S1 #5 | Can we engineer our way out of this?

Contents: introduction, guest appearances, further reading, transcript, sources, credits

"We can put it right back down the very same well that we got the oil and gas out of" (Katherine Romanak)

Measurable, instant, continuous carbon capture, and safe, reliable, permanent storage. Sound too good to be true?

Actually, this is exactly what engineered solutions like DAC (Direct Air Capture) and geological sequestration claim to bring to our carbon removal toolkit. The former promises technological innovation that does a tree's job better than a tree. The latter offers one of our surest bets that once we've got the CO2 down, we can keep it down, out of the atmosphere for as good as forever.

Naturally, however, these unnatural solutions have catches, complications... even controversies. Are we engineering our ways out of one problem and into several others?

In this episode, Tom and Emily suck it up, dig deep and take a plunge into some of humankind's most tech-heavy attempts at fixing our carbon problem.

This episode's guests

Many thanks to our excellent guests in this episode:

Want to delve deeper now you've listened to the show? Look no further than the list below of articles, podcasts and other resources. They helped us to learn more about engineered approaches to carbon capture and storage, and we think you might like them too...

Our Reading List & Sources

NamePublisherPublishing/Release DateSourceSummaryTag(s)Type
Solar PV costs fall 82% over the last decade, says IRENA
June 3, 2020
10 Carbon Capture methods compared: costs, scalability, permanence, cleanness
November 11, 2019
A CO2 Direct Air Capture Plant Will Help Extract Oil in Texas. Could This Actually Be Good for the Climate?
July 31, 2019
Carbon Engineering - Our Story
November 10, 2021
Transporting CO2 - Fact Sheet
Assessment of the major hazard potential of carbon dioxide (CO2)
June 1, 2011
Between a Rock and a Hard Place: the science of geosequestration
August 13, 2007
Development of a CO2 transport and storage network in the North Sea
November 6, 2007
What is carbon capture and storage and what role can it play in tackling climate change?
May 1, 2018
Carbon Visuals
November 10, 2021
How underground CCS works: low leakage risk, 2%
March 16, 2020
Start-ups test ideas to suck CO2 from atmosphere
July 15, 2020
US policy ideas to advance CDR (focusing on DAC)
Different approaches to changing policy around Direct Air Capture
Driving CO2 emissions to zero (and beyond) with carbon capture, use, and storage
June 30, 2020
An investigation into the CCUS space, assessing the technologies and economics behind several CCUS scenarios over the next decade.
Carbon useCCSEconomics
S2E8: Salvation in the Air
The Economist
August 1, 2019
"At the dawn of the 20th century, chemists dreamed of extracting nitrogen from the air and turning it into a limitless supply of fertiliser. Sceptics thought they were crazy -- it was possible in theory, but it was unclear if it could be done in practice. What happened next changed the course of 20th-century history, and provides inspiration to innovators pursuing a different dream today: sucking carbon dioxide out of the air to avert climate change. Might they not be quite so crazy after all?"
DACScaling upInnovation
Money is pouring into carbon removal technologies, but the companies involved struggle to pay for it
March 6, 2021
This video gives an overview of carbon capture, DAC, case studies (Carbon Engineering and Climeworks), and how policy can address the difficulties that DAC and similar companies face in generating revenue.
Carbon useEconomicsScaling upDACPolicy
Breaking down the case for massively scaling up carbon removal tech
January 14, 2021
A useful summary of a Nature Communications study, which models what a massive scale-up in DAC across the world could look like.
DACScaling up
Carbon Dioxide Removal Primer
Various authors
January 1, 2021
A summary of all things carbon dioxide removal related, written by several experts in the field. An invaluable resource, available as a book or freely available online.
Direct Air Capture: Leveraging technological innovation to safely remove carbon dioxide from ambient air
The Economist
June 1, 2020
Part of a series from The Economist, investigating the potential, risks and readiness behind different carbon removal technologies. This article focuses on DAC.
Carbon180 Deep Dives
February 1, 2021
Three-page introductions to the key areas of carbon removal - forests, agriculture, DAC, carbon use and BECCS.
Carbon useBECCSDACAgricultureTrees
Exxon Mobil 2021 Investor Day Webcast
Exxon Mobil
March 3, 2021
Particularly relevant here are slides 14-17, where ExxonMobil show the potential they see in CCS technologies.
Carbon useCCS
Carbon Capture and Storage: technically possible, but politically and economically a bad idea
Richard Jones
June 23, 2019
An argument outlining the perils of reliance on CCS technology to reach net zero emissions

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Tom Previte 0:02 Emily, something that's been on my mind is trying to visualise, you know, what does a tonne of co2 even look like?

