The new plant will have the capacity to capture and store more than 800,000 tonnes of CO2 per year, which is more than the annual emissions from the Swedish capital's road traffic, said Anders Egelrud, CEO of utility Stockholm Exergi, which is leading the project.

It "is going to be the largest project of this kind in Europe and one of the largest in the world," Wopke Hoekstra, the European climate commissioner, told reporters as construction began.

The investment amounts to 13 billion kronor ($1.4 billion) and the technology will be used to separate, liquefy, and permanently store CO2, generating so-called negative emissions.

Stockholm Exergi, which produces heat and electricity for the Swedish capital, already uses residual products from the forestry industry, such as wood chips.

The new facility will enable the capture and storage of carbon dioxide released from their own production.

Funding comes from subsidies and loans, including from an EU fund and the Swedish state, as well as purchases of emission certificates by private companies.

The captured CO2 will be temporarily stored on-site before being shipped to Norway for permanent storage in the "underwater" CO2 cemetery Northern Lights, off the coast of Norway.

In practical terms, after capture, the CO2 is liquefied and transported by ship to the facility near Norway's Bergen.

It is then transferred to large tanks, before going through a 110-kilometre (68-mile) pipeline to be injected into the seabed, at a depth of around 2.6 kilometres.

"In the Nordics, you simply have the geography to relatively easily ship it and store it," Hoekstra told AFP.

CCS technology is complex and costly but has been advocated by the UN's Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency (IEA), especially for reducing the CO2 footprint of industries like cement and steel, which are difficult to decarbonise.

The world's overall capture capacity is currently just 50.5 million tonnes, according to the IEA, or barely 0.1 percent of the world's annual total emissions.

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