Why we need to remove carbon dioxide from the atmosphere, with Carbon180’s Anu Khan

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Good Clean Energy is a podcast that tackles one of the most existential questions of our time: how to build a world with abundant, affordable, carbon-free electricity. TAE’s Jim McNiel dives into deep conversations with experts ranging from scientists to innovators to changemakers about the challenges our current energy systems face and updates on the race for game-changing, clean ways to power our lives.
In this episode, Jim is joined by Anu Khan, Deputy Director of Science and Innovation at the nonprofit Carbon180, to discuss the ins and outs of removing carbon dioxide from the atmosphere.

Throughout the industrial era, we’ve emitted roughly 2 trillion tons of carbon dioxide, 1 trillion of which is still in the atmosphere today and is going to continue to cause warming for an extended period of time, Khan said.

Most of that warming is caused by the burning of fossil fuels for energy, and reducing emissions is crucial to keeping global warming below the goal of 2°C. But the challenge doesn’t end there. That’s where carbon dioxide removal comes in.

While there are a few ways to actually remove the carbon dioxide and there’s the question of who should really pay for it, it’s clear that CO2 removal is necessary.

“It’s fundamentally a climate justice solution, and carbon removed anywhere benefits everyone globally,” Khan said.

Covered in this episode:

  • [3:28] The role of carbon in our planet
  • [5:42] Why we need carbon removal in addition to clean energy
  • [7:38] The difference between carbon capture and carbon removal
  • [11:28] How much carbon dioxide we need to remove from the atmosphere
  • [15:11] The suite of carbon removal solutions
  • [16:38] Who pays for carbon dioxide removal
  • [21:04] The personal carbon offset market
  • [22:27] The potential for cost-effective CO2 removal
  • [25:05] The leading approach to direct air capture
  • [28:57] The most compelling argument for CO2 removal
  • [32:19] A vision for 2035

The following transcript has been edited for clarity.

Twenty years ago, when I was traveling with my family, we flew from Chile to Easter Island to explore the most remote location on the planet, really. It’s also known as Rapa Nui. You stand on the beach and you look up at these huge statues that are lined up like little soldiers. You know, some are six feet tall, some are 30 feet tall. The men would set out to carve a likeness of their chief in stone, and originally these were modest things. They were, you know, four or five feet tall. But as time went on, each subsequent chief wanted a bigger representation of their greatness.

Each statue became bigger and bigger and pretty soon they couldn’t just rock them down the road, they got so big that they had to lay them down and roll them. And to roll them they had to cut down trees. And the idolization grew and the mythology grew. They were chopping down their trees. And as the trees left this forested island, soon after, the topsoil did. And when the topsoil left they couldn’t grow taro or their other crops. And so they had a food crash and then they had a civil war. What happened? Did they not realize that if they cut down all their trees they were gonna ruin their environment?

I think of this story when I think about the situation we’re in today in terms of understanding what’s going on on our planet, and what impact humans are having on how our world is changing.

Since 1840, we’ve emitted 2 trillion tons of carbon into the atmosphere. One trillion gets consumed by the normal carbon cycle, but a trillion remains. And we’re still putting gigatons in every single year. And the science tells us that that warms up the environment, and it’s going to provide catastrophic weather. We should be aware of this, we should acknowledge it, and we should say, “Hey, there’s something we need to do about this.”

On Good Clean Energy, we talk about, how do we make clean energy that is sustainable? But a big part of that conversation is how do we reverse the trend of putting carbon into the atmosphere? And how do we take the carbon that we put into the atmosphere and remove it?

On today’s episode, we’re joined by Anu Khan, Deputy Director of Science and Innovation for Carbon180, a non-governmental organization that’s focused on figuring out ways to remove gigatons of carbon from the atmosphere. It’s a conversation about different approaches, pro and con, and how we make it happen. My name is Jim McNiel, and this is Good Clean Energy.

McNiel: Anu, welcome to Good Clean Energy.

Khan: Thank you for having me.

The role of carbon in our planet

McNiel: I think a good place to start, Anu, is to make sure people understand the role that carbon plays in our atmosphere. So can we just start with the basics about what role carbon plays in the cycle of the planet?

