When we consider carbon emissions, the focus is rightly on reducing them. But alongside carbon reduction there is another route deemed an essential part of the toolkit to reaching net zero: capturing gas that is produced and storing it underground, so it never reaches the atmosphere.
This technology, known as carbon capture, utilisation and storage (CCUS), has been used in various ways since the 1920s, such as in separating gases for commercial use and pumping CO2 into greenhouses to boost plant growth.
Only in the past few decades, with global warming increasingly prioritised on the global agenda, has CCUS gathered momentum as a climate change mitigation technology. Industries such as oil and gas, cement, iron, steel and chemicals are now looking at it as a way to decarbonise production.
Though widely regarded as an essential tool for decarbonising these industries, the utility of CCUS has been debated as it captures carbon dioxide, rather than prevents it being produced in the first place. The financial climate think tank Carbon Tracker has argued that CCUS should be reserved for the “hardest-to-abate” emissions, while environmental campaign group Friends of the Earth Scotland has previously said carbon capture “cannot deliver the urgent action we need to cut emissions this decade”.
In April this year, in recognition of the urgency and overwhelming nature of the challenge, the UN Intergovernmental Panel on Climate Change (IPCC) identified CCUS as a “critical decarbonisation strategy in most mitigation pathways”, which will need to be deployed alongside drastic emissions cuts to keep global temperature rise between 1.5ºC and 2ºC.
In the UK, independent advisory body the Climate Change Committee has also said that CCUS is a “necessity not an option”, and the International Energy Agency has echoed this by saying that reaching net zero will be “virtually impossible” without CCUS, “the most cost-effective approach” to curbing emissions from heavy industries such as iron, steel and chemicals.
The potential for CCUS in climate change mitigation in the UK is significant – research from trade body the Carbon Capture and Storage Association (CCSA) found that CCUS could remove 70 million tonnes of carbon dioxide emissions every year by 2035.
CCUS works by capturing the carbon dioxide released during fuel combustion or industrial processes. It is then compressed and transported either via ship, road or pipes to permanent storage deep underground, often under the seabed, via injection. Research shows that carbon dioxide can be safely stored underground for thousands of years, and likely to be in perpetuity where it becomes part of the storage site rock over time. The Sleipner project in Norway has been storing roughly a million tonnes of carbon dioxide under the seabed every year since 1996.
Dominic Cook, director of energy at leading engineering professional services firm WSP, says that the UK can make use of the technology in its transition to a net zero economy, given that it has the right geology for CCUS, and the added benefit of easy access to the North Sea. “Oil and gas reserves have been proven to hold gas for millennia,” he says. “The UK’s geology is very stable and not in an active seismic region.”
The same might not be said for countries with more volatile terrain, but Cook says the UK should be making use of the resources at its disposal. “It might feel UK-centric, but we have got things that we need to do to decarbonise ourselves,” says Cook. “CCUS is part of that transition journey and the UK is providing a global lead on developing the carbon storage industry.”
Other methods of capture and storage are also possible, including turning carbon dioxide into stable, solid materials such as carbonates and capturing the gas directly from the air, though the latter is more expensive and difficult, requiring separation from other gases, says Ruth Herbert, chief executive officer at the CCSA.
The “utilisation” element of CCUS is a different matter. Rather than storage, this involves reusing the captured gas across different industries that require carbon dioxide to function – such as in the production of carbonated drinks, fuel for the aviation industry or plant growth in horticulture. This “recycled” carbon reduces the overall amount of carbon that ultimately ends up in the atmosphere. However, this approach is limited, says Herbert, as it ultimately still results in carbon emissions. “[Reusing the carbon] for aviation fuels does have some climate benefit,” she says. “But we need to be doing a lot of storage as well. If you’re talking large quantities, we’ve got to get it permanently underground.”
The UK government has made CCUS a core part of its Ten Point Plan, which lays out the future of the UK’s energy market. It has promised to establish four CCUS industrial “clusters” – hubs bringing together multiple big carbon emitters with storage facilities and shared transport infrastructure – across the UK by 2030, which will collectively capture 20-30 million tonnes of carbon dioxide every year. The government also aims to boost employment by using the UK’s existing proficiency and skills in the oil, gas and engineering industries to make it happen.
But Herbert says that the government’s ambitions have not yet matched reality. With the aim to have four CCUS clusters operational by 2030, only two clusters have so far been confirmed (HyNet North-West and East Coast Cluster), and many companies are still waiting on the results of the second part of a government funding competition. A shortlist was announced this month but final decisions around funding have not yet been made.
“This is not a lot of time to build quite major infrastructure,” says Herbert. “This is an industry that needs to go from nothing to quite a lot in a short space of time. The government’s strategies are good – we just need delivery.” The CCSA is calling for a clear deployment plan from government looking at the next five years.
CCUS is also tied in with decarbonising other means of energy production, such as hydrogen. Hydrogen can be produced in different ways, but the main types are “blue” and “green” hydrogen – the former produced by mixing natural gas with hot steam and a catalyst, and the latter produced by renewable sources like wind, water or solar power. The UK government aims to connect blue hydrogen plants with its CCUS clusters, to prevent carbon emissions in the production process. Some argue that blue hydrogen is reliant on natural gas, and so should be avoided at all costs – but Herbert says this is a practical, interim solution while the appropriate infrastructure is set up to switch purely to green hydrogen.
Cook agrees that blue hydrogen can be a “stepping stone”, especially given that renewables are currently in high demand – offshore wind, for example, is being increasingly dominated by the electric vehicle market. “It’s about pragmatism,” he says. “Do we wait until we have sufficient renewable energy to drive green hydrogen, or do we start to move the dial now?”
One of the major challenges facing CCUS is its association with oil and gas, which Herbert says is a “brand problem”. However, these companies are crucial to the UK’s adoption of CCUS, given that they have the relevant expertise in geological offshore storage.
“The way to look at that is, let’s not let these companies off the hook,” says Herbert. “Let’s make them fix the problem with the resources and skills that they’ve got.” In terms of prosperity, investing in CCUS will also help to boost employment in the UK’s industrial regions. Herbert says that, to improve public perception, the government needs to communicate the range of technologies that are necessary to meet our net zero targets more clearly to the public.
Ultimately, CCUS is part of a diverse mix when it comes to climate change mitigation. “We need to stop using gas-fired power plants without carbon capture,” says Herbert. “I’m very pro-offshore wind, and I think CCUS now needs the same attention that it took offshore wind to get going. We need to put [a lot] into this because it’s a big piece of the puzzle.”