Emily Swaddle 0:09 Well, it's a good job of doing a podcast, Tom because it's all about visualisations on a podcast, I can actually help you. There's this company called Carbon Visuals, and they've got some great images that help you figure out sort of these abstract numbers that we keep throwing around. So I've got a picture here that demonstrates one ton of carbon dioxide, and it's a cube that is 8.13 metres high. And it's sat next to a kind of average, suburban, semi detached house, just for scale. And I can tell you that this cube is quite significantly taller than the house, and definitely wider than this house.

Tom Previte 0:50 So one ton is roughly the equivalent of a semi detached house in terms of size.

Emily Swaddle 0:55 Well, no it's like a big, semi detached house, semi detached mansion, maybe.

Tom Previte 1:00 Oh wow okay. You learn something new every day, and we haven't even started yet.

Tom Previte 1:12 Hi, listeners, and welcome back to the Carbon Removal Show. I'm Tom Previte, and as ever, I'm joined by my wonderful co-host, Emily Swaddle.

Emily Swaddle 1:20 Welcome back everyone. In today's episode, we're going to be asking if technology can help us overcome some of the hurdles that we've discussed so far. Last time, we finished by discussing BECCS, but we really only gave you half the picture. I think we were pretty clear on the "BE" and on the "CC". But in this episode, we want to address "S" - storage.

Tom Previte 1:43 We want to go into that and further. We're going to be looking at the storage element of BECCS, and also taking a look at the technological innovations that might allow us to store without the need for burning plants in the first place.

Emily Swaddle 1:57 Yeah, every solution we've talked about so far has involved plants or biomass in some way or another. And as we've mentioned many times, it is super important to restore and protect natural ecosystems, as well as getting our agricultural land in better shape. But we also know that in terms of carbon capture, these solutions have limits in scalability, due to land use and other resources. And they lack the permanence and measurability that we really need for this industry to gain traction.

Tom Previte 2:29 Exactly. Biomass may be the natural way to draw down carbon. But is it the only way? As we continue piecing together a fuller picture of the opportunities out there, we're going to look at more tech based solutions, such as DAC or direct air capture in this episode to understand whether human engineering can provide an additional solution to the problem. And importantly, do we want it to?

Emily Swaddle 2:54 Okay, let's talk storage.

Tom Previte 2:57 You know it's hard to believe we've mentioned permanence so many times. And this is the first chance we've actually really had to looking at storage beyond hope the soil holds on to a lot of carbon.

Emily Swaddle 3:07 Yeah that's very true. So back to my favourite acronym briefly, BECCS. The CCS part is often heard as a standalone thing without its BE pals. CCS or carbon capture and storage has been around for decades on a small scale on conventional fossil fuel plants. We'll get into that later because yes, it has its flaws and controversies. But let's start with what it is and what it can do.

Tom Previte 3:33 Well, we already know that the CCS in BECCS allows us to store carbon that was previously floating around the atmosphere and was then captured by our plant friends.

Emily Swaddle 3:43 Right. But what do we do with the carbon once we've captured it? One way to be sure it goes somewhere and stays there is to take it out of the carbon cycle entirely and store it somewhere like back underground. Yeah, exactly. One of the most developed and most promising storage techniques is geological sequestration. That's a fancy way of saying that the carbon is compressed into a liquid, and then pumped deep down beneath the earth. We spoke with Dr. Katherine Romanak. She's a research scientist at the Bureau of Economic Geology in Texas. And she's an expert in environmental monitoring at geological co2 storage sites. Dr. Romanak asked us to think about this process in terms of the reverse of oil and gas production. We're putting something back where it came from.

Katherine Romanak 4:30 That's kind of a tagline. It's like we're putting it back where we got it. Because there's a lot of people that have a hard time understandably understanding geology, and how does that work? And I don't understand, how do you put carbon dioxide deep in the earth, isn't it a rock, and how do you get it in there and all that. But I think that if we think of it as the reverse of oil and gas production, because we know that there are fluids that reside in the earth, oil and gas and salty water, reside within the small spaces that are deep in the earth, and so we know that oil and gas can be trapped for millions of years. And we know that we can extract it, and we can burn it. And we can get energy and carbon dioxide. And then if we capture that carbon dioxide, we can compress it into a liquid. And we can put it right back down the very same well, that we got the oil and gas out of. So it's, it's literally putting it back where we got it. But there's one thing to be very, very aware of. And that is that we are not only talking about fossil fuels here, we're talking about many, many industrial sources of carbon dioxide. It's not just the burning of fossil fuels, it is cement production, iron and steel production, many other industries that are emitting carbon dioxide.

Tom Previte 5:51 This brings to mind the carbon cycle that we talked about back in episode one, you can really clearly see where this captured carbon will sit with Katherine's description, you know, deep, deep underground. So we really have sort of removed it from the cycle.