Khan: Yeah, absolutely. So, as many of your listeners probably know, we are facing a climate challenge that is largely due to humans burning fossil fuels and putting carbon dioxide into the atmosphere, and carbon dioxide and other gasses are trapped in the atmosphere and cause warming. Most of the warming is really coming from carbon dioxide, and that’s because carbon dioxide, unlike other greenhouse gasses, stays in the atmosphere for thousands of years and continues to cause warming.

McNiel: I’m confused. Cause I thought the carbon, you know, kind of had a life of like a hundred years. You’re saying it’s thousands of years.

Khan: It depends on how you cut it. So, as we’re emitting more and more carbon into the atmosphere, there are a few things that happen to that carbon dioxide. Some of it is taken up by plants and goes into kind of what we refer to as the fast carbon cycle, so it gets sucked back out of the atmosphere. About 25 percent of carbon we emit is taken up by plants or other places in the land sector and in the ocean. Another 25 percent is taken up directly by the ocean as CO2 dissolved in the ocean, and then the last 50 percent or so remains in the atmosphere and causes warming. That CO2 that remains in the atmosphere can stay up there for thousands of years and continue to cause warming, so the sort of chemical destruction of the CO2 takes a long time, but the uptake of CO2 into other parts of the global system can be a lot shorter.

“The last 50 percent or so [of carbon dioxide emitted] remains in the atmosphere and causes warming.”

McNiel: So the CO2 that’s in the atmosphere today, it could be from, you know, a coal furnace from the middle ages based on your numbers.

Khan: Exactly.

McNiel: It could be from the 1840s or it could be from a Model T that, you know, rolled off the line in the 1900s, right.

Khan: Yes, and as I said, some of this CO2 that’s going into the atmosphere is being taken up relatively quickly by forests, by the ocean, but a lot of it is staying up there and is going to continue to cause warming for an extended period of time.

McNiel: Right. Which brings up the balance between the contribution of carbon based on the combustion of fossil fuels versus deforestation. And I think fossil fuels is in the lead, right?

Khan: Yes, most of the warming is really caused by human consumption of fossil fuels for energy.

Why clean energy isn’t the entire solution

McNiel: So if we just convert our energy production to renewables like wind and solar or fusion or nuclear fission, doesn’t that solve the problem?

Khan: So that is an extremely important part of the solution. We absolutely need to decarbonize as much as we can. We need to stop putting CO2 into the atmosphere. That said, there’s a couple of reasons why we need carbon removal, or a process that takes carbon out of the atmosphere and puts it somewhere else where it doesn’t cause warming anymore. One of the reasons we need carbon removal is to address hard to abate emissions, or what are often called residual emissions. So when you look at the work that the U.N. is doing or the Intergovernmental Panel on Climate Change [IPCC] is doing, they’re thinking about what is going to be really, really hard to prevent emissions from, and can we use carbon removal to help us get to net-zero.

That said, even if we do that, even if we get rid of all of our emissions. There’s still CO2 in the atmosphere today that’s causing warming. And on our current trajectory, we’re likely to see pretty high levels of warming in excess of 1.5°C or 2°C that is the goal of the Paris Agreement. And so to get back down to 2°C and eventually to 1.5°C, to address all of the carbon that’s accumulated in the atmosphere, you still need carbon removal in addition to deep, deep decarbonization.

McNiel: Yeah. So the basic measure of carbon in the atmosphere can be determined by parts per million, right? So in 1840, what do we have like 200 something, 280 parts per million. And today we have what 420 I think is what it is?

Khan: Yes.

McNiel: And then if you’re, if you’re really interested in doing this, you can multiply that by 2.13 and you end up with gigatons in the atmosphere. Is that correct?

Khan: Yes, I believe we’ve in total emitted about 2 trillion tons of CO2 into the atmosphere in this industrial period, and about 1 trillion tons is still in the atmosphere.

McNiel: Wow. That’s a lot.

Khan: It’s a lot.

The difference between carbon capture and carbon removal

McNiel: That’s a lot. So let’s talk about one topic, which as soon as you start looking in, you know, carbon removal, you end up in like a little bit of a spirited debate about the pros and cons of carbon capture and sequestration versus carbon dioxide removal. Can you kind of clear up the confusion between those two terms? Because they seem like the same thing.

