 I would now like to introduce Kate Maher. Kate is a professor in the Department of Earth System Science at Stanford, and Kate will be facilitating our session on carbon mineralization and introduces two speakers. Over to you, Kate. Great. Thank you, Sarah. Good morning, everyone. It's my pleasure to introduce the topic of mineral carbonation and our two speakers. So the idea that carbon dioxide reacting with silicate minerals to form stable carbonate minerals, the idea that this can present a nearly permanent sink for carbon was first proposed in 1845 by a French mining engineer named Jacques Abelman. If we fast forward 180 years, we now know that the general process of mineral carbonation has been responsible for the long-term stability of Earth's climate by setting the base level removal rate of atmospheric CO2. We also know that the rate at which carbon is processed naturally through the scheme of CO2 reacting with silicate minerals is about a factor of 80 to 100 times slower than the rate at which we are emitting CO2 today. So you can really think about what that means in terms of volumes of reactants and products to scale this idea of mineral carbonation up to the level that we need it to be. And so I know we don't have a lot of geologists in the meeting, so one of the additional things that I'll add as context about mineral carbonation is that many of the minerals and glasses we would like to react with CO2 for alkalinity and base cations are actually really similar in structure to materials, including the glasses and ceramics that we think of or that have been proposed for permanent storage of nuclear waste. And so we're dealing with materials that, at least at the level of the rocks that they're encompassing, tend to be very, very non-reactive. And so that's an overarching challenge that we will discuss and consider in this session. And so given these constraints on volumes and rates, how do we scale this natural process to be part of the solution? So to that end, our speakers will introduce us to two strategies. The first will be in-situ or geologic storage in igneous or volcanic rocks. And the second speaker will talk about ex-situ or above ground storage, largely working with waste products. And then of course at the end, we will have a conversation about the areas of convergence and divergence in terms of technical and technological needs. So please feel free to hold your, to provide your questions now or hold them at the end and we'll do our best to address them. And so with that, I want to introduce our first speaker who is Don DePaolo. Don received his PhD in geology from Caltech and he's been a professor of geology and geochemistry first at UCLA and then at UC Berkeley. He is now currently the graduate professor of geochemistry and the chancellor's professor emeritus at UC Berkeley. Don is a member of the National Academy of Sciences, the American Academy of Arts and Sciences and is widely recognized for his research using isotopic measurements as tracers and kilometers. I'll also just add quickly that Don was director of the LBNL or Sciences Division as well as associate laboratory director for energy sciences at LBNL. So you have a long history of thinking about the context of geology and energy systems and including leading a US DOE energy frontier research center on nanoscale controls on geologic CO2. So thank you Don and feel free to share your screen and take it away. Okay, so let me start with this perspective. So this is kind of the challenge with mineralization and Kate mentioned this. We're currently putting CO2 in the atmosphere at about 37 gigatons per year and this diagram comes from a paper that I did a few years ago and we're just dumping it into this upper box here that has the atmosphere the biosphere soils in the surface ocean processes within those redistribute it but the only output back to the geologic reservoirs is the natural carbon mineralization by rock weathering and that's estimated to be about one gigaton per year. So the problem basically the climate problem is that one is a lot smaller than 37 and the challenge for carbon mineralization is scaling it up to the point where it can make a difference and I think that you know the way to look at this is that we've managed to increase the emissions from one which is the normal background to 37 and it might very well be possible to increase the mineralization from one to at least four or five so that it's contributing to this to mitigation. So a few statements that show where I'm coming from with this. Subsurface mineral carbonation is kind of a form of carbon storage but it's maybe attractive because the CO2 ends up in a permanently immobilized state. Rocks that are appropriate for mineralization as Kate mentioned have sufficient abundance of calcium magnesium and iron so that they can combine with CO2 to make carbonates and those rocks are typically basalt andesite and puridotite. To achieve subsurface mineralization this is a point that I think is important takes a little time probably hundreds of years at scale and it's not generally instantaneous so some people have been sort of selling this as an instant way to turn CO2 into rock. I think at the scale we're talking about gigatons it won't be instantaneous I'll show you some modeling on that. To achieve extensive mineralization requires getting the CO2 charged water into intimate contact with a large volume of rock that's not easy but it's possible and keeping the CO2 and the subsurface long enough to allow the mineralization. So this is a key issue here how do you keep the CO2 down there long enough to allow it to react and I think another general point that I'd like to make is that using igneous rocks, volcanic rocks largely for