 Good afternoon everyone. So good to see you here. Welcome to Purdue Engineering Frontieria Lecture Series. My name is Luna Lu. I'm Riley Professor of Civil Engineering and also Associate Dean of the Faculty at Purdue Engineering. Today is my great pleasure and truly the greatest honor to invite our speaker, Professor Ilan Yablavitchi from UC Berkeley. Professor Yablavitchi is a person. Do not need any introduction. So many people know him for his impactful discovery. If you have not known him, but I'm sure you interacted with the technology he invented. How many of you use cell phone? Pretty much everybody, right? He invented the antenna used in every single cell phone in this planet of the earth. So let me just highlight a few of his impactful discovery. Professor Yablavitchi introduced the idea of stringed semiconductor laser that has better performance due to the reduced valence band or a whole effective mass with almost every human interaction with the internet that enabled optical telecommunication occurred by the string semiconductor laser invented by Professor Yablavitchi. He is also regarded as the father of photonic crystal, photonic band gap concept. If you're a physicist or electrical engineering, I'm sure you heard of the term photonic crystal that actually invented by Professor Yablavitchi as well. And in his photo attack research, Professor Yablavitchi introduced the four n squared light trapping factor that is worldwide used for almost almost every single commercial solar panels. His mantra that a great solar self also needs to be a great LED is indeed the basis of a word to record the solar cells. A single junction reached 29.1 percent of efficiency double junction 31.5 percent at the quadril junction 38.8 efficiency at only one song energy. Again, as we talk about his cell phone antenna company called Ethertronics shaped over two billion antennas used in every single cell phone, right? And we were interacting every single day on a daily basis. Of course, as you can imagine, he is a member of National Academy of Engineering, National Academy of Science, National Academy of Inventor and also is a foreign member of Royal Society in UK. So again, with a great pleasure and honor, let's invite Professor Yablavitchi to the stage. Thank you so much. It's great to see the large group here. Thank you very much for that terrific introduction. I'm going to talk about something that it's a little bit technological and maybe a little bit has to do with politics and society. And that is to do with the recognition that has been very, very highly trumpeted that were in grave danger of having too much CO2. Indeed, the amount of CO2 in the air has gone up quite a lot. And so we're entering sort of an unknown region and we need to have a way to solve it. So what this talk is going to be about is how to get CO2 out of the air. We know how to get it into the air. We just burn stuff or fly in a jet. But we have to get it out of the air. And now some people want to completely eliminate the use of hydrocarbons. I think this is going to be very difficult. For example, if you want to go to another continent, there's no real substitute for jet fuel. Jet fuel is, as the highest energy density, is very important for staying in the air for a long period of time. And I can give you a rule of thumb. If you're going to another continent, the jet will use double your personal weight in fuel. So a very long trip, and then the energy to mass ratio is very important for the fuel. There's no substitute for hydrocarbons. We also have a problem with winter summer energy storage is that we don't have very good ways of storing energy, except if you store it as hydrocarbons, then it works very well. And then we have another problem is that there are some countries that, let's say we were in a world where we were greatly reducing the amount of use of hydrocarbon fuels. What do you do about the countries that don't cooperate? And it's not something that you'd want to start a war over. So you'd have to pull out their carbon dioxide, too. So there's always going to be some carbon dioxide going into the air. And unless we extract it, we're going to be stuck. So we have to have a way to extract it. That's what this talk is about. And I'll mention one more speculative reason why we want to pull carbon dioxide out of the air is that there are some models where the permafrost in the Arctic, as it melts, it would release more CO2 or more methane, which is also a very severe problem. So what it says is that five years ago everybody talked about being carbon neutral. And then it was recognized being carbon neutral is not enough. We actually have to pull carbon dioxide out of the air. We have to have carbon negativity. But some people object that I shouldn't use the negative word, but there it is. So what happened also about five, six years ago, notice was taken by the various national academies that we need to have. We can't just do carbon. We need to pull carbon dioxide out of the air. So they wrote a bunch of studies on removing carbon dioxide from the air. And this one is from the National Academy of Sciences of the United States. This one is from the European Scientific Advisory Council, which is sort of the same thing. And they actually used the negative word. And there was a Physics Day article capturing carbon dioxide from the air. You can see already they're going to have a problem because they have these pipes here and they're actually forcing the atmosphere through these pipes. They're going to pull the carbon dioxide out. You can imagine what it's going to cost to push the entire atmosphere