In Sweden, meanwhile, a number of passenger trains now run on methane extracted from the entrails of dead cows slaughtered for food. However, car designer Christopher Maltin, the British pioneer of unleaded petrol, has developed a system to convert organic waste into fuel, and recently showcased a car powered by manure which pumps out only water and carbon dioxide. Scientists are currently exploring ways of converting methane into fuel for use in transport.WHERE CAN I GET ITNowhere in the UK, yet. When released into the air, methane that traps 20 times more heat than carbon dioxide, but when burned, it releases up to 25 per cent less carbon dioxide than the combustion of the same mass of coal, and does not emit the nitrogen and sulfur oxides known to damage the environment. ORGANIC WASTE WHAT IS IT? Every bit of organic matter on Earth will eventually rot, generating methane (below right).

Despite this, a number of supermarket petrol stations now sell petrol containing 5 per cent bioethanol as standard – a practice expected to spread as the Government works to meet its 2010 renewable-fuel target. Another concern is whether there is enough grain, rapeseed and vegetable oil to produce the volumes of bioethanol and bio-diesel needed to make these green fuels a viable alternative to petrol. Also, as most petrol stations are owned and operated by the oil industry, they have little interest in selling it. REALITY CHECK For the time being, bioethanol is more expensive than petrol because of the cost of producing and distributing it. Ordinary cars are capable of running on a mix of 95 per cent petrol and 5 per cent bioethanol or biodiesel, without any modifications. To move beyond 5 per cent, however, an engine must be modified, which essentially means replacing rubber seals and aluminium parts with materials not eroded by bioethanol.

A pilot scheme was recently launched in Shropshire, where seven independent petrol stations now sell B5 biodiesel produced from rapeseed or vegetable oil. They produce 65 per cent fewer greenhouse-gas emissions than petrol because carbon emissions during production and consumption are almost equal to the amount removed when the crops from which they’re made are grown, according to the UK government agency, the Central Science Laboratory.WHERE CAN I GET ITE85 – a mix of 85 per cent bioethanol and 15 per cent petrol – is already available in parts of the UK, including Somerset. “But at around a third of the price of petrol per litre, most people choose it because of its cost – which is why it’s so popular in countries like Turkey and Poland.” GRAINS & VEGETABLE OILS WHAT IS IT? Bioethanol and biodiesel are green fuels made from grain, rapeseed and vegetable oils. REALITY CHECK Although LPG produces less carbon than petrol, its emissions exceed those of “greener” fuels, and recent Government plans to set future fuel duty to reflect fuels’ impact on the environment have prompted car-makers to switch their attentions elsewhere.

“People like the feel-good green association you get with LPG,” says alternative fuels consultant Jo Burge. “Bi-fuel” models able to run on LPG or petrol are also now available, or you can pay around £500 to have your petrol engine converted to run on LPG. Research is linking a sharp decline in the population of the ring ouzel, a close blackbird-relative which lives on cool mountain tops and high moors, to rising atmospheric temperatures.. LIQUID GAS

WHAT IS IT?
Liquified Petroleum Gas, or LPG, is currently the most widely available “green” alternative to petrol. Although a fossil fuel, LPG is a bi-product of petrol which, for many years, oil companies simply “flared off” from oil rigs. It was endorsed by the UK Government in 2001 because of its lower carbon emissions.WHERE CAN I GET IT1,400 UK petrol stations now sell LPG and, encouraged by Government support for the fuel, a number of car-makers, including Toyota, have launched LPG vehicles in this country.