How Long Is Your Tailpipe?

Monday 16th May, 2011
There are constant disputes between Electric Car fans and their sceptics regarding the true emissions that these vehicles create. We have seen adverts banned by the ASA for claiming "zero emissions" from electric cars and the motor industry is now forced to wave around odd phrases like "zero emissions whilst driving" which don't really capture the whole picture. As usual, I'm going to try and fill in the gaps to try and explain why it's all so complicated.

Let's start at the basic level, the cars. We all know that a car like a Golf GTi is likely fuelled by Petrol. We know that a Ford Transit fan is fuelled by Diesel. But what is a Nissan LEAF fuelled by? If you answered Electricity, not only are you wrong but you're proving how complicated this is. Electricity isn't a fuel, it's actually just a form of energy.

You may remember, from science classes at school, that there are many different forms of energy in the Universe. Energy cannot be created nor destroyed, merely converted from one form to another. The concept of "wasting" energy to a scientist makes no real sense but you can, of course, end up with a shortage of one form of energy and a surplus of another.

So which form of energy makes the LEAF move? If you said electricity, you're wrong again. Kinetic energy is what makes a car move. But which form of energy is the kinetic energy made from? Nope, wrong again, not electricity. The kinetic energy is actually derived from Magnetic energy, in the motor, which is itself powered by electric energy. But where does this electricity, temporarily stored in the batteries, come from? In most comes from FUEL.

"Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. A fuel contains energy, mostly heat, that can be released and then manipulated." states the Wikipedia article. This is basically chemical energy and examples include the petrol for the Golf I referenced above, diesel for the Transit and other things like wood, coal and natural gas. To extract the energy from these, we usually burn them. So back in our Golf GTi. The chemical energy, from the petrol in the tank, is burned in the engine to make heat. This heat expands the contents of the engine cylinder, creating kinetic energy from the pistons that turn the wheels.

Notice that, in either the Golf or the LEAF, the wheels aren't driven directly by fuel - it can't be. Fuel is not energy, it's a form of stored energy, and to use it we have to convert this fuel from chemical energy into kinetic energy either directly or indirectly. In the Golf, this is done using the onboard engine under the bonnet. This creates those all too famous CO2 emissions from the exhaust pipe. In future hydrogen fuel cell vehicles, as the name implies, hydrogen is the fuel and energy is converted on board from chemical hydrogen and oxygen to electrical energy, which powers a motor to create magnetic energy and turn the wheels with the kinetic energy output from it. It still has an exhaust pipe but, in this case, the only emission is these are also often referred to as zero emissions. In the case of the LEAF this isn't done on board, so it doesn't need a tailpipe, but without fuel to generate that electrical energy in a power station, your EV isn't going anywhere. So the EV fans are keen to convince people that their cars are "zero emission" but, in reality, this is only because the fuel that powers them isn't actually carried or converted on board. I find this misleading and so did the ASA when they banned numerous adverts that claimed it.

Many EV fans are slowly accepting that the "zero emissions" claim is perhaps a bit unrealistic but feel that including the emissions generated outside the electric car is a bit unfair and biased in favour of the old petrol and diesel cars. They argue that if we look at the emissions created from generating the electricity, then we should look at the emissions generated by petrol stations, oil refineries etc. They argue that petrol comes from Crude Oil which creates a lot of emissions when being refined, when being pumped and when being drilled. In reality, this cuts both ways though...let's look in a bit more detail.

Petrol comes from a petrol pump, powered by electricity, adding to emissions in a power station. It gets to the petrol station in a fuel tanker, that uses diesel..from a petrol station. The tanker brings it from the oil refinery, which uses a lot of electricity, adding to emissions in a power station. The oil arrives at the refinery in barrels by truck or train, which have their own emissions footprint. The oil is pumped in from rigs in the North Sea which also create numerous emissions during the process. All these places have workers which also need to get from home to work which means more emissions. It all adds up and there is no denying that the process of getting some petrol or diesel into your tank is a complex one. This is the "long tailpipe" argument.

Likewise, however, there are loads of emissions from the generation of electricity. A large proportion of electricity in the UK comes from coal fired power stations - they burn coal chucking the fumes out of a chimney. The coal, like the oil, has to be delivered by train or truck. Most of the coal even comes from Russia these days, a massive transport footprint. Some power stations are powered by natural gas which again needs to get to the generators by pipeline or tanker, often from the North Sea like the oil. Drilled like the oil, the same footprints as the oil. Some electricity comes from wind turbines which, at first glance, look clean but if you look a little closer you'll realise they are enormous, need to be made in and transported from a factory and also need massive foundations to be dug and filled with concrete which itself has a massive footprint from the extraction and transport of materials required to create it. Nuclear power looks reasonably emission free, from the outside, but again it needs to be powered from refined uranium, in a plant with thick concrete walls etc. Solar panels provide a small, almost insignificant contribution to the National Grid, but even these need to be made in a factory from raw materials that all need to be transported etc.