CO2 disposal may be important because many populated areas around the world do not have appropriate geology for saline formation geological carbon storage. You saw the nice maps that were shown in the context with BEX of the United States which has lots of storage potential most places in the world are not like that. Okay so here's a simple actually a little bit complicated table of various targets for mineral subsurface mineralization and then some of the characteristics that you'll have to deal with. So what I've listed here is onshore basalt formations, onshore volcanic sedimentary formations and onshore ultramafic rocks and then if you go to the marine settings you can look at coastal volcanic rocks and volcanic sediments and deep sea basalt. So things that you want to think about is are there any opportunities for structural trapping that will keep the CO2 down there and actually one of the things that comes into play in submarine environments is that the bottom of the ocean is very cold and actually below about 500 meters it's cold and at those temperatures CO2 hydrate is stable so CO2 may freeze in the presence of water. Perosity permeability and I could have written injectivity there probably it's about the best you can do for these rocks because unlike sedimentary rocks where you can potentially produce oil they haven't been drilled a lot and characterized a lot in detail so we're guessing a lot on how permeable and what the injectivity might be. The other question is whether you need to pre-dissolve the CO2 in water before you reject it. You may be familiar with the carbfix experiment in Iceland. Their strategy is to pre-dissolve the CO2 before and then inject CO2 charged water into the system. This means that you don't have to worry about structural trapping but it reduces the amount of CO2 you can you can inject per well by a large factor partly due to the fact you need to use a lot of water. So the injection rate I put here are numbers that have come from the people working on this for onshore basalt like at carbfix it's about 10 kilotons per year which is a pretty small number but I think there are places where you could potentially inject supercritical CO2 directly and maybe get up to half a gigaton or half a megaton or am I talking about 500 kilotons half a megaton per year per well. Okay let me sort of talk about this in terms of a standard CO2 storage situation this shows you the sort of context of a reservoir scale simulation where you have an injection well you have a layer of a reservoir porous permeable sandstone at about two kilometers depth that's maybe 40 meters thick and it's got a lid on the top of it a so-called seal formation with very low permeability and you just inject the CO2 through the well and let it go out into the formation and imagine this being sort of a radially symmetric situation and so to test the mineralization efficiency we can just sort of vary the amount of reactive minerals that have calcium magnesium and iron in the sandstone and we can do this in an imaginary fashion you're going to have to have a real sandstone and just see what happens and if you look in the literature this has been done quite a few times and I think the figure on the left here is the main thing that I want to I want to show you which is that if you plot the percent of the CO2 that's been mineralized after 500 years in the simulation against the volume percent of reactive minerals in the rock you get a very simple relationship here now most of these people are using similar software in fact the same software in many cases but this is what you expect that there aren't any very many other factors coming into play other than if you have the right minerals there you have the availability of these cations you will mineralize the CO2 and the finger on the right tries to give you an idea of how variable the time scale is for the mineralization and it varies if you don't have very much mineralization going on it's a little variable but once you get up to the point where you are it's not variable it's pretty well determined okay so one of the issues is how fast is that mineralization process actually happen there's about three or four factors that go into calculating that but one of them is the inherent dissolution rate of the key minerals so two of the key minerals are clino pyroxene and plagioclase and these other chemical formulas in case you've forgotten them and this is a plot of the reactive or the dissolution rate constant so basically this is one factor that you need to know in order to predict how fast these minerals are going to dissolve it's on a log scale and basically at the temperatures of typical CO2 storage you're talking if you look at the range of values that are have been used in the literature they expand about three or four orders of magnitude between 50 and 80 degrees C so this is a kind of problem so if if you have a model like the previous one I showed you if you pick reaction rate constants that are close to the top of this range you'll get a lot of mineralization in a hundred or 500 years if you pick something near the bottom you won't get any mineralization so this you know looks like a big problem but I think this is something we can address there haven't been very many recent experiments done on this but this is something we could firm up I think okay the last thing I want to talk about is this the idea of how do you keep CO2 in the subsurface long for a long time and I want to tell you about a project that we're working on in Hawaii the idea of injecting CO2 into volcanic rocks in the oceans this little dot here is the right at the Hilo airport if you've ever been there and this is offshore bathymetry up in the upper right here's a sort