Khan: Yeah, absolutely. That’s a question that I hear a lot. And so when we talk about carbon removal, we’re really talking about taking carbon that is in the atmosphere already, it’s already in the air, and pulling it out and putting it into a different reservoir. That can be a lot of different things. That can be plants, it can be forests, it can be the ocean, it can be storage underground, but it’s really about taking carbon out of the atmosphere and putting it somewhere else.

That is a different process from point-source carbon capture. Point-source carbon capture is a form of emissions reduction where you’re trying to prevent CO2 from ever entering the atmosphere. So for example, if you have a fossil-fuel power plant or you have a cement facility or a steel facility where these processes generate CO2, you can put point-source capture on that system to prevent that CO2 from ever entering the atmosphere. So it’s a form of emissions reduction.

But there are of course, other ways that we can think about emissions reduction, we can just not burn the fossil fuels in the first place. We can switch to cleaner technologies that don’t emit CO2 in the first place. And that is a distinct process and a distinct solution in our climate toolkit from carbon removal. So, carbon removal from the atmosphere, point-source carbon capture, preventing the CO2 from getting into the atmosphere in the first place.

McNiel: OK, so if I’m going to play that back and understand it, there are processes we do where we produce carbon and we need to mitigate that carbon release and those processes may be things where there are alternatives. And then the second category would be there are processes where carbon gets produced, but you can’t avoid it like making concrete or steel or cement. So that’s where, you know, carbon capture makes a lot of sense because you don’t want, you can’t avoid it. I mean, you can’t avoid, you know, getting CO2 out of making cement, right?

Khan: Not quite. I would go back and put fossil power plants, cement, steel, all in the category of things that generate CO2. And for some of them, you can use point-source carbon capture. So people are actively looking at point-source carbon capture for power plants, for cement, for steel. And those are ways of preventing CO2 from entering the atmosphere from any of these kinds of facilities. And it’s harder in some cases or more expensive in some cases. But all of those things, I would put in the category of places where you could do point-source CO2 capture.

We want to develop climate policy that enables us to decarbonize as much as possible, even things that to the day seem hard to abate. And once we’ve done that, we’re still going to need massive amounts of carbon removal to address the CO2 that’s already in the atmosphere.

McNiel: OK, and then there’s other categories. One is carbon capture for, you know, compensatory functions. Like for instance, if you’re an airline and you want to show that you’re, you have a net-zero footprint, you’re going to buy carbon credits. I guess that’s one category. And then the last category is just carbon removal and storage long term. And that’s a net-negative pursuit, right?

Khan: Yeah, that’s a really great point. So, we can think about net-zero and net-negative. As you said, net-zero is this idea that there are some emissions that we’re still going to have, they’re going to be really hard to abate. If you have 1 ton of CO2 in one place, if you remove 1 ton of CO2 somewhere else, then one plus minus-one is zero. And once we’ve achieved net-zero, if we continue to do removals, and we’re still taking CO2 out of the atmosphere, then you get to a place that is net-negative, and you’re actually eliminating legacy emissions from the atmosphere.

How much carbon dioxide we need to remove from the atmosphere

McNiel: OK, so what’s the annual budget in terms of production of CO2 today?

Khan: I think today we’re on the order of 30 gigatons.

McNiel: So 30 gigatons a year are being produced. So first we have to get rid of that, don’t do it. And then we still have to draw down carbon that’s in the atmosphere. So is the goal to get to like 20th century levels or 19th century levels? What’s the ideal target?

Khan: Yeah, that’s a really good question. I just looked it up, and so the IEA [International Energy Agency] number is 36.8 gigatons from energy-related emissions. So that’s not total greenhouse gas, that’s CO2 from energy sector. In terms of what is our target for carbon removal, when I think of this question, I look to the most recent IPCC report. I think it’s the sixth synthesis report from the IPCC. And that report really made it clear that we need large-scale carbon removal and attempted to quantify when and where we would need it. And depending on how you cut the numbers, there are sources that would say that there’s probably 1 to 3 gigatons of annual emissions that are extremely hard to abate. That’s things like agricultural emissions that we need in order to produce food that are highly distributed. There’s really no meaningful way to do point-source capture on something like that. We’re probably going to have a really hard time getting rid of that last 1 to 3 gigatons. And so that’s where you might see the use of carbon removal to mitigate residual emissions.

