The pressure is on for car manufacturers to produce and people to buy vehicles that either consume less fossil fuel or even none at all. Climate change and a looming oil shortage are forcing the environmental and monetary price of old driving habits through the roof.

The British parliament is debating its pioneering Climate Change Bill. The EU is discussing its controversial proposal that 10 percent of road fuels within the EU zone should be biofuels by 2020. The UK government wants the CO2 emissions levels of new cars to average 100g/km by 2020 and will seek EU support for this aim
The UK government wants the CO2 emissions levels of new cars to average 100g/km by 2020

From October 2008 London will exempt vehicles emitting up to 120g/km of CO2 from paying the capital's congestion charge while charging owners of vehicles emitting more than 225g/km £25 (about R400) a day.

And, by 2010, first year road tax for cars emitting more than 225g/km will be £950 (R15 350) while cars emitting up to 130g/km will gain a 12-month exemption.

While drivers consider their options, automakers are starting to produce vehicles that are, or could be, less damaging to the planet than their predecessors.

Old cars can, mind you, be relatively green. The longer you keep a car, the lower the CO2 impact of its manufacture. Our best hopes, however, lie with state of the art and future cars frugally propelled by fossil fuels or powered by electricity, hydrogen and hybrid combinations.

First-generation biofuels can be very damaging to the environment and, while some argue the case for second and third generation biofuels, the jury is out on their overall environmental impact.

Sadly, automakers' claims about how eco-friendly their creations are can be misleading. Tiny electric cars and swanky bioethanol sportsters alike are constantly, wrongly, described as "emissions free".

How do you know whether a "zero emissions" electric car produces more or less CO2 at the power station than a hatchback? How do you rate hydrogen against bioethanol?

Until the manufacturers (with the honourable exception of Reva, maker of the G-Wiz) produce breakdowns of the ultimate greenhouse gas emissions from all alternative fuels, knowing what is the best and most environmentally friendly vehicle won't be straightforward.

One day a large share of our electricity may come from renewables, making calculations simpler for vehicles powered by electricity or hydrogen which is produced either from fossil fuel or by using electricity to extract it from water. But, for the immediate future, most electricity will continue to be generated using fossil fuel.

So, here's a greenwash free look at what's available, and at some of the exciting future models that could give the planet, and us, breathing space.

LOW-EMISSIONS CARS

Polo BlueMotion 1.4 TDi, Toyota Aygo, Mini Cooper D, Seat Ibiza Ecomotive, Citroën C1, Peugeot 107, Smart ForTwo, Ford Focus Econetic

How does it work?

Small, light cars yield 99g/km CO2 for BlueMotion and Ecomotive; each is under 120g/km.

How green is it?

Pretty green. Petrol and diesel cars convert fossil fuel to power more efficiently than electric cars charged from the grid.

Pros and cons

No road tax, no London congestion charge from October 2008 but diesel produces dangerous hydrocarbon particulates. Super exhausts help take care of this.

Can I buy one?

Yes. Polo BlueMotion from £12 120 (R196 000); Toyota Aygo from £6945 (R112 000); Citroën C1, £6990 (SA price R89 995); Peugeot 107, £7195 (SA price from R89 900); Seat Ecomotive to launch in April 2008, Econetic follows.

THE ALL-ELECTRIC CARS

G-Wiz, Piaggio Porter MPV, Nice Mega City Car.

How does it work?

Electric motor powered by batteries that are recharged from the mains.

How green is it?

Very, potentially. Zero on road emissions, but the G-Wiz generates 63-66g/km CO2 at the power station.

Pros and cons

Cheap insurance. Free charging points in London. No road tax or congestion charge. Electricity from the equivalent of 10-16c/km but range is limited.

Can I buy one?

Yes. G-Wiz, £8895 (R144 000); Piaggio Porter MPV, £18 794 (R304 000); Nice Mega City, £10 847 (R174 000); Mega City, £11 347 (R183 000).

HYDROGEN COMBUSTION CARS

BMW Hydrogen 7.

How does it work?

Dual fuel vehicle burns hydrogen or petrol with no loss of performance. BMW is using this fast, 195kW V12 flagship muscle car to sell hydrogen combustion.

How green is it?

Hydrogen is made from fossil fuel or from water by using electricity, thus releasing CO2. There isn't yet enough "green" electricity to power a worldwide hydrogen-based transport industry.

