The operator of the UK’s electricity grid says environmental rules will force the closure of almost all its coal-fired power plants by 2023.

European Union and British domestic rules intended to curb carbon emissions will be in place in the next few years, and National Grid Plc’s projections have shown a “very aggressive” shutdown of coal stations will be triggered.

“The closure of the coal power stations means that additional generation is required to maintain the security of supply standard, resulting in new gas-fired generation commissioning, particularly from 2018-19 to 2021-22,” National Grid said in new report.

Some authorities are now wondering if new gas plants designed to ease the transition off fossil fuels can come online quickly enough, National Grid said in the report.

Due to the requirements of the EU’s Industrial Emissions Directive, the U.K. will have disconnected all of its coal-fired power stations after 2030 in the drive toward increased renewable generation, it says.

Already, around 8.2 gigawatts of coal generation has been shut-down since December 2012 , and a further 13 gigawatts is deemed to be at risk of closing by 2023.

In the first quarter of this year, coal-fed generation supplied 37 per cent of U.K. electricity, compared with 23 per cent for gas, according to government figures.

About 19 per cent of the UK’s power came from wind, hydro and bioenergy in the same period.