Emily Swaddle 6:06 Yeah, it's deep underground. And it's not in a form where it might burn or decompose or be released into the atmosphere in any way. Tom, I mean, I don't know if I dare say this, but you know what, this is right?

Tom Previte 6:22 A miracle? Lifesaver? I don't know. What is it?

Emily Swaddle 6:27 Yeah I mean, it's all those things because it's permanence!

Tom Previte 6:31 Permanence, yes! So we can finish this podcast, let's, let's wrap things up now then.

Emily Swaddle 6:39 If only my friend, if only. Okay, let's, we have to break this process down. And we can think about it in two parts, getting it down there and keeping it down there. So getting the carbon down there requires a space wherever down there is an a way of getting the carbon there. So infrastructure to do that. In terms of the storage space, we're looking for large spaces around kind of like one kilometre or more underground. These might be natural saline or basalt formations, or they might be pre existing oil fields, gas fields, or coal seams.

Tom Previte 7:14 Nice. In those cases, presumably, some of the existing infrastructure then can be useful in getting that carbon back underground.

Emily Swaddle 7:21 Yeah, it really is useful to have some existing infrastructure in place, for sure.

Tom Previte 7:26 I really like the circularity of that in a way. We, you know, we kind of took it out in the first place and now we're putting it right back where we found it.

Emily Swaddle 7:34 Yeah, I agree. It feels right, somehow. The thing is, when we're talking about infrastructure, we're talking about more than just like a couple of mobile offices and a portaloo. You know, there's infrastructure needed for the capture process, of course, and the storage process. And then also, the transportation in between. Transport can take the form of ship, tanker, or pipeline, so there's more infrastructure needs to be aware of. And once we've done all of that, to get the carbon underground, we also have to make sure it stays down there. Katherine explained how to ensure permanence.

Katherine Romanak 8:08 What we have found is that, first of all, we know the right places to put co2, we're not just going in and slapping it down there, we need to find places that have room in the rocks to put it. And we also go through a lot of effort to ensure that above that reservoir above that place, we're going to put the co2, there are rocks that are so tight, that have no space in between, that will cause a barrier. So the co2, even if it tried to rise up, it couldn't rise up, because we have what we call ceiling layers above. And so we do a lot of work to make sure that at first we find the right places to put co2. So really, the main concern that we have about co2 coming back up would be through the wells themselves, because it's the wells that actually punch holes, if you will, through those ceiling layers. And so it's the wells that we need to ensure are constructed correctly. And what we have for that are regulations. And we have rules for how you are to drill a well and complete a well and operate a well. And so what what we really need to do is we need to make sure that the regulations are followed and that they're good. And then they're you know, the regulations are enforced.

Tom Previte 9:32 It's sort of ironic that the only major risk factors for co2 release are the oil and gas wells, which were the things that led to a lot of this problem in the first place. If we just back up a second, what kind of leak are we actually talking about here? I can see how a sort of puncture in a bicycle tire size leak could be really manageable, but is it possible to get something like a volcanic eruption sized leak?

Emily Swaddle 9:57 That's a good question, Tom. The first thing to note is that that size eruption, as you say, is actually really unlikely. And that's because the sites are chosen really carefully, and they're very well suited to storing carbon. Oftentimes, you know, they're sites that have actually been storing carbon in the form of oil or gas for a really, really long time. However, that doesn't mean we can sort of go easy on the monitoring thing.

Tom Previte 10:22 What are the risks we're looking at?

Emily Swaddle 10:24 Well, one risk is oxygen displacement. CO2 is very dense and can displace oxygen, creating a risk of asphyxiation for those nearby any leak. The good thing is that wind and diffusion will quickly spread this around. So that risk is temporary. But there was one natural disaster that I read about that I want to share with you at Lake Nyos in Cameroon. So like I said, this was a natural disaster. So it's not really the same thing. But hundreds of 1000s of tonnes of co2 erupted from the lake. And in this instance, the effect of that co2 killed 1700 people and 3500 livestock, so it was a really big deal. We should also note that the amount of co2 that erupted in this instance is like orders of magnitude more than we would expect from any kind of eruption from carbon storage underground that we would be undertaking. But again, it just highlights the seriousness of all this.

Tom Previte 11:21 Are there any other risks?

Emily Swaddle 11:23 Yes, there are some we know of. If there were to be a leak, it could indeed affect local plant life.

Katherine Romanak 11:29 As far as the biosphere goes, so much research has been done. And you can actually get information on specific crops. But basically, the impacts are very localised, so they're not spread out, there'll be a small patch or a localised patch, where yes, you can get some some of the biota can be damaged, some of the plants can be damaged. And again, then that's only going to come back once you stop the leak. But once you stop the leak, then that can be recovered as well.