BMW claims this car is "virtually emissions free" at 5g/km CO2 (when running on hydrogen) but a figure including CO2 from hydrogen production would be higher. Using petrol, it's a 332g/km beast.

Pros and cons

Main on-road emission in hydrogen mode is water vapour. It can go for 200km on a tank of hydrogen and up to 700km with petrol but burning hydrogen gives off smog producing nitrogen oxides and you might be waiting some time for hydrogen at your local garage.

Can I buy one?

No; you wait for BMW to invite you to have one of only 100 Hydrogen 7 units on loan. Brad Pitt is among the chosen.

FUEL- CELL CARS

Honda FCX Clarity.

How does it work?

A hydrogen fuel cell generates electricity by splitting protons from electrons. The waste product is water. A tank of hydrogen feeds the 100kW cell.

How green is it?

Depends. Fuel cells guzzle hydrogen more efficiently than combustion and are zero-CO2 on the road – but how is the hydrogen produced?

Honda claims that, all in, the Clarity produces "less than half" the CO2 of a conventional car. Recapturing power from braking is very eco. Honda claims a 4.2 litres/100km energy equivalent.

Pros and cons

Goes 430km on one tank of hydrogen. Zero CO2 on the road - but there's no hydrogen supply infrastructure.

Can I buy one?

The Clarity will be leased to a few Californians later in 2008.

'SERIES' OR 'PLUG-IN' HYBRIDS

Opel Flextreme, an MPV-style electric concept car.

How does it work?

It has an electric motor powered by lithium-ion batteries and a turbodiesel generator to recharge the batteries when the car is moving. Or plug it in. The electric motor propels the car, the diesel unit is not connected to the wheels.

How green is it?

Very, on paper. GM claims it would emit about 40g/km CO2 half that of the greenest diesel, the Smart ForTwo. Electric motors are highly efficient and the diesel generator can spin at optimum revs.

Pros and cons

Goes 50km on the battery; then use the generator for up to 700km. Should save you a lot at the pumps. Video cameras and widescreen display instead of rear view mirrors but try explaining to the AA man that the diesel isn't connected to the wheels...

Can I buy one?

Not until GM is happy with the battery but you can watch the Flextreme in simulated action at www.youtube.com/watch?v=kMv-DOznBe8.

BIOETHANOL CARS

Saab 9-5 2.0t BioPower, Ford Focus and C-Max Flexifuel, Volvo C30 1.8F SE Sport.

How does it work?

Bioethanol vehicles use an internal combustion engine and run on various ratios of bioethanol/petrol, or just petrol. E85 fuel is 85 percent bioethanol, 15 percent petrol hence its name.

How green is it?

Jury's out. Some "first generation" biofuels can, taking all effects into account, create higher CO2 emissions than fossil fuels. Bioethanol is less potent than petrol, so fuel consumption is higher.

On the road, the Ford Focus Flexifuel produces 169g/km CO2, the Volvo 168g/km. These figures may be reduced by fuel crops "fixing" CO2 but by how much, after all impacts are considered, is highly debatable.

Pros and cons

Reduced road tax but E85 is only available at some branches of Morrisons supermarkets.

Can I buy one?

Yes. Volvo C30 1.8F SE Sport, £19 295 (R312 000); Saab 9-5 2.0t BioPower, £26 710 (R432 000); Ford Focus Flexifuel, £14 435 (R233 000).

PETROL-ELECTRIC HYBRIDS

Honda Civic hybrid, Toyota Prius, three Lexus models.

How does it work?

Petrol engine is coupled to a generator, battery and electric motor. Electric motor assists petrol engine or can take over from it. There's no plug; the electric charge comes from braking and deceleration energy. Complex engineering controls couple the power sources.

How green is it?

Not bad. Civic Hybrid emits 109g/km CO2, the Prius 104g/km, in government tests that play to their strengths, especially in urban cycle. On the road, the figure would be 135-155g/km, based on the fuel consumption figures obtained by reviewers. Lexus GS 450h emits 186g/km, but it's an executive cruiser.

Pros and cons

No London congestion charge but the engineering increases the cars' weight and the CO2 impact of their manufacture.

Can I buy one?

Yes. Civic and Prius, from £17 775 (R287 000 Prius SA price 269 000); Lexus GS 450h, from £39 965 (R645 000). The Independent, London

By Nigel Pollitt

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