S1 #4 | Biochar + BECCS: can we do more with plant power?

Emily Swaddle 0:01 Okay, Tom, I have some really exciting news for you.

Tom Previte 0:15 Oh, yeah?

Emily Swaddle 0:18 Did you know that you can actually start contributing to the carbon removal space in your own back garden? And it only costs like 700 quid. And I'm not talking about buying a very expensive tree and planting it. Okay, I'm gonna paint you a picture of like, my ideal life; living on a farm, lots of goats, vegetables, and in the bottom of the garden, just a little, a little place where I gather all of my organic waste and throw it in a kiln, make some biochar.

Tom Previte 1:21 Amazing. So what are you going to do with the biochar?

Emily Swaddle 1:23 Well, and then I can use it in my garden, I can feel good about myself, because I'm storing a lot of carbon in my soil. I mean, I think it's just gonna be the perfect little eco homestead really. Kind of looks like a chimney that comes up to about sort of hip height. So maybe I could have a few you know, if I started saving up now,

Tom Previte 1:42 Could they double up as like a fire pit as well? Or?

Emily Swaddle 1:45 Not really? I mean, they do give off heat. But you're not like seeing the actual fire. But yeah, you can hang around one if you wanted to, to tell some stories, sing some songs.

Tom Previte 1:55 To the goats.

Emily Swaddle 1:56 Why not? Yeah! Me and my goats. You're welcome to join us, Tom.

Tom Previte 2:01 I'm sure I'll have to come down for a weekend. Amazing shall we crack on?

Emily Swaddle 2:05 Let's do it.

Tom Previte 2:13 Welcome back to the Carbon Removal Show. My name is Tom Previte and I'm joined as ever by Emily Swaddle.

Emily Swaddle 2:19 Today, we're going to be talking about biochar and BECCS; what they are and what they can do for us.

Tom Previte 2:26 So far, we've zoomed in on natural processes that regulate carbon in the atmosphere, the current state of those cycles, and how we can adapt our behaviour to get them back into balance, you know, restoring the natural carbon cycle to what it was pre industrial times. In reality, that is a small part of the carbon removal picture.

Emily Swaddle 2:47 Right now as the world functions in 2021, we actually need to go quite far beyond that. Back then, in the pre industrial era, we weren't emitting gigatons of co2 a year. So those natural cycles were enough to deal happily with the carbon in the atmosphere. And even if those cycles could be restored to their former glory, the scale at which we currently emit co2 doesn't line up with the pace at which these cycles regenerate. It's almost like those natural cycles are running a marathon and alongside that human emissions are breaking the world record for the 100 metres.

Tom Previte 3:21 Did you watch any Olympics this summer Emily?

Emily Swaddle 3:25 Maybe a little bit.

Tom Previte 3:27 Okay, so now we're going to zoom out little by little to reveal that bigger picture of the carbon removal ecosystem with an understanding that we need to go further and faster than natural solutions can take us.

Emily Swaddle 3:40 Yeah, human activity got us into this mess. So human intervention needs to be a big part of getting us out of it.

Tom Previte 3:46 Damn straight. So let's take our first step to zooming out. In this episode, we're going to talk about two technologies BECCS or B, E, C, C, S. And biochar. Now they both share several features, but are distinctly different. Both BECCS and biochar initially capture carbon through biomass or in other words, you know, plants. The biomass can either be crops grown for the sole purpose of being used in a BECCS or a biochar process. Now, that could be a maize or a miscanthus crop, or that biomass could be a waste material from agricultural processes.

Emily Swaddle 4:24 Yeah, and then it starts to get really interesting because both of these processes go a step further than the solutions we've looked at before. Rather than kind of leaving the carbon stored in the plant or in the soil both these processes then use this biomass for some useful purpose and with it, taking that carbon of course. And when I say useful, I mean a practical use, but also something that's going to help us reach our climate goals faster. It's exciting stuff.

Tom Previte 4:53 It is exciting stuff, indeed. And we've been looking into how these technologies might or actually are even working in practice today, you know how viable are they at removing carbon dioxide from the atmosphere? What challenges lie ahead if they become a major part of our carbon removal toolkit? Crucially, we want to know, can they take us further than the natural solutions of reforestation and aforestation, soil health? And will they offer the permanence that we're looking for at the gigaton scale that we need.