So where do we draw the line? Well, that's up to you but I think we need to be realistic and put the line in a similar place for each type of vehicle. This, for me, is by looking at the emissions generated from the fuelling of each vehicle. Not the energy used, but the fuel emissions. So this means, for a petrol or diesel car, it's what comes out of the tailpipe. That fuel only goes to one place, it's used to power the car. Every bit of emissions that comes out of the tailpipe is directly attributable to driving the car, the energy derived from it doesn't go anywhere's a no brainer.

An EV is powered by electricity which also cannot be used for anything else. If you use 24kWh of electricity to fully charge a LEAF, those 24Kwh were only used to power the LEAF and so we can look at the emissions generated by the power station to create those units from fuel. Of course this varies across the grid as it uses a mix of sources - at time of writing that is 40.8% from natural gas, 31.7% from Coal, 20.5% from Nuclear, 4.6% from wind and 2.4% from hydro. Some, like the wind and hydro, don't use fuel so can be regarded as zero emissions from my perspective. Others, like gas and goal, have very high emissions. So what they do is take an average which, as I type, is 550g of CO2 for every kWh of electricity generated. So this means that our Nissan LEAF will generate 24 x 550g of CO2 when you fully charge it which means 13,200g of emissions for 100 miles, or in the familiar form 82.5g/km. This means that it is almost as high as many Petrol/Diesel cars, in terms of CO2, and worlds away from the claimed zero.

So, moving forward, I'm going to refer to the emissions generated from the fuelling, not the powering, of each vehicle as "Stage One" emissions. Over time, as the National Grid cleans up its act and switches to more renewable sources, those Stage One emissions for EVs will go down and likely be significantly less than those for standard ICE vehicles. In fact, this may even change if we progress to better systems of measuring emissions from cars. The current standard test is largely regarded as inaccurate and it's apparently fairly easy for a car manufacturer to make the CO2 output look low during the standard test but actually be much higher at other times to create a car that's more fun to drive. I personally believe that Stage One emissions for an EV are better than any ICE vehicle at urban speeds up to around 40mph on a warm day. Above those speeds, or on very cold days, I feel that a petrol hybrid is the better option by far. Diesels can also have low CO2 but, as I've mentioned many times, the other emissions from those vehicles are a particular concern that I would choose to reserve for freight vehicles.

What I'd like to see in future is standard emissions testing that measures the CO2 output of each ICE vehicle at idle and then at 10,20,30,40,50,60 and 70mph. We could also measure the electricity consumed by an EV at the same speeds and convert that to a CO2 equivalent as I did above. That way we could then give each car an energy rating, like the sticker on a new Fridge/Freezer, that shows how efficient it is on urban, extra urban and motorway journeys. If you mainly drive short journeys around town, you would focus on a car that had a green rating for urban travel and look towards an EV. If you mainly munch motorway miles, you'll look at something like a petrol hybrid or perhaps even a diesel which would be green rated there. If you do a big mix of both, then a plug-in hybrid will likely have a green rating in both areas and be the best of both worlds.

So that's my perspective on the tail-pipe argument, feel free to share yours below.

  1. 1) Paul McCulloch Said: (16/05/2011 12:36:13 GMT) Gravatar Image
    How Long Is Your Tailpipe?


    'natural gas which again needs to get to the generators by pipeline or tanker'

    its all pipeline, tankering wouldn't keep up. Any tankered LPG fuel is used for pilot lighting duties only.

    I think the real benefit to switching to ev's in the reduction in local pollution, NOx, SOx etc rather than CO2. Image a city with ev's or hydrogen powered transport, the air quality would be significantly better for the inhabitants. Then, as you state, its coming for point sources which can be cleans (like eu large combustion directive is doing on NOx etc) or change to more renewable sources

  2. 2) Ben Rose Said: (16/05/2011 13:04:08 GMT) Gravatar Image
    How Long Is Your Tailpipe?


    Thanks for the feedback. As tankered LPG exists, I gave it a mention, but it's not really critical to my analysis at this point.

    As for "local pollution" you remind me of an old Tommy Cooper joke:

    A guy rings the swimming pool and says "hello, is that the local swimming baths?" they said "I dunno, depends where you live."

    Sure, EVs may help get emissions out of city centres where where aren't any power stations but it moves it to other areas where those power stations are actually located. Sure, an EV in London will help Marylebone Road being quite so deadly, but what about the residents of Ratcliff-on-Soar? As demand electricity increases, with the uptake of EVs, power stations like Ratcliff are going to be running more hours a day to keep up with demand. Coal and Gas fired power stations that currently go to minimum or nil output overnight (allowing French nuclear to fill the minimal gap) are going to see the value of their units increasing and stay on-line...possibly all night, so people can charge their cars whilst they are in bed. Arguably, this could cause a right in stage one emissions in the short term. Not in Central London, no, but where somebody lives for sure.