Emily Swaddle 12:02 These risks remain very localised and temporary, but they do deserve some of our attention. Ultimately, the overall benefit of negative emissions to the biosphere is like very likely to outweigh the risks, to be honest. Just one more I want to mention is acidification of groundwater, which in turn releases metals into the water system.

Katherine Romanak 12:22 First of all, if you talk about groundwater, so drinking water sources that we get from our shallow aquifers, so our concern is not the carbon dioxide in the water, right, because if you put co2 and water, you get Perrier, you just get, you know, something that people pay more money for than the stillwater, right? But the concern there is that when the carbon dioxide enters the aquifer, you get a lowering of the pH, so you get an acidification which I think your listeners can understand that. And then what can happen then is that some of the minerals that are in the rocks where the water is residing, can dissolve. And if there's some small traces of metals within those minerals, they will be released into the groundwater. So there's been a lot of study on this, we do see an increase in the metals that are released into the aquifer water, but they never go above drinking water quality standards. And it always reverses itself. So it's a short lived phenomenon. So that has made us feel much better about the fact that if there was a slight chance of a leak into the aquifer, that it would be very easily remediated. And that the that the impacts would not be as bad as we first thought that they might be.

Tom Previte 13:40 So drinking water remains safe. That is reassuring.

Emily Swaddle 13:43 Yeah, it is. But it's still something to keep in mind.

Tom Previte 13:47 So I suppose all the potential risks impact how these processes are carried out, rather than whether they're carried out then.

Emily Swaddle 13:55 Yeah, exactly and also, where. When building the infrastructure for all this, we need to think, okay, where are the pipes going? Which communities are going to be at risk should a leak occur? And, you know, certainly if we're utilising existing mines, or oil or gas fields, these may be in communities that are already less affluent or less supported, which could affect you know, ease of access to health care, for example. It quickly becomes a social justice issue. So it has to be taken into consideration from the very beginning.

Tom Previte 14:24 Yeah, agreed. This is such an important aspect of all this. And I'm just thinking, it's obviously vital to be aware of the risks, but also to think about that risk probability impact matrix. From what Katherine has said, it seems quite unlikely that something like a leak would occur, given the regulations and the monitoring that are in place. And even if it did, I mean, compared to the damage, say an oil leak might have, and we've all seen the photos of that sort of devastation.

Emily Swaddle 14:52 Yes. In most cases, the risks of leakage are like far less than the risks from fossil fuel production. In addition to the risks, I want to mention a few of the challenges that this technology faces as it's developing. It seems like it really has a lot going for it. But like with everything, there are hurdles to get over.

Tom Previte 15:12 I've got one hurdle, who's going to pay for this? Sticking my capitalist hat on, it might be great for our planet and all but that doesn't pay the bills.

Emily Swaddle 15:21 Yeah, you nailed it, Tom. It can be a costly process. And as you say, sequestering something means there's no real economic incentive, pushes from policy could really help with that, which obviously requires political will to prioritise this process. In order to improve this technology and scale it up. We need incentives.

Tom Previte 15:40 And oftentimes, political will follows public will. So in general, is this something people are getting behind?

Emily Swaddle 15:48 Well, unfortunately, CCS has had some PR problems. I mentioned it's been around for decades. Well, it's actually mostly been used not in BECCS, but by the oil and gas industry. So firstly, CCS allows oil and gas companies to reduce the carbon released from burning fossil fuels, and meet emission reduction targets. And secondly, for those drilling oil, the captured carbon is actually useful because it can be injected into an oil field, and it allows them to get more oil out in a process called enhanced oil recovery. So CCS has a complex history. And this has led to some negative public perceptions around the process. And we agree that we need to scrutinise how it's used. And its environmental impact on probably like a case by case basis, really,

Tom Previte 16:37 What we're looking at here with CCS, although it can lead to a negative emissions outcome, for example with BECCS, it's not a negative emission technology on its own. The carbon capture part of this isn't necessarily removing co2 from the atmosphere, it's merely abating or preventing it from entering the atmosphere.

Emily Swaddle 16:56 Exactly. CCS is just a tool, how it's used is the thing that really makes the difference. Ultimately, though, we've talked a lot about permanence throughout this series. And we've looked at methods of sequestration that promise us 10 years, 100 years, and so on. But even if we trust the world will significantly decarbonize over the next few decades. We don't want to create a time bomb for ourselves. Katherine explained why geological sequestration has the edge here.

