Over the last two weeks, Stuart Milne has been looking at green fuels and the cars that run on them.

In this, the final instalment, he has spoken to leading industry experts to find out whether bio-ethanol is a bona fide fuel of the future or a load of old fizz.

We certainly opened a can of worms over the last few weeks, and many of you wrote in to tell us what you think on the subject.

Tim Pearce was just one reader who thinks that a wholesale switch to bio-ethanol could spell disaster for the world's ancient, carbon-consuming rainforests. He told us: "I don't think biofuels are going to be all that green in the long term. In fact they may end up being just about the most destructive fuel ever."

This is a point echoed by the leading biologist, Jeffery Duke who said in 2003 that if the fossil fuels we burn were made from crops - to create biofuels such as bio-ethanol - we would use four centuries worth of plants and animals.

So, what do the policy makers and lobby groups think?

The Department for Transport is satisfied that their processes will ensure that there is a balance between the benefits of using biofuels and avoiding mass deforestation. According to a DfT spokeswoman: "The Government will ask the oil companies for reports on carbon saving and sustainability. We don't want to solve one problem and create another.

"The Renewable Transport Fuel Obligation will ensure that 5 per cent of all fuels will be renewable. That will remove 1 million tonnes of carbon dioxide; the equivalent of removing 1 million cars from the roads."

The use of biofuels must be integrated, said a spokesman for the Society of Motor Manufacturers and Traders. "Bio-ethanol is proving to give excellent benefits over the well-to-wheel emission cycle of the vehicle. The current UK trials are using a range of locally-produced bio-product for turning into the fuel. This demonstrates the industry's desire to see sustainable generation of the fuel.

"But this must be part of an integrated approach. All those involved in the process - agricultural industry, fuel providers, UK and European governments, the motor industry and motorists themselves - must all join together to make sure that the fuel we use is sustainable in its generation and use."

Jim Footner, energy campaigner at Greenpeace is more hesitant: "We see bio-ethanol as a useful interim measure, but to bring it to mass market, we would need to cover the planet with biofuel-producing crops.

"It could be possible to fuel Britain's cars with UK-produced materials, however the energy needed to ship ethanol from abroad will negate the carbon dioxide savings.

"The Government is using bio-ethanol as a flagship tool. It will make a small impact, but it's a tiny drop in a big ocean - and we're already drowning. We need to stop driving so much."

At face value, policy makers and lobby groups' positions on bio-ethanol are predictable; but it is clear that switching to ethanol is not the solution to all our problems.

It needs to be combined in a package of measures which includes affordable and reliable alternatives to the car.

Unless the Government spends the cash to create suitable infrastructure; motorists are not going to get out of their cars; green fuel or no green fuel.

And taxing them off the road won't help either.