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Hybrid cars – Should we be concerned about VOCs?

8 December 2021


SepSolve and Markes instruments used as part of an investigation looking at VOC emissions from hybrid cars

British investigative current affairs documentary series Dispatches aired an episode entitled “The truth about electric cars” on Channel 4 in November 2021 about current issues with hybrid cars.

Featured in the programme was a section about exhaust emissions from hybrid cars – cars with a battery-powered electric motor and a petrol or diesel internal combustion engine. With an electric motor, hybrids can reduce exhaust emissions of carbon dioxide, nitrogen oxides and particulate matter, but, according to the programme, that’s not the full story when it comes to emissions. Volatile organic compounds (VOCs) are also emitted as gases from petrol and diesel, and at certain levels, some cause cancer as well as damage organs or cause breathing problems. They can also be responsible for ground-level smog.

Emissions Analytics: Experts in measuring vehicle emissions

To investigate further, Dispatches teamed up with Buckinghamshire-based company Emissions Analytics, who are experts in measuring vehicle emissions. The team gathered data on the levels of VOCs emitted by hybrid cars and compared them to petrol-only and diesel-only vehicles.

Using a thermal desorption (TD) instrument from Markes International and SepSolve’s GCxGC–TOF MS instrument (INSIGHT® and BenchTOF) with the ChromSpace instrument control and data-mining platform, the team analysed emissions from nine vehicles – six petrol hybrids, two diesels and one petrol vehicle. While the cars were driven on the open road, the setup on the vehicles enabled the VOCs to be fed into TD sampling tubes, which were then taken to the laboratory for analysis.

The team found that during cold starts (the time at which most VOCs are emitted), “the [levels of] VOCs from the electric vehicles were often much higher than the diesels, and the diesels were even cleaner than the petrol engines,” said James Hobday, Business Development Director at Emissions Analytics. “So, the prevailing wisdom that electric vehicles are clean when it comes to VOCs – it just isn’t the case.”

In fact, one of the hybrid cars had VOC emissions 70% above the others tested. The VOCs found included notable amounts of benzene and formaldehyde, which warrants further investigations to determine acceptable amounts of these emissions, according to Hobday.

Many emissions are not regulated by the UK government

Many VOC gases that are emitted from exhausts, including formaldehyde, are not measured or regulated by the UK government. However, as Mike Hawes, CEO of the Society of Motor Manufacturers and Traders, said in the programme: “The testing facilities and requirements have evolved over time. There will be another iteration of requirements coming in the next couple of years, which will be even tougher [than current regulations, which look only at quantities of emitted hydrocarbons, nitrogen oxides and particulate matter].”

Meanwhile, Emissions Analytics are taking their research a step further by investigating not just tailpipe emissions, but also VOCs generated through tyre wear and those released by the materials used in the interior cabin, such as carpets and adhesives, as well as the ingress of pollutants from the urban environment. They hope to discover more about the VOCs released and improve our understanding of how all aspects of vehicle use will impact health and the environment.

Watch the whole programme on YouTube

‘Dispatches: The Truth About Electric Cars’ is available to watch here on YouTube.

Further details on Emission Analytics research can be found in their newsletters, particularly ‘The rise of unregulated exhaust pollutants’

For information on the instrumentation used, please click on the links below:

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