Katherine Romanak 17:23 Permanence is a really important topic as well. There's a lot of talk about nature based solutions for capturing co2, for example, you know, forestation and all of these really great ways that we can use our biosphere to store carbon dioxide, we have to realise the fact of permanence. And I think that's one thing where geological co2 storage is absolutely one of the best things we can do. Because once we put it down there, it's down there, it's not coming back. If you have a forest fire, or if your land use practices go away, you know, then the nature based solutions may not be as permanent. But again, these are great solutions. They're they're solutions that we need. But I do want to outline the fact that the permanence of geological co2 storage, it can't be matched by any other technology.

Tom Previte 18:24 So we've talked about how CCS can help us abate and sequester carbon that's being released through human activities, and either as an add on to otherwise carbon positive technologies like fossil fuel burning or industrial processes, or to more carbon neutral sources like biofuel. But what about all that carbon that's getting into the atmosphere anyway? And the many years of emissions that we're currently dealing with that legacy co2 that's already warming up the planet?

Emily Swaddle 18:51 Yeah, if there's anything we've established over the past few weeks, it's that there's a lot of carbon out there. We've got gigatons of this stuff, and some of it as a result of things like aviation and cement production, they're going to be really slow and difficult to decarbonize.

Tom Previte 19:07 A solution, which is getting a lot of people excited at the moment is DAC, or D, A, C, which stands for direct air capture. And just like how trees or other biomass capture the co2 that's already in the atmosphere through photosynthesis, DAC is designed to pull carbon dioxide directly from the air.

Emily Swaddle 19:26 Yeah, it sounds like the clue's sort of in the name with this one. Alright, quick confession, Tom. Months ago, when we first started looking at all these solutions, I remember struggling to understand some of the differences between DAC processes and the CCS process. I genuinely sometimes get them confused. As I understand it, they both sort of work like a large scale filter almost for carbon dioxide, even though we use them in very different places.

Tom Previte 19:54 I think that's totally understandable. I too, was struggling to kind of draw the line between these different technologies. And so something to bear in mind is that capturing co2 in the atmosphere is a very different challenge to capturing it at a point source. For example, from a flue stack or through BECCS. I spoke to Steve Oldham, the CEO of a direct air capture company called carbon engineering to learn more about this difference.

Steve Oldham 20:18 It's completely separate technology. And the reason is it's the quantity of co2. So in a for example, flue stack, the co2 quantity within the flue stack emission is much much higher. So it's a lot easier to pull out the co2. It's a bit like panning for gold, the more gold that's in there in the first place with your your sieve as you pan for gold, the easier it is to find some. In the atmosphere, it's 400 parts per million. So this is a lot harder to do, which is why direct air capture has taken longer to develop. And also, frankly, why today it's more expensive, because it's inherently harder to do. So flue stack capture is great, fully support everybody doing flue stack capture, but it's an easier problem. And of course, the problem with flue stack capture is you capture the co2 in all these locations, but then you have to do something with it, you have to pipe it across the country to somewhere where it's safe to put co2 underground. Direct air capture can go anywhere, because air is everywhere. So we eliminate the need for those pipelines, we build our facilities on top of the sequestration site.

Emily Swaddle 21:23 Okay, sounds good. What's actually going on here, though, what does a DAC facility consist of? I'm picturing sort of like a metal rainforest.

Tom Previte 21:33 Okay, so Emily, Imagine you're driving in driving in an electric car, obviously. You're driving past the direct air capture facility. And the first thing that you would see is this big wall of fans towering overhead blocking out sunlight.

Emily Swaddle 21:47 Okay, one question, what kind of fans are we talking like? Do they look like wind turbines? Is it like the fan I have on my desk? Is it like, sort of pretty lacy number that a flamenco dancer might use?

Tom Previte 21:59 Probably less likely to be the last one. But-

Emily Swaddle 22:01 That would be pretty though I quite like to see that on the side of the road.

Tom Previte 22:05 Yeah, well, who says carbon removal technologies can't be beautiful. But it's not quite. If you imagine more like a slow moving jet turbine, and you have these stacked on top of each other. Now these fans play an important role, but are not actually the part where the thing happens. Fans draw in the ambient air. So imagine a hairdryer if you put your hand in front of the back of it, it's sucking it in. In layman's terms, the air then slips through these fans, then makes contact with some sort of contactor. So that's either a solid solvent or a liquid solvent. And now this, this is where the magic happens. The contactor separates the co2 from the air, and the co2 is then pried off the contactor. And what we're left with is one, cleaner air and two, a concentrated form of co2.

Tom Previte 22:23 That does sound like magic. Nice.

Tom Previte 22:59 Steve Oldham's company, Carbon Engineering is one of the handful of DAC companies who are taking this technology out of the laboratory. Steve described Carbon Engineering's particular approach to this process.

