TransAlta Corp. says it will stop mining coal at its Highvale mine by the end of 2021 and will no longer use coal to generate power in Canada effective Jan. 1, 2022.

In a Wednesday report of its third-quarter financial results, TransAlta said it was closing the mine, which is located south of Lake Wabamun, about 70 kilometres west of Edmonton, four years ahead of schedule in an effort to accelerate its environmental, social, and corporate governance goals.

The Highvale mine, which has been in operation since 1970, is one of three TransAlta-owned surface coal mines and Canada’s largest surface strip coal mine, covering more than 12,600 hectares, according to the Calgary-based company’s website.

TransAlta CEO Dawn Farrell said in a conference call that the company is on track to reduce its greenhouse gas emissions by almost 70 per cent from 2005 levels by the end of 2022.

“TransAlta has more than met its fair share of the Paris Agreement,” said Farrell.

Under the agreement, Canada committed to reducing its emissions by 30 per cent below 2005 levels by 2030.

At TransAlta’s coal power generating stations, Keephills Unit 1 and Sundance Unit 4 will stop firing with coal and will only operate on gas, reducing their maximum capability to 70 MW and 113 MW, respectively.

It’s really related to overall the economics of producing power in Alberta on coal with the carbon tax. If you look at Alberta, we’ve currently got a $30 (per tonne) carbon tax, it’s be $40 by next year, $50 the year after. Coal plants get less economic and they’re less flexible in a merchant market,” said Farrell.

TransAlta reported a net loss attributable to shareholders of $136 million for the quarter ending Sept. 30, compared with a profit of $51 million in the same quarter last year. The difference means a loss of 50 cents per diluted share this quarter, compared with a gain of 18 cents in the same quarter of 2019.

The company said the decrease was largely due to lower revenues, a write-down of its coal inventory, higher depreciation, and an increase in asset impairments and power purchase agreement termination payments, which were partially offset by foreign exchange gains and income tax recoveries.

Its revenue for the quarter was down to $514 million from $593 million in the same quarter last year.

TransAlta operates more than 70 power plants in Canada, the United States and Australia.