If you drive in the UK, the last time you filled up your car you might have noticed an array of new signs and posters proclaiming the virtues of “E10”, the new standard blend of petrol available everywhere. The government makes some wondrous claims about it on their site, like the switch will reduce CO2 emissions by 750,000 tonnes per year, or “the equivalent of taking 350,000 cars off the road, or all the cars in North Yorkshire” – but is it all it’s cracked up to be? I have a sneaking suspicion that’s a bare faced lie, but let’s take a look and see…
First, you’ll need to understand what E10 is. Petrol, as we know it, is almost exclusively sold as a blend of both raw petrol (gasoline) and some amount of ethanol (alcohol). We’ve been using around 5% ethanol content since 2008, so this is hardly new, but the main change here is that in the last few years it’d actually been labelled “E5” and now “E10”.
When the “E5” labelling was introduced, the blend was officially made of 5% ethanol – specifically bioethanol, ethanol from a ‘renewable’ source like crops. E10, then, is the same deal but now with 10% bioethanol content and 90% petrol.
But, why bother mixing them at all? Well, there’s a few reasons, the primary of which that the companies like to talk about is emissions. Pure ethanol produces around a third less CO2 than pure petrol when burning the same volume of each – so reducing CO2 output by a third is a pretty big win right!? Yes, but there’s a catch.
The energy density, how much energy is stored in a given volume, is considerably lower in ethanol, funnily enough it’s just about a third less energy dense too. More specifically: it’s about 35% lower emissions and around 30% less energy dense, so it is a touch cleaner but not by much. It’s worth noting this is CO2 emissions alone, and doesn’t include the 0 methane produced by ethanol, or a slight reduction in other emissions like particulates and NOx.
That sounds great, but you may have already spotted the problem here. If it’s 30% less energy dense, that means you need to pump more of it into your engine per cycle to get the same power output, and unsurprisingly having to burn more fuel to get the same result makes that emissions difference a whole lot less significant.
If you take the emissions figures presented in this US Energy Information Administration report from 2014, which are 19.64 pounds of CO2 per gallon of pure gasoline, 18.95 pounds per gallon of E10 and 12.72 pounds per gallon of pure ethanol, we can work out what our current “E5” fuel produces. That works out to 19.29 pounds per US gallon, meaning E10 produces around 1.78% less CO2 per US gallon of fuel. But remember, ethanol is less energy dense, meaning E10 is about 1.5% less energetic per litre than E5 so we need to use more to get the same energy output.
When you correct the volume to get the same energy output, you’ll find that E10 only produces around 0.273% less CO2 emissions than the same energy output from E5. 0.27%. That’s not exactly setting the world on fire – pun intended. When you apply that to the UK’s annual petrol consumption which the RAC estimates at 16.9 billion litres for 2019 – which is insane – you’ll find that we are only producing around 100,000 tonnes less CO2 annually, not the 750,000 tonnes the government claims. You get that number by conveniently forgetting to include the increased consumption required by switching to a less energy dense fuel – my maths says just under 700,000 tonnes but I’d call that within the margin of error. The real reduction counts for just 0.00027% of our collective annual emissions – or what I call “hardly making a dent”.
But Andrew, that’s still less CO2 and that’s a good thing! You’re right, it is, and the reduction in other pollutants is fantastic too, but what it’s not great for is your wallet. Since you need to use 1.5% more fuel to travel the same distance (all other factors being equal), you need to spend more filling up more often. At the current (and insane) nationwide average petrol price of 143.91 pence, and with the average 7,400 miles driven annually, you’ll be spending about £20 more to do the same journeys – and that’s not factoring in any price increases as petrol continues to skyrocket in cost.
There’s another problem too, compatibility. Most relatively modern cars are fitted with flex fuel sensors so they can detect the ethanol content of the fuel going into the engine and vary how much fuel it sprays each time it opens an injector. But, if your car doesn’t have a flex fuel sensor, or it’s old enough that the fuel lines aren’t rated to carry ethanol, you’ll need to stick with E5 which is still available but only as the premium “super unleaded” option at some stations. If you need to stick with E5, you’ll be forking out almost £130 a year more based on current pricing and average mileage – and unsurprisingly it’s the people who are knocking about in early 2000’s bangers who’ll have to fork out more.
Don’t get me wrong, this is still a net-positive change, anything we can do to reduce emissions of all kinds is welcomed and people in a fortunate enough position to afford a bit of extra fuel cost (like me) will be plenty fine shouldering a few quid extra per year, but it’s far from a perfect solution. While technically bioethanol is a ‘renewable’ resource, it’s ‘carbon neutral’ at best and even then it’s only 10% of the fuel being burned. It takes up land that could otherwise be used for food, or even better forest or woodland that can actually capture and retain carbon rather than capture it to instantly release it. The proper solution is to not need to burn hydrocarbons, but that’s a topic for another video.
The government’s claims that it’ll save 750,000 tonnes of CO2 being produced, at least by my calculations, is a complete lie, and the whataboutism explaining away the lower fuel efficiency (and therefore higher cost to operate your vehicle) is laughable. This could very easily have been discussed truthfully, including focusing on not burdening already increasing costs on those who are most likely to be struggling, and a push for more zero carbon solutions, not less. But hey, I’m an idiot on the internet, what do I know?