Biodiesel is seen in some circles as a positive environmental solution - an alternative fuel that can reduce emissions and help motorists achieve their objective of green driving. However, others deem it a questionable solution and suggest its advantages are outweighed by its environmental impact.

This guide to biodiesel will examine both arguments.

What is biodiesel?

Biodiesel is a non-petroleum based diesel fuel. Typically this is made from vegetable oils or animal fats which can either be used alone or blended in with conventional diesel in a diesel engine. Usually biodiesel is derived from plant oils including rapeseed oil, palm oil and soybean oil.

The extent to which it is blended in depends on the bio-matter within the mixture. This can be as little as five per cent bio-matter with 95 per cent fossil-diesel (B5), a typical average of 30 per cent bio-matter and 70 per cent fossil-diesel (B30), all the way up to 100 per cent bio-matter (B100).

In 2008, the UK Government issued a directive stating that at least 2.5 per cent of all road transport diesel must be biodiesel. This will increase to five per cent in 2010. This is known as the Renewable Transport Fuel Obligation (RTFO).

The advantages of biodiesel

Potentially biodiesel offers significant CO2 savings as it greatly reduces emissions. The UK Government estimates that 2.5million tonnes of CO2 will be saved by 2010 thanks to the 2.5 per cent RTFO introduced in 2008. In the United States, biodiesel is the only fuel to have completed the Health Effects Testing requirements implemented by the Clean Air Act of 1990.

Biodiesel also has the advantage of being readily available and does not require any changes to the current refuelling infrastructure in order to be implemented on a wider scale.

The disadvantages of biodiesel

The main issue with biodiesel is that cultivating crops for its production can upset or destroy natural habitats. It is also feared that it is causing an imbalance in developing countries that are growing the crops rather than producing sustainable food. Friends of the Earth criticised the deforestation for biodiesel and oil companies have vouched to produce biodiesel from sustainable sources.

It’s also difficult to quantify the CO2 produced by biodiesel as it is necessary to take into account the cost of growing the crop, transportation and its processing costs. It is questionable therefore as to whether biodiesel is really a long-term environmental solution.