Steve Oldham 23:12 If you're going to capture co2 from the atmosphere, you have to absorb it into something, you have to have a chemical reaction and absorb it into something. So what do you then do with that something and you know an analogy here would be imagine spilling milk on the floor, you get a sponge, and your sponge fills up with milk. And then you either have to wring it out, or you replace the sponge. So we go the former model, we regenerate the chemicals that we use. And that's really important. Because if you're going to do this at large scale, you can't be throwing away the chemicals that you use as part of your process on a continuous basis, you're just going to run out of those chemicals, and you create another problem somewhere else in having to dispose of them all. So our technology actually remakes the absorbent on a continuous basis. Think of it as constantly wringing out the sponge and restarting again. And we think that's a critical element of making this technology available at large scale.

Emily Swaddle 24:05 I love the commitment to reuse there. Something we're learning all the time is that these technologies have environmental and resource costs. Does this process actually work though? Like honestly, I'll be honest, I haven't seen too many DAC plants around the place as I've been on my travels, you know?

Tom Previte 24:21 Yeah, it absolutely does work though, Emily. But at the moment, it's only being utilised on a very limited scale. So carbon engineering, they're a Canadian based company, and they've got a test plant in British Columbia. This isn't designed to be commercial yet, but it has been operating and proving the concept since 2015. And it's able to remove about one tonne of co2 every day. For scale, that's about three weeks of the average American citizen's emissions. So the need to scale it up is clear. But if you don't trust my optimism, perhaps you will be swayed by some of their investors like Bill Gates or some fuel companies even Chevron and BHP.

Emily Swaddle 25:01 Big names, big names. Yeah, I mean, I can totally see why fossil fuel companies might want to invest sort of in carbon removal technologies in general. And we'll probably dig into that later on. But when we're looking at the choices that we've already discussed, you know, I'm just thinking that carbon dioxide concentration at a flue stack is obviously much higher. And so therefore, capturing it there makes so much more sense to me than in like a random field in Canada, where the level of co2 is like so much lower. And beyond that, considering the challenges of DAC, why choose this for investment over so many of the other great ways that we've talked about over the episodes to draw down that carbon?

Tom Previte 25:41 Well, there are several potential benefits, which bring DAC together as this pretty unique approach in this space. The first, which we've already touched on is that DAC allows us to capture carbon that's already in the atmosphere. So in this sense, it's much like trees or other biomass. But added to this, it has the potential to store this carbon more permanently, and is likely to be less vulnerable to changes in climate or natural disasters, like our nature based friends. Secondly, as Steve mentioned earlier, DAC facilities can theoretically go pretty much anywhere. With the CCS technologies, we need the technology and infrastructure at the point of emission. And with DAC, we could locate these the point of sequestration, for example, which would reduce energy and the transport burden. And we could also focus these on areas that are preferable, you know, for other reasons, such as to minimise ecosystem disruption or to generate jobs where, where they're needed. And finally, DAC is less needy in terms of land use than many other methods. You know, Steve claim that Dak delivers 100 times more carbon sequestration per acre than any other currently viable method, and that we could deal with the world's entire emissions by building DAC plants over an area equivalent to say, just the island of Tenerife. Not saying that we want to build everything on the island of Tenerife. And we've talked so much about the competing demands on our land over recent episodes, that this feels like a game changer.

Emily Swaddle 27:13 Yeah, I see what you're saying. And it does sound like DAC is a bit of a no brainer if we can get it to scale. Obviously, as you said, hopefully leaving the island of Tenerife with some land that isn't DAC based. Here's the thing though, Tom, I've been around this podcast world long enough to know that we're going to start diving into some of the complications now. You've been paying me a beautiful picture, but come on, hit me, what's the downside?

Tom Previte 27:39 So as with any solution, we need to think about resource intensity. And with DAC, the first of these is actually water usage. I knew it, I knew there'd be something. So we understand that different methods of DAC have different water needs. And Steve made the point that carbon engineering method is actually less water intensive than the equivalent of aforestation for example. But some methods do still require significant water input. And this could compete with human or irrigation requirements in parts of the world where water is or is becoming scarce. The second is energy intensity, that plants require a big energy input. And if we're sourcing this from unclean sources, we're exacerbating the problem we're trying to solve here. Steve described how Carbon Engineering is dealing with the issue.

Steve Oldham 28:28 We power our plants mostly through renewable electricity. Our early plants will also use natural gas. That's a part of the process we we heat up calcium carbonate in a piece of equipment called the calciner, and that allows us to regenerate the sponge to go back to that analogy. Very important to say when we do that all the emissions from the natural gas are captured as part of that process. So when I talk about one megaton plant, it's one mega tonne of atmospheric co2. And then we also capture any co2 from any natural gas we use. Again, the beauty of direct air capture is the location independence. So what we do is we we will build a plant with additional renewable electricity. So we don't go and build a plant in some large scale city where renewable electricity is needed to replace fossil fuel. We're actually building new renewable energy plants alongside our plants, so that we take all of the energy from those plants and power our plant. So that energy wasn't going to be used for anything else. It's in a remote location or wherever you happen to be. We also get the benefit because we're not using storage or transmission, the cost of that energy is a lot cheaper. We're in the process of designing a plant that will replace the use of natural gas. But we figure the world needs this technology now. And we need to bring it to market now. So we'll use natural gas in the near term, we'll capture all the emissions. So it's there's no climate impact.

