Your Car

When it’s time to look for a car it’s hard to decide which model would do the least damage to the planet and to humans –  as well as suiting your pocket and your lifestyle.

Broadly speaking Petrol cars have the highest CO2 emissions, that cause global warming whereas Diesel cars have the highest pollutants, that cause ill health and death. Electric cars (EVs), charged from a local renewable source, are the cleanest in terms of both CO2 and pollutant emissions. EVs charged from the mains cause an amount of CO2 and pollutants (at power stations) and Hybrids vary, but Next Green Car has a NGC lifecycle index of emissions, making it easy to choose a car that will be as clean as possible.

Energeasy has a simple ‘select the right vehicle for you‘. Next Green Car lists the top 10 low carbon cars, ranging from a luxury Tesla model c70 at £53,935, with a range of 275 miles, down to the runaround Renault Twizy at only £6.895, with a range of only 62 miles. Middle of the road models include the Nissan Leaf OTR  at £24,990 with a range of 155 miles. Electric Streets also lists current electric models at new cars, and motor bikes at bikes with details of purchase and running costs.

There is even a growing sport of Formula E electric racing cars to raise the profile of Electric cars and also an innovative hydrogen car powering electric engines in each wheel being tested – the Riversimple Rasa.

Dirty and Clean cars

The Low Carbon Vehicle Partnership says that “Road transport is responsible for approaching 20% of the UK’s total emissions of CO2 and most of the critical emissions (particulates and NOx) which can have damaging health impacts in areas of high pollution concentration.” So the meaning of ‘dirty cars’ here is for models that have high levels of CO2 and pollutants, whereas ‘clean cars’ have low levels.

Emissions Analytics label

Emissions Analytics, an independent testing body, has introduced the EQUA Air Quality index based on the level of emissions of nitrogen oxides (NOx) in grams per kilometre.  Click here to see which specific models are rated A (Euro 6 limit for diesels, Euro 4 limit for petrols) to H (roughly equal to 12+ times Euro 6 limits). Not all diesels are culprits and not all hybrids are angels. The Department of Transport also commissioned a partial Real Driving Emissions (RDE) test of a cross section of vehicles “from the Vehicle Certification Agency’s site in Nuneaton” that came up with similar results: “On average our measured road test NOxemissions from Euro 5 vehicles were 1135mg/km – over six times higher than the 180 mg/km official legislative NEDC laboratory test limit.

Although there are days and locations where the levels of pollutants are low, London Air explains that “During still hot weather pollution is able to build up to harmful amounts, leading to what are known as pollution episodes.” and this occurs in cities all round the world and even along busy rural roads. London Air has a mobile App to track current air pollution level.

  • The Low Carbon Vehicle Partnership explains that “The UK is legally obligated under the Climate Change Act and European regulations to reduce emissions of both types. “

    However, Which reported in Jan 2016: “In our tests, 95% of diesel cars, and 10% of petrol cars, pump out more NOx than limits allow. The majority of petrol cars we’ve tested also exceed EU carbon monoxide (CO) limits, and some hybrid cars are not as innocent as claimed.” See Which’s Worst Offenders for lists of the dirtiest cars.

    The tests were conducted since the realisation that laboratory tests based on New European Driving Cycle (NEDC) do not accurately reflect the amount of air pollution emitted during real driving conditions (and have sometimes been cheated) so these were based on more stringent tests.

    The Oct 2015 the EU passed a regulation for Real Driving Emissions (RDE) tests for diesel cars from Sept 2017. Transport Emissions reported that the EU “agreed to weaken the limits for nitrogen oxide (NOx) emissions from new diesel cars. The effective new ‘Euro 6’ limit, 168mg of NOx per km, is more than double that agreed in 2007 (80mg/km). From 2020, all new cars will still be allowed to emit 120mg/km.”

  • The London Air explanation includes: “Nitrogen dioxide (NO2) is one of a group of gases called nitrogen oxides [NOx refers to NO2 and NO]. Road transport is estimated to be responsible for about 50% of total emissions of nitrogen oxides, which means that nitrogen dioxide levels are highest close to busy roads and in large urban areas”

    Nitrogen dioxide inflames the lining of the lung and reduces immunity to lung infections such as bronchitis. Studies also suggest that the health effects are more pronounced in people with asthma compared to healthy individuals.” According to Transport Emissions “Emissions from diesel cars are responsible for the widespread exceedances of nitrogen dioxide (NO2) limits across Europe and cause 72,000 premature deaths each year.” 

  • The London Air explanation includes: “Carbon Monoxide (CO) is a colourless, tasteless, odourless, poisonous gas produced by incomplete combustion of fuel. This can include ‘cold’ or badly tuned engines… It is estimated that road transport is responsible for almost 90% of all carbon monoxide emissions in the UK, and thus ambient concentrations will generally be highest close to busy roads.”

    “Breathing in low levels can result in headaches, nausea, tiredness and difficulty in thinking clearly. Exposure to high concentrations can kill, but this would almost never happen outdoors.” 

