SMMT 2011 CO2 Report - The Small Print

Friday 18th March, 2011
I'm sure you were made aware of the SMMT 2011 CO2 report that came out this week, along with the great news that the motor industry reduced the CO2 emissions of cars sold in 2010 compared with previous years.

But did you read the small print?

We have to go all the way to "Annex 3" on Page 39 to find the details of other pollutants, those nasty ones that affect our health like CO,NOx and PM10s. A glance at table 19 on this page shows us that all is good and these other pollutants are headed in the right direction. Or are they?

The data shown is actually from 2008, long before most manufacturers started retuning their cars for Euro 5 emissions compliance. In fact, by reference to table 18 on the SMMT report, you'll see that all this shows is the results of the successful implementation of Euro 4. Since then, we've seen extensive taxation based around CO2 and a "showroom tax" applied to the most polluting (CO2) vehicles.

But what's happened to these other pollutants since then and why aren't they shown in a 2010 emissions report compiled in 2011? In my eyes, there's no reason, the VCA clearly compiled data in 2010 just as they did in both 2008 and 2009. The claimed lack of data for other emissions since 2008 made me suspicious and led me to investigate further.

Take the Audi A3 Sportback 2.0 TDI 170ps with DPF M6 which was on sale under Euro 4 regulations. According to the corresponding VCA emissions report,  151g/km CO2, 216mg/km NOx, 230mg/km THC+NOx, 79mg/km CO

Then the car was retuned for Euro5 and became the Audi A3 Sportback 2.0 CR TDI 170PS with DPF M6. A glance at the updated VCA report shows us it now emits 139g/km CO2, a 12g reduction, the SMMT would be proud. But what happened to the other emissions?

NOx went down to 139mg from 216mg, a massive reduction of 77mg. Good news, better for health. NOx is often formed when Nitrogen, in the air, is accidentally oxidised by the highly efficient catalytic converters that modern emissions regulations demand. A reduction in NOx can actually be achieved by better tuning or...a less efficient cat. So lets look at the other pollutants.

THC+NOx is now 184mg, a 46mg reduction. Another reduction, good stuff. Or is it? We know the NOx actually dropped 77mg, so surely the THC component, those unburned hydrocarbons, have actually gone up overall. Before THC could be worked out as something like 230-216=14mg, now it's looking more like 184-139=45mg - over 3 times bigger with an increase of something like 31mg. Could it be that if you don't burn all the hydrocarbons in the fuel, dumping them out the tailpipe, that you don't generate as much CO2 and potentially get in a lower tax/VED bracket? You can ponder over that whilst we look at the choking carbon monoxide.

CO in the Euro 4 car was just 79mg. In the Euro 5 car, this is now 312mg - 4 times as much and an increase of 233mg!

Well done Audi, you appear to have inserted a LESS efficient catalytic converter, are now Euro 5 compliant, the SMMT are happy, it looks good in the report but your CO has gone through the roof as the cat appears to no longer be doing the required business. Not only all that but, despite both cars being fitted with a Diesel Particulate Filter (DPF), the newer one appears to give more PM10 particulate emissions too. Of course, if you don't burn all the carbon and leave it as soot particles, this reduces your CO2 output, so that will keep everybody happy, right?

So let's just publish the "Other emissions" data from 2008 at the back on Page 39 shall we? Maybe nobody will notice...

I contacted Paul Everitt, Chief Executive of the SMMT, before writing this article. He informed me that "the data on CO/NOx/PM10 is the latest available and illustrates the downward trend in all emissions".

This isn't just an Audi thing, they're just unfortunate enough to be the first car I looked at in the list. With many models from many different brands all having higher "other emissions" under Euro5, is it any wonder UK Air Quality is going down?

  1. 1) Richard Aucock Said: (19/03/2011 07:14:24 GMT) Gravatar Image
    SMMT 2011 CO2 Report - The Small Print

    Very interesting, Ben - I'd be fascinated to hear if it's actually so. Any of your readers work in emissions science? You've opened my eyes to the fact emissions are far more than just CO2...

  2. 2) Ben Rose Said: (19/03/2011 09:10:39 GMT) Gravatar Image
    SMMT 2011 CO2 Report - The Small Print

    The science side is fairly simple to explain and, as you've expressed an interest, I'll try to explain in a little more detail.

    Fuels like petrol and diesel are composed mainly of hydrocarbons - that is, molecules containing just Hydrogen(H) and Carbon(C) atoms. Diesel, for example, is often assumed to be C12H22 - 12 carbon atoms and 22 hydrogen.