Emily Swaddle 5:25 Big questions. We are joined in this episode by two experts in these respective fields. And we actually spoke to them individually. So this should be a fun learning experience for both of us, Tom.

So I get to start with biochar. Let me paint you a picture, Tom.

Tom Previte 5:44 Paint away, Emily.

Emily Swaddle 5:45 Okay, so we start with that biomass that we've already introduced. And as you say, maybe it's been grown, especially for this purpose maybe it's a waste product of another process. That biomass is then heated to a really high temperature without oxygen. And this process is called pyrolysis. And it concentrates that carbon that's in the biomass, and you're left with kind of a purer form of carbon in the end.

Tom Previte 6:13 Cool.

Emily Swaddle 6:13 Yeah, that's the broad strokes picture. But there are actually many ways to go about this. I had the pleasure of talking to Henrietta Moon. She's the co-founder and CEO of Carbo Culture. And she explained how she does it. She calls it bio carbon rather than biochar. But it is the same thing.

Henrietta Moon 6:31 So basically we outsource the carbon capturing part to our solar powered allies, that is trees and all crops. And biomass takes down hundreds of gigatons, hundreds of billions of tonnes of carbon every single year, of carbon dioxide. And so if that biomass, for example, we're using peach pits, or walnut shells, if those are left on the ground somewhere in some years, they will decompose ultimately and return to the atmosphere. So instead, we take those like nut shells and we put them into our reactor, and we take them to a very high heat for a very, very short time. And then we starve them of oxygen so that they can't keep on burning and turn into into gases. And so essentially, we get a solid carbon out that's almost like a carbon copy of what it was originally but smaller. And that is something that we can weigh we can send to a laboratory and they can tell us exactly how much carbon it contains. So it's a very kind of safe and tangible way of actually measuring the carbon that's out. And then we make gases and then we make excess heat that we can sell to, for example, district heating or other processes nearby who use a lot of heat.

Tom Previte 7:45 I love that they're using peach pips walnut shells; that's such a great use of waste biomass.

Emily Swaddle 7:52 Yeah, I was excited about that, too. And the fact that it's very measurable, that's a breath of fresh air after the natural solutions we've looked at. What most of these different versions of this process have in common is that they create a couple of different outputs. So first of all, you actually get a bit of energy off this process such as in the form of biofuels. But more significantly, you get that carbon rich material. It's kind of charcoal like substance and it's called biochar or bio carbon. In Carbo Culture's case, the content of that material is actually 83% fixed carbon.

Tom Previte 8:28 83% actually sounds like quite a lot.

Emily Swaddle 8:32 Yeah it's dense stuff, I think.

Tom Previte 8:35 Okay so, so then what am I supposed to do with this lump of biochar? I'm guessing I'm not gonna stick it in a barbecue.

Emily Swaddle 8:42 No, it's just come from the barbecue. No, we use it - and you're gonna love this Tom - to enhance soil health and carbon storage capacity. Love it.

Tom Previte 8:55 I'm liking this already. It feels like it's another solution which has got multiple benefits beyond just carbon removal. And I'm kind of surprised by how many of these solutions kind of have these multiple benefits to them as well.

Emily Swaddle 9:07 Yeah, many layers. So let's talk about some of those layers. So number one, we've got the soil improvement. Biochar added to soils has significant benefits for soil quality. That is, you know the answer we've all been looking for, us newly anointed soil lovers. It reduces degradation of the soil. So it's going to maybe improve the productivity in the long run. And it's also able to actually surpass the normal point of saturation for soil carbon. So when we're thinking back to regenerative agriculture, it can increase the amount of carbon that is stored in every hectare. That's amazing news.

Tom Previte 9:43 Could this replace the need for things like nitrogen fertiliser then in the soil?

Emily Swaddle 9:48 I'm not quite Henrietta emphasised that it's important not to confuse biochar with some miracle drug for our crops.

