The UK’s top scientists working on carbon capture technologies do not believe they will be developed and scaled up in time to reach net zero and limit global heating to 1.5C.
Experts speaking at a Greenhouse Gas Removal Hub event in London warned that these techniques, including direct air capture, biofuels, biochar, afforestation and advanced weathering, are not a silver bullet and should make up just a fraction of the efforts to decarbonise. Of 114 scientists in the audience, 57% said they were “not confident” the UK would meet the 2030 goals in the net zero strategy of 5m tonnes of engineered greenhouse gas removal, and 30,000 hectares a year of tree planting; 25% said they were quite confident, and 11% said there was no chance.
Gideon Henderson, the chief scientist at the Department for Environment, Food and Rural Affairs (Defra), said: “GGR [greenhouse gas removal] is hard and expensive. And we cannot afford to see it as a surrogate to compensate for continued emissions in sectors that can be decarbonised. It is not an excuse not to decarbonise, so we must drive down emissions anyway.” Henderson said afforestation is the “poster child” of GGR, because “everyone seems to love it, and it’s nice to have more trees”. However, he said trees “are not a panacea” because of the amount of land they need, which is taken out of food production, which then causes tensions with food security. There is also a tension between woodland, which has more biodiversity benefits but is slower growing, and forests, which grow quickly and lock in more carbon sooner.
Prof Mark Taylor, the deputy director of energy innovation at the Department for Business, Energy and Industrial Strategy (BEIS), said: “People see it as having the biggest market, there’s been funding from American companies – it feels like a silver bullet, there are lots of people who like it. Ministers like it because they think: ‘Oh, that sounds easy, you can take it out the air and that’s it.’ And that’s the thing that gets investment..."
Storing carbon in soil is a popular method, according to Henderson there are concerns over how long the carbon can be stored in the soil and how it is measured. If the soil begins to release carbon again shortly after it is stored, this could cause problems, especially if it is not being measured effectively and counted in net zero targets. He explained: “I think that if we see significant financial resources coming into this area to incentivise storing soil carbon without being able to measure it, and being sure of its permanence, there’s a risk of continued emission from storage which isn’t permanent or sufficiently well measured.”
The idea of a machine that can suck carbon dioxide out of the atmosphere and stick it permanently in rocks is a very attractive one, and it is perhaps unsurprising that this is the most popular technology for scientists trying to solve this problem.
But it is currently a very energy intensive process. Taylor explained: “We need to use energy to extract the CO2, the pure stream CO2 from the solid, so what we’re looking for an integration that can drive down the costs of DAC, and particularly drive down the cost of extracting the CO2 and the energy costs of extracting the CO2. Because at the moment, there’s no point in capturing CO2 from the air and then using natural gas to run a heat process to extract a pure CO2 stream.”
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