Part two: Fuelled by alcohol
A blend of 5% ethanol with 95% gasoline (E5 blend) is sold as standard unleaded by major suppliers such as Tesco and blends of up to 10% (E10) will run quite happily in most unmodified car engines.
Higher percentages are far less widely available since they require changes to existing engines (e.g. for the 25% blends used in Brazil) or else specially designed engines such as those in flexible fuel vehicles (FFV’s) that can use 85% ethanol blend as well as normal petrol without any adjustment. All major car manufacturers are developing FFVs which are cheaper than hybrid cars.
The Ford FFV 1.8 Focus is only £350 more than the standard version, for example. The idea of flexible fuel vehicles is almost as old as the car itself since the 1908 Ford Model T was designed to run on gasoline or pure ethanol with only a simple adjustment to the carburetor.
In terms of its physical chemistry, ethanol, a two-carbon alcohol is quite different from standard petrol. It has a lower energy density and is less volatile which means it is difficult to cold start. An even bigger issue is that ethanol absorbs water causing it to be corrosive to pipelines, tanks and engines.
Pure ethanol therefore cannot be used in existing gasoline storage/transportation infrastructure which puts it at a major disadvantage to its nearest competitor – biodiesel.
Despite this, global production of bioethanol (over 20 million tonnes) currently far exceeds that of biodiesel. It should also be remembered that ethanol does offer other big advantages over standard petrol, not just in terms of its carbon neutrality, but also in terms of engine performance. It actually has a higher octane rating and better combustion efficiency than petrol: pure ethanol has been used in all US IndyCar races in the last few years.
The USA and Brazil account for most of the global production although these two major producers derive their bioethanol from different feedstocks. Brazil uses sugarcane which is fermented to ethanol by yeast in exactly the same process that is used to make wine and beer. In the USA the main source is corn grown on the vast plains of the Midwest which is first milled then converted into sugars by enzymes called amylases.
This is followed by the same yeast fermentation step as used for sugarcane. In both countries, the final fermentation broth is around 10% ethanol which is concentrated by distillation, as for vodka or whisky, although in this case all the water is removed to produce pure anhydrous ethanol.
A litre of bioethanol still costs more to produce than a litre of fossil derived petrol (anywhere outside Brazil at least) but future global demand will be driven by legislation rather than price. The European Union Biofuels Directive requires 5.75% of transport fossil fuels to be replaced with biofuels by 2010 rising to 20% in 2020. Ethanol blends in the US are subsidized by a 51 cents per gallon federal tax credit.
Recently, however, policy-makers enthusiasm for bioethanol has been tempered by criticism over the environmental and social costs of bioethanol production. Although the Brazilian government insists that mass cultivation of sugarcane does not lead to destruction of rain forest, there is no doubt that bioethanol feed crops compete with those for food. This has caused charities and the UK Environmental Audit Committee to call for a ‘rethink’ on the current policy of increasing biofuel consumption.
Weighing in on the other side of the debate is the fact that bioethanol offers the potential to reduce carbon dioxide emissions and global warming and also to leave the more of the planet’s dwindling oil reserves to be used as valuable chemical feedstocks rather than simply burnt for energy.
In the future, the food vs. fuel debate is likely to become irrelevant as soon as second generation bioethanol comes on stream. This will use genetically modified microbes to convert non-food sources such ligno-cellulosic materials (woods, grasses, agricultural wastes) into bioethanol.
Second generation bioethanol is some way off but there is very active research into creating the production hosts and processing routes to deliver the massive scale-up required. Another collaboration between global giants Dupont and BP is working to re-engineer microbes to produce bio-butanol – a longer chain alcohol that is more compatible with standard gasoline than bio-ethanol
Alcohol and driving don’t mix, we are frequently told, but in the future we could all – even the tee-totallers amongst us – be ‘consuming’ a lot more alcohol thanks to our love affair with the car.