After that, the IPCC is really focused on the Paris Agreement of below 2°C of warming. And on the current trajectory, we’re looking at up to 10 gigatons per year of carbon removal in the second half of the century, in order to correct for any overshoot and make sure that we stay within the range of the Paris Agreement.

McNiel: What should we say to the faction that argues that carbon dioxide is good for plants and agriculture, and so having more carbon dioxide is not a bad thing? What should we say to them?

Khan: Yeah, that’s a really interesting argument, and as we mentioned, plants do take up CO2. So of the CO2 that we’re emitting, about 25% is actively being taken up by plants on an annual basis. That said, all of the other impacts of climate change and climate warming from the 50% of CO2 that isn’t being taken up, and even from the 25% that’s being taken up by the ocean causing acidification, leads to massive, massive challenges for human society. And so, yes, there’s a small amount that gets taken up by plants and we’re better off for having that and having that not contribute to additional warming. But there are so many profound negative impacts from continued warming and CO2 accumulation in the atmosphere that massively outweigh any benefit from some small amount of plant uptake.

McNiel: Well and I guess you could also consider that the number of plants that are involved in reducing carbon are actually in the decline because of deforestation. And so we’d have to do a lot more afforestation to make a bigger splash in terms of carbon take up by plants, right?

Khan: Yes, and a lot of governments and academic groups try to do this analysis of what will land sector CO2 uptake and emissions look like in the future. And what you often find in these analyses is that the land sector — because of warming, because of increased wildfire risk, because of loss of soil carbon and reduced soil health over time — that these sectors end up being not sinks of CO2 that are taking CO2 out of the atmosphere, but actively sources of CO2 that are putting carbon into the atmosphere in the long run.

The suite of carbon removal solutions

McNiel: So what are the best methods available to us? Or let’s start with what are the different methods available?

Khan: Yeah. I think there’s a suite of carbon removal solutions, and we’re going to need all of them. There isn’t one silver bullet that’s like, this is the thing that takes CO2 out of the atmosphere and we don’t have to worry about anything else. So I think we really do need and want to actively foster a portfolio of carbon removal solutions.

The way that I usually think about it — there’s of course many pathways, there’s forestry or afforestation, reforestation, there’s soil carbon, there’s direct air capture, there are ocean carbon removal methods — but I think there’s sort of two important things to think about in terms of CDR [carbon dioxide removal] pathways. The first is, how do you take the CO2 out of the atmosphere? And there’s basically two ways to do that. Either photosynthesis through plants and algae and things like that, or human-engineered chemistry. Those are our two options. Is it photosynthesis or is it chemistry?

And then once you’ve taken the CO2 out of the atmosphere, you need to put it somewhere. And again, the sort of question, how do you store the CO2? There’s two options. You can store it as organic matter or plant stuff or biomass, or you can store it as inorganic materials like minerals. Or injecting CO2 underground to form minerals. So those are kind of the main ways to think about carbon removal.

How do you take CO2 out of the atmosphere? Is it photosynthesis or chemistry? And where do you put that CO2? Is it stored as organic matter or something else like minerals?

Who pays for carbon dioxide removal

McNiel: You mentioned direct air capture. I mean, obviously any of these methods are going to have power and resource requirements. At what point does this become economically viable? Is this something that we’re always going to have to pay for with tax dollars, or is this something that becomes part of our global economy because it’s a profitable business to be in?

Khan: Yeah, that’s a really great question. So to the point of direct air capture specifically, or carbon removal more broadly, any climate solution is going to have some set of resources that you need in order to deploy the solution. For carbon removal, ones we often talk about are land use — that’s across nature-based or more engineered solutions. Water use, of course, is also really important in a warming climate. And as you said, energy use, how are you going to power these solutions? And how does that tie into price? I think when we look at what governments are doing in the carbon removal space, in particular, the Department of Energy in the U.S. has put a lot of resources behind building the carbon removal sector in the last few years. They set a price of $100 per ton. That’s really where you start to see carbon removal become economical in the broader decarbonization landscape.

