It sounded like the perfect answer. Carbon trading could halt global warming, boost 'green' investment in the developing world and make money for city traders. Four years on and Europe's complex system to cut emissions from our factories has comprehensively failed. Despite vast amounts of money and effort being thrown at the scheme the current phase of carbon trading has, according to one report, cut emissions by a third of one per cent. In 'Costing the Earth' Tom Heap asks if capitalism's big idea has a future or just a murky past.

Back in the 1990s, in a desperate attempt to get the United States to sign up to binding reductions in the emission of greenhouse gases the concept of carbon trading was developed. The idea was that polluting industries would be forced to buy the right to pollute in the form of carbon credits. If they wanted to pollute more they'd have to pay. If they polluted less then they could make a profit by offering their surplus credits to other businesses. Over time the number of credits would be reduced, bringing worldwide carbon emissions tumbling in a relatively pain-free way.

The truth, as Tom discovers, is very different. The US has refused to take part, Japan and Korea have shelved plans to join in and the issue splits the Australian government. Only in the European Union has a system been developed and even here corruption, theft and a vast surplus of credits have combined to damage the policy's reputation and blunt its effectiveness.

Despite doubts about the system it's influence is spreading fast. Many businesses are using a system of voluntary carbon off-setting to ease the conscience of their customers. Buy a flight or a 4 x 4 and you'll often be asked to pay a little extra to fund carbon-reduction schemes in the developing world. Closer to home the idea of habitat banking is gaining ground. This could give developers the chance to build on a wildlife-rich area as long as they pay to create the equivalent habitat elsewhere. It's a concept that's popular within the coalition government and supporters expect it to become a major part of conservation policy in England within the decade.

Should we worry about this commodification of our environment or embrace the arrival of money and markets into the campaign to save our planet and improve the green space on our doorstep?