of picture of what the subsurface might look like and what the temperatures are and and the density of CO2 so because the temperatures happen to be low because there's cold seawater circulating through the rocks the CO2 is pretty dense so the the attractiveness of this type of environment is that the low temperatures make the CO2 less buoyant there's a huge amount of basalt there there's actually six kilometers of thickness of basalt under Hilo you could presumably inject pure CO2 you don't have to pre-dissolve it and there's a combination of dissolution capillary and mineral trapping as well as CO2 hydrate formation that could come into play in immobilizing the CO2 so I mean just as an example we've done some injection models of this we've simplified the geology here this shows how cold it is in the subsurface in this drill core that we have there and and basically we we've done a simulation of injecting 50 million tons of CO2 over 100 years and it stays down there and over on the right you can see that about somewhere between 50 and 75 percent of it gets either mineralized or dissolved over 500 years so this is an environment that hasn't been considered very much but I think has potential and could be you can find similar places around the world so the summary is there are a number of different onshore offshore and coastal options there's a trade-off between injecting as pre-dissolve CO2 or as supercritical or liquid CO2 pre-dissolving CO2 limits the amount you can inject per well and requires a lot of water the mineral dissolution rates at low temperature should be firmed up mineralization in general will not be instantaneous when injection is at the scale needed to make a difference and these low temperature marine settings may have some advantages for results so our next figure is Greg Dippel from the Department of Geological Sciences at the University of British Columbia Greg studies processes and driving forces for mineral fluid interaction and you know students over the years have conducted a bunch of really wonderful field experimental and modeling studies to show that weathering of alkaline mine waste is vastly accelerated over background levels and so getting at this problem of these slow inherent natural rates and so thank you Greg and feel free to start great thank you Kate good morning everyone yeah I'll continue on with a discussion of carbon mineralization focusing specifically on XC2 mineralization and I thought I would just take take the title and dissect it a little bit to explain what I mean by that so we're really looking at processes that happen above ground in mineralization we're taking cations such as calcium and magnesium predominantly and we're combining them with carbon dioxide in the context of carbon removal we need to do that from air either directly or indirectly the cations are derived typically from minerals or industrial solid waste and the co2 can come directly from the air or it can come in more concentrated streams like we might get through DAC or BEX as we saw earlier this morning the ultimate fate of the minerals can depend on the deployment they can end up in soils essentially in the process of weathering within soils they can end up being stored long-term within the industrial waste storage facilities these are large facilities that already exist on the scale of billions of tons per year tens of billions of tons per year there's a potential utilization component in terms of developing building products that may have some application and finally some some people actually consider that the this material could reside or reside long-term as alkalinity within aqueous solutions such as rivers or oceans but I won't focus on that today given that mineralization to me generally would mean that we make minerals not dissolved minerals hit one here so I'm going to quickly go through the take-home points that I wanted to make today and then I will maybe highlight a few of these points one is the the capacity in the long term is probably going to be on the order of five to ten gigatons per year probably closer to five the cost is typically quoted at thirty two hundred dollars per ton for a number of reasons including some raised earlier today I think you know we really should be thinking about processes that are closer to two hundred dollars a ton especially if we're doing both the capture and the mineralization this increases the capacity and it also highlights that mineral storage being effectively geologic means that it's extremely durable and would have potentially fairly high value the capacity that's listed on the order you know five to ten gigatons per year the real issue here is that most of that capacity currently isn't deployable at a rate that's significant so the issue here is around finding ways to use that capacity and accelerating processes so that it happens at a rate that means something and generally we can do that through either prospect prospecting or seeking out the reactive material that's inherently highly reactive or using treatment treatments or enhancements to create that reactivity in terms of research needs to move this forward we need to think about capacity in terms of rate and so we really need to start to look inventory what is being produced what exists historically and what might be produced in the future we need to we need to figure out these treatments or enhancements for reactivity and be able to deploy them at scale and at relatively low cost and lastly many of the models being or the methods being put out for for carbon mineralization are relying on relatively simplistic geochemical models and we need to we need to really up the game on these reactive transport models that involve exchange between the gases