Expert View: Five ways to clear the air as fossil fuels march on

All predictions of world energy demand suggest rapid continued growth. The International Energy Agency, one of the more sober forecasters, sees it rising more than 50 per cent by 2030. Over four fifths of the increase is expected to come from the use of fossil fuels. According to the IEA, carbon-based sources will be responsible for more of the world's energy in 2030 than they are today.

But it would not be right simply to point the finger at China and India for the march of fossil fuels. Despite the high carbon emissions from burning coal, the US has plans for as many as 150 new coal-fired power stations, and Germany for another 26. Renewable sources are not keeping pace with the apparently inexorable rise in world energy use.

For a moment, let's be optimistic. I believe there are five carbon-reduction technologies with a reasonable chance of becoming financially viable. Don't expect instant success, but they all have the potential to cut fossil-fuel use at little or no extra cost.

Advanced, thin-film solar panels. Today's photovoltaic cells are expensive and relatively inefficient at turning light into power. They use huge quantities of silicon and the electricity they generate probably costs four times that of coal stations. The next generation of thin-film solar panels will be very different. Within a few years, bendable panels little thicker than a sheet of paper will be laid as a membrane over large roof areas. The cost of solar energy may fall to roughly the same level as fossil-fuel power, at least in sunny countries.

Cellulosic ethanol as a substitute for petrol. Around the world, governments are demanding that a growing proportion of motor fuels comes from biological sources. Here in the UK, sugar beet is used to create ethanol, a substitute for petrol. In the US, maize performs a similar function. So far, the results have been disappointing: bio-ethanol is expensive to make, saves little carbon and forces up the price of food as the raw material is diverted to the refineries. Cellulosic ethanol is different, using organic waste materials such as stalks, leaves, even wood. It reduces CO₂ much more than conventional bioethanol. But breaking down the cellulose into simple sugars is hard. Only in the past year have we begun to see progress that suggests we will one day be able to produce ethanol at a competitive price.

Carbon capture. This is the ultimate prize. If we can find a technology that cheaply captures the CO₂ coming out of power stations, the planet may have a chance. So far, European energy companies have been more willing to talk about carbon capture than they have to invest. But last month a large US electricity producer committed to a full commercial trial of technology developed by the French giant Alstom. Unlike its European peers, the American company appears to be prepared to invest in carbon capture without state handouts.

Algal biodiesel. Simple algae contain a high proportion of oil. CO₂ helps these algae to grow quickly and is absorbed in the process. So an algae farm attached to a power station may be able to capture carbon and produce a valuable fuel at the same time.

Power from tidal currents. This ought to be easy: tides are smooth, predictable and contain huge amounts of energy. So far, pro-gress has been slow - building installations that survive harsh saline environments is hard. But in the past few months, power producers have begun to place orders with some of the innovative manufacturers building simple, reliable tidal generators.

None of these technologies has yet proved it can replace fossil fuels cheaply and effectively. All look promising, but it will be several years before we know how cost-effective they are. Disturbingly, you will look hard to find any British businesses at the forefront of these technologies. UK engineering firms don't seem focused on the vital challenge of ensuring that the growth in world energy use doesn't mean an acceleration in carbon emissions.

Chris Goodall's 'How to Live a Low-Carbon Life' is published by Earthscan. c.goodall@which.net