through some pipes. So what emerged from this is a number of ideas that were extremely expensive. So so-called direct air capture where you pull the CO2 out of the air using chemical compounds called amines and then you have to heat them up to reuse them. And so direct air capture at that time was $600 a ton of CO2. So that I will calibrate you in the cost in just a minute. The $600 a ton can be converted to cents per gallon of gasoline and then you understand what it's costing. But the $600 a ton, this has been trumped by recent inflation reduction act payments by the government. The government is actually today paying $1,000 a ton, which is completely ridiculous. So this was a report from the American Physical Society. It was too expensive obviously. Now this is from the table of contents of the European report. They looked at all the different ways of pulling carbon dioxide out of the air. You had afforestation manipulating the forests, land management who increased the storage of carbon and soils. And they're particularly going to farmers, trying to get the farmers to change their form of agriculture. And the farmers don't want to change anything. Okay. Bioenergy, essentially biomass and then burning it and then capturing the carbon dioxide from burning the biomass. That has an acronym BEX, which communicates nothing. But if you're in the in that field, then you'd know what it means. And hence weathering. So there are certain rocks that actually absorb CO2. And they're not so common, but they can be used. And this one is the one that's very expensive, direct air capture and carbon storage. So they capture the carbon dioxide, they pump it underground. And that costs money too. And then there are various ideas to fertilize the ocean. Right, fertilize the ocean. So the idea there is that you fertilize the ocean, the algae grow. And then if you're lucky, the algae fall into the very deep crevices into the ocean. Unfortunately, a very few, a very small percentage actually falls into those crevices. And most of it just comes back as CO2. So it doesn't quite work. Now, the one thing that is missing, which is to me the most obvious thing, is the safe burial of agricultural biomass was not even listed, was not even considered by this European committee. But apparently they have a more up-to-date version of this. Maybe I should check to see if they acknowledge that the burial of agricultural biomass can be very good. So every spring season, so we're in spring right now, the plants as they grow, they pull carbon dioxide out of the air. And the people who monitor the carbon dioxide in Hawaii, on the mountains in Hawaii, they actually see the carbon dioxide go down in the spring. So plants, agriculture can actually observably reduce the amount of carbon dioxide at least in months like April and May. So who am I copying here? But the ideas are not original. So the idea of using plants to pull carbon dioxide out of the air is due to Freeman Dyson. So Freeman was a, I would say, regarded as the most imaginative physicist of the 20th century. He was very famous, was at the Institute for Advanced Study for his entire career and wrote a paper in 1977, which was quite a while ago. He wrote a paper that said why don't we just take trees and toss them into the ground and that's enough to solve the carbon dioxide problem. So he was very good, like most physicists, very good in dealing with orders of magnitude. So the orders of magnitude were correct, but he was not aware that if you throw biomass into the ground, the biomass decomposes. And then if it decomposes, you get back carbon dioxide, but you also get back some methane, which is really bad. And so it was a good idea, but incomplete. But I can't say this idea was original to me. And this is the oldest reference I could find, is Freeman Dyson. And more recently, there is a, the recognition that we actually need to remove carbon from the atmosphere was recognized by the X Prize. So there is now a competition going on, $100 million prize. And they were even, they have already given out part of it. And, but the grand prize, we're waiting for the grand prize, but it's for carbon removal. And so it's sort of a recognition that this is an important thing. It's a little too late to enter this competition, because there were some preliminary things you had to do. But let me mention one of the reasons why it's so difficult to remove carbon dioxide from the air. Let's compare carbon dioxide concentration in the air versus let's say carbon concentration in wood. So in wood, a lot of wood consists of carbon, a good fraction of it, maybe half. And so you're taking a very low concentration, which is maybe, well, now it's 400 parts per million. And you're comparing it to the full concentration, which is let's say in wood. I mean, you have a concentration ratio. So the plants give you a concentration ratio of the order of 10 to the eighth in pulling carbon out of the air and forming wood. Now, when you concentrate something, you reduce its entropy. And you reduce its entropy essentially by K log of that concentration ratio. And the corresponding entropy is 17 K. And that converts to an energy of 17 K T. And it's close to half a volt. So for every carbon that the plant pulls out of the atmosphere, it costs half a volt. So already you see there's a difficulty. Where does the plant get the energy? It gets the energy from the sun. It's doing some work that way. So the plants provide the free energy. But it's one of the reasons why it's difficult to do. You have to actually supply energy to concentrate carbon. But I said we're going to allow