liquids and minerals and we need to validate and calibrate them with with large-scale field studies and with those kinds of tools we can I think better assess the issues in terms of impact for land water usage cost potential pollution and other impacts. Permanence as I referred to earlier is for virtually geological so it's highly durable I'll talk a little bit about verification and maybe some paths forward for this for this approach. So the process here is one whereby we dissolve cations we combine them with CO2 and we use them to make carbonate minerals which gives us virtually permanent storage. The idea here is that in capture from air we're typically limited by the rate of CO2 capture and when we supply concentrated CO2 like you might do from Dacrobex then we really are limited by mineral dissolution so to increase rate we need to make those minerals dissolve quickly. The capacity numbers are typically thrown out come from papers like this from Renforth and Birling this looks at rates of alkaline waste production for several different scenarios into the future. Another thing that's talked about is mineral amendments to soil this is actually an amalgamated figure I put two figures together from the Birling et al paper and the point here is it really shows in the green lower numbers on a country by country basis the amount of capture gigatons of CO2 per year as a function of deployment versus the actual amount of solid material needed. So the mineral amendments isn't really included in that 5 to 10 gigaton scale it has a total of about two gigatons per year but it's going to require a lot of mining to get there not a lot of new mining to get there. So these are some data from some studies we've done when we look at mineral dissolution rates we see typically that that industrial materials and mine tailings which are finely crushed rock as a waste stream from mine really have two classes of reactivity we have a fraction that reacts hundreds of times faster than hundreds of times faster than bulk stoichiometric mineral dissolution which would kind of be your textbook rate. So the key here is finding those materials where a significant fraction is in that labial fraction and so in this case here the plot on the left is an actual mine tailings from a mine that produces 11 million tons of tailings per year and if five to seven percent of those tailings reactive capacity is labial that means we have an option for actually using it for direct air capture and the plot on the right just shows some of the diversity across a number of different minerals, mines and industrial waste types that we've looked at and we can see that it's extremely variable and that the reaction rate varies over many orders of magnitude and these data come from far from equilibrium of flow through dissolution reactor studies that we do at UBC. Just as we can we can prospect for these highly reactive materials we can also move curves from the left to the right through chemical treatments and enhancements. So it's just a quick point on how we might look to prospect for these materials this is a result of a recent study Mitch and Synodallic preliminary report was released late last year final report and do it later this year and by Geoscience BC which is government funding agency this map on the left runs through Central British Columbia from the Washington border all the way up to the Yukon border and this study basically looked at existing geological and geophysical data to do inversions of over 200 ultramarific rock bodies to identify those that were highly serpentinized because we find that serpentinized ultramarific rocks have a much higher proportion of labial magnesium and from that we estimate that there's enough serpentinized the left enough labial magnesium and serpentinized ultramarific rocks in the top kilometer of the crust within British Columbia to mineralize 56 gigatons of CO2 in total this is about 800 years of BC's greenhouse gas emissions to put it in in perspective of course we don't want to mine all the thousands of cubic kilometers as that implies but it allows us to identify opportunities where we might be able to co-develop this with development of precious or battery metals or other opportunities so this is the idea that we can use tools from mineral exploration to identify optimal areas to deploy carbon mineralization as well for large-scale validation we really need to to do reactive transport modeling in these complex systems but we need to do them at large scale and deploy them with with validate them and calibrate them against field data this is a result of one such model which just looked at the effect of of moving a mine in western Australia to different climates around the world and showed how the anticipated rate of CO2 capture from air can be substantially affected by climate in this particular instance so as we develop and improve and calibrate and validate these models they're going to give us a lot of important information on impacts as well as permanence and durability monitoring and verification I think is in mine tailings is relatively straightforward we certainly deploy a combination of geochemical techniques measuring solid carbonate content before and after large-scale fields experiments and we couple them with soil gas chamber flux systems and eddy covariance systems essentially we're comparing mass balances from the gas phase and the atmosphere above the mine tailings and contrasting that against cumulative carbonate uptake as measured by the total carbonate content in the material after a period of time and when we find good convergence between those methods essentially comparing mass balance in the solid mineral phases against mass balances in the gas phase above