Henrietta Moon 9:57 So you know, if you've read some studies where biochar did not magically grow your crops 30% in the first year, that's true, because it's not a it's not a miracle drug like nitrogen or phosphorus or something that you can pump into the soil and it grows your crops magically. So that's definitely not what biochar is. And it shouldn't be, it shouldn't be mixed up with being a fertiliser or something like that. But what it does do is it does improve the soil structure, which means that it has aeration or better drainage or more surface area and these types of things that might be physical properties that are important to the soil, but we don't perhaps value as much today because we're just looking at okay, what is the crop yield? How much money do I get for this? But we are starting to understand problems like nutrient leaching, for example, is one of the biggest biological catastrophes that we have in this world today. And there biochar can actually also play a part. So there's a couple of things that haven't been, like, monetarily that important because you could just dump as much nutrients as possible into the soil and hope for a really good crop. But now we're starting to understand that maybe this doesn't work like that and that we need a kind of like different approach to it. And I think biochar can play an important role there in the future.

Emily Swaddle 11:18 But not to worry, soil health is only one of the strings in the biochar bow. It also helps for storing water. Biochar is very porous, so it stores water in soils, therefore reducing the risk of wildfires and mitigating against carbon loss that comes from wildfires. It's good for the water cycle in general, actually, to have that porous material in the soil.

Tom Previte 11:38 Playing devil's advocate here for a second, we already have some great organic matter, which has a bunch of carbon in it, and it's called compost. So why would we need to heat this up to 1000 degrees.

Henrietta Moon 11:51 So if you have green waste lying around, like your yard waste or something else, if you put it in a composter, it'll quickly turn to earth and then you can use it in your garden, which is great. And it's food for microbes. And there's a lot of delicious things to to enhance your soil quality. But biochar is actually like near pure carbon. So there's not like a fungi that'll eat it, it's not like good food for microbes, there's not a lot of things that are going to take it apart. So essentially, it's just structure for the soil. So these two things are very different. And the compost, of course, breaks down lots faster than than what stable carbon does. According to our lab tests and research around this topic, our bio carbons are have a half life of about 1000 years. So in 1000 years, half of the material will still be here. And that is kind of like the minimum that we're looking at. But if you think of, you know, leaving leaves on the ground or something like that, it's less than a year that they're gone right. So so that's the kind of like stability difference that you have with material that's quickly decomposed and re-returned to the atmosphere and biochar.

Emily Swaddle 13:03 So this biochar is stable for hundreds or maybe even 1000s of years. And we actually know this - this is super cool - we know this because it's been practised for centuries on a small scale, such as in the terra preta zones of the Amazon basin. And in those regions, we've actually found biochar it still exists today. You can see it for real!

Tom Previte 13:27 What?!

Emily Swaddle 13:28 Yeah, it's crazy.

Tom Previte 13:29 For reals?

Emily Swaddle 13:29 For reals.

Tom Previte 13:31 Wow. That's awesome.

Emily Swaddle 13:32 I know. Yeah, the indigenous people of the Amazon region used charcoal to enhance the fertility of their soil. And it's been dated back to at least two and a half thousand years, and some of it as far back as six thousand years old. Crazy stuff. And what's really interesting, actually, is the effect that this richer soil had on human life in that region. You know, there's evidence that thanks to the biochar, the agricultural processes of these civilizations, were able to feed a much bigger population than historians once thought.

Tom Previte 14:05 Traditional ancient techniques coming to the fore once again, that's super cool. I'm keen to see how we can adapt and modernise these practices. You know, how can biochar benefit human life now in the 21st century and beyond?

Emily Swaddle 14:19 So as I said, there's actually a lot of potential side benefits of biochar. It can help us move away from that reliance on finite fossil fuels because it is actually producing energy. In some processes it can also produce heat that we can harness. And of course, it can also help with waste management because we're using biomass from agricultural processes which would otherwise go to landfill.

Tom Previte 14:40 Okay, great. Now, I'm waiting for a catch. This all sounds like a perfect solution again, so there must be some sort of downsides or challenges.

Emily Swaddle 14:49 Yes, of course, as with everything. So in this case one of the things to be mindful of is energy use through transportation. If we're shipping that biomass from place to place and then also on the other end of the process shipping the biochar around that really has to be done in a low impact way. Otherwise, we're going to be negating some of the benefits of this process. So an example, you know, have your biochar production plant right next door to the factory that's producing your organic waste.

