Biodiesel refers to a fuel created from natural, renewable sources, such as plants; which can be utilized in unmodified diesel-engine vehicles. Essentially, it's just vegetable oil.

Biodiesel is touted as one of the answers to our dependence on crude oil; but here's an interesting fact - it's been around for well over a hundred years. In fact, the inventor of the diesel engine, German engineer Rudolf Diesel, powered his creation originally with peanut oil. For some years afterwards, diesel engines ran exclusively on vegetable oil.

Diesel engines differ to gas engines in that in a gasoline engine fuel is mixed with air and the resulting vapors are ignited by a spark plug; whereas in a diesel engine air is compressed, heating it to a point that when the diesel comes into contact with it, it is ignited.

So what happened? How did the diesel engine wind up being powered by petroleum derived diesel?

In the 1920s, crude oil as a source of diesel became more popular as it was cheaper and in abundance. Here's the kicker - car manufacturers then needed to redesign diesel engines to make them more suited to the use of petroleum derived diesel. As a result, we wound up with vehicles that emitted more soot, carbon monoxide and other harmful emissions.

World diesel consumption in 1990 was 454,747 million litres (about 100 million gallons). In 2003, that had grown to 684,022 million litres. That's a massive jump. While biodiesel certainly presents a partial solution to diesel needs - it's not the entire answer. The real answer is a drop in consumption; something I fear that most of us won't accept too well.

My major concerns with biodiesel have been the amount of land needed to produce the fuel, the diversion of food to fuel purposes and price increases of our food as a result.

But even on this front great progress is being made with alternative cellulose sources being considered. For example, soy beans can generate 50 gallons of biodiesel per acre annually, but some species of algae can produce up to 8,000 gallons per acre!

For a very interesting article on the challenges posed by the increasing production of Biodiesel and possible solutions, read Biodiesel: Cultivating Alternative Fuels.

It's just a shame that Rudolf Diesel's creation wasn't continuously run on the fuel originally intended - we may have made a great deal more progress in biodiesel technology by now. If you're planning on buying a new car soon; perhaps you may want to consider a diesel engine so you can take advantage of this somewhat reincarnated alternative fuel source - you'll see it increasingly available in diesel blends in the years to come.