I AM afraid that Leo Enticknap and others have been sadly misled if they believe that hydrogen fuelled Nirvana is just around the corner.

Even if solutions are found to the problems of safely storing, transporting and using a colourless, odourless, highly explosive gas that requires extremely high pressures to liquefy, there is still the fundamental law of physics. This states that you cannot get more energy from burning hydrogen (to form water) than you put in to extract it from the water in the first place.

Unless that input energy comes from a renewable source hydrogen power is not "green". However it is a marvellous technology for absorbing vast quantities of research grants.

As for LPG I am afraid it isn't a "green" fuel - LPG is still a fossil fuel and is in finite supply, although producing lower levels of some pollutants. The reduction in carbon dioxide out of the exhaust pipe is around ten per cent.

However there is a renewable fuel which can be produced from crops grown in this country or from a waste product, can be used in a sizeable proportion of current cars with no modification, is available now and is widely used in Europe. Why aren't we all using this wonderfuel?

Because the Government still taxes rapeseed methyl ester at a higher level than even LPG.

More commonly known as biodiesel, I have been using it in my car for a year with no problems apart from availability. Although RIX produce a five per cent bio mix which is quite widely available, pure 100 per cent bio is only available from one outlet near York that I know of and they produce it from waste vegetable oil (see www.biodieselfillingstations.co.uk).

DJ Mitchell,

Main Street,

Alne,

York.

Updated: 11:04 Wednesday, October 27, 2004