Tom Previte 15:17 And what about purpose growing crops?

Emily Swaddle 15:18 Yeah that's a good point and in that case, it's all about land use. It's such a big consideration. We, you know, we need to think about what that land might have been used for otherwise and would that have ultimately had a bigger impact? There are many complexities to be considered as with everything and it's about striking a balance. Henrietta described how Carbo Culture has navigated some of these issues.

Henrietta Moon 15:42 I mean, right now we're using food production side streams. So essentially, like all sorts of nut shells and peach pits and compressed biomass waste from some food production units. So we have a demo facility in California where we're testing all sorts of things. So yes, we have we have some transport, especially if the test material comes from further away. But that's very, very small scale. It's not like a commercial size unit. But we're parked behind a nut processing facility. So if we were running full steam just with that one feedstock and not testing other ones, then the transport would be very small, not needing trucks or anything in between. So that's how we envision ourselves that we can go and park next to some of these processes that are making a lot of waste and in that way, we don't need to have excessive transporting. And yes, we can use all sorts of different kinds of waste. And that's why we're testing, testing different kinds of feedstocks. If we're processing just water or air, you know, like if it's very, very, very moist, the material or something else, of course, then it kind of eats into our process itself. So then we're not doing it as effectively as we could. So that's why, you know, generally speaking, a little bit more dry feedstock is great.

Emily Swaddle 16:59 So ultimately, this can and is happening on a small scale - hopefully on my future goat farm. And it has been happening for 1000s of years among indigenous communities. There are some bigger scale projects also, but it is worth noting that they're not really considered commercially viable yet. So I asked Henrietta, as an entrepreneur in this space with, you know, an interest in getting this as far as we can. How does she imagine getting biochar to a gigaton scale,

Henrietta Moon 17:27 getting to a billion tonnes of carbon dioxide removed by biochar would mean that we would have to have about 300 million tonnes of it physically made. And now you can imagine what moving a billion tonnes of biomass around would look like. And and so obviously, you want to be moving as little of that as possible and moving the 300 million tonnes of bio biochar instead. And so you'd probably have like localised biochar systems next to the sources of the biomass. So in heavy farming areas, or food processing, or things like that, and hopefully, you know, we can think about different forms of biomass to use where we don't need to actually put pressure on land use. So there's a lot of things that are going to change in the in the next years and, and of course, legislation and everything plays a part in it. Like, how do all these pieces fit together? It requires a lot of work and infrastructure and partner negotiations and all sorts of things to even get to a million tonnes would be a significant feat. And now, you know, getting from there to a billion is just something incredibly incredibly arduous. That needs to happen.

Tom Previte 18:47 Emily, you just ended there talking about scale. So I think I think you're going to love BECCS: B, E C, C, S. Now this stands for bioenergy with carbon capture and storage.

Emily Swaddle 19:00 I love it already; catchy acronym. That's how to reel me in.

Tom Previte 19:04 And as we mentioned before, on the surface of things, BECCS has some similarities with the biochar process. Principally, it utilises that wonderful plant biomass. Yeah, so far so familiar. However, in this instance, the focus is actually on maximising that energy output, creating a tantalising alternative to using up finite fossil fuel reserves, which none of us want. As we'll see shortly, there are high hopes that BECCS, if deployed on a large scale, could really change the face of our energy sector.

Emily Swaddle 19:38 So with biochar, the energy output was a bit of a byproduct, whereas with BECCS, it's actually kind of the main focus. Well, that I mean, you know, I love the fossil fuel alternative.

Tom Previte 19:48 To find out more I spoke with Naomi Vaughan. Naomi is a senior lecturer on climate change at UEA and she's also the co-lead for reaching zero emissions theme at the Tyndall Centre in the UK, so she knows her stuff. And she gave an overview of the process.

