One of Australia's dirtiest power plants will be shuttered as it is no longer economically viable, its owner said Thursday, in a move hailed by environmentalists.

After decades of belching pollution, the Hazelwood brown coal-fired power station in Victoria state's Latrobe Valley will close in March after the decision of French energy giant Engie.

Some 500 people are set to lose their jobs when the plant shuts down, with another 250 remaining until 2023 to manage the decommissioning of the power station and rehabilitation of the adjoining mine site.

Engie said it was also looking to sell the brown coal-fired Loy Yang B power station in the Latrobe Valley and the gas-fired Kwinana plant in Western Australia.

‘Hazelwood is now more than 50 years old. It has been a wonderful contributor to the National Electricity Market but we have now reached the point where it is no longer economic to operate,’ Engie's Australia chief executive Alex Keisser said in a statement.

‘Engie in Australia would need to invest many hundreds of millions of dollars to ensure viable and, most importantly, continued safe operation. Given current and forecast market conditions, that level of investment cannot be justified.’

Hazelwood -- which supplies around 22 percent of Victoria's energy requirements and about four percent of the nation's -- is 72 percent owned by Engie and 28 percent by Japanese trading house Mitsui.

Paris said late last year that Engie -- partly owned by the French government -- was going to stop investing in the development of coal-fired power plants, the biggest source of man-made CO2 emissions.

- 'A climate crime' -

Brown coal is considered ‘dirtier’ than black coal, with environmentalists welcoming the closure.

‘Hazelwood is the dirtiest power station in Australia and one of the dirtiest in the world,’ Australian Conservation Foundation's chief executive Kelly O'Shanassy said.

‘This is a key moment in a transition that is already well under way -- the switch from dirty energy to clean energy -- and Australia's energy policy is now at a fork in the road.’

Friends of the Earth France said continuing to run the site would have been ‘a climate crime and extremely harmful to the local population’ and hailed its closure as ‘a positive sign’.

But it added that there was a lack of transparency and consultation around the decision.

‘Engie must now honour its commitment to total rehabilitation of the site, and assist the transfer of everyone directly or indirectly employed there,’ campaigner Malika Peyraut said in a statement.

The federal government unveiled a Aus$43 million (US$33 million) support package for the workers, alongside Aus$22 million from the state government.

Federal Energy Minister Josh Frydenberg said he would closely monitor the impact of the closure on energy supply across the nation.

It follows question marks over energy security after the entire state of South Australia was left without power in September following a severe storm.

The Hazelwood closure also comes after the shuttering of several other coal-fired power stations across the country in recent years.

Some 63 percent of electricity generation in Australia is from coal, government data for 2014-15 show. The country sits just behind the United States in terms of carbon dioxide emissions per capita, according to 2013 World Bank figures.

Morocco hosts the UN climate conference known as COP22 next week, a year after the landmark Paris Agreement which requires countries to cap rising temperatures through carbon-cutting and under measures.