[EXCERPT: read the whole article here. -Ed.]

The ecology of the Thames changes as it passes through east London, on its way to the barrier and the North Sea beyond. As it enters the shadow of Barking power station - the 1000 megawatt colossus that supplies London with much of its electricity - excess heat pumped out by the station lifts the temperature in the river.

Ecologists may bemoan the impact on aquatic life, but for the Greater London Authority (GLA) there is a bigger environmental crime: the 400MW of heat flushed into the river is so great it would be enough to heat the equivalent of 120,000 new homes planned for the Thames Gateway over the next 15 years, according to Mark Watts, the mayor of London's senior adviser. Capturing it and distributing it to homes and businesses is what London intends to do as one of its first major actions to deliver Ken Livingstone's ambitious plan to cut London's carbon emissions by 60% by 2025. "To achieve the sort of carbon emission cuts that are necessary in London, we have to move from a society based on huge waste of energy to one that finds every available method to create energy without adding to carbon emissions," says Livingstone.

London is not alone in recognising that the UK's centralised system of transmission and distribution, with power produced at remote power stations, then distributed along power lines to homes, is inefficient and wasteful. Woking in Surrey is renowned for cutting carbon emissions by a breathtaking 77% through creating a network of 80 local generators, all independent of the National Grid. Woking could make the economics stack up, because one other thing the centralised system wastes in vast amounts is money: only 37% of a homeowner's utility bill actually goes to producing the energy itself.

The roll call of other cities that have dipped a toe in these waters, known as decentralised energy, is short, but interest by councils across the UK is strong. Department for Environemt, Food, and Rural Affairs last month stumped up £250,000 to help three major cities, Bristol, Leeds and Manchester, to develop climate change strategies that will take them down the decentralised energy road. And many other cities will be watching their progress. Michael King, associate director of the Combined Heat and Power Association, says: "A lot of local authorities are developing sustainable energy strategies rather than just the eco-bling of sticking up a few windmills."

Photo credit: Evan Leeson