McNiel: Let’s understand what that means. $100 per ton in terms of cost for removal or the cost for the credit?

Khan: $100 per ton for the total cost of end-to-end removal and storage to be on the order of other mitigation solutions.

That said, carbon removal, from our perspective, is a public good. It’s fundamentally a climate justice solution, and carbon removed anywhere benefits everyone globally. And so we believe carbon removal in that sense should be treated as a public good. And we should be thinking about public policies that build the carbon-removal ecosystem and treat it as pollution management or waste management. And we think the government will always have a pretty big role to play in supporting the carbon-removal industry as a public good. In part because there’s no natural market for putting CO2 underground. It’s really different from something like solar or wind or renewables where there’s an existing market for energy, and if you use innovation policy and other tools to get the cost of solar and wind down, it can then compete in the energy market. There really isn’t something like that for carbon removal because it’s a public good, because it’s really waste management.

“Carbon removal, from our perspective, is a public good. It’s fundamentally a climate justice solution, and carbon removed anywhere benefits everyone globally.”

McNiel: Well, I think that’s a really important point, because it comes down to who pays for it. So right now, I think the U.S. has allocated $3.5 billion over the next five years or $3. 6 billion to support carbon capture. Is that correct?

Khan: So, there’s a number of different policies in place that support carbon removal broadly, both across the more sort of chemistry-engineered solutions and the more land-based photosynthetic solutions. A lot of the more engineered solutions live in the Department of Energy in the U.S. federal government. The more land-based solutions live at the U.S. Department of Agriculture and other agencies. There’s been quite an uptick in the last few years in overall carbon removal funding, particularly around RD&D, so Research, Development and Deployment funding. I think specifically you’re referring to what is called the Regional Direct Air Capture Hubs program, and that is Congress authorized $3.5 billion to build four regional direct air capture hubs. So that’s four facilities around the country that are capable of removing 1 million tons of CO2 per year from the atmosphere.

McNiel: Which people should understand is not a gigaton; a gigaton is a billion.

Khan: Yes, yep, so it’s a small step on the path to the total amount of removals we’ll likely need.

McNiel: So this is being paid for by tax dollars, but what do you think is the right economic model? I mean, shouldn’t most of carbon capture be paid for by the emitters, the people that are producing the carbon in the first place?

Khan: Absolutely. So that’s definitely our perspective at Carbon180, that government can play a really big role in helping to support this innovation, support this industry as it grows, and to help set the rules for how to purchase high-quality carbon removal that creates a real climate benefit. But I think what we’re moving towards is a system where you can think about and potentially have more of a polluter-pays mechanism or a carbon take-back obligation. That it’s not entirely on the taxpayer to clean up all of the CO2 pollution in the air.

The personal carbon offset market

McNiel: With that said, what is your take on purchasing carbon offsets for your own personal footprint?

Khan: Yeah, so I think one thing that’s really important to think about in the sort of broader conversation about carbon markets is that the vast majority of offsets or credits in the voluntary carbon market are not removals. They’re reduction credits. So the idea is that someone wants to emit a ton of CO2 and they pay someone else to not emit a ton of CO2. And if you think about this in sort of the carbon math, it’s like saying 1 ton of emissions plus 0 tons of emissions is still 1 ton of emissions. And that is really different from having removals, which is one plus minus-one equals zero, and it’s like actually achieving net-zero. 

My concern with the offset market today is that it is really, really rooted in this idea of reductions and trading reductions. But if our goal is to reach true net-zero or true zero, move as close as we can to eliminating all of our emissions, we want to move away from this reduction-crediting model and towards a model where we’re funding high-quality removals, that we’re actually taking CO2 out of the atmosphere, in addition to doing every possible thing we can to eliminate emissions and decarbonize all of our sectors.

The potential for cost-effective CO2 removal

McNiel: Are there any signs that we’re actually going to get there? That we have cost-effective carbon removal methods available to us?