Naomi Vaughan 20:05 So if I was explaining and describing BECCS, I would break it down into three parts. That first is the growing of the biomass. So you might be growing biomass anyway, because you're growing an agricultural food crop. And just when you do that, there is some waste products that are not a food that you need. For example, when we grow wheat, we just need the wheat grain, we don't need all the straw. You might be growing it as a dedicated bioenergy crop, then there's lots of different types. And they have different impacts and different effects both socially and environmentally. So it matters which type and I talk about how that plant during the growth of its life in some format has taken co2 out of the atmosphere. And it's then in that biomass. And that's what you're then going to take and use in the next part of our process, which is some form of energy conversion. So we are talking either taking that plant biomass and using it to generate electricity, a bit like we would with a gas powered turbines or you're generating principally electricity. You might be taking it and fermenting it and generating a liquid biomass transport fuel, so something to either mix with or replace entirely petrol or diesel in your car. Or you might be trying to make some hydrogen, there was people working on that about how you might go to make hydrogen using some biomass. And then the final step is where you capture the co2 in that energy conversion process. At some point, either during your fermentation, you're releasing co2, or when you're combusting it, you're burning the biomass, you're releasing co2. And when that co2 is released, you want to capture it. Then you use some chemical engineering processes by just either a liquid or a solid that really wants to grab hold of that co2, essentially.

Emily Swaddle 21:41 Yeah I've heard of biofuel. You know, I've seen the big green buses driving around that have big letters on the side "powered by biogas". To be honest, so I'm always a bit sceptical, like how green actually are they?

Tom Previte 21:55 Okay, so that's the "BE", or the B, E, of BECCS: bioenergy. Biofuels in particular, are already used at a pretty large scale the world over, they power things, from buses, to trains to agricultural machinery. And as Naomi mentioned, biomass can also be used to generate bio-electricity. These types of energy production are already preferable to fossil fuels, because they have the potential to be carbon neutral, even carbon negative.

Emily Swaddle 22:25 Okay, so when you're burning fossil fuel, you're releasing carbon that's been stored underground for millions of years and sending it straight up into the atmosphere. Whereas when you're using biomass, presumably you're just re-releasing carbon that was only recently captured by that plant. That is the biomass.

Tom Previte 22:43 Exactly. Now, it's not quite right to say that biofuel or bio energy is necessarily always carbon neutral. There are other factors on both sides of the equation that can really like tip that scale, or that carbon balance either way. On the one hand, you've got to consider the what and the how much energy you're using in the production and the transportation process, similar to biochar. On the other when we grow that biomass we know now that some of that carbon can be drawn down into the soil, the permanence of which depends on what agricultural practice that you choose to use. So it's a complex, it's a varied situation. But BECCS is actually going a step further. As Naomi touched on there, in BECCS most of the carbon released through the processing of that biomass is then captured, and it's stored underground. So in theory, that is net carbon negative.

Emily Swaddle 23:36 So you're saying carbon negative because carbon is pulled from the air and sequestered for the long term?

Tom Previte 23:42 Yep. That is the the "ccs" or the C, C, S, of BECCS. It stands for the carbon capture and storage.

Emily Swaddle 23:51 Yeah, that sounds pretty promising. So tell me though, what are BECCS people doing differently than the biochar people because it's getting quite a different result here.

Tom Previte 23:58 You took the words right out of my mouth, Emily. I put that question to Naomi.

Naomi Vaughan 24:03 Whenever you burn biomass like this, imagine a piece of wood in a stove, there is always three parts, you'll get out of this, you'll get solid, liquid and gas. Now most of that gas has gone up the chimney. And most of that solid is the ash that you have to clear out from your wood burning stove. And the thing that you get told off by by the chimney sweep is the tar because you've burned it too low, and you've ended up with a kind of oil component, or liquidy, sticky tar component that coats the inside of things, right. So with biomass, it's all about the temperature, you burn it, and therefore the higher the temperature, the more complete combustion. My point is, whenever you burn biomass, you will get some fraction of each of those three parts. Now if you want biochar out of your process, you will change the temperature and the duration of the burn and the pressure potentially even that it's done under in order to maximise a solid fraction coming out, which is the bits of charcoal. You can burn your biomass to maximise that and you can get up to about as if I'm recalling the numbers right 50% can come out as a charcoal. If you want to maximise the gas bit, which is nice chunk of heat which you can use in a BECCS power station, for example, to heat water, to generate steam to drive your turbine that is going to generate your electricity. So the problem is, you will always get a little bit of solid material out of the biomass combustion. If you're doing it to generate electricity, you want as little as possible if you're doing it to generate biochar, you want to change the settings to maximise it. So you will have some kind of char product as a waste product from biomass combustion that you have to deal with in some way. So you could use it for biochar. So that's a nice kind of co-benefit.