  3. 3) Keith Ruddell Said: (16/05/2011 16:07:47 GMT) Gravatar Image
    How Ridiculous Is Your Argument?

    Wow! All that based on your definition of what you consider fuel to be. Who cares?

    If I don't use one gallon of gas or diesel, then whatever amount of crude oil doesn't have to be extracted, transported, refined, etc. All those emissions evolved are gone, not just what comes out the tailpipe. Same thing for electricity. To exclude any steps in the production of either to make your point is just wrong.

    Also, according to the Wikipedia definition you used, the chemical reaction in the batteries of an EV would be considered the fuel. Therefore, an EV is truly CO2 emissions free during operation.

  4. 4) Ben Rose Said: (16/05/2011 16:19:01 GMT) Gravatar Image
    How Long Is Your Tailpipe?


    Did you actually read the article? Or did you just come here to copy/paste the same boring "I don't use a single gallon of gas" that all the pro-EV people throw around? The electricity has to be generated this uses tonnes of coal and natural gas fuels. They are burned and produce emissions, just like oil products. I'm not excluding any steps at all, simply going from the turning wheels backwards to a common point for both vehicles - where energy is turned into fuel. Accurate data for any further back just doesn't currently exist right now so it's the only fair comparison.

    Also, no...batteries could only ever be considered fuel if you burn them on a fire. You don't. They are simply a temporary storage container for electrical energy and in no way comparable to a fuel.

    Sorry if I burst your bubble.

  5. 5) Paul McCulloch Said: (16/05/2011 18:00:58 GMT) Gravatar Image
    How Long Is Your Tailpipe?


    Legislation is coming in to tackle the emissions, so as ev numbers are going to ramp up slowly over the next 20 years, its probably not going to be that much of an issue. Any new stations in the UK now must be designed to fit carbon capture, i.e have the land and the connections on the flue gas system to install. Some of the UK coal fleet retires in 2015, end of life & too costly to upgrade, so the mix will change potential quite significantly later in the decade, especially if you add in London array et al for wind, might even see take up of pv at a domestic level in significant numbers

  6. 6) Keith Ruddell Said: (16/05/2011 18:27:41 GMT) Gravatar Image
    How Long Is Your Tailpipe?


    Yes, I read the complete article. Thanks for being so condescending. So I'm boring? I've been called worse. Still doesn't change the fact that the basis of your argument is wrong.

    The petroleum industry is one of the biggest users of electricity and natural gas. If you wish to exclude those emissions from the petroleum side, then it is only fair to exclude them from the EV side. Oh look at that, EVs became emissions free. Amazing what you can do with a slight of hand.

    I suggest you work on your reading comprehension skills. The Wikipedia definition states that "Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner." Extract doesn't mean burn. I know you anti-EV, pro-petroleum dinosaurs have difficulties with that concept, but give it a try.

    One more quote from Wikipedia to help clarify "Some well known alternative fuels include biodiesel, bioalcohol (methanol, ethanol, butanol), chemically stored electricity (batteries and fuel cells)". See, chemically stored electricity, burning not required.

    I've seen some of your previous comments in other articles about EVs, so I highly doubt you will admit that you are wrong. You will bleat on about dirty electricity and EVs aren't any better than an economical diesel, yada, yada, yada. Sorry, but science and common sense don't agree with you.

    My bubble is just fine BTW.

  7. 7) Ben Rose Said: (16/05/2011 19:47:47 GMT) Gravatar Image
    How Long Is Your Tailpipe?


    My argument isn't wrong, my argument is simple fact. Look at all these dictionary definitions of the word "fuel" { Link } - notice how they don't mention electricity or batteries? That's because they are not fuel.

    You're not going to achieve much by selectively quoting from the article to suit your own purposes. I linked to it specifically so people could read it in full. You'll note the article (which isn't exactly a comprehensive science paper) specifically says "A fuel contains energy, mostly heat, that can be released and then manipulated" - right there in the sentence after the one you quoted. Amazing, huh? Also, you'll notice that nowhere does it mention about batteries being a fuel, nowhere at all. Funny that, because they are not.

    I've not excluded any emissions from any side, I've simply drawn a line at what I've called "Stage One". Everybody else seems to understand that and I've already had bigger electric car fans that yourself compliment me on the article, it's not exactly difficult to understand if you take those rose tinted specs off for a moment. Stage One doesn't include the "production" of the fuel, just the usage of it. All kinds of fuel require considerable production efforts, be it mining, transport or purification/refinement but those figures simply aren't incorporated into stage one.

