Shaft of sunlight illuminates oil rig in North Sea

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Going underground

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For decades removing harmful carbon from the atmosphere and storing it safely under the sea was a mere pipe dream. Edinburgh researchers are helping make it a reality.

For attendees at this year’s COP26 meeting in Glasgow, the summer of 2021 has provided plenty of climatic portents. Scenes of deadly floods and uncontrolled wildfires will be on the minds of delegates from nearly 200 nations.

These symptoms of climate change are becoming more extreme and more frequent, making finding solutions all the more urgent.

“Burning fossil fuels has been the foundation of our industry and wealth,” says Stuart Haszeldine, geologist and Professor of Carbon Capture and Storage (CCS). “We are now facing the unpalatable consequences of rapidly rising CO2 emissions causing global warming, an increase in sea levels and extreme weather events.”

The 2015 Paris Climate Agreement, which COP26 will revisit, is clear on what needs to happen. Global average warming must be limited to 1.5 degrees Celsius compared to pre-industrial levels to avoid the worst effects of climate change.

In this spirit, in April 2021 the UK set its climate change target into law to slash emissions by 78 per cent by 2035 compared to 1990 levels. This will pave the way to achieve Net Zero — a state in which greenhouse gas emissions are balanced by the amount of carbon removed from the atmosphere — by 2050.

But how do countries like the UK – and every other nation attending COP26 – achieve that? Professor Haszeldine and colleagues at the University of Edinburgh have spent decades investigating different technologies that might help keep the world cooler. Prime among them is the idea that, if there’s too much carbon in the atmosphere, why not get rid of it?

Bringing balance

The idea of capturing CO2 has been around since the 1970s, but it wasn’t until the 1990s that governments really started to show interest in developing technologies to capture and store CO2 as a way to mitigate climate change.

Both the UK Committee on Climate Change report in 2019and the Intergovernmental Panel on Climate Change report in 2021highlight the crucial role that CCS needs to play to reduce greenhouse gas emissions. “Any one tonne of fossil carbon that is extracted needs to be balanced with a tonne of fossil carbon injected back underground,” Haszeldine explains. “We are nowhere near that balance at the moment.”

Research led by Haszeldine and a large group of collaborators with expertise in geosciences, engineering and social sciences at The University of Edinburgh, is helping to ensure that CCS technologies are applied not just in the UK but all over the world.

Diagram showing how Carbon Capture and Storage work
Onshore power generation and industry produce emissions which can be captured, and transported by pipeline to secure offshore storage

“Our work on climate modelling, geological extraction and permanent storage of carbon, methods of CO2 capture and separation, pipeline engineering, as well as on the public’s perception of CCS and viable business models, is contributing to inform policy and incentivise the deployment of CCS,” he says.

As part of efforts to decarbonise industry, in 2020 the UK government committed to spend up to £1bn to support CCS innovation and deployment in the UK. “We’ve been providing evidence to industry putting bids in for this funding, including for the Acorn project,” Haszeldine explains.

Acorn works with industries in the east of Scotland to capture their CO2 and send it offshore using a redundant pipeline that used to bring hydrocarbon from oil fields. The CO2 in liquid form can then be injected underground for permanent storage.

A large part of Haszeldine’s research focuses on examining sites where CO2 has been naturally stored for millions of years, and exploring new sites for safe storage all around the world.

“The offshore geology of the UK is especially well suited to carbon storage,” he says referring to the large areas of porous sandstone rock covered by impermeable mud rock that can trap the CO2 and prevent it from floating towards the surface for hundreds of thousands of years. The Scottish Carbon Capture and Storage (SCCS) research partnership has calculated that the Central North Sea alone has enough capacity to store one hundred years’ worth of Europe’s CO2 emissions.

One part of the solution

Experts agree that to have a better than 50 per cent chance of avoiding average temperature rises above two degrees Celsius, humans must not emit more than one trillion tonnes of carbon into the atmosphere in total. “Since industrialisation we’ve accelerated through three-quarters of the way through our budget,” says Haszeldine. If global emissions continue at current rates and do not start declining rapidly, this budget will be exhausted by the mid-2040s. CCS can rapidly help to buy more time for change by capturing and permanently storing massive quantities of CO2 emissions.

To decrease carbon emissions as fast as possible, climate change experts say energy consumption must be reduced and made more efficient. Industry and consumers will need to switch from fossil fuels to renewable or sustainable, low carbon energy sources. Any carbon emitted should be captured and stored. Yet, because CO2 can linger in the air for thousands of years, such changes won’t reduce the levels of carbon collected in the atmosphere since the mid-18th century.

Smoke billows from power plant at night

Dr Vivian Scott, senior researcher in the School of Geosciences currently on secondment to the UK Committee on Climate Change, is working on several projects to understand the status and potential of different carbon removal approaches on a planetary scale.

He admits that some sources of emissions, such as agriculture and aviation, will be extremely difficult to capture and may need an equivalent amount of carbon removed from another source to balance the global budget. Achieving this will require Negative Emissions Technologies (NETs), tools that take more CO2 out of the atmosphere than they put in. Many NETs have been proposed, including Direct Air Capture (DAC), which sucks CO2 out of the air and, as with CCS, securely stores it in rocks deep underground.

“In the past five years, we’ve seen a handful of small-scale DAC pilot plants operating in real-world conditions which are starting to show the viability of these technologies,” says Scott. “A large facility with the capacity to fix up to one million tonnes of CO2 annually is in the works in the US.”

‘We have no choice’

Cost is another major challenge for CCS technologies. “Continuing to burn cheap fossil fuels and planting trees to offset carbon emissions may seem easier, but trees only store carbon until they are cut down,” says Simon Tett, climatologist and Chair of Earth System Dynamics. Unless forests are kept in perpetuity, he explains, the carbon will eventually be released back into the atmosphere.

“The cost of using fossil fuels is deferred,” says Haszeldine. “We are starting to pay the price of our parents and grandparents burning them and our children will pay to clean up what we use.”

A helicopter tackles a forest fire in Thailand
A helicopter tackles a forest fire in Thailand

Professor Tett is using climate models to estimate the sensitivity of Earth’s climate to increases in atmospheric CO2. “The latest IPCC reports reduce the uncertainty about the relationship between higher CO2 levels in the atmosphere and climate warming,” he says. He is also examining the role of human activity in increasing the risk of extreme weather events. “We are already seeing big changes in the risk of extreme temperatures and moderate changes in extreme rainfall,” he says.

The researchers agree that if we do nothing, or too little, the average temperature could increase by four or five degrees, with record temperature highs and lows that will make many areas uninhabitable. Now is the time to scale up CCS technologies as part of the solution to reduce carbon emissions, they say.

“As the planet gets hotter and hotter, we frankly have no choice. You don’t get to negotiate with physics!” says Scott.

Picture credits: oil rig – piola666/Getty; smoking chimneys – crofty136/Getty; forest fire – Toa55/Getty