it when we find convergence we have a fair bit of confidence that the carbonate is being sequestered and mineralized in real time the last point I was wanted to make was that you know there's a lot of complexity within these individual systems I thought I'd use the example of battery middle mining in particular nickel mining to show some of the complexity so these bars here are tons of CO2 mineralized or emitted per tonne of tailings finally ground rock per year the red bars on the left show three different existing mines depending on whether or not it's high pressure acid leach laterate nickel mine versus a nickel sulfide mine versus a nickel mine running in a jurisdiction like British Columbia where the electricity generation is by hydroelectricity we can see that the carbon footprint there's there's fleet emissions which are difficult to grab as a point source often we have electricity generation on site within a mine so we potentially can use electricity generation as a point source of CO2 we find that the labial fraction or the reactivity of tailings actually depends on the concentration of CO2 so single tailings sample will have a different capacity or a different labial magnesium fraction depending on whether or not we're feeding it air flue gas or a hundred percent CO2 but a lot of the reactivity it comes can be can be accessed simply with reaction with air we can think that we can match the dark colors against across the horizontal axis here and we can use air captured offset truck emissions point sources to for flue gas capture and if we prospect for the highly reactive tailings that would be the green column on the far left that represents an opportunity for many of these mine operations to operate negative in terms of CO2 emissions and on the far right I show a you know where we're going to into the future so first of all I think that we will be driving we will be driving the mining of metals like nickel that are essential for electrification of transportation away from deposit types like laterites which inherently have a high carbon footprint towards the sulfide type deposits which have an inherently lower carbon footprint of mining once we move them across to renewable energy and we look at transformation of the haul fleet away from fossil fuel combustion we and if we also combine that with prospecting for highly reactive mine tailings materials we have the potential to create a significant capacity to not only completely offset the emissions of mining but also generate net negative mining and carbon removal from the atmosphere in the same industrial processes that we are using to generate the nickel which we need for our Teslas and our car batteries so I put this forward as an example that I think these kinds of these are the shorter turn up term opportunities that will give us confidence and pathways to deploying mineralization at larger scales so with that I will leave it at that just again emphasizing the points some in from five through ten really emphasizing some future needs and areas of focus for future research great thank you Greg we're going to go ahead and turn to the panel discussion and I want to I want to ask both Greg and Don for their perspectives on mineral kinetics but I want to start with Greg because you talked about the need for either prospecting to find these more labial materials or developing treatments and so I'm curious if you could comment on you know what are some of the treatments that seem most promising what are the different factors cost energy that need to be considered are there any that look like they might be cost effective and then on the flip side of that in terms of the prospecting what controls the label labial magnesium fraction and are the mining companies at all incentivized to help map out that potential quality great thanks yeah no good good questions you know in terms of um accelerating mineral dissolution to create more labial cations um you know the the the the gold medal there would be to to optimize uh feldspar discussion because there's feldspar and so abundant in the crust and also so many of the largest metal mines in the world are in feldspar and feldspar rich rocks that's an incredibly hard nut to crack I'm not sure but if someone could figure that out that would be a massive game changer in terms of of of mineralization I think you know we're currently going back and looking at at modifications or treatments that we dismissed five or ten years ago as being too expensive because now we really see the long-term carbon price at being closer to 200 per ton and that actually allows you to think about using techniques that you know we certainly had set aside previously because we were focused on sort of $50 per ton solutions I think if we're doing capture and mineralization we should actually be targeting the one to two hundred dollar per ton processes because those would be deployable at a significant scale and maybe generate the benefit that we the benefit that we need in terms of the prospecting for our um labial cations it's very much it's predominantly mineralogically controlled and we're starting to build a good understanding of that we see that it's highly variable we've done that we've we built sort of proxy models where we can compute mineralogy from exploration geochemistry and we've developed um you know based on eight or ten thousand exploration analyses we've built three-dimensional models of the distribution of labial cations within say a billion ton nickel deposit we find it's highly variable and that the top you know two to three percent of the material has extremely high labial cation contents and and we've validated that by by going out and collecting that material and analyzing it in the lab