    Incidentally, to counter your accusation, I'm not "anti-EV" in any way. Sure, I don't think it's quite ready yet, but EV in some form, be it from rechargeable batteries or fuel-cell, is undoubtedly the future of transport and will no doubt be cleaner than all the vehicles currently on the roads...including current EVs. I'm not on any "side" except for the side of the facts and that's why I write these articles and why many people choose to read them.

    Your final quote, regarding batteries being fuels that you took from the "Alternative fuels" document on Wikipedia { Link } , is actually incorrect and out of context. In the context of an electric car, the battery is nothing more than a large capacitor...not a source of chemical fuel. Very different things.

    If you claim to have read me explain that EVs aren't any better than an economical diesel, then you clearly have the wrong person. I will always rank an EV higher than a diesel, due to the horrible polluting emissions that the latter creates. But when compared to a modern petrol hybrid, as I explained above, I don't believe there is much in it.

    Talk about science not agreeing with me all you like, I'm a trained Scientist and have extensive qualifications to back that up.

    Your bubble may be intact, but it's got plenty of CO2 in it.

  8. 8) Mark Tebbutt Said: (16/05/2011 21:50:12 GMT) Gravatar Image
    How Long Is Your Tailpipe?

    Hydrogen isnt burnt in a fuel cell yet you still class it as a fuel? Hydrogen is an energy carrier like a battery.

  9. 9) Ben Rose Said: (16/05/2011 21:54:27 GMT) Gravatar Image
    How Long Is Your Tailpipe?

    Hi Mark,

    Did you watch the Space Shuttle launch today?

    Hydrogen is very much a fuel...

  10. 10) Paul McCulloch Said: (17/05/2011 12:05:33 GMT) Gravatar Image
    How Long Is Your Tailpipe?

    Hydrogen is reacted in a fuel cell. reacted or burnt it still isn't the same after use as before, its been converted into a energy plus byproduct. Where as a ev battery is essentially the same whether is full or not in my mind, its just a fuel tank for electricity

  11. 11) Ben Rose Said: (17/05/2011 12:10:12 GMT) Gravatar Image
    How Long Is Your Tailpipe?

    Precisely Paul, glad somebody else gets that.

    You can put zinc and copper electrodes into a potato and make a basic cell but, once it's run out of's dead. In this case, the potato acts as fuel. You can't recharge a potato.

    This is not the case in the Li-ion cells that form a modern EV battery.

  12. 12) Alex Willmer Said: (17/05/2011 23:13:21 GMT) Gravatar Image
    How Long Is Your Tailpipe?

    Hi Ben

    I won't wade into the fuel definition(s), except to say I try to stick with the terms energy carrier/source. I would also use the terms Tank-to-wheel, well-to-wheel, plug-to-wheel and station-to-wheel which are used in the scientific literature. I think your "stage one" emissions would correspond to TTW and STW, yes?

    The practice of attributing emissions/outputs to things is called Life Cycle Analysis. Rather than give a mangled description. I'll pass on some links in rough descending ease of reading/ascending specificness. I've gathered these in the last year or so:

    Needless to say I've not read all of those in full.

  13. 13) Charles Denham Said: (18/05/2011 22:54:53 GMT) Gravatar Image
    How Long Is Your Tailpipe?


    Despite not wanting to feed the trolls (or probably stirring them up with that comment).

    I find your Stage one definition quite useful. You know my background in physics and business, so I'm not exactly a dummy in these areas (those who don't, not important really, as it is who you are now that really counts). It does produce a relatively fair comparison between the black stuff sources (petroleum products) and the EV consumption.

    The fuel sources in any motor can never be conjured out of thin air (not with our existing technologies anyway), so this is a good, not flawless, basis for emissions understandings.

    I would be interested to see where/how we can measure fuel cell emissions under your stage one definition. The cell, as mentioned above is just a battery in reality, although when the hydrogen is used, it does, if I'm not mistaken, produce H2O, so is that going to be used as the emission, or are there figures available for the carbon (ironically) emissions for the production of hydrogen.

    I don't think I will go into my opinions (whether they be bad or good) on the "emissions" or pollutants involved in the production of the batteries used in EV vehicles, as I'm not sure that would be helpful for anyone in the discussion of your stage one definition.

    For the moment, I'm sticking with my black fuel burning fat executive car (for the fat executives) until they can come up with a reasonably priced fuel cell vehicle and the fuel distribution network to feed my transport desires. Either that or I would be interested if anyone can point me to a road legal 40Mph / 40 mile range Segway ... Oh there you go, fuel distribution, defining fuel for you in a different way. If I had meant that I'm cleverer than I look.

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