Tom Previte 29:58 Carbon Engineering's approach here shows that this is possible to do in a way that doesn't create an energy burden. But it does start to highlight the complexity of this problem.

Emily Swaddle 30:09 Yeah, I mean, we need to think about not only what type of energy we're using, but also where it's coming from. And whether we're competing with existing infrastructure or communities for that energy. Just the premise of having to create more energy to clean up the mess created by our existing energy sources. I don't know it just kind of gives me a bit of a headache. And it does sometimes feel like we're like over engineering our way out of this crisis.

Tom Previte 30:33 Yeah, I can see where they're coming from Emily, every solution creates yet more problems. And on top of all of this, we need to be aware of the chemicals that we're using in the process. As Steve already touched on, they've chosen the liquid solvent, which allows them to reuse the chemicals. But there are diverse approaches here.

Steve Oldham 30:50 So our friends at Climeworks and Global Thermostat, they use a solid absorbent, we use a liquid absorbent, so our sponge is actually a liquid. So there are pros and cons, our technology is more energy intensive. However, we remake our absorbent the solid guys don't. And also the solid absorbents have to operate in a vacuum. And it's hard to do vacuum at large scale, you can't make a big area a vacuum. And if you do smaller ones, you need to replicate many, many times. So we our view is that liquid solvents are the better way to go for large scale. And our climate problem is large scale. But again, Let me emphasise every tool, brought the problem is a good tool. So we think Climeworks , Global Thermostat, they absolutely will have a role to play here.

Tom Previte 31:38 It's obviously a balancing act. And again, this shows the complexity of the calculations these companies are making. Finally, and partly as a result of this resource intensity, DAC is a lot more expensive at the moment than many other forms of carbon removal. Now there's a tendency to talk in terms of cost per tonne of co2 removal, and another DAC company, Climeworksm estimate that the current cost of co2 removal through this process is in the region of about $600 a tonne. Now the expectation is that this will reduce to $200 to $300 a tonne over the coming years. And future hope is that if this is deployed at the large scale, prices could reach as low as $100 a tonne in the long term.

Emily Swaddle 32:23 I know we need to be super sceptical on making these sorts of comparisons with these figures. Because we're dealing with like wide ranges, and a really high level of uncertainty as to future costs. You know, everything's just being modelled right now. But it's worth noting that a lot of the methods we've looked at so far, although at the time we didn't really talk about cost per tonne, are already indicating a cost well beneath that $100 per tonne mark. So I can see why this is a really big hurdle.

Tom Previte 32:49 Absolutely. But Steve explained why we shouldn't see this cost as representing the whole picture.

Steve Oldham 32:57 So the danger is if we said tomorrow, the worldwide price on carbon is $50. Great, that will encourage progress up to the point where the cost of abatement is $50. But what happens is my company I go off and play golf, because $50 doesn't allow you to do direct air capture. So we just killed off all the innovation required for all the rest of the curve. And fantastic, we'll make great progress up to the $50 point. And then we stop. So the counter to that people will say well, then we go to $100. But this type of technology like direct air capture would have been coming down the cost curve becoming more affordable and more available if we enabled it from day one. So I think you need a system in which you enable the technologies which we're going to need to deal with the harder parts of the abatement curve and the legacy emissions while also encouraging people to put a price on carbon that's affordable and that people can start at the electoral level. So to me, there needs to be a differentiation of some sort. Otherwise, we will halt the development of these technologies like ours that are going to be needed before we're done.

Emily Swaddle 34:06 Yeah, I also think we need to move a bit beyond the cost per tonne concept. Because we've seen how not all co2 removal is equal, you know, if DAC is really promising that permanence that we've been lacking, thanks in large part to my good friend geological sequestration might I add, then we can't really compare it against the sort of sequestration we're getting from aforestation or regenerative agriculture and those other examples. They're just such different processes with different benefits and different costs for these benefits. I suppose you know, if we're looking at a pure carbon sequestration measure, DAC certainly has a lot of potential.

Tom Previte 34:41 Agreed. no two tonnes are created equal. And Steve's point here is that we need to invest in it now to start bringing down that cost. And we don't know what our emissions picture is going to look like in 10 or 20 or 30 years and if we need DAC to help us reach net zero, we want to make sure that we've given it a fighting chance to deliver in a way that we can stomach economically to deal with these cost considerations, and to help this technology become more viable, many DAC companies have looked at how they can generate revenue from the co2 they've captured. There are a number of ways to do this. But a popular one, depending on who you talk to, is selling it to those who want to use it for enhanced oil recovery.

