The UK's biggest power station is to start an 18-month trial to burn the controversial fuel petroleum coke.
Campaigners fear the new fuel will lead to health problems
Drax power station, near Selby, North Yorkshire, was given permission to burn a mix of petroleum coke and coal by the Environment Agency last year.
The Agency will be monitoring pollution levels in the air during the trial.
Friends of the Earth would prefer the fuel not to be used but said it would wait and observe the results of the trials before commenting further.
Drax power station, which produces almost 10% of the electricity in England and Wales, has had £1m of modifications for the trial.
The plant will burn a mixture of coal and up to 15% petroleum coke (petcoke), an oil-based fuel which is a by-product of the petroleum industry.
The fuel has been linked with health and environmental problems because of its sulphur content.
Peter Emery, Drax production director, said: "We are fully aware and appreciate all the concerns expressed by interested parties in the run-up to this trial.
"We are committed to working with the Environment Agency and local councils throughout the trial and we intend to be completely open about the results of the monitoring to ensure that any impacts of the trial are fully understood."
The Environment Agency has been monitoring air pollution levels around Drax since granting permission for the trial in June 2004.
The data collected while petcoke was not being burnt will allow them to draw comparisons with the period in which it will be.