    If you burn pure hydrocarbons, in an atmosphere or sufficient pure oxygen, all you will have at the end is CO2, from the oxidised Carbon atoms, and H2O(water) from the oxidised Hydrogen. In our example, C12H22, 1g of fuel will emit 3.2g of CO2 when the heavy Oxygen atoms are bound to the Carbon. The water generated comes out as steam and can easily be seen coming out of the exhaust on a cold morning.

    Of course, fuels like petrol and diesel aren't pure hydrocarbons; there are other things in the mix too. Also, we don't burn in anything like pure oxygen - we burn in atmospheric air which is only around 20% Oxygen.

    So, on each intake cycle, the engine must take in a measure of fuel and also enough air to provide enough oxygen to combust it. On cold days, the air will contain a higher density of oxygen, so fuelling has to be carefully measured to match up to it - why a car uses more fuel but is also a bit more nippy on those cold mornings. Needless to say, even with the use of lamda/O2 (oxygen) sensors, it isn't always a perfect science and we don't always get the perfect combustion we want.

    If any carbon from the fuel isn't fully oxidised, instead of relatively harmless CO2, you get poisonous Carbon Monoxide (CO). This was choking our towns for years and resulted in the introduction of the catalytic converter - a magic box on the tail pipe that takes in CO and, when hot, gives out CO2. The clever process they use didn't work with lead in the fuel, so you may remember that unleaded fuel was introduced to our pumps at around the same time as cats were fitted to new cars.

    So, armed with a cat, we could easily oxidise the poisonous CO to CO2 but it also offered other benefits. If any fuel came out of the engine that hadn't been burned, quite common when slamming the throttle closed at high revs, the catalytic converter can also oxidise this to water and CO2 - like should have happened in the engine.

    Any Carbon Monoxide that isn't treated by the cat appears in those CO figures on the VCA document. Likewise, any remaining hydrocarbons appears in the THC count.

    The carbon in the fuel can only come out in 3 forms. The "best case scenario" CO2, the poisonous CO or, finally, completely uncombusted Carbon in the form of soot. On older inefficient engines, the smoke particles were very large and you basically saw smoke out of the exhaust. Or a modern "lean burn" injection engine, soot is kept to a minimum and hard to see but still very much there. The scientists call these particulates and we count those larger than a certain size as pollutants. The number in the name PM10 refers to the size of those soot particles and can be seen in the particulate count on the VCA document.

    At the time the cat was introduced, emissions began to change. You could easily recognise a new car with a cat by the characteristic "stink bomb" smell. This was an unwanted side effect as sulphur in the fuel reacted on the cat to form hydrogen sulphide (H2S) gas. This being pretty undesiderable, you will have noticed a recent move to ultra low sulphur petrol and diesel (ULSP/ULSD) which has significantly reduced this unwanted emissions. Also, low sulphur diesel was required to make modern Diesel Particulate Filters (DPF) more efficient. Switching to ULSD allowed vehicle manufactuers to fit new diesels with a DPF and reduce those particulate emissions by catching the soot on the way out and oxidising it CO or, hopefully, CO2.

    Sadly, however, Hydrogen Sulphide isn't the only side effect of installing a cat. The air we use to burn the fuel is around 78% Nitrogen. Whilst normally pretty unreactive, in the high exhaust temperatures found in a modern engine, it can easily be undesirably oxidised by the cat into compounds like NO2 which cause ill health and can generate other side effects like acid rain.

    The better and more efficient the cat, the more NOx come out. No cat at all, NOx is at a minimum, but then our friends CO and THC come back to haunt us. Finding a balance is difficult but, given the recent focus on CO2, vehicle manufacturers have a primary target of getting CO2 down which has clearly generated a rise in other emissions. The future introduction of Euro 6 legislation requires these high NOx emissions to be addressed, and companies like Mercedes are making extensive use of urea based additives like Adblue to treat NOx output and convert it back to more healthy compounds like N2O.

    I think CO2 taxation was wrong in many ways. I completely agree that we need to reduce our consumption of Carbon based fuels, indeed they may even run out one day, but measuring CO2 wasn't a healthy way of doing it. If you want to ultimately reduce CO2 coming out, you need to put less fuel in. Less in, less out - it's not rocket science. We already heavily tax people on the fuel going in, so we're easily addressing the worst consumers without any need to measure CO2 emissions at all. We know if we put in 1g of diesel, we'll get 3.2g of diesel out if all is working as intended.

    What we need to do is address those who AREN'T emitting CO2. The emissions like Carbon Monoxide and particulates need to be addressed. Unburned hydrocarbons are a waste of fuel and there are measures to reduce NOx albeit at a cost. Carbon usage is taxed at the pump so, in future, I hope to see vehicles being taxed on those more important emissions and the dirtiest engines being taxed the highest.