Khan: Yeah, absolutely. I think there’s been a ton of activity in the last few years that makes me personally really optimistic that we’re moving towards high-quality removals. There’s of course a lot of momentum in the government that we discussed. In the bipartisan infrastructure law, there’s the $3.5 billion Direct Air Capture Hubs program that we just spoke about. In the CHIPS and Science Act, there was $1 billion for CDR research and development. In the infrastructure act, there’s an expanded tax subsidy for storing CO2, which is what you need to do after you take the CO2 out of the atmosphere. There’s a ton of activity in the E.U. around what they call their Carbon Removal Certification framework. So really building that regulatory architecture for governments to think about high-quality removal. The Canadian government’s doing something similar and the U.N. through Article 6 of the Paris Agreement is also doing something similar. So we’re seeing a lot of activity on the government-side to increase the supply of high-quality removals, but also to define what it even means to do high-quality removal.

And that activity is, I think, in large part matched by some really amazing momentum in the private sector. In the private sector side, you’re seeing dedicated venture capital funds that are investing entirely in carbon removal solutions. So, Lowercarbon Capital, I think, is one of the prominent ones in the U.S. You’re also seeing buyers’ coalitions that are uniquely focused on quality. So we’re moving away from this like, “Well, I’ll just buy the cheapest offset I can and just, like, call it a day” towards buyers who are really thinking about their social responsibility and investing in innovation and removal. I think Frontier and the advanced market commitment that they have announced for $1 billion of carbon removal purchasing is a really, really great example of this. And then you’re starting to see industry incumbents take carbon removal seriously. You’re starting to see things like big purchases of carbon removal startups. You’re seeing Verra, which is the world’s largest carbon registry, think really hard about how to create credits from removals and what the rules should be there and how they can enter that market. And you’re seeing dedicated marketplaces just for removals that don’t have any kind of reduction credits; they’re purely focused on removals. 

So, overall, I’d say we have a ton of momentum, but the amount of removal that’s actually happening today is so small compared to the gigatons that we’re going to need in the long run. So there’s a lot left to do.

The leading approach to direct air capture

McNiel: So along those lines, what is the leading approach to direct air capture, and how does it work?

Khan: Yeah, so there are a few ways to do direct air capture, but two that are most common if you’re looking at recent announcements. One of them is called liquid solvent direct air capture, and so this is really creating a fluid that when you flow air over it, it can capture CO2, and then you regenerate the fluid and keep circulating that.

The other main way of doing carbon removal is a solid material. So, honestly, quite similar. You flow air over a solid, and then you take that solid into a different unit, and you heat it up, and the CO2 comes back out again. Those are the two main ones that you’ll hear about. And so a company like Carbon Engineering does the liquid solvent approach, and a company like Climeworks that has their facility in Switzerland and in Iceland, you may have heard about, they do the solid sorbent approach.

McNiel: Well, you said in the liquid form that they actually recycle it. Don’t they have to store it and put it away somewhere?

Khan: Yep, so in pretty much all forms of direct air capture, you have either your liquid or your solid that you use to capture the CO2 from the atmosphere and then you regenerate that material. In the regeneration process, you separate out usually gas-phase CO2 that then needs to be stored. It can be stored sometimes in durable value-add products — like concrete is something that’s really interesting. A lot of folks are thinking about how to put CO2 into concrete and then use that material to reduce the carbon intensity of buildings. You can also think about storing CO2 as a solid mineral. And then, of course, you can think about storing CO2 as a supercritical fluid that gets injected underground. And most of the CO2 storage happening around the world today is probably in that form, of taking CO2 as a gas, compressing it, and then injecting it underground.

McNiel: And then once it gets underground, does it just reside there or does it cool and then become solid?

Khan: Yeah, that’s a really great question. So there are a number of different processes that happen underground that keep the CO2 trapped. And I should note, this is really, really far underground. It’s well below the water table, below anything–

McNiel: This is miles underground.

Khan: Yeah, it’s hundreds of meters underground. And in the U.S., it’s regulated by the EPA such that there is a sealing rock, a cap rock, that separates any CO2 that’s stored underground from drinking water. And once that CO2 is underground, there are a few different things that happen, but a lot of it essentially becomes immobilized. It doesn’t move around underground, it is essentially trapped well, well into the subsurface.