Emily Swaddle 35:23 Oh, here we go. Again,

Tom Previte 35:25 Which we have already touched on, yes. And although this retains the benefits of the initial removed carbon, it also enables further fossil fuel emissions. So you'll then want to capture that carbon at source to prevent this contributing to further atmospheric co2.

Emily Swaddle 35:40 Sorry it just sounds like the beginning of another hard to get out of cycle, you know, we capture carbon, use it to pump oil out of the ground only to capture the carbon it releases again, and keep using it for fossil fuel production and round and round we go. We're not actually solving the issue of too much carbon in the atmosphere.

Tom Previte 35:58 Yeah. But some of the only people who can afford to pay for this in the first place are oil and gas companies, shouldn't they be paying the high price for this new technology in order to lower that cost in the long term such that others can afford it? Another possible revenue stream is the generation of synthetic fuel from the carbon itself, creating this carbon neutral energy source. Now, this is obviously far from the permanent sequestration that we're looking for, again, and leads us into a wider argument, which Steve addressed. He explained that in order to make the technology viable, we need to face the reality that we live in a fossil fuel powered economy.

Steve Oldham 36:35 The plants that we're building in the Permian Basin, we have all said from from day one, that some of those plants will be used for negative emissions, and some of them will be used for what you call enhanced oil recovery. And we've said that the ratio and the speed of that depends on the market. If nobody wants to buy negative emissions if the government policies don't come into place, enhanced oil recovery helps us close the economics. But I want to emphasise enhanced oil recovery in this context is maybe not as bad as some people would perceive. What happens when we do enhanced oil recovery as we're pulling more co2 out of the air than is contained in the crude that comes back up. So just stop and think about that for a second. Imagine if I called you up and I said, I just invented carbon neutral fossil fuel, I've just found out that fossil fuel actually doesn't have to have a carbon footprint. Everybody in the world is uses fossil fuel today. It's raised our standard of living. It's essential in many economies all around the world. So if you had a way in which you could make it carbon neutral right now, is that a bad thing? I don't think that's a bad thing. I think we have to face the reality that we can't stop using fossil fuel overnight or even anytime soon.

Emily Swaddle 37:47 I'm not fond of that reality. But I suppose it's true. I take his point. But it feels like we have a lot of slippery slopes here. You know, we're really having to trust these DAC companies to ensure that their overall process is carbon negative, because there are just so many areas where it might lead to further emissions, whether that's from the energy required to power it, the enhanced oil recovery it might enable, or the synthetic fuels it might help to produce. As you touched on Tom, Carbon Engineering has received investment from and is partnering with fossil fuel companies. And I know from reading about this space that this is true of other DAC companies as well. Fossil fuel companies have a lot of interest in this technology, not only because it helps them offset or reduce their emissions, but also because it might help them get the most out of the fossil fuel reserves that we still have left. I feel like this is a really strong relationship. And I'm just keen that we don't let DAC become another excuse for business as usual for the oil and gas industry.

Tom Previte 38:47 This is definitely something to be aware of. And there's certainly some public unease about this. And DAC in a way is a tool similar to CCS. We have no control over who uses this tool, especially in its infancy. And it really depends on who's willing to invest.

Emily Swaddle 39:05 For the past few episodes, we've been talking a lot about permanence. We never shut up about it. And it felt like for the first time in this episode, we actually got a sense of what that might look like, in real life. You only need to have seen the news of forest fires this year, all over the world to get the sense that carbon stored in biomass really isn't safe for long periods. And as much as we really should be reforesting and regenerating these natural lungs of the earth. We also have to deal with this huge surplus of co2 We've got floating around in the atmosphere. We want it gone, and we don't want it coming back again.

Tom Previte 39:43 Yeah, and it's worth mentioning that geological sequestration isn't the only form of permanent sequestration. There are other exciting solutions that also get rid of this carbon dioxide in a fairly permanent way. You could think of enhanced weathering which basically mineralizes carbon and locks it away in the form of rock. So if anyone's interested in alternatives, there are a lot out there, but pumping it underground, and often back where we've taken it from seems like a promising approach.


The Carbon Removal Show is a Restored.cc and Cofruition production. We are sponsored by Patch. Here's who made this episode happen:

  • Emily Swaddle & Tom Previte - co-hosts
  • Ben Weaver-Hincks - producer
  • Henry Irvine - researcher
  • Sam Floy & Patrick Carter - project managers
  • Mercy Barno - editor
  • Sam Carter - music producer

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