Drax, which has received billions of pounds in green energy subsidies from the UK government, has been accused by a BBC Panorama investigation of cutting down environmentally-important forests.
The company runs Britain's largest power station, which burns millions of tonnes of imported wood pellets. The BBC said it had "discovered some of the wood comes from primary forests in Canada", whilst claiming Drax said it "only uses sawdust and waste wood.
The Panorama investigation involved analysing satellite images, tracing logging licenses and utilising drone filming. One of its reporters, Joe Crowley, "followed a truck from a Drax mill to verify it was picking up whole logs from an area of precious forest".
The investigation further stated it had discovered Drax purchased logging licenses to cut down two areas of environmentally-important forest in British Columbia.
One of the Drax forests is a square mile, including large areas that have been identified as rare, old-growth forest, the BBC said.
Drax's own responsible sourcing policy says it "will avoid damage or disturbance" to primary and old-growth forest, although Panorama's latest satellite pictures "show Drax is now cutting down the forest".
The company told Panorama many of the trees there had died, and that logging would reduce the risk of wildfires.
Drax told the BBC it had not cut down the forests itself and said it transferred the logging licences to other companies.
But Panorama said it checked, and the authorities in British Columbia confirmed that Drax still holds the licences.
Drax said it did not use the logs from the two sites Panorama identified. It said they were sent to timber mills - to make wood products - and that Drax only used the leftover sawdust for its pellets.
The company said it does use some logs - in general - to make wood pellets. It claims it only uses ones that are small, twisted, or rotten.
The BBC said documents on a Canadian forestry database show that only 11% of the logs delivered to the two Drax plants in the past year were classified as the lowest quality, which cannot be used for wood products.
Drax later admitted that it did use logs from the forest to make wood pellets. The company said they were species the timber industry did not want, and they would often be burned anyway to reduce wildfire risks.
The company also said the sites identified by Panorama were not primary forest because they were near roads.
But the UN definitions of primary forest do not mention proximity to roads and one of the sites is six miles from the nearest paved road.
The UK government is due to publish a new biomass strategy later this year, which will set out its policy for natural fuels like wood.
A Drax spokesperson said 80% of material in its Canadian pellets is sawmill residuals, which would be disposed of anyway.
They also said that Drax applies stringent sustainability standards to its own pellet production as well as suppliers, with verification from third-party certification schemes.
"We are constantly reviewing these policies to ensure we take account of the latest science," they added.
Drax accused of “cutting down environmentally-important forests”
