Portugal shut down its last remaining coal plant over the weekend, ending the use of the polluting material for electricity generation. It becomes the fourth country in the European Union to do so.
Environmental group Zero said in a statement the Pego plant in central Portugal had been the country's second-largest emitter of carbon dioxide, adding that "freeing ourselves from the biggest source of greenhouse gases was a momentous day for Portugal".
Although the licence for the power plant is technically in place until the end of the month, its final stock of coal ran out on Friday. That made Saturday the first day that electricity was produced in the country without the use of coal.
The move comes nine years before Portugal's targeted end of the use of the fossil fuel by 2030. The process began in 2017 when the country signed a declaration to exit coal use at COP23.
Belgium, Austria and Sweden are the other three European countries to have already stopped using coal for power generation.
Although a hefty 60 to 70 per cent of its electricity comes from renewable sources, Portugal still relies heavily on imported fossil fuels to meet overall energy needs.
Portugal's exit from coal comes after the European Commission announced it would be suing the country for failing to take action on poor air quality.
A concerning conversion
Despite the early shift to coal-free power, there are concerns the Pego plant, run by the privately held group Tejo Energia, might now be converted to burn wood pellets.
"The challenge now is to ensure utilities do not make the mistake of replacing coal with fossil gas, or unsustainable biomass," said Kathrin Gutmann, campaign director at Europe Beyond Coal.
"Ditching coal only to switch to the next worst fuel is clearly not an answer," said Zero's president Francisco Ferreira. "Instead, the focus should be on rapidly upscaling our renewable energy capacity in wind and solar."
A draft document seen by Reuters in June showed the EU was considering tightening rules on whether wood-burning energy could be classified as renewable.