Emily Swaddle 25:33 You know, Tom, if you've got sticky chimney issues, Santa's is definitely going to have something to say about that for sure.

Tom Previte 25:41 You know, I reckon that'll get you on the naughty list.

Emily Swaddle 25:43 I can just imagine him you've stuck in the chimney and being like you're burning your biomass at the wrong temperature! So by going down the BECCS line we're losing out on the brilliance that is biochar and all of the benefits that come along with it, but we're gaining tonnes of energy.

Tom Previte 25:59 Sure, and so the way I see it backs offers two distinct benefits. Firstly, it's that source of good clean energy and offers the chance to seriously reduce our carbon emissions. But secondly, and of particular interest to us, it offers a chance to store that carbon. I'd even suggest that it can be even more permanent than biochar. Underground storage, for example shouldn't be susceptible to any natural loss of carbon that could occur using a biochar in soil, for example.

Emily Swaddle 26:31 Oh, Tom, that's controversial. Some fighting talk. Yeah, might need a bit more convincing on that. But I will say something I've noticed reading about negative emissions over the past few months is that BECCS comes up a lot. And it's always presented as kind of a silver bullet for this issue.

Tom Previte 26:50 Yeah. So over the last few years, most of the noise and hype in the carbon removal space has been around BECCS. And there are some good reasons for this. BECCS may be cheaper than some of the even more tech heavy permanence type solutions. It can even be as low as $15 per tonne. And it has the potential to offer a twin solution to both our fossil fuel dependency and our need to draw down carbon. Finally, because you're creating an output, which is energy, there's also a built in market for it. So you're actually creating sought after products that you can sell, which should help the technology scale. Given this, it's perhaps understandable that the 2018 IPCC models rely heavily on BECCS as a route to climate change mitigation.

Emily Swaddle 27:41 I'm noticing, Tom, as you talked about this, there's a lot of words like may and should and potentially coming up in this conversation. So from what I understand, we're actually quite a long way off living in that BECCS powered utopia, if that's where we're headed. So currently, Tom, how much carbon is currently being sequestered through BECCS right now?

Tom Previte 28:04 Well, the data that I have from the global CCS Institute in 2019, says that there's currently five active BECCS facilities around the world, and they are capturing a total of 1.5 megatons of co2 per year.

Emily Swaddle 28:18 1.5 megatons. I know megasounds like a lot, but a megaton is actually only one-thousandth of a gigaton. Bit of maths: from what you're saying, we're currently only sequestering about one thirty-three-thousandth. That's one over 33,000 of our annual emissions through BECCS that is a very tiny little fraction.

Tom Previte 28:44 Yeah. And what I should add is that overall, these facilities are actually still emitting more co2 than they're capturing. And that's mostly because of the co2 emitted during the production of their biomass.

Emily Swaddle 29:00 So it, it really isn't ideal right now. They're currently emitting co2. But you know, that that really talks to the systems change we're looking at here. Honestly, just the amount that people talk about BECCS I would have thought that it would have been more than that that we're currently sequestering through this process. But you know, if it's currently 1/33,000 of our annual emissions, I'll take it, you know, as long as we're moving up, as long as we're going in the right direction. You have to start somewhere.

Tom Previte 29:28 Yeah, and critically, we know we can do it, we know it can work. Now, I'll admit that there is still a long way to go to get the technology to deliver at the scale we need. But as we're talking about our future pathways, while it's important to recognise the hurdles, I think we do need to focus on that potential. Now, a lot of people are talking about BECCS at the gigaton scale. And as I mentioned, the IPCC are working on the basis that this is doable. Let's talk estimates. Estimates are varying wildly and carbon plan's really brilliant CDR primer has a low end range of 1.2 to 5.2 gigatons per year of carbon dioxide removal and higher end range of 31 to 77 Giga tonnes per year. To put that into context, these ranges are going from as low as 2%, to as high as 150% of our current annual emissions. When I spoke to Naomi, she wouldn't be drawn on specific figures, because she said that it was highly dependent on other factors.