the plants to do it. So here are some plants. And it depends upon the region of the world. We are adjacent to Illinois. So the best plant in this region is miscanthus, which is a perennial. It grows for about 20 years. And it produces a lot of biomass. And much of what I'm saying about the biomass was worked out for me. I didn't have to do any extra effort because about 20 years ago the energy world sort of went crazy about biofuel. So they worked all this stuff out. It's where to get the biomass and how much it's going to cost and so forth. And in Florida it's a different plant. It's Napier grass. In England, which is quite far north, even there they had a candidate. And in Mexico they have a different candidate. I'm circling the man. I should be circling the plant. So the agriculture is known on how to do this. And they're very efficient. These plants are very efficient. For example, around here corn is grown. Corn is quite efficient, but these are even more efficient. They're approximately three times more efficient at converting sunlight into cellulose. So the cellulose is about 40% by weight carbon and you can extract many tons of carbon from each acre. So this all worked out. And every country publishes agricultural statistics, the productivity of the land, the particular crop, and you can look up on the Chicago Board of Trade what the crop is costing. So you know everything you need to know. And it would take quite a large area of land, nonetheless, to remove all of the carbon from the air. But large, but not ridiculous. It would be a major agricultural product. So I have to introduce, I've already introduced Freeman Dyson. Let me introduce Al Rose. When I was young he was my mentor and I was working on solar cells. So I got into this through solar cells. And he said, the young whipper snapper, you think you're so smart with those solar cells, do you realize you're going to have to compete with plants? You're going to have to compete with agriculture. And he challenges me in the following way. He says, why don't you find out the productivity of corn? He was specific to corn. And figure out what it costs on the Chicago Board of Trade, how much the yield is per acre. This is all known things. And figure out how much energy you get per acre. So he wanted to know the cost of corn, not in bushels, but in dollars per megajoule. You can convert dollars per megajoule and compare it to gasoline in dollars per megajoule. Now in case you want to do such a conversion, there are about 160 megajoules in a gallon of gasoline. So you can you can do the conversion, that part of the conversion yourself. So I went and did the conversion. And he was teasing me. I didn't realize he was teasing because he had just published this. He had published this in this article when he asked me this little riddle. And the answer was kind of shocking is that the cost of gasoline, it was actually during one of these high cost periods of gasoline, the cost of gasoline in dollars per megajoule was similar to the cost of corn in dollars per megajoule, which was kind of amazing. So it gave me the idea, oh my, the solar cells will have to compete with corn. And I think that will happen one day, not with corn but with other crops. And so what do you do about Freeman Dyson? He already said bury the biomass. And so I have here an example of burying the biomass. Now you have to bury the biomass in a specific way. And I'm going to tell you the punch line right now. How do you prevent biomass from decomposing when you bury it? And the answer is you dry it. Well, every farmer cannot sell his crop until he dries it. So you dry it. But then you have to keep it dry. How long do you have to keep it dry? Well, you could easily keep it dry for thousands of years. And this would satisfy any environmentalist if you can get the carbon dioxide out of the air for thousands of years. What does it take to do that? When you dry it, you seal it up with four millimeters of polyethylene. So this is the key. Four millimeters of polyethylene. That stuff does not look like a shopping bag, polyethylene shopping bag. That stuff is very, is like semi-rigid, very, very strong, yet somewhat flexible. And you say, well, that's a crazy idea. Who's ever going to do that? So that's already being done. So for example, if you had breakfast this morning, you generate, let's say, a yogurt cup or some other garbage and in the most modern landfills, it gets sent to one of these landfills and it's sealed off with polyethylene. And the why is this a requirement? The reason is that the authorities don't want the garbage to contaminate the water table. We are in exactly the opposite situation. We don't want the water table to make our biomass wet. And so it's pretty much for the same reason. And one of the things that's extremely well known is how fast water diffuses through polyethylene. And yes, a four millimeter thickness will keep water out for thousands of years. So it's somewhat surprising. So we published this in last April. So it's now April again. So we published it a year ago. And I can tell you some of the things. So I had a lot of interesting reactions to this paper. But I'll mention one thing that gets people upset a little bit is that when we bury the biomass, the biomass is essentially cellulose, you see that the carbon is already partially oxidized, because this is the approximate tangible formula for cellulose. And so you already have one oxygen in there. Now, as I mentioned 15, 20 years ago, biofuel was all the rage. And you're starting with the same thing with cellulose, but it's already half oxidized because it's