Achieving the UK’s net zero emissions target will require not only reducing current emissions but also removing carbon dioxide already present in the atmosphere, using so-called negative emissions technologies. One technology attracting growing attention for this purpose is Direct Air Capture (DAC) – the process of extracting CO₂ from ambient air and storing it underground. A recent Times Radio interview of Professor Paul Fennell by Hugo Rifkind

https://www.thetimes.com/radio/show/20250806-28988/2025-08-06 (11.04-11.10)

discussed both the potential and the limitations of DAC within the UK’s broader decarbonization strategy. The interview is summarized at the end of this posting. This commentary aims to provide a neutral overview of DAC’s role and implications for policymakers and energy professionals.

 

What is Direct Air Capture and Why Consider It?

                                                                                           
DAC is a relatively new carbon-removal technology that uses chemical processes to capture CO₂ directly from atmospheric air. The captured CO₂ can then be injected deep underground—for example, into depleted oil and gas reservoirs or saline aquifers—where it is intended to remain permanently (see imperial.ac.uk). In effect, DAC provides a means of reducing atmospheric CO₂ concentrations rather than merely cutting emissions at their source. This capability is viewed as vital for achieving net zero, particularly for counterbalancing emissions from sectors that are difficult to fully decarbonize, such as aviation and agriculture. However, DAC technology remains in its early stages of development and is currently both energy-intensive and costly.

 

Governments, including that of the United Kingdom, are exploring DAC as part of a broader greenhouse gas removal (GGR) portfolio. Analysts caution that while DAC can contribute to achieving net zero, it must be considered alongside, and not in place of, more conventional mitigation strategies.

 

Capturing CO₂ at the Source vs. from the Air


It is considerably more efficient and cost-effective to capture CO₂ from point sources—such as industrial chimneys or power-plant exhausts—than from ambient air. This is because the concentration of CO₂ in industrial flue gas is hundreds of times higher than in the open atmosphere. DAC systems must therefore process vast volumes of air to extract each tonne of CO₂, resulting in higher energy demand and greater costs per tonne captured (see https://ccsknowledge.com/ ).

 

A 2022 study by the Fennell group at Imperial estimated that current DAC facilities operate at costs between $320 and $540 per tonne of CO₂ removed (assuming access to low-cost energy) (imperial.ac.uk). These costs are roughly an order of magnitude greater than those associated with capturing CO₂ from concentrated industrial sources, which typically range in the tens of pounds per tonne under favourable conditions.

 

By contrast, capturing CO₂ before it enters the atmosphere - for instance, by retrofitting power stations or cement kilns with carbon-capture units - is generally more cost-effective and energy-efficient. Carbon capture and storage (CCS) at large point sources has been demonstrated to remove up to 90% of emissions at comparatively low cost. Consequently, DAC is often considered a complementary measure, suitable for addressing diffuse or legacy emissions that cannot be captured at source.

 

DAC: A Promising but Limited Tool


While DAC offers unique advantages, its potential contribution to overall emissions reduction in the near term is limited. Technological learning and innovation may drive down costs and improve efficiency in the coming decades, but the current scale remains small relative to global needs. The International Energy Agency’s Net Zero scenario, for example, projects that DAC could remove only about 60 million tonnes of CO₂ globally by 2030, compared with the 1.6 billion tonnes captured through CCS - representing only 3-4% of the total (ccsknowledge.com).

 

DAC may nonetheless play a valuable role as part of a diversified climate strategy. It can act as a long-term insurance mechanism by addressing residual emissions from hard-to-abate sectors and by providing a means to counteract potential overshoots of carbon budgets. Developing DAC capacity and expertise today could also enable the UK to establish an early position in a potentially important clean-technology industry.

 

Implications for UK Climate Policy and Next Steps


For UK climate policy, the most effective approach is to integrate DAC within a comprehensive carbon-management framework that prioritizes emissions prevention and reduction before large-scale atmospheric removal. The government’s ongoing funding for “Direct Air Capture and Greenhouse Gas Removal” trials reflects recognition of DAC’s long-term importance (see, for example, UK plans scheme to suck CO₂ from the air), but support should remain focused on improving efficiency, reducing energy intensity, and ensuring reliable CO₂ storage.

 

Parallel efforts to deploy CCS in power generation and industrial sectors, and to expand nature-based carbon sinks with appropriate safeguards, must continue without delay. In this context, DAC should be regarded as a strategic complement—an enabling technology that can enhance the resilience of the UK’s net zero pathway, but not a substitute for immediate, large-scale emissions reductions.

 

Further reading:

  • Fennell, P.S. et al., “Carbon capture and storage (CCS): the way forward,” Energy Environ. Sci. 2018 – (overview of CCS, BECCS, and DAC in climate mitigation)pubs.rsc.orgpubs.rsc.org.
  • Sendi, M. et al., “Geospatial analysis of regional climate impacts to accelerate cost-efficient direct air capture deployment,” One Earth 5(10) (2022): 1153–1164 – (study led by Fennell on DAC costs under different climates) imperial.ac.uk; ccsknowledge.com.
  • Imperial College London News, “Imperial researchers move closer to net-zero by modelling direct air capture” (Jan 2023) – (Fennell’s team finds DAC costs ~$320–540/t in optimal sites) imperial.ac.uk
  • International CCS Knowledge Centre, “A Future for Direct Air Capture” (Dec 2022) – (notes DAC’s high costs today vs. optimism for <$100/ton in future, citing Fennell’s research) ccsknowledge.com
  • BBC Science Focus, “In pictures: World’s largest carbon capture plant in action” (Sep 2021) – (details on Climeworks’ Orca DAC plant in Iceland turning CO₂ into stone) sciencefocus.com.