McNiel: Well, I guess if it gets into your groundwater, you’re going to have Perrier instead of still water, right?

Khan: But it’s almost like physically impossible for that to happen.

McNiel: I mean, that kind of brings us into this whole idea of repurposing CO2. So if you take CO2, when you use it, you capture it from the atmosphere and use it to make jet fuel, eventually it just gets reintroduced in the atmosphere. So that’s kind of a, you know, it’s not a net gain. It’s a net loss, right?

“If we can have that circular carbon economy, we can decarbonize, we can stop extracting additional CO2.”

Khan: Well, I think in some ways it’s still a really valuable set of technologies to pursue because a lot of products use fossil CO2 that we’re actively pulling CO2 out of the ground in order to put them into products, and if we can shift that to a circular carbon economy where we don’t have to do additional extraction. We’re using the CO2 we already have to make products like carbonating beverages. Every couple of months you see an article about a beer company that’s using captured CO2 or something like that. If we can have that circular carbon economy, again, we can decarbonize, we can stop extracting additional CO2.

But even if we replaced all of those products with direct air capture CO2 from carbon removal, there would still be gigatons, gigatons of CO2 in the atmosphere that need to be removed and durably stored.

The most compelling argument for CO2 removal

McNiel: Can you make a really compelling argument why we need to pull carbon out and why everyone should be on the same page?

Khan: Absolutely. So, for me, the most compelling argument for carbon removal is that it is fundamentally a tool for climate justice. So, my family’s from Bangladesh. Bangladesh is still going through an energy transition. It’s still building out a reliable grid. And still relying on fossil fuels to get its energy. And that means more CO2 going into the atmosphere. In the long run, that causes more warming, it causes more harm, it causes sea level rise, hurricanes, flooding — all of these impacts that primarily affect the most vulnerable people around the planet. Carbon removal is basically the only tool we have to take CO2 back out of the atmosphere and redress that harm from warming. And so for me, that’s really the case for carbon removal. It is fundamentally a public good and a tool for addressing the harms of climate change and a tool for climate justice.

We need to invest heavily in decarbonization. We need to stop putting CO2 into the atmosphere. We need to stop extracting and continuing to put CO2 in the atmosphere. That, of course, is extremely important and needs to happen and the lion’s share of our work in climate is going to happen in emissions reduction. We also need to look at adaptation. We need to make sure that vulnerable people are protected. And when these extreme events happen more and more often, that we’re prepared for them.

“Carbon dioxide removal is fundamentally a public good and a tool for addressing the harms of climate change and a tool for climate justice.”

McNiel: What if you pull out too much carbon and we go back to the ice age?

Khan: That would be extremely hard to do. I think it’s much more likely that high-quality carbon removal is supply limited and will remain supply limited basically indefinitely, because ideally we don’t want to take CO2 out of the atmosphere. It’s an extremely energy intensive process. Carbon in the atmosphere is at 420 parts per million. From a climate perspective, that’s a lot. From a chemistry, trying to fish the CO2 out of the atmosphere perspective, it’s very dilute. It’s a hard problem to take CO2 out of the atmosphere. So we want to do as little of this as possible, and we want to put our energy towards other productive things that make people better off. But we’re in a position now with the climate, with climate change and having continued to emit and still not having really decarbonized our economy that we will need to take carbon back out of the atmosphere.

McNiel: Well, is a gating object the fact that you need to have carbon-free power to do direct air capture if you’re going to make it a significant contribution? I imagine you can’t do it with fossil fuels. It’s kind of a pointless effort. So if you have unlimited carbon-free baseload power, that could change the equation significantly, right?

Khan: Absolutely. I think that raises a really good point about net removals. When you’re thinking about a carbon removal project, it’s not just the amount of CO2 that you store underground or in concrete or somewhere else. It’s that whole end-to-end process or life-cycle process that you need to establish net removals. How much carbon was emitted from the very first step to the very last step and then you subtract that from what you’ve actually put into storage to get your net removals. And in order to maximize net removals, we need to create carbon removal processes that are very energy efficient, don’t use a lot of materials and whatever energy and materials they do use are themselves decarbonized.