so there are as a small fraction that's highly reactive within individual deposits and continuous over several meters of drill core length when these when these deposits are grilled if those really if that few percent of these ultromethic rocks can if we can figure out how to mine them selectively in a way that has a low carbon footprint and not and not to not a large stripping ratio then we really are enabling you know that would be that would be a game changer within these deposits you can imagine if you had capacity within British Columbia alone for 50 plus gigatons you only if you only got one percent of that that would still be a very significant rate of carbon mineralization within within the context of British Columbia alone and also you'd be really reducing the amount of mining if you can if you can find ways to do this selective mining so those are technologies and approaches that the mining industry has to come up with in reference to your last question they are strongly motivated you know several of the biggest mining companies in the world have declared that they will become carbon neutral and they have no idea how they're going to get there by and large I think but also there's a significant players in the mining industry are the junior companies they're the ones that actually find the deposits most of the nickel deposits we work on are being developed by junior companies and they just want to sell it up the food chain to the larger companies and if they can demonstrate high really high reactivity to CO2 in the last 12 to 18 months that's become a game changer in how the interactions between the juniors and the multinationals go so there's a huge amount of motivation within the mining industry to figure this out. Interesting thanks Guy. Don I want to turn to you with a similar question in terms of your perspective on you know chemical treatments or other physical treatments that you guys have been thinking about for volcanic rocks to to manage some of the injectivity problems that you might face you know what do you see as being potentially important to address in that in that area of the kinetics of in situ injection? Well I think the the biggest problem is to get some reliable data on what the rocks are like as they are now. You know if you're working on materials sitting at the surface you can do some tests on them but you have to work in wells and you have to it's expensive to work downhole and so the question is whether there's going to be enough interest from people who are willing to fund this kind of thing to do the downhole work that's going to be necessary to characterize things like reactivity and injectivity in basalts as you know the ones that we think might be reasonable targets. Once we have that information we might have some ideas about how to improve it but I think you know the problem with operating at scale is that if you're going to do gigatons you sort of have to have the natural resource giving you what you need. It's hard to change it and do that economically especially if it's underground. And kind of related questions on you know you've mentioned the majority of demonstration sites, CarpFix and the PNNL site were really low injection rates and often CO2 mixed with water. If you really were able to propose you know what's the next step up in scale that we should be thinking about to understand this process better. Do you have like a conceptual model on hand in terms of a field test that you would like to see happen? Well what it comes down to is what is the vertical permeability of sections of basalt that are thick enough that you would be confident to be able to inject into them at the appropriate depth. You know right now CarpFix, the other problem is you know if you could instantly mineralize the CO2 then you wouldn't have to worry about it. I just don't think that that's likely. CarpFix in their second you know the first version of CarpFix they only injected a couple hundred tons of CO2 and they got most of that mineralized I think but now they're injecting about 10,000 tons per year but they're injecting it into a geothermal system at 250 degrees C where they can pretty much guarantee that the reactions are going to go fast enough to mineralize the CO2 but you know restricting the that strategy to geothermal systems in basalts is very restrictive. I mean that's not going to be very many places around the world where you can do that or would you where you would want to and they're still only up to 10,000 tons per well per year so I think we need to find places where we can you know throw the CO2 in there as pure CO2 and expect it to stay down there and be dissolved mineralized frozen into hydrate or whatever it takes but I think in the long run it will get mineralized but it might be a thousand years before it gets mineralized. The main point is to make sure it doesn't come back up and you're not going to have a shale or some you know really low permeability sedimentary rock to cap it but there may be enough variability and low permeability layers in these basalt sections that it will stay down there but we need to do those those will be field tests and again once there's a commitment from you know in the U.S. it would be the Department of Energy or some private you know philanthropists to say well okay we've got to figure out what we can do with basalts then the this level of funding might be available to do the downhole test to get started. You're making me wonder too about characterization methods because I my understanding of seismic characterization that's so widely used in oil and gas does not work very well in these basaltic basins. Where do you see as a sort of characterization need in all of this? Do you have to do it from