How does carbon capture work, and is it effective?

Rishi Sunak has announced an expansion of oil and gas drilling in the North Sea despite spiralling warnings of the threat of global warming.

The prime minister will use a trip to Scotland on Monday to confirm that the government will issue 100 licences off the coast of Scotland to companies that want to extract oil and gas from the North Sea, in a bid to create dividing lines with the Labour Party.

Number 10 the licences will “boost British energy independence” and “reduce reliance on hostile states”.

The news has prompted outrage from climate campaigners, and shadow climate change secretary Ed Miliband accused the prime minister of moving towards “a culture war on climate” to make up for “13 years of failed Tory energy policy”.

The prime minister has also confirmed locations for two new carbon capture usage and storage clusters, to capture carbon dioxide emissions from across the country for offshore storage in the North Sea. The government says it could support up to 50,000 jobs.

Technology that captures carbon dioxide from our atmosphere has existed for decades and is considered a key way to tackle climate change.

Here’s what you need to know about how carbon capture and storage work.

How does carbon capture work?

Existing strategies to tackle climate change focus mainly on eliminating carbon emissions from processes such as power generation or transport.

However, carbon capture and storage takes CO2 directly from the atmosphere or at the point of emission, and stores it safely within the natural environment.

Burning fossil fuels such as oil, gas and coal to generate electricity emits CO2, which is the main driver of climate change.

The carbon capture process stops most of the CO2 produced from being released, and either re-uses it or stores it underground.

How does the technology work?

Carbon capture and storage take two basic forms:

• Biological carbon capture and storage: when the natural environment — such as forests and oceans — sequesters CO2 from the atmosphere.

• Artificial/geological carbon capture and storage: when CO2 as an emission is extracted from human-made processes and stored in vast underground facilities.

Biological carbon capture and storage happens on a much larger scale than geological carbon capture and storage — but the technology to stimulate both has traditionally been viewed as expensive and impractical at scale. This is changing, however, as investment and research into carbon-capturing technologies take off.

Carbon sinks are natural forms of carbon capture and storage, and are huge spaces where the natural habitats capture CO2 from the atmosphere. They include forests, oceans, grasslands and wetlands.

Scientists recognise that the preservation and cultivation of carbon sinks could increase the amount of carbon taken from our atmosphere in the shortest space of time. In particular, coastal wetlands store more carbon per hectare than other habitats like forests.

Then there are deep saline aquifers, which are underground geological formations; they are vast expanses of porous, sedimentary rock, which are filled with salt water. CO2 can be injected into these and stored permanently; saline aquifers have the largest identified storage potential among all other forms of engineered carbon capture and storage.

The Endurance aquifer, located in the North Sea off the coast of the UK, is one such formation, which is approximately 1.6 kilometres (just under a mile) below the sea bed. It allows carbon dioxide to be injected into it and stored safely for up to thousands of years.

In China, companies have developed experimental commercial air filters, which are huge towers that clean air of pollutants on a vast scale. These purify the air by drawing it into glass rooms, which are heated using solar power creating a greenhouse effect. This hot air is pushed up the tower through a series of filters, before being released back into the atmosphere as clean air.

Manufacturers believe they are close to developing even larger towers, where just one could clean enough air on a daily basis for a small city.

The most recent advancements in carbon capture and storage technology include new types of liquids, which are highly effective at absorbing CO2_.

In Denmark, Project Greensand is the first venture to achieve cross-border carbon capture and storage, by shipping CO2 from Belgium and injecting it into a depleted oil field below the Danish North Sea.

The project aims to safely and permanently store up to eight million tonnes of CO2 every year by 2030, which is the equivalent of 40 per cent of Denmark’s emission reduction target and more than 10 per cent of the country’s annual emissions.

Is carbon capture effective?

The World Economic Forum says the future of carbon capture looks promising. It says it will play an important role in the energy transition, especially in heavy industries such as power, steel, cement and oil and gas.

However, it is expensive and needs to be used widely to be effective. It also should not be used as a substitute for releasing more carbon into the atmosphere.