German-owned RWE npower said yesterday it would take 30,000 tonnes of processed coppice willow annually from ESD Biomass, in a deal which would help it meet tough new rules on renewable energy.

Biomass is usually mixed in a ratio of ten per cent with low- sulphur coal and is seen as one way Britain could cut carbon dioxide emissions which are blamed for contributing to global warming.

The two firms said the pact represented a major boost for the embryonic biomass sector.

'This is the first time producers and a large energy generator have agreed a long-term relationship to co-fire specifically-grown energy crops within existing power stations, rather than making use of biofuels that happen to be around,' RWE npower spokesman Kevin McCullough said.

The agreement also represents an important new market for some UK farmers who are keen to diversify into new areas in the wake of recent EU agriculture reforms, the company said.

ESD Biomass spokesman Neil Bryson said his firm was now calling on growers to sign up to its new 'power plant contracts' so that supplies will be available in time - it takes three years for the willow trees to mature.

Several other UK power firms are testing biomass fuels such as wood chips, chicken litter and cereal pellets to generate electricity, including the country's largest coal-fired plant Drax, which is owned by a group of banks.

Environment experts say if the trial at one of Drax's six power units is successful, willow-based biomass could eventually provide five per cent of the power station's fuel by 2009 and cut out 700,000 tones of carbon dioxide emissions.

Worcester-based RWE npower, Britain's third biggest energy supplier, says it is merely planning ahead.

'By March 2009, generators will have to make sure that an increasing proportion of the biomass they use comes from purposely- grown energy crops including willow,' it said.