wells or are there other things we could be trying to to develop to really map these basins and their potential? I think they're you know obviously if you can do seismic you're a lot better off because you can characterize large volumes of the subsurface that way. Electromagnetics might be helpful too but eventually you have to ground truth some of it with well data so the whole thing needs to be done. We need more well information coupled with tests on what we can do with seismic and electromagnetic. Greg I also had some some questions for you thinking about sort of the second step in the process so we've talked about reactivity and kinetics there's this CO2 delivery stage and I think you mentioned both being able to use tailings as direct air capture as well as kind of point source. I'm also curious how those would differ and what opportunities there might be from a more industrial type of setting but also you know you've sort of touched on this but I'm really curious about water how much water do you need to really make the direct air capture an efficient process for these tailings? Yeah, no water is a major issue so we're kind of pushing two different technologies one is reaction definitely with the atmosphere and for that we are manipulating and managing the surfaces of these large tailing storage facilities so at a typical nickel mine the tailing storage facility might have a surface area of about 15 square kilometers. So there are large industrial storage facilities and we can substantially increase the rate by which they capture CO2 from air by managing the water content and by doing essentially churning or stirring so that we're bringing up fresh material keeping in mind that these tailings storage facilities they continually laying down fresh material so on the time scale of months or so the surface will be refreshed with new reactive material already but on the basis of the industrial process and so it's really the water content that we manage for is you know 10 to 20 percent of tailings by mass which is what it will normally inherently hold if it's drained so usually the water issue for air capture is too much water not enough and then water is recirculated within the process circuit within an operating mine so that it's it's not new water usage it's more the usage of the of the process water unfortunately almost all mines have a water problem either they have too little water or they have too much and so there's always water management is one major issue for mines generally and so it will have an impact on operations if you're trying trying trying to do that for the capture at higher concentrations we rely basically on injection and so for that to work we really need the higher concentrations of CO2 and we also need pneumatic permeability within the tailings so we typically look at you know some mine types like diamond mining they already generate both a fine and a coarse stream and we find that by blending those back together in the proportion at which they're produced produces a material that's both reactive but also has relatively low permeabilities at these similar water contents so the technology that's being scaled up and starting to be used in mines is is something called dry stack tailings that's where the industry is moving because it gets rid of the need for water saturated tailings and large dams which have huge safety risks and so the industry is moving towards new storage technologies that are actually quite well situated to allow for injection within those materials if the tailings are reactive respond is there any calculation method to predict the release or behavior of cations in different rock structures um if i understand the the question right i mean at what rate will they be released from the minerals to be available to make make new carbonate minerals yeah i think the question is is related to your maybe your slide don where you were talking about you know we know the kinetics of these different minerals we have a big amalgamation of different minerals how can we what methods do we use to predict the release from those rock packages um well what we do is use the parameters that we can get out of literature that come from experiments and apply them to the rocks and the way this works is that if the reactions are going really fast then there's a lot of things that can come into play to slow them down but if they're not going that fast then you we can predict it reasonably well and it comes down to whether we know those reaction rate constants well enough and um so my view of this is we can predict these things but we need to need to be a little bit more confident in the basic data that we're inputting and i think also just to add to that the surface area that's actually exposed to the fluid in a real porous media is also a challenge that's very hard to characterize we can do things for some single minerals but it's hard to get to that composite porous media without adding a lot of uncertainty yeah i mean if the reactions are going fast the surface area term is going to be really important if they're going slow that may not be the limiting issue because the surface the surface area that you need is going to be going to be exposed on a long time scale so um it depends on what you're trying to do if you're trying to do what greg is trying you know talking about at the surface you want the reactions to go fast you need to know the surface area that you're exposing to the to the reactive liquids think of the subsurface you'll get the exposure on a hundred year time scale thanks don i see sarah popping on which probably means that we're out of time and needs to move to the next panel great thank you uh greg don and kate that was a wonderful discussion