  • The London Air explanation explains that Ozone is “normally formed when other pollutants, including nitrogen dioxide, react in sunlight. Therefore, on sunny days in polluted air concentrations of ozone can increase leading, in severe cases, to summertime “smog”. “ 

  • The London Air explanation includes:  “Particles originating from road traffic include carbon emissions from engines, small bits of metal and rubber from engine wear and braking as well as dust from road surfaces. Others include material from building and industry as well as wind-blown dust, sea salt, pollens and soil particles.”

    It also includes “secondary inorganic aerosols (SIA) and specifically ammonium nitrate” according to “How important is the ‘foreign’ contribution to UK particulate matter pollution?” The Sunday Times reported on 3rd April 2016 based on this research explaining that  what used to be called Saharan dust, turns out come from farmers across the channel. Our farmers send the same pollutants the other way when the wind changes but Defra don’t want to agree to the EU banning it as Defra wants to use more fertilisers to raise more cattle.

    The health effects of particle air pollution have been widely studied, and include premature death and the worsening of heart and lung disease, often increasing admissions to hospital.

  • The London Air explanation includes: “Sulphur dioxide (SO2) is colourless gas with a strong odour which is produced when a material, or fuel, containing sulphur is burned. In the UK the major contributors are coal and oil burning by industry such as power stations and refineries”

    Although concentrations in this country present a low direct risk to human health, it can cause pollution in another ways, mainly by contributing to the formation of particles.”

  • The UK Committee on Climate Change reported on Impact of real-world driving on emissions from UK cars and vans in Sept 2015. “Passenger cars and vans contribute to 17% of the UK’s total carbon dioxide emissions, and therefore have an important role to play in meeting future CO2 targets. Despite rapid falls in the official CO2 emissions of new cars sold in the UK in recent years, evidence of a growing ‘gap’ between official and real-world driving CO2 emissions for new cars has received much attention, and Government has become increasingly aware of the risks this poses to the UK’s CO2reduction efforts.”

     Car Pages says that “The average CO2emissions rating is 138 g/km (grams of carbon dioxide per kilometre driven), the lowest being 0 g/km and the highest 398g/km. 

    It has quick lists of CO2 emissions for SUVs, estates etc etc listing carbon emissions in g km for current models.

    The cleanest option for a car is where renewable electricity, such as solar PV, is available to charge up an electric car. Where electrical power comes from a 100% renewable supplier, the carbon emissions are also minimal – see switch your electricity. Even using electricity from an average fossil fuel mains mix does incur some carbon emissions, said by Next Green Car to be 40% lower per mile compared to a conventional car. Nitrogen oxides (NOx) and particulates (PMs) will also have been emitted at the power station, but these will not add to poor air quality along roads.

Electric Cars

Next Green Car lifecycleschematicAccording to Next Green CarThe life cycle carbon emissions for a typical electric car using the average UK mix electricity are around 100 gCO2/km…… the emissions for a small new car…..  is approximately 170 gCO2/km.” So buying an electric car, (especially if using 100% renewable electricity for charging) will reduce your driving emissions and do your bit to address global warming.

Car Pages assumes that electric models use zero carbon electricity and ignores the other lifecycle emissions, arriving at zero CO2 emissions , and this is why it is widely accepted that widespread adoption of electric cars will be needed to combat global warming and bring down deaths in polluted Cities. “MEPs have been told decarbonisation is required and that while ‘biofuels are limited resources, electrification of transport is inevitable’. Electric mobility, which includes public transport and bicycles as well as cars, is ‘a double fundamental innovation with great potential for the transport as well as the electricity sector’ according to the Transport Environment News in Feb 2016.

This does not account, though, for the emissions relating to the source of the electricity. Switch your electricity gives CO2 emissions for different sources of electricity and also links to the fuel mixes of different electricity suppliers. If you are able to charge an electric car at home switching to a 100% renewable plan or installing your own supply will achieve clean motoring.

However, motorists are not familiar with buying electric cars and are concerned that they will cost too much, have short ranges and be difficult to charge.

  • Electric cars typically have a higher upfront cost than petrol or diesel, but compensate to an extent with very low running costs. Next Green Car’s Whole Life Cost Index calculates a vehicle’s total cost of ownership for a private (non-business driver) in terms of pence per mile over three years. This takes into account a purchase subsidy up to £4,500 (usually included in the stated price); a home charging point grant of £500; a £0 Vehicle Excise Duty (car tax) and a £0 London congestion charge . Using renewable electricity surplus to domestic needs would mean that the running costs would also be tiny, and in any case there are the benefits of producing low carbon, zero NOx and zero particulates.

    See also the Next Green Car fuel cost calculator.

  • The average car in Britain travels around 20 miles a day, a distance most modern electric cars can sustain for almost a week without needing to charge. (according to Ecotricity) Even for models with the longest range, such as Tesla’s 275 miles though it is vital to be confident that your car can be charged before it runs out of power.