    Get the Vehicles Manufacturers to convert as much of their exhaust as possible to CO2 and then simply tax the fuel to reduce carbon emissions. Job done.

  3. 3) Jan Wijmenga Said: (21/03/2011 21:33:13 GMT) Gravatar Image
    SMMT 2011 CO2 Report - The Small Print

    The article and the reply by Mr Rose give quite a complete picture. In the 80s and 90s our focus was mainly on controlling toxic emissions like CO, NOx and PM. Since the start of this century the focus shifted to CO2. Within the limits of the framework set by the EU, car makers can optimise their vehicle performance - and do so. With the introduction of Euro 6 standards, a new test cycle and the tightening of CO2 requirements for new vehicles, the room for optimisation of cars for one instead of all pollutants is less likely to continue at the same level.

    That is why companies like Mercedes are now turning to different techniques like urea injection.

    Of course this needs to be closely monitored, but also for this requirements have been strenghtened.

  4. 4) Ben Rose Said: (22/03/2011 07:37:25 GMT) Gravatar Image
    SMMT 2011 CO2 Report - The Small Print

    Thanks for your comment, Jan.

    Clearly, Euro 6 is going to be a big game changer, the future is very unpredictable right now.

  5. 5) John Baldwin Said: (16/04/2011 13:17:18 GMT) Gravatar Image
    SMMT 2011 CO2 Report - The Small Print

    Section 3.2 say "Why, according to some sources, do electric cars produce approximately 80g CO2/km?"

    We still have the 2 white lies – the first is that EVs are replacing average CO2 cars and the second is that they use grid average electricity mix. This is nonsense, avergae includes nuclear and renewables which is max 13 GW. Every time an EV is charged it uses MARGINAL electricity which is coal/gas. This is around 50% higher.

    Why can’t a publication like this tell it as it is – EVs replace small cars with much lower co2 and they use marginal electricity?

    If the story is London air quality OK or if it is building capacity for 50 years OK, as long as realisation that for next >20 years its clear that they increase CO2 emissions!

  6. 6) Mike Said: (29/04/2013 16:04:04 GMT) Gravatar Image
    SMMT 2011 CO2 Report - The Small Print

    Perhaps a reduction in NOx is actually good thing? Accidental oxidation of Nitrogen by catalytic converters could well be a significant factor in Air Quality Management issues affecting many of our big cities, Some of which have significantly worsened since 2001 see: { Link } (note Defra 2012 response is to enlarge the AQMA areas again.)

    It is unlikly the increase in CO is good but it's still many times lower than than hisistric levels

    Until we can migrate to zero city centre emissions, there will always be a trade-off.

    @John Baldwin: Assuming that everything that gets added to the grid is added at the top end of emissions can be considered correct only if there are no other changes to the grid. The marginal argument totally fails to address the fact that renewable generation is being added to the grid, and various other reductions on demand are being made to other parts of the grid.

    Your end user wire is one supply, made up from many sources, you can't buy 100% green electricity and you can't use 100% Coal energy either. You have to reflect each individual supply as it is, as a whole grid. As long as we keep adding renewable and low carbon faster than we are increasing demand on the grid (say by EV's), then we are going in the right direction. and the faster we can take pollution emitters out of populated areas the better.

  7. 7) Ben Rose Said: (01/05/2013 07:04:00 GMT) Gravatar Image
    SMMT 2011 CO2 Report - The Small Print

    Hi Mike,

    Somewhat ironic that you use an electric car in Nottingham, immediately next door to the massive fossil fuelled power station in Ratcliffe. Using an electric car in London likely adds to air pollution in Nottingham and using one locally can only be regarded as choking yourself! You force them to generate more power which means they need more coal - so add on the emissions from a load of diesel freight to get that to the power station too!

    Renewable generation is indeed being added to the grid...slowly. We're also planning to decommission a load of power stations over the coming years - including low carbon nuclear plants. Removing these will make the Carbon footprint even higher.

    Going in the right direction? I doubt it, the reduction in nuclear capacity is likely to scupper any carbon benefits offered by renewables over recent times. So are we investing in nuclear? Well no, not enough. Even private power firms are struggling to sign the contracts.

    With nuclear power stations not generating a single amp for the first 15 years, we need to get planning quickly. That's where the investment should be going. Not into electric vehicles. Not into factories to make cars that nobody is buying. Not into chargers for cars that nobody wants. It needs to go into making the grid cleaner.

    Until the grid is cleaner, EVs offer approximately zero benefit and all current models will likely be in landfill before it is.

Add Comment
Web Site:
Comment:  (No HTML - Links will be converted if prefixed http://)
Remember Me?