Two high-level members of the European Union delegation announced that the carbon neutrality designation given to biomass energy — replacing coal with wood pellets — will come under critical review by the EU as a result of current science showing that biomass burning produces significant amounts of carbon emissions.

The unexpected announcement came during a press conference Thursday, December 12, at the 25th United Nations climate summit (COP25).

“The issue of biofuels needs to be looked at very carefully,” said Frans Timmermans, executive vice president of the EU and a Dutch politician. “We have to make sure that what we do with biofuels is sustainable and does not do more harm than that it does good.”

Timmermans’ view is significant because the conversion of coal-fired power plants to the burning of wood pellets is one of the fastest-growing energy sources in the United Kingdom and EU. Because trees can be replanted, wood pellets have been classified as renewable energy on par with carbon-zero wind and solar energy by the UN for more than twenty years.