Most cars run on petrol or diesel. Our favourite fossil fuels are cheap, convenient, relatively easy to store and transport, and readily available on every road and in every town across the developed world. But these aren’t the only fuels that will power an internal combustion engine. With a few modifications, you can run a petrol or diesel car on biofuels, wood, LPG, heating oil, or even second-hand cooking fat. You can power a car with pretty much anything.
In addition to the growing number of battery-electric, plug-in hybrid and hydrogen fuel cell cars on the road, there are plenty of good old-fashioned internal combustion engines running on something other than pure fossil fuels. The most common additive is bioethanol, which is routinely blended with unleaded petrol in small quantities for sale on forecourts around the country. But some people go one step further, and modify their cars to accept an increased amount of ethanol in their fuel mixture.
Everybody “knows” that Prince Charles had his Aston Martin converted to run on wine, but that’s a slight oversimplification. The Aston Martin in question was in fact modified to run on a fuel called E85, which is a mixture of bioethanol and petrol. Bioethanol, a biofuel and fuel additive, can be derived from a huge number of sources – including, but not limited to, waste biomass such as surplus wine.
What is bioethanol?
Think of a flaming sambuca. You can set fire to the ethanol contained in sambuca using a cigarette lighter, and a generous shot glass might burn for up to a minute before eventually spluttering out. This energy can also be used in more productive ways, such as heating a home, or powering a car; bioethanol as a fuel is similar to a flaming sambuca, except it’s got much more booze in it than anything you’d buy in an off licence, and nobody’s going to add a coffee bean.
We call it “bioethanol” to distinguish it from ethanol sourced from petroleum. Most bioethanol is produced from fuel crops or surplus biomass, which is fermented to produce alcohol, which is then isolated using distillation. Bioethanol is only useful as a fuel at these higher, concentrations – wine, at around 14 percent, won’t power an engine, but the pure ethanol contained within certainly can.
How does bioethanol work in a car?
If you drive a petrol car in the UK, it probably has a bit of bioethanol in its tank. Unleaded fuel sold in Britain might contain up to five percent bioethanol without you realising, an amount which won’t cause any compatibility problems with existing vehicles. This fuel is known as E5; that is, five percent ethanol, 95 percent petrol. By blending bioethanol into fuel mixtures, fuel manufacturers can, it is believed, significantly reduce the total carbon impact of their products.
E10 (ten percent bioethanol) is beginning to appear across the United Kingdom. This fuel is compatible with the vast majority of modern cars, though older models may struggle with it. According to the AA, a single accidental fill of E10 in a non-compatible car is unlikely to cause problems, but continued use might, and drivers of cars built before the year 2000 should speak to the manufacturer before starting to buy E10 or higher-ethanol fuels.
The concentration of ethanol in fuel increases incrementally all the way to E100, which is (in theory) pure ethanol. Very few cars are designed to run on alcohol alone, not least because it doesn’t work very well at low temperatures, so E85 (85 percent ethanol, 15 percent petrol) is a common compromise. Vehicles can be modified to run on this fuel, or manufactured as ‘flex fuel’ models which can be filled with either E85 or pure petrol.
Will using bioethanol save me money?
No. Not in Britain, anyway. The small quantities currently being added to conventional petrol are unlikely to have a substantial effect on the cost of motoring, and there are no incentives to convert a modern car to run on something like E85. High-strength bioethanol also incredibly difficult to find in the wild, with most being supplied for use in specialist racing cars at high prices. What’s more, it’s likely to cause wear and tear on engines and fuel systems at a faster rate than plain petrol. Oh and you'll use more of it, as bioethanol is less energy-dense than petrol.
Is bioethanol good for the environment?
In theory, the amount of carbon dioxide absorbed by these fuel crops as they are growing will mitigate the amount produced when biofuels are used in a car’s engine. It’s not as simple as that, though, and there are several other environmental issues associated with bioethanol usage and production. Some studies suggest that the quantity of carbon dioxide removed from the atmosphere by fuel crops is actually far less than what comes out of the exhaust, while other critics point to the environmental and food chain implications of devoting land to growing industrial crops.
Bioethanol can also be produced using waste biomass, as in the case of Prince Charles’ wine. But whether this represents a significant environmental gain over conventional petrol or diesel isn’t necessarily as clear as it seems; bioethanol, along with biodiesel and LPG, still needs to be combusted by an engine, and will still produce harmful emissions at the tailpipe. Converting a classic Aston Martin to run on E85 was arguably a step in the right direction, but this is far from the greenest car on Britain's roads.