  • Most car owners have access to off-street parking (70 per cent apparently) and are able to charge at home at night” (according to Ecotricity). Where this is the case the owner can charge their car, either slowly using standard mains power or with a dedicated charge point, such as from Energeasy.

    If you do not have off street parking, Energeasy says that “your Local Authority may be able to help via a central Government grant to install a charge point by or near to your home.  For this to be possible, your Local Authority must have applied to join the Government scheme which makes this funding available to them.” Energeasy also shows the types of charging points that they sell.

    Where this is not possible, there is a network of charging points for electric cars and bikes in London. And across the UK there are maps of charging points at ‘Charge your Car’ – download an app from here and/or from Zap Maps.

    In Jan 2016 the Department of Transport announced funding of £40m across London, Milton Keynes, Bristol, and Nottingham and Derby to help schemes that will help encourage thousands of people to consider switching to a plug-in car. For London:

    London was awarded £13 million, including £3.5m to create ‘Neighbourhoods of the future’ prioritising ultra-low emission vehicles (ULEVs) in several boroughs across the capital. In Jan 2017 the awards were announced New funding announced to improve air quality across London . The schemes came to £2.5m (£1.4m from the DfT) for Haringey, Hackney/Islington/Tower Hamlets, Heathrow and Hammersmith and Fulham.

    The Haringey scheme was awarded £609K to trial a rapid charging taxi rank and provide “specialist business and community engagement to drive awareness of green technology and encourage behaviour change.”

    For motorway journeys Ecotricity provides 100% renewable charging at service stations and at some Ikea stores. The service is provided free and the fast charge charges from 0-80% in around 20-30 minutes.

  • Selling petrol and diesel cars on does move their carbon dioxide emissions elsewhere, but the other pollutants may do less damage when moved from areas of polluted roads to owners in less polluting parts of the country. Replacing them with electric cars in Cities will positively reduce ill health due to pollutants.

    Disposing of an electric car can offer opportunities to store renewable electricity, thus helping to smooth the peaks and troughs of sunshine and wind. For instance Batteries are at the heart of the Everest system in East Anglia which is “a modular energy storage device, using second life battery packs from electric and hybrid vehicles, to act as aggregated grid support.” It uses second-hand batteries from Renault electric cars, but demonstrates potential for EV battery re-use going forward.

    Similarly the prize winning entry from Brunel student Carlton Cummins of Aceleron, was for a blueprint to recycle lithium electric car batteries by sending them to developing countries, so that the solar they generate can be stored for use at night.

Plug In Hybrids (PHEV) and standard Hybrids

Plug in Hybrids combine all the advantages of Electric cars with the ability to resort to petrol (or diesel) if a charging point cannot be found. It can be seen at Car Pages Saloons that a PHEW such as the Mercedes emits 65g kw CO2.

It also shows that standard Hybrids, such as a Toyota Prius emits 101g km CO2, similar to many other models. Hybrid generate electricity whilst the vehicle is being propelled by conventional fuel, enabling good MPG and low CO2.. Hybrids do have good miles per gallons (MPG), but not necessarily as good as smaller cars and often not as many as diesel cars. 

Though Hybrids as typically much less polluting the Aqua Air Quality Index shows that all the Petrol Hybrids for Euro 5 and 6 were rated A, the Diesel Hybrids were much lower, and a (Porche) plug in hybrid was only a B.

See also the DVLA search facility for CO2 information.


Petrol Cars

Petrol cars emit more CO2 per mile than diesel. See Next Green Car for Miles per Gallon and Car Page for CO2 emissions.

Typically they have lower levels of pollutants than diesel cars. However note the exceptions discovered by Which in Jan 2016) and the Aqua Air Quality Index also discovered polluting petrol models – some worse than some diesel models.

Diesel cars

Diesel cars tend to be more expensive to buy, but this is off-set by the fact that they usually cost less to run”, according to Next Green Car.

As a good general rule, diesel engines produce fewer CO2 emissions than petrol engines, explained by Next Green Car as “CO2 isn’t the only pollutant that needs to be considered though as there are a number of other gases that come out of an exhaust pipe. NOx (nitrogen oxide) emissions are gaining increasing amounts of coverage as it has one of the most noticeable effects – it is one of the key gases in the build-up of smog. Diesel engines produce a higher amount of NOx than petrol engines (though this can be reversed as the engines get older) and diesel units also produce soot-like particle emissions. Engine manufacturers are tackling these problems, though at a slower rate than first anticipated.” The results at Aqua Air Quality Index show that only 7 of the 130 Euro 6 cars rated A were diesels.

If you’re going to mainly drive on motorways and A roads a diesel car will emit less carbon than a petrol car. It is the realisation that they emit very high levels of pollutants that means that driving diesel close to humans is harmful that makes them a ‘dirty’ choice for urban areas.

Therefore, at a global level, replacing petrol and diesel cars with electric ones will save lives as well as reducing global warming. The big challenge for the motor industry and governments is to make sure that clean cars are affordable and convenient to charge so that they progressively replace dirty cars.