Fuel types: the pros and cons

Ethanol

For: Ethanol's main attraction is its renewability. It is made from corn and grain, which can be regrown, unlike oil. Researchers at the University of California estimate that replacing petrol with ethanol will reduce greenhouse gas emissions by 13 per cent. Ethanol also produces up to 50 per cent fewer smog-forming emissions than petrol. The growing of crops has a carbon offset effect, as the plants absorb carbon dioxide (CO2) from the atmosphere while they grow. Ethanol can be produced by non-edible crops such as grass and wood.

Against: Corn and grain are food sources, which raises the ethical question of using them for fuel while children are starving. Ethanol production also creates its own greenhouse gas emissions; farmers drive diesel tractors and electricity is used in the refining process. Ethanol production also requires plenty of water - another scarce resource. Ethanol fuel contains less energy than petrol, which means you need more of it to travel the same distance you would using petrol. Experts estimate that fuel economy can be 20 to 30 per cent less than petrol.