The fuels of tomorrow

Worried about the greenhouse gases your car pumps out? Sustainable energy is the future, but what's available? Meg Carter reviews the alternatives to petrol




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.


1,400 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. "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.


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. "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."



Bioethanol and biodiesel are green fuels made from grain, rapeseed and vegetable oils. 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.


E85 - a mix of 85 per cent bioethanol and 15 per cent petrol - is already available in parts of the UK, including Somerset. A pilot scheme was recently launched in Shropshire, where seven independent petrol stations now sell B5 biodiesel produced from rapeseed or vegetable oil. 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.


For the time being, bioethanol is more expensive than petrol because of the cost of producing and distributing it. Also, as most petrol stations are owned and operated by the oil industry, they have little interest in selling it. 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. 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.



Every bit of organic matter on Earth will eventually rot, generating methane (below right). 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. Scientists are currently exploring ways of converting methane into fuel for use in transport.


Nowhere in the UK, yet. 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. In Sweden, meanwhile, a number of passenger trains now run on methane extracted from the entrails of dead cows slaughtered for food.


"Converting organic waste into fuel is an elegant and sustainable solution," says Burge. "However, biogas is a local fuel - it's most efficient to use close to where it has been generated, as moving it around the country is costly and may, in turn, damage the environment."



Cars fully powered by electricity sounds like the ultimate green transport solution - plug them into the mains overnight, and away you go!


A small number of electric cars are now on the market, including the G-Wiz - a two-door hatchback created by the Reva Electric Car Company. Motorists are being offered free parking in Westminster and the City of London, and a congestion charge waiver, as an incentive to buy electric vehicles.


Fully electric cars cost almost twice as much to buy as standard vehicles. And although they produce no emissions they're only as green as the electricity used to power them, says John Roberts, director of the consultancy Arup Energy. "Arguably, their biggest limitation is their range [typically, they run out of juice after 50 miles] and the weight of the battery," he adds. That said, a new generation of electric cars is in the pipeline with Nissan and Mitsubishi due to launch models in the near future.



Hybrids are powered by a combination of electricity and petrol. Car-makers claim they are greener than standard vehicles because an integrated electric motor helps the engine by boosting it during acceleration, improving fuel economy. The electric motor also runs the car when stationary to minimise emissions, and the battery that powers this motor charges itself up with energy recovered during deceleration.


The Toyota Prius and the Honda Civic are two of the best-known hybrids currently on the road. BMW, Peugeot and Citroën also have comprehensive development programmes for hybrid electric and petrol, and electric and diesel, cars.


Confusion over what constitutes a hybrid is widespread. Half of British drivers think the term refers to two cars that are welded together, according to a recent UK consumer survey for Honda. Moreover, many experts question just how green hybrids really are. "Essentially, hybrids are a fuel-saving device," Burge claims. "They can be pleasant to drive - quiet, and smooth - but they're still basically driven on petrol and struggle to better the efficiency of the latest diesel models."



Hydrogen-powered vehicles typically run on a fuel cell (which is a bit like a battery) in which hydrogen mixes with oxygen to produce water - a process that creates electricity, which in turn powers an electric motor. Although water vapour is the only emission, how the hydrogen is made in the first place is a more realistic indicator of whether hydrogen can be called a truly green fuel. Hydrogen can be made in a number of different ways including electrolysis - the splitting of water into hydrogen and oxygen. It is then cooled to turn it into liquid hydrogen, which is distributed in pressurised cylinders.


Honda is one of a number of car-makers developing hydrogen-fuelled vehicles. Its FCX model is currently being piloted in Japan and the US, where the Spallino family of Redondo Beach, California recently took delivery of the first hydrogen-powered fuel cell car in private use. Closer to home, a two-year project in London involving single-decker buses powered by hydrogen fuel cells recently ended.


"This technology is new, and we're ahead of the game," Honda UK environment manager John Kingston claims. Even so, you'll have to wait a while before you can buy one. "Cost is a major issue," he admits. "Without an established infrastructure to distribute hydrogen fuel, investment by car-makers will be limited. And until more models are produced, production costs will make cars like this prohibitively expensive for most people to buy."



Typically, a much of the energy released when petrol is burnt is lost through a car's exhaust system as heat. BMW, however, promises its Turbosteamer will cut the amount of energy lost by 80 per cent, by ensuring energy from exhaust gases is used to power a steam engine which in turn powers the car.


Nowhere, yet - it's still at the test stage. However, the plan is that eventually the Turbosteamer could be fitted to all BMW models.


"The BMW system is a clever way of recovering energy that would otherwise be lost," says Burge. "But this is still a petrol-driven car."



Solar energy seems an unlikely form of car fuel - not least in cloudier climes. Yet car-makers have been experimenting with solar power for a number of years. In 1993 the Honda Dream won the World Solar Challenge, crossing from Darwin to Adelaide using only the power of the sun. Today, manufacturers are continuing to look at ways of incorporating solar panels into car design.


Nowhere, yet. But Ford's recently announced plans for the new Reflex include solar-powered headlights.


"Solar panels to power lights is all fine and well," says Roberts. "But it won't solve the problem of what's the greenest alternative fuel. The future won't be about just one solution, but a combination of many."

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