An Introduction to Bio-Diesel

We've all heard about the possibility of running diesel cars on old vegetable oil from your local chippie. It's true; it is possible in certain circumstances. Don't for a minute think that the fuel companies are trying to sell you used chip fat in the form of bio-diesel though; it's a very different thing.

While it is true that bio-diesel is produced from vegetable oils of animal fats (though it can be produced from a huge variety of sources), the 'feedstock' undergoes a significant amount of chemical processing (called "transesterification" if you must know) before it qualifies as a bio-diesel. Where as used vegetable oil is, well, oily, bio-diesel is much closer in its consistency to regular diesel made from fossil fuel sources.

You're likely to have seen bio-diesel for sale in a service station or two, as its availability is increasing, although it is still not as widespread as the government would like it to be. Nearly all modern diesel cars can operate on bio-diesel without modification, though owners should consult with the maker before taking the plunge.

Despite its relative scarcity, the concept of bio-diesel is not a new one. The inventor of the diesel engine, Mr Rudolph Diesel himself stated in 1912 that "the use of vegetable oils for engine fuels may seem insignificant today but such oils may become, in the course of time, as important as petroleum and the coal-tar products of the present time." That's quite prophetic given the focus on alternative fuel sources today.

Back in Mr Diesel's day, the production of bio-diesel was a more difficult (i.e. more expensive) process, so fossil fuel sourced diesel came to the fore. In recent times, the balance is shifting towards bio-diesel, especially given its positive impact on the environment.

Over the life of the fuel, emissions of carbon dioxide are greatly reduced, as, during the creation of the feedstock (i.e. the crop from which the oil is produced - usually rape seed or soya) carbon dioxide is extracted from the atmosphere. This part appeals to the government, with its tough targets for reducing the output of greenhouse gases. For that reason, small percentages of bio-diesel are often added to regular diesel by the fuel companies and many countries are in the process of requiring it by law.

Most other harmful exhaust emissions are reduced by the use of bio-diesel, except for oxides of nitrogen, and the fuel also has properties that help clean and lubricate an engine's internals. As a bonus, it should be possible to extract more performance from a modern turbodiesel unit optimised to run on bio-diesel, although cars must still be capable of running on regular diesel for the foreseeable future.

Like bio-ethanol, it is not yet conceivable that the world will convert to 100% bio-diesel use in the near future. There are concerns regarding the use of land for fuel instead of food. Saying that, there are many potential sources of bio-diesel, including waste products such as old tyres and even algae. There isn't enough waste vegetable oil in the world to go around though!

Thursday June 7