already got one oxygen on it. So in order to make biofuel, you have to grow two acres of biomass in order to effectively to get one acre of biofuel. So inherently, it's going to be a large-scale agricultural enterprise that would be twice as big if we made biofuel. If on the other hand, we simply bury the cellulose, you get credit for one acre and you've put the full amount of carbon into sequestration. So of course, the biofuel people don't like when I say that, but that's the way it is. Now, but if you simply bury it, it gets eaten. You can see here various insects will eat the biomass. If you seal it off against oxygen, doesn't matter because there are anaerobic bacteria. And forget about simple burial. It all turns into carbon dioxide and methane. And so the simple burial will not work. And what we're saying is, oh, this is yet another slide telling you that simple burial will not work. Well, it sort of works a little bit. And in the following sense, that if you take wood, it's very famously mostly consists of cellulose, but it also contains lignin. Now, lignin is a compound that is responsible for the grain and wood. So you have wood, you see the beautiful grains, because there is lignin in the wood. The lignin turns out to be extremely durable stuff. So it was a tremendous headache when they were making biofuel. They couldn't figure out how to process the lignin because it lasts a very long time. So you will get some credit. If you simply bury the wood, you'll get 30% credit because the lignin will not decompose very rapidly. So it's not like you didn't do anything. You did something, but it's only 30%. The cellulose decomposes right away. So I mentioned the solution is dryness. So now we introduce a scientific concept. How many of you have heard of a concept called water activity? The chemical engineers? Sure, you're afraid to show your hand. Okay. So water activity is like the relative humidity. We're all experiencing relative humidity, but you wouldn't assign relative humidity to a solid object. Suppose the solid object was a stake, okay? And then you wouldn't say there's a relative humidity inside the stake. You would say there's a water activity. The concept is exactly the same, but it applies to solid materials. So we don't call it humidity. We call it water activity. So it applies to food and biomass generally. And you could ask, well, what is the relative humidity in equilibrium with the stake? And that relative humidity in equilibrium with the stake is the water activity. Okay. And so it's a very similar concept. Now who worries about this? Two government agencies worry about this. The Food and Drug Administration wants to know that the food on the supermarket shelf is safe. And so you have some new product. You want to put it in the supermarket? You have to tell them, okay, what's the water activity? Oh, the water activity is below 60%. No problem. Wrap it up in cell pain and put it on the supermarket shelf. But it was over, it was over 60%. So it's no good. It's not going to last on the shelf. It would be unsafe, unsafe food. The second government agency that has investigated this is NASA because they're interested in the requirements for life on other planets. And they've investigated many different forms of life. And the conclusion is once again, in the most worst cases, you still need at least 60% water activity or metabolism stops. Why does metabolism stop? You have to move chemicals around inside the cell. And to move the chemicals around, you need a certain amount of water. And so metabolism stops at 60% water activity. And so that's the idea is that if you keep something below 60% water activity, it's going to last a, as far as we know, it'll last for thousands of years. Okay. And so this is a chart of all the different things. Bacteria seems to require about 95%. Yeast about 85%. Mildews and so on and so forth. And weird kinds of mildews that I don't know what they are. But finally, you get to 0.6 or 60% water activity and metabolism comes to a stop. And of course, the ancient natives knew about this. For example, this is just a photograph of a salmon in the Pacific Northwest that are being dried by the natives. They knew very well that if they dry the salmon in the summertime, that it would be preserved so they could eat the salmon in the wintertime. So drying is very effective. Now, then you ask, how much, how do you compare the weight of water, the percentage weight? So in the vertical axis, I have the fractional weight of water in a crop. In the horizontal axis, I have the water activity, which is like relative humidity. And so if you look at different things, different crops, hardwoods and miscanthus and so forth, around 12% by weight water, you have about 60%. So if you dry below 12% weight by water, you drop below 60% water activity. And it's kind of similar for other crops. So I come back to, I come to a place like Lafayette. And I really appreciate the strong agriculture. It's amazingly efficient. And it was started here even before the Civil War. So it's been this way. And in Chicago, they pay for the crop, let's say for the corn. And it is, since before the Civil War, if you wanted to sell your corn, you had to dry it below 14% water concentration. And so somehow they knew it would be safe to ship if the farmer dried it enough. And every farmer has equipment for drying his crop, because you can't really ship it or sell it on the sugar or trade, which doesn't want to buy water anyway. It wants to pay you only for the corn part. So you had to keep it dry. And if you kept it dry, you could ship it long distances. And so this is a