A vision for 2035

McNiel: So Anu, picture that this program takes off, that we get access to abundant fusion power, which does not produce carbon, which can run carbon removal processes, that can run desalination processes, that can do afforestation or reforestation. What do you think the world looks like in 2035 if that happens?

Khan: Yeah, that’s awesome. I think 2035, maybe a little bit longer out in 2040. What we’re looking at is deep, deep decarbonization of the energy sector, industry, transportation. We’ve pulled all the levers, turned all the dials to bring our emissions down as far as possible, and at the same time, we’ve used these 10, 15 years to innovate in carbon removal, to really learn what works, and to invest in net removals, energy-efficient carbon removal processes, and we’re deploying them at gigaton scale. So we’re starting to do meaningful amounts of removal from the atmosphere. That said, I think one of the most important things that we’re going to learn in these early days of carbon removal deployment is how to do carbon removal projects in a way that is equitable and just.

“We have the opportunity…to start from scratch and build something that is fundamentally much more equitable and much more aligned with principles of environmental justice.”

Historically, the development of new industries has not been equitable. It has primarily placed burdens on communities that are already burdened and vulnerable in different ways. We have the opportunity with the CDR industry in the next five, 10 years to start from scratch and build something that is fundamentally much more equitable and much more aligned with principles of environmental justice. So for me, that’s really the opportunity that we have in the next 10 years, alongside doing the tech development and making sure we have carbon removal as a solution. We have an opportunity to build a brand new industry that is in the public service and is fundamentally more equitable and just than other industries have been in the past. And I think one of the ways that we do this is that in the near-term, we set really good standards for what it means to do carbon removal. We set really good rules through government and through private buyers that say we’re only going to buy the good stuff that’s deployed in a way that is equitable and just and takes into consideration what communities want and need.

McNiel: Well, I think that’s an excellent summary. And if someone’s keeping a score at home, you know, what’s the best measure to look at just to kind of know whether we’re going in the right direction? Is it PPM [parts per million], CO2 in the atmosphere, or is it, the gigaton budget? What do you think we should look for?

Khan: PPM is a fantastic indicator, but one that will take a little while before we see a change due to carbon removal directly. I think what I look for when I see news about climate and news about carbon removal is, how are communities engaged? Who’s buying the carbon removal and how much are they buying? Are they really — are buyers and corporations like Stripe and Microsoft, Shopify and Frontier — are they investing in the good stuff, stuff that’s proven to remove carbon from the atmosphere? And then I think we can also look at how much funding is moving into this space. How much funding is coming from the government? How much funding is coming from private industry? So we can see these indicators that are going to move us towards meaningful deployment before we’ll see real change in PPM from carbon removal.

McNiel: So I know if somebody is a concerned citizen and they’re a big supporter of reversing climate change, is there an offset out there that they should consider? I mean, they should be careful about what they’re buying. What do you recommend? 

Khan: Yeah, that’s a great question, and I know this offsetting approach has become really popular, but I personally think a much more impactful thing to do in supporting the carbon removal industry and supporting good climate action is to donate to nonprofits that work in this space. Donate to environmental justice groups that are thinking about climate solutions. Donate to groups that are thinking about supporting innovation, that are filling in gaps in the ecosystem. I think that’s one of the most effective ways to really think about supporting the carbon removal ecosystem. But if you’re looking for places where you can sort of track companies that are doing high-quality removal and are ready to sell removals, I really recommend cdr.fyi. They have a whole list of folks who are in the carbon removal space. Some of them have subscription services for individuals to contribute to purchasing carbon removals. And then I also really recommend the OpenAir Collective. So that’s a community based, volunteer-run organization that does a ton of really cool work related to carbon removal, and they have lots of opportunities for folks to get involved directly.

McNiel: That’s great. Anu, thank you very much.

Khan: Yeah, thanks so much. This has been super fun.

Good Clean Energy is produced by Jennifer Hsu. Mixing and sound design by Wade Strange and Mike Clemow at SeeThruSound. Digital production by Katherine Wiles.

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