairs of the New York City Department of Environmental Protection, and author of books and articles on recycling and other conservation themes.