Nearly 100 small vehicles in Oxford City Council's fleet will be partly run on cooking fat.

The authority has pledged to use biodiesel - the name given to a variety of ester-based oxygenated fuels made from soybean oil, vegetable oils or animal fats.

The idea is that vans will use five per cent blend of biodiesel with the regular fuel, reducing carbon dioxide emissions by three per cent.

Warranties dictate how much biofuel can be used at any time, but no engine conversion is required.

Using alternative fuels forms part of the council's 'green fleet' initiative.

The council used to have 18 electric vehicles, but now just has five.

Eventually, however, the authority's entire fleet could be run on electricity or hydrogen cells as technology advances.

Biodiesel is fast replacing liquid petroleum gas (LPG) as the preferred renewable fuel.

LPG, once at the cutting edge of renewable 'green' fuels, is now hard to find at garage forecourts and engine conversions are considered expensive - between £2,000 and £3,000 a time.

City council transport fleet officer Paul Einon said: "Oxford City Council is committed to running a green fleet, which means we chose the most environmentally friendly vehicles wherever possible.

"With modern technology always changing we needed to review our current policy and we are now looking to stock only biodiesel for use in the diesel vehicles currently on the council's fleet.

"The 90 diesel vehicles in our fleet will be able to use up to five per cent biodiesel. There is no cost implication as you can just add the biodiesel to the normal supply of diesel.

"I am aware one manufacturer produces cars and light vans which allow up to 30 per cent use of biodiesel which we will look into when we need to purchase vehicles."

Earlier this month the Oxford Mail reported how a successful five-month trial by Thames Travel, in which a single-decker bus was converted from diesel to run on soybean oil, could lead to its entire fleet being converted.

Experts think LPG will become a distant memory with advances in so-called fat fuel technology.

The concept of using vegetable oil as a fuel dates back to 1895 when Dr Rudolf Diesel developed the first diesel engine to run on vegetable oil.

Mr Einon added: "With the more common availability of higher blends of biodiesel in the future, the advantages of diesel can only be magnified."