University raises air quality concerns after testing VW diesel

University of Manchester team presents findings from Volkswagen diesel engine tests and calls for real-world testing regime

Researchers at the University of Manchester have today (September 6) echoed widespread concerns over the air quality impact of diesel vehicles after carrying out tests on a Volkswagen diesel engine.

The University of Manchester

A research team from the University of Manchester has been testing emissions from a VW diesel engine

Publishing their findings that the VW engine they tested emitted more pollution than suggested by the official testing regime, the researchers called for the introduction of a new testing regime which better reflects real-world driving.

German carmaker Volkswagen is currently embroiled in a scandal following its admission that it fitted software to some of its diesel cars which was designed to give a false impression of the amount of nitrogen oxides emitted (see story).

But, before the scandal emerged last month, results from testing undertaken by the Manchester research team had already begun to show “the true picture of just how dirty diesels can be”, the University said, with findings having been presented recently in Milan and the USA.

The team attached a VW engine to a specially-made atmospheric chamber, which is designed to accurately monitor which pollutants are being emitted and how they react with sunlight to create secondary pollution.

The tests found that high levels of nitrogen oxides and particulate matter were emitted at elevated levels under real world conditions not represented in the current laboratory-based testing protocols.

These emissions were also found to react strongly with sunlight to create secondary pollution such as ozone and particulate matter.

In addition, the research team also found that the engine was much more polluting when first turned on and then when rapidly decreasing — two elements not accounted for in the current testing regime.


Dr Rami Alfarra, the research fellow at the National Centre for Atmospheric Science who led the work, said: “It has been known for a while that diesel engines were emitting more dangerous fumes than the tests were picking up.”

He added: “And it has not been adequately considered what happens to the pollutants once they get into the atmosphere. That is the key to our work. We want to know how these components of pollution are reacting in the real world and just how much additional pollution they are causing in our towns and cities. We have found that pollutants such as ozone and particulate matter are being produced as a result of further reaction of the emissions in the atmosphere and these would be at street level so would be breathed in by everyone.

“We are the only researchers in the UK looking at this aspect of the engines and hopefully our work will inform and help make engines cleaner in the future.”

He added: “Before catalytic converters have a chance to warm up they are not very effective. This means that when engines are first turned on diesel cars are much more polluting. In general the community has become aware that the levels of pollution measured are much worse than is being suggested by current tests. There has been a mismatch. What we need is real world testing of these engines.”

Dr. James Allan, another scientist working on the project, said: “This experiment is allowing us to look at the composition and properties of exhaust particles and gases on a level of detail not previously possible and it really is striking to see the differences once the engine is taken outside of its comfort zone. If we are to understand the real impact of these engines on air quality, we must perform experiments like this, rather than rely on standard test cycle data that give an incomplete and misleading picture.”

The research work was funded by the Environmental Research Council (NERC) and is a collaboration between the universities of Birmingham and York.


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Bob Moody
Bob Moody
8 years ago

Perhaps someone should calculate whether current technology can achieve current regulations using petrol or diesel fuels .It should be possible to put replaceable particle filters at the end of exhaust systems where they can easily be replaced cheaply and regularly. All cars could be compulsorily retrofitted, not just new cars.

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