Copenhagen has opened the world's first ski slope on the roof a huge incinerator that produces power by burning through waste rather than fossil fuels.

Key points: The project's architect has described CopenHill as 'hedonistic sustainability'

The project's architect has described CopenHill as 'hedonistic sustainability' It allows visitors to ski down a 450-metre slope as a power plant churns below

It allows visitors to ski down a 450-metre slope as a power plant churns below It's seen as a key step to becoming the world's first carbon-neutral capital

First conceived in 2011 by Danish architects to promote both recreation and sustainability, the CopenHill ski slope allows visitors to soar down a 450-metre ski slope with views of Copenhagen, as some 450,000 tonnes of waste churns below.

Work to develop the concept began in 2017, and this weekend the slope finally opened its doors to the public.

Designed by Danish architect Bjarke Ingels, the plant is seen as an important step in realising Copenhagen's ambitions to become the world's first carbon-neutral capital.

Skiers use an artificial ski slope at CopenHill's waste incineration plant. ( AFP: Steffen Trumpf )

"The ski-slope idea came from realising that Copenhagen has a cold climate with several months of snow, but absolutely no mountains," Mr Ingels said last year.

"Copenhageners have to travel several hours by car to reach the ski slopes in Sweden. The roof [of the incinerator] is not only going to function as a ski slope, but as a real mountain with a green forest area, a hiking trail, and climbing walls."

"Economically, environmentally, and socially profitable — a perfect example of what we call hedonistic sustainability!"

The plant will also burn waste from about 600,000 residents and 68,000 businesses to produce electricity and heating, while also recycling some of the waste.

'It's fantastic that one can ski without snow'

The roof — which reportedly cost some $US670 million ($990 million) — is covered in a material called neveplast, which makes it look just like a ski slope, except it is green.

The design is intended to promote sustainability and recreation at the same time. ( Reuters: Steffen Trumpf )

"I think everybody is surprised to start with when they look at it and it's not snow," CopenHill director Christian Ingels told reporters last year.

"It's green dry-slope material — after one or two runs, your mind is automatically adjusting so you feel exactly like skiing."

The CopenHill ski slope is an attempt to build a waste-treatment plant that local residents are happy to see come to their town.

"It's fantastic that one can ski without snow," skier Tommy Christensen said.

"It's a slightly different experience than to skiing in real snow, but it's my second run and I'll try it again. It looks promising."

Copenhagen is pushing to become the first carbon-neutral capital in the world. ( ABC News: Foreign Correspondent, file )

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