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Erica Sullivan
Research Assistant Bilingual
Asked a question last year

E10 petrol more environmentally friendly than E5? The higher ethanol content means less energy in the fuel, so drivers can expect to see a reduction in their MPG. This will result in drivers using more fuel. Will this mean more or less emissions?

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E10 contains up to 10% Bio ethanol as opposed to E5 which is up to 5% bio-ethanol.

It might be expected that bio ethanol is carbon neutral: i.e. the carbon is absorbed when the source is grown and emitted when burnt. However energy is used to produce bio ethanol, farming it fertilizer, harvesting, processing, transport: I have not seen a recent paper in 1995 it came out at between 138% and 262% output for energy input: depends on the source crop, method of farming and other products: would be interesting is someone is able to provide genuine more up to date figures. Of course energy also needs to be input to produce petrol: extract, transport, refine Petrol (gas) but I could see any comparable analysis on percentage return: but again this would be a range depending on source, refining process, transport.

E10 will produce some reduction in Carbon Monoxide and particulate matter but it is still 90% petrol.

Apparently there would be a small reduction in MPG but overall there is a reduction in CO2 emissions. Some older cars may not be able to run on E10: in UK all cars manufactured from 2011 can run on it but some pre 2011 cars may not: if UK E5 will still be available.

E10 petrol is already widely used around the world, including across Europe, the US and Australia. It has also been the reference fuel against which new cars are tested for emissions and performance since 2016.

It has been widely adopted and I have no doubt it is based on detailed analysis so I would have to assume it is environmentally more friendly but it is still 90% petrol.

An electric vehicle of course uses no petrol and produces no tailpipe emissions although the reduction on CO2 will depend on the source of the electricity.

Bio fuels may well be part of the future balance of transport but EVs seem to be the way forward as the mainstream for private cars as to seek to 100% replace petrol with 100% biofuels would result in competition with food production or alternatively further loss of natural habitat: it does not make environmental sense to cut down rainforest to grow a crop for fuel.

Looking at the environmental impact of biofuels is a complex area. I understand some biofuels can be produced from what would otherwise be waste from food production which is clearly the best option: but I would have thought the volumes would only allow for a small percentage of vehicles to run on biofuels: perhaps some of those where battery is not practical.

Would be interesting to hear from someone who really has experience in bio fuels.

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