slide I showed you before. But we have now a little bit of information is that if you dry it enough, it will last for 10,000 years, largely because the polyethylene keeps out the water. Now, how efficient is it? The polyethylene, if you have liquid water on one side and you want to find out how much water gets through, then in every year, two microns equivalent thickness of water gets through every year. But this dry biomass is typically about 100 feet. You'd have sort of a landfill that's 100 feet thick. And so with two microns of water getting through, it will last for 10,000 years. The scale is given here. It's roughly that's a 30 meter marker. It would be maybe a couple of hundred yards by a couple of hundred yards in size. And the thickness would be about 20 meters or 30 meters, rather. And so that's how it will last. So I have here a bunch of numbers, which I'm not going to go through these numbers, except to say that every year the world injects 20 billion metric tons of carbon dioxide in the air, and you have to pull it out, or we would have to pull it out. So it represents a big effort. But in the course of the biofuel research, they investigated how much agriculture you would need. And so this is an official Department of Energy report. And I can go a step further. Is it another report from the Department of Energy and all of these funny units? And I can summarize the whole thing. Worldwide, this would be a pretty big crop. It would be equivalent to all the corn and all the wheat. So it would be a very large crop to pull all of the carbon dioxide out of the air, but it's quite doable. But people worry about this, so let me show you what's going on. This horizontal axis represents all the land on the earth, and some of it is useless, like at the North Pole and South Pole, it's covered in ice. So that's kind of useless. So let's talk about the stuff that is usable. So all this is usable, and it's for agriculture, for forestry, some of it are just shrubs, and even a little bit is representing things like cities and lakes and things of that sort. Now, of the agricultural part, this represents the row crops, corn and other things. This represents pasture land. How's that? We're showing up. Okay, good. And the amount that you would need for agro sequestration would be this blue bar. So I think it's safe to say that, yes, it would be a huge amount of agriculture, but it's within the realm of availability, that land is actually available for this. So the availability is there. What about the cost? So you can figure out the cost in various ways. My preferred way is I go to the Chicago Border Trade, I figure out what they're paying for the crop, and what is the yield of the crop. I can figure out how much money the farmers are getting per acre, and then I'll make the claim that growing a non-food crop is if anything easier than growing a food crop, because the food crops you're competing with insects and the non-food crop, you're not necessarily competing with insects. So it's a little bit easier to grow, but I'll take those costs, and we've done it both ways. We did a bottoms-up analysis of what the farmers are, all their costs, including the renting of the land, which is the biggest part of the cost, and I flipped it around and figured out what the farmers were being paid to the Chicago Border Trade, and we got similar results. So approximately $30 a ton of CO2 equivalent for the agricultural part. This campus is slightly better than some of the others, and then you have to build the environmental chamber. How do we know the cost of the environmental chamber? Because there are contractors who build exactly these types of landfills today. You can go to those contractors and say how much does it cost to build a landfill of this size? And so it came out to be also similarly about $30 a ton. And the other crops are a little bit worse, switchgrass, not quite as good, loblolly pine trees, also not quite as good, but loblolly pine trees are very effectively grown in the southeast United States, so you do find that there is actually a lot of biofuel from the southeast. So now I promised you a unit's conversion. First of all, what does it come out to? It was $30 plus $30, it was $60 a ton, and I mentioned the government is now paying $1,000 a ton for CO2, and we're at $60 a ton. So what does that add to the cost of gasoline? So this is high school science chemistry exam. If you have $60 a ton of CO2, and now you have to figure out how much that is in gasoline, but there's a certain amount of carbon in the gasoline, you figure the whole thing out, and it comes out to be $0.53 a gallon of gasoline. So what this says is that we could solve the CO2 crisis if people were willing to pay $0.53 a gallon extra for the gasoline. Now in California, if I was giving this talk in California, people would laugh. The price of gasoline goes up and down by a couple of dollars, at least a dollar in either direction. All the time the regulations change. Because of the regulations, gasoline is a lot more expensive there than it is here, and so there's the cost. And the amount of CO2 we have to pull out is two billion tons a year, and then we can figure out what is this going to cost the world economy. So you convert the $60 a ton, you can convert that, and it ends up being $1.2 trillion a year, which sounds terrible, but the world economy is $100 trillion a year. And so it would set back the world economy by 1.2%. And I'm not saying this is good, but it's not bad. And it's not a disaster. I really started this project because one of my good friends was very worried about his grandchildren