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An Introduction to Ethanol-Fuelled Cars

There is understandably some confusion amongst the general population regarding alcohol-based fuels. Britain is fairly late to the game, with our newfound awareness of the creation of greenhouse gases, but some countries have been using them extensively for years. Brazil for instance, boasts a fleet of new cars of which 80% can run on any combination of alcohol-based fuel or traditional petrol.

This perhaps is where some of the confusion lies. In Europe, bio-ethanol is usually sold as E85, a name which indicates that the fuel contains 85% ethanol, with the remainder petrol. In fact, the ethanol should be referred to as bio-ethanol, as it is obtained from biological sources (i.e. plants).

There are several terms used to denote a vehicle that can run on a combination of alcohol-based fuels and petrol. The car makers have their own names for these vehicles. The most common are flex or flexi-fuel vehicles (FFVs). So what's the point?

To understand why bio-ethanol is gaining popularity as a vehicle fuel, we need to look at what its advantages are. First up, an engine can run at a higher compression ratio if running on ethanol thanks to a higher effective octane rating. Admittedly that's no good for an engine that must also reliably run on petrol, but it does mean that engines with advanced valve control and knock sensing can run higher effective compression ratios and more spark advance while running on ethanol. There is the potential for a significant increase in performance, especially in a supercharged or turbocharged engine.

Due to the chemical make-up of ethanol, the amount of carbon monoxide and oxides of nitrogen produced when burning ethanol are significantly reduced. The reduction in the emission of carbon dioxide ('greenhouse gas') is negligible, but the argument is that CO₂ is extracted from the environment in growing the crops to produce the fuel in the first place. The car makers talk about the 'whole life' of the fuel as a net reduction in carbon dioxide.

There are plenty of downsides too though. In practical terms, engines require modification to allow optimal running on ethanol, while the lower energy density of the fuel means that an engine uses more of it over a given distance. At present, there are not enough filling stations around the country to allow owners make full use of the fuel, but the situation is changing. That said, the current production method for bio-ethanol requires huge swathes of land to produce the crop and it will never be practical to switch all of the world's vehicles to the fuel until an alternative production method is found. Mark my words though; it's being looked into.

Tuesday June 5

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