The decision was immediately attacked by the local council and MP. People living around the huge, 2,400 megawatt Drax plant near York are concerned about the plans to burn 30,000 tonnes of petroleum coke, or petcoke, this autumn.
Its owner, National Power, says it has to find cheaper ways of running Drax; petcoke could be a solution. As a waste product it costs less than coal mined nearby which feeds the station.
But petcoke is substantially more polluting than coal. It contains higher levels of sulphur, which causes acid rain, as well as higher levels of nickel - a potentially hazardous heavy metal - and the rare element vanadium which irritates the lungs and throat.
During the trial the fuel would be mixed with four times as much coal, then consumed in one of station's six burners.
Drax is Europe's biggest coal-fired power stations, and cleanest, because it has pounds 640m worth of anti-pollution equipment. This removes nearly all the sulphur dioxide produced when coal is burnt.
But maintaining this complex equipment adds to its running costs by up to 10 per cent, according to National Power. So Drax is at a disadvantage compared to gas, nuclear and other coal-fired power stations.
The result is that a station built to run continuously at full power is being closed down for more and more hours during periods of low electricity demand when it cannot compete.
``Western Europe's biggest power station is being forced slowly out of business, slipping down the merit order,'' said a National Power spokesman.
The company insists that far from substituting for British coal, petcoke might offer the few remaining mines a more secure future by helping keep Drax running for longer hours.
But John Grogan, Labour MP for Selby, said: ``It is economic and environmental madness to trial burn a dirty by-product of American oil refining rather than the much cleaner Selby coal.''
Petcoke is burnt in some British cement and lime kilns as well as being mixed in with some household coal. A few power stations in Europe and the USA already use it. The fuel is difficult to ignite but burns at a very high temperature.
National Power said there would be no substantial increases in pollution from Drax during the trial, and since it had the pollution-curbing equipment it was the best power station for petcoke. Emissions will be carefully monitored in cooperation with the Environment Agency, which will also examine the environmental threat posed by the station's ash which will contain raised levels of nickel and vanadium.
If the trial is a success then National Power is expected to apply to the agency for permission to burn petcoke permanently at Drax - although it will always be mixed with coal.
Selby District Council's deputy chief executive Mike White said he had not yet received assurances that the trial would be properly monitored. ``We're very disappointed,'' he added. The Environment Agency said burning petcoke at Drax could be of environmental benefit if it helped the power station out-compete other, dirtier coal-fired stations.