 

Professor Paul Fennell, Professor of Clean Energy (Lead author)

Professor Martin Blunt, Professor of Flow in Porous Media

Professor Sam Krevor, Professor of Subsurface Carbon Storage

Professor Niall Mac Dowell, Professor of Energy Systems Engineering

Professor Geoffrey Maitland, Professor of Energy Engineering

Professor Ronny Pini, Professor of Multiphase Systems

Professor Martin Trusler, Professor of Thermophysics

Imperial College London, Transition to Net Zero Group

 

 

Times Radio interview with Professor Paul Fennell on Direct Air Capture and Net Zero

Introduction

Hugo Rifkind (Interviewer): "The Energy Secretary, Ed Miliband, has begun talks to set up the UK's first commercial project to suck carbon dioxide directly from the air as part of the government’s net zero strategy. The captured carbon would be stored in old oil and gas fields under the Irish Sea. Ministers are set to begin negotiations with the Swiss firm Climeworks, which is developing the world's biggest direct air capture facility in Iceland. Professor Paul Fennell of Imperial College London joins us now to discuss this. Hello, Paul."

(Paul Fennell is a Professor of Clean Energy at Imperial College London.)

How Direct Air Capture Works

Hugo Rifkind: "Thank you for being with us. Tell us about this technology of sucking carbon dioxide directly from the air. Is it a new concept – is it new technology?"

Professor Paul Fennell: It's reasonably new – it has really only taken off in the past ten years or so. Essentially, direct air capture works by drawing in air and passing it over special materials that capture CO₂. Those materials trap the carbon dioxide, which can then be released as a pure stream of CO₂. In other words, you concentrate it from about 0.04% (the CO₂ level in air) to nearly 100% purity. That concentrated CO₂ then gets piped away to be stored underground – for example, a couple of kilometers beneath the Irish Sea in a geological storage site – where it can be safely stored for the long term.

Efficiency and Scale: Capturing at the Source vs. from Air

Hugo Rifkind: "And how efficient is this? Presumably we’d have to do an awful lot of it to counteract, say, the emissions from a gas power plant. Is it possible to do this at the kind of scale that really makes a difference?"

Professor Paul Fennell: In practice, it makes a lot more sense to capture CO₂ from the exhaust of a gas-fired power station or industrial source, where the CO₂ might be maybe 3% of the exhaust, rather than from ambient air at just 0.04%. In fact, that's what the government is mainly focusing on with its carbon capture and storage (CCS) initiatives. They plan to capture most of the CO₂ directly from the exhausts of large emitters – power stations, industrial processes, hydrogen production plants, and so on. On top of that, they’re also looking at taking a little extra CO₂ out of the air and adding it into the melange, then sending all of that captured carbon to be stored securely under the Irish and North Seas.

Technology vs. Trees: Using Biomass and Carbon Capture

Hugo Rifkind: "I’m struck by the fact that there are already things that pull CO₂ directly out of the air – and they’re called trees. Is this technology much more efficient than trees?"

Professor Paul Fennell: Direct air capture has different features than using trees. Trees are great (I love trees!) and they do capture a lot of CO₂ from the atmosphere. In fact, one idea people are considering — at quite a large scale — is to combine biology with technology. For example, you let trees capture CO₂ as they grow, then you harvest those trees and burn the biomass in a power station that has carbon capture on its exhaust. Drax, a large power station in the UK that currently burns biomass, is considering this approach of adding carbon capture technology – so-called Biomass Energy with Carbon Capture and Storage (BECCS). If they do that, you can achieve very large-scale CO₂ removal from the air (via the trees' growth) and then permanently sequester that CO₂ underground.

However, if we rely on trees alone to capture carbon, you have to make sure those forests are preserved for a very long time. They must not, say, inconveniently burn down or be cut down, because that would release all the CO₂ back into the atmosphere. This is why it's advantageous to capture the CO₂ and store it underground safely — we know that once it's down there, it will remain trapped for geological time periods (thousands and thousands of years).

Gimmick or Game-Changer? The Role of Direct Air Capture in Net Zero

Hugo Rifkind: "Fundamentally, Paul, is this direct air capture idea real and scalable, or is it just a gimmick? If we’re aiming towards net zero (and we are), can we do it with technologies like this — basically keep doing what we’re doing and just suck the carbon dioxide out of the air? Or is this really just small beer compared to completely changing how we produce our energy in the first place?"

Professor Paul Fennell: Honestly, I think we need to do both. We absolutely need to transition our energy generation to low-carbon sources like renewables and nuclear. We might also keep some gas-fired generation, but if we do, it should have carbon capture and storage on it. Once we've done that — once we've cut emissions at the source by capturing as much CO₂ as possible from power station and industrial exhausts (where it's much easier to capture than from the air) — then we can start thinking about pulling the remaining CO₂ out of the atmosphere.

Direct air capture is a good technology to get up and running now. It’s useful for us to test it, see how well it works, and find out what it really costs in practice. (It will definitely cost a lot more per tonne of CO₂ captured than taking CO₂ from a power station flue, as I mentioned.) It’s worth doing as part of the toolkit to reach net zero. However, I wouldn’t want to rely on it for our whole climate solution or our entire energy future — it's more of a supporting technology rather than the primary answer.

Hugo Rifkind: "Understood. Thank you very much indeed, Paul. That was Professor Paul Fennell, Professor of Clean Energy at Imperial College London, discussing direct air capture technology and its place in the UK's net zero strategy.”