Naomi Vaughan 30:35 Lots of times what someone really wants me to tell them is, what's the maximum amount of BECCS and how much land is there going to take? And I annoy the pants off them every time by saying, okay, well, in your future world, we need this amount of BECCS, how have we got there? So you can take the worst possible combination, assuming you're having massive land expansion to achieve it. And you've got exactly the same dietary trends. So you're really limited on what land might be available, you're starting to directly compete with natural habitats and stuff, right? Versus the other end of the spectrum, where you have a dietary shift globally, that means you've got more land available because you need less land area to feed a diet without or with much less livestock in it and either dairy, livestock for meat consumption. And or you're using residues from that agriculture anyway. Or you're possibly going into using other waste streams, like some people have explored ways of using municipal solid waste for filtering into bioenergy. And so that is why I am never drawn on the answer of I'm not going to give you multiples of the area of Wales to tell you how much land area is required. Because it is such an interdependent question on how hard you work on decarbonisation, choices you make about agriculture and choices actually, you make about aviation.

Emily Swaddle 31:46 Yeah, I find the whole question of the land use so important and really interesting. It's something that came up in my conversation with Henrietta as well. And as we've spoken about land is precious, you know, we have a large global population that we need to feed. And so for every hectare, that's growing biomass, that's a hectare that we can't use for food production, or indeed, you know, give over to forests or natural habitats.

Tom Previte 32:11 Right. I think there's a couple of important considerations here though. The first is what biomass you use really matters. With biochar impacts. We know that you can use waste biomass, or you can use a specially grown crop. Obviously, if we're just focusing on bioenergy output, a specially growing crop is going to deliver an optimal performance. We can control where we grow, what we grow, and how we grow. But when we're thinking about the bigger picture, this is going to cost us in terms of that land and resource use. Another great thing about BECCCS is that we have so much waste biomass already from agriculture, so forestry and so on, that we can do quite a lot with just this. And that's, you know, potentially gigatons per year.

Emily Swaddle 32:57 Gigatons that we need to share between biochar and BECCS. I want some of that waste biomass as well!

Tom Previte 33:05 Very true, very true. And the other point I want to make is that even once we're using up all that waste biomass for BECCS, I don't think we should disregard using specially grown energy crops entirely. Something we're discovering is that when it comes to the carbon sequestration conundrum, not all land is created equal. We know there's land that's less suitable for food production. And if we can utilise this for BECCS, that's no bad thing, right. Also, as Naomi said before, if we change our agricultural practices and or our diets, we can actually reduce our total land use for food production, which would definitely free up potential capacity or additional capacity. It's obviously a complicated picture, right? And Naomi explored this in more detail with me, comparing the carbon storage potential of BECCS to aforestation to illustrate her point.

Naomi Vaughan 33:55 So when we come to compare aforestation to BECCS, we've got one kilometre square, if we plant it with trees, and we left it alone for 20 years, right and those trees will grow and they'll mature. Brilliant, that's great. We've stored some carbon, it's now standing in the trees and it's in the soil underneath those trees. That's great. That same kilometre could have been planted and harvested for those 20 years annually with a BECCS crop with a miscanthus crop. So all the co2 the miscanthus took out was then captured, stored, and we grew some more. And then it was captured and stored, and we grew some more. So that's where on a just carbon direct comparison, you'd say, well, if you want to maximise removing carbon, just plant a bioenergy crop and keep taking it out, right. But we don't want to just remove carbon. When we think about how we use our land. We want to grow food. We need biodiversity and wild spaces and nature to be protected to give us that resilience. There might be other roles. So for example, we were just talking hypothetically about a nice flat square that used to be wheat, but how about a kind of slopey hillside that currently has some sheep on it? Grass rough grass? Is there some tree mix that we could plant on that you're not going to do a bioenergy crop miscanthus cropping and then harvest it if it's too slopey, right, because it's too hard to get on. So once it comes down to what bit of land actually the decision about what you choose to do with that land, is it left to be a rewilding project? Is it regenerative agriculture? Is it very intensive agriculture? Is it raising cattle or sheep? Or arable crop? Are you planting it with trees? If trees, what type of trees? Is this the timber industry? Are you planting a stand of trees that are going to be turned into timber industry? Is it for paper, which would get used quickly and back into the atmosphere within a year? Is it for fencing but a 10? year lifetime? Is it for building materials? Are you building a piece of furniture that's gonna stay around in someone's home for 20 years? 30 years? Are you building a building, which is going to stay up for 30 to 50 years plus, right? So it gets really messy. And this is what we found in our research. We have a lovely phrase real world complexity and diversity, right? It's not a simple answer. But when it comes to using land, there's trade offs are quite- are very nuanced.

