The best way to get here is by helicopter.

Taking off from Esbjerg Airport, a remote platform in the North Sea, is a rare visit by the media.

This is not quite the typical oil facility you might imagine.

This is the Siri platform, which will be used for an innovative environmental purpose.

It's the final stage in a carbon capture process, a way of permanently storing planet-warming carbon dioxide beneath the seabed.

Chemical giant INEOS is behind the plans.

"The potential is actually quite big. So, if you look at some of the geological studies done, Denmark has the potential to actually store more than several hundred years of our own emissions. So, we are able to create an industry where we can support Europe in actually storing a lot of the CO2 here. So, plenty of potential to do that," says Mads Gade, CEO of INEOS Energy, Europe.

Siri is close to the remote Nini oil field.

Used to extract fossil fuels from beneath the seabed, this project will give the field a second lease of life.

In a process that almost reverses oil extraction, INEOS plans to inject liquefied CO2 deep down into depleted oil reservoirs, 1,800 meters beneath the North Sea.

The carbon capture and storage (CCS) efforts are named Greensand Future.

"With this new green transition, we're actually going to do the same thing, but instead of taking oil out of the reservoir, we're actually reversing the flow and adding the CO2 to the reservoir, instead giving us a future out here and also a big contribution to the green transition," says Peter Bjerre, maintenance manager, INEOS Energy.

When the project begins commercial operations next year, Greensand is expected to become the European Union’s first fully-operational offshore CO2 storage site.

It will initially begin storing 400,000 tonnes (363,000 metric tonnes) of CO2 per-year, scaling up to as much as 8 million tonnes (7.2 million metric tonnes) annually by 2030.

Greensand has struck deals with Danish biogas facilities to bury their captured carbon emissions into depleted reservoirs of the Nini oil field.

A “CO2 terminal” — to temporarily store the liquified gas — is being built at the Port of Esbjerg, on the western coast of the Danish Jutland peninsula.

A purpose-built carrier vessel — dubbed “Carbon Destroyer 1” — is under construction in the Netherlands.

Proponents of carbon capture technology say it is a climate solution because it can remove the greenhouse gas that is the biggest driver of climate change, and bury it deep underground.

They note the Intergovernmental Panel on Climate Change, the world’s top body of climate scientists, has said the technology is a tool in the fight against global warming.

The EU has proposed developing around 280 million tonnes (254 million metric tonnes) of CO2 storage per year by 2040, as part of plans to reach “net zero” emissions by 2050.

Gade says carbon capture and storage is one of the best means of cutting emissions:

“We don’t want to deindustrialise Europe,” he says. “We want to have actually a few instruments to decarbonise instead.”

Experts at Denmark’s geological survey say Greensand reservoir sandstone rock is well-suited — almost a third of the rock volume is made up of tiny cavities, perfect for storing the liquified CO₂, says senior researcher Niels Schovsbo.

“We found that there (are) no reactions between the reservoir and the injected CO2. And we find that the seal rock on top of that has sufficient capacity to withhold the pressure that is induced when we are storing CO2 in the subsurface,” adds Schovsbo.

“These two methods makes it a perfect site for storage right there.”

But while there are many carbon capture facilities around the world, the technology is far from scale, sometimes uses fossil fuel energy in its operations, and captures just a tiny fraction of worldwide emissions.

The Greensand project’s aim to bury up to eight million tons of CO2 a year by 2030, compares with the nearly 38 billion tons of CO2 emitted globally last year, according to the International Energy Agency.

And while the chemical giant ramps up carbon storage efforts, it’s also hoping to begin development at another previously unopened North Sea oil field.

Environmental campaigners say CCS has been used as an excuse by industries to delay cutting emissions.

“We could have CCS on those very few sectors where emissions are truly difficult or impossible to abate,” says Helene Hagel, head of climate and environmental policy at Greenpeace Denmark.

“But when you have all sectors in society almost saying, we need to just catch the emissions and store them instead of reducing emissions — that is the problem.”