A CATTLE shed near Edinburgh sucking up methane emissions and a team altering the acidity of seawater in the English Channel might seem unlikely prospects for avoiding increasingly dangerous climate change. But they are just two of 24 projects taking part in a .
Governments worldwide have been waking up to the need to develop ways of removing emissions from the atmosphere to meet net-zero targets, which now . And last year’s .
To date, such technologies have largely existed only in virtual simulations. But 2022 looks to be the year that pilot schemes will get off the ground. “They are filling a really useful niche, going from computer models to fields and factories, where we can see how they work in real life,” says .
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Share of global economy with net-zero targets”
The UK is near the forefront of the international race to develop carbon dioxide removal technologies, but is far from alone. The US . Norway is working on a multibillion-dollar carbon capture and storage project, dubbed , and other .
As well as the UK’s £100 million competition, there is a , from grinding up rocks to increase their surface area and spreading the dust on farm fields to speed up their natural CO2 absorption to planting fast-growing grass to absorb carbon. The two dozen schemes hoping to win a share of the competition funding in April are a diverse bunch.
“Our children may decide to unwind some of the climate change and go beyond net zero”
One aims to reduce the pH of seawater so that most of the carbon within it becomes CO2, which can be captured and stored. The pH is then ramped back up and the carbon-depleted water is pumped back into the sea, where it naturally absorbs more CO2 from the atmosphere. “We’re accelerating the natural processes of the ocean,” says Paul Halloran at the University of Exeter, UK, who is working on the project, dubbed SeaCURE.
He says the big attraction is that CO2 concentrations in seawater are 150 times higher than in the air. This also brings costs down, he says: £300 a tonne of CO2 removed versus $600 (£442) cited by Climeworks, a Swiss direct air capture firm. Another attraction is that, unlike approaches using trees and crops, it doesn’t compete for land.
The idea’s weakness is monitoring. Once the carbon-depleted seawater is released back into the ocean, verifying how much carbon it takes up is nigh-on impossible. That might be an issue for firms using the approach to meet their net-zero targets, because they will have to rely on modelled estimates of the carbon saved, rather than hard figures.
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Another candidate in the competition is ““, led by Carole-Anne Duthie at Scotland’s Rural College (SRUC). The idea is to adapt a shed where beef cattle are housed during their final stage of growth, turning it from a fairly open structure into a well-sealed one, then suck out the high levels of methane from it. The power to do this removal comes from an on-site anaerobic digester fed by cattle waste.
Farm power
Like seawater, a cattle shed has higher-than-normal concentrations of greenhouse gases. Another plus is that it can be used with little disruption to farmers. “We’re not changing the farming enterprise,” says Duthie. Still, how we can store huge quantities of methane economically is an unanswered question, and the scale of the removals remains to be seen.
Such ideas are very much in the early stage innovation camp. “Some of them might work, some of them might not. That’s OK at the demo stage,” says Emily Cox at Cardiff University, UK. But the UK cannot rely on such solutions to remove millions of tonnes of CO2 and meet current carbon targets, she says.
In the short-term, that role will fall to nature-based approaches, mostly tree planting and peatland restoration, says David Joffe at the Climate Change Committee (CCC), an independent group advising the UK government (see “From food to forestry”). The reason such measures come first is that they are inexpensive and can take years to draw down carbon.
However, there is only so much land, and so much carbon that trees can absorb, meaning climate targets won’t be met without engineered removals in the medium term too. The first big prospect is bioenergy with carbon capture and storage, also known as BECCS, which energy firm Drax wants to deploy in the north of England to burn biomass for power and pipe the CO2 into old oil and gas reservoirs off the coast. The second is direct air capture (DAC), machines using fans, heat and chemicals to take CO2 directly out of the air, a technology that Canadian company .
Funds for UK CO2 removal competition”
“They are the main front runners,” says Joffe. “Others we regard as, to some extent, speculative. Which is not to say they cannot contribute, but we don’t think they’re proven enough to include in our scenarios.” Keeping alternatives in play is still worthwhile, he says, because there are physical limits to how much biomass can be grown in the UK for BECCS. And DAC is energy intensive, so too much deployment in the next 15 years could consume renewable electricity needed for cars, heat and more.
The scale of the challenge is huge. By 2050, the UK government thinks engineered technologies will need to remove between , up from zero today. Even getting to net zero by 2050 with BECCS, DAC and tree planting is a stretch, says Smith. But they are our best bet, he says. Other ideas aren’t worth banking on for 2050, but may prove useful on longer timescales. “Our children may decide we need to unwind some of the climate change we’ve experienced, and go beyond net zero to net negative. In which case, having started on these technologies will help,” he says.
There remain many obstacles. Large-scale storage and transport infrastructure needs to be built, although in the , the governments are already working to enable the pipes and vaults needed. “If we don’t make progress on those this decade, there’s a bottleneck later on,” says Joffe. Old oil and gas reservoirs mean the two countries may end up as big stores for the EU’s CO2, says Ruth Herbert at the Carbon Capture and Storage Association, a UK trade body.
Tonnes of CO2 that the UK needs to remove from the air in 2050”
Another issue is that there are still almost no incentives for companies to remove and store CO2, beyond private-sector initiatives such as firms like and . That means, for the most part, there is no “route to market” for company boards mulling investment decisions.
Then there are public attitudes. The 108 people on the UK’s first Climate Assembly in 2020, which aimed to weigh the views of the general public, were . “The crucial thing in bringing people along is to have a clear public strategy to say this is what the removals are for: counterbalancing those remaining emissions where we just can’t get to zero, not to allow companies off the hook,” says Joffe.
Given all those hurdles, “there is a world in which none of this happens”, says Smith. Two possible triggers for failure are hostile public opinion and governments not giving incentives to scale up the innovations that schemes like the competition in the UK are producing, he says. Fortunately, Smith thinks that is unlikely, not least because countries are beginning to realise that avoiding more dangerous climate change means not just CO2 reductions, but CO2 removal. “We essentially need to solve this problem in our generation,” says Smith.
From food to forestry
There is a lively debate about how UK farmland will need to change to boost carbon dioxide removal. About a fifth of agricultural land should be turned over to tree planting and other carbon sequestration, says the UK’s independent Climate Change Committee, enabled by a shift to more plant-based diets.
Some farmers, such as Andrew Blenkiron in the east of England, are already turning over land used for cereal crops to fast-growing Paulownia trees. Pat Brown, the chief executive of plant-based “meat” firm Impossible Foods, is talking to UK farmers about replacing pasture with trees to store carbon. But a shift from food to forestry will be hard.
UK environment secretary George Eustice says farmers are being supported to remove CO2 through the government’s and, longer term, through the . “The key thing really is to expand woodland cover,” he says, pointing to the government’s target of 30,000 hectares a year. Peatland restoration is also important, Eustice adds, along with technology and innovation. He cites a project in Cornwall capturing methane from livestock and using it instead of red diesel, a fuel used in farm vehicles.
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