Emily Swaddle 35:59 Real world complexity and diversity. I love it.

Something I think we're both realising as we get deeper into this process and look at more solutions is that there are incredibly complex relationships between land use resources, and so on. None of the solutions we're looking at exist in isolation, you know, it's all a system, and their potential will be impacted by other decisions that we're making. It's just a big balancing act, really.

Tom Previte 36:32 So my key takeaway from these discussions has been that both BECCS and biochar have huge potential, right. But neither is going to be right in every circumstance,

Emily Swaddle 36:43 context is so important. And it's not really a case of which is the best solution overall, but of where each solution is most appropriate. So, you know, we need to consider several factors. For me, the first big factor is land use. It's huge. If grown specifically for banks or biochar, can these crops be grown sustainably? What are the resources that we need? There's so many implications for other things like biodiversity, you know? These crops may also be in competition with food crops, both in terms of land use, and other resources like water and nutrients. And in some parts of the world where there's like less food security, that could be such a problem. And particularly as climate change comes in and impacts crop yield. And as we've seen, land use change, how we manage the land, can actually emit carbon. So we really need to be careful there.

Tom Previte 37:35 That's all really true. And beyond the land itself, we need to think about what we need to scale these up. Something I've been really struck by is actually how different these two processes are in terms of their kind of infrastructure requirements. I really enjoyed Henrietta's description of biochar production, as it's, you know, quite a decentralised process. At the end of the day, it's easy to do at a small scale. So you could even have a farmer, thanks to those biochar kilns who could be using that on their land and replace open burning of biomass. And you're then limiting the need to transport biomass over large distances. With BECCS though you obviously can't have a bioenergy facility in your back garden. So this is going to be requiring a lot more infrastructure, kind of a more of a centralization.

Emily Swaddle 37:35 Yeah, that's very true. See, both are just as important as each other in different instances. And even once we've solved these problems, there's also the question of commercial viability. Both BECCS and biochar are promising in this regard, because they're creating a product which can be sold. But, you know, I know that the cost needs to come down to make BECCS, in particular, competitive with other energy sources.

Tom Previte 38:48 Okay, so we've got a couple more complications or risks that we should be considering. Both of these approaches require energy inputs, you know, heating, transportation, those sorts of things.

Emily Swaddle 38:58 Yeah. And I think we also really need to consider how we measure the effectiveness of both of these technologies. We talked about this in the last episode a lot, you have to kind of outweigh the current carbon cost of the process to the carbon saving the carbon sequestration that's happening, thanks to this process. I think it's really exciting that we're starting to talk about tech more as we work through these episodes, Tom, but the complexity I think, is really just going to keep ramping up. There are so many layers that you know, in our carbon fueled world are all going to be in some way costing carbon. And so I really think that needs to be a huge consideration as we move forward with all these technologies.

Tom Previte 39:44 Yeah, to me, it feels like a very complex, organised system that we haven't quite fully grasped yet at that macro level.

Emily Swaddle 39:52 And don't get me wrong. I don't think that the complexity should put us off investing in these technologies at all. I just think it's really important to be aware of these factors? Because we know that we need these technological processes. Just how they interact with all the systems has to be a question on our minds, what we'll be looking at next. And this whole process of carbon removal is what we do with the carbon when we're trying to store it. We could talk about just storing carbon as is it's the easiest thing in the world. But what actually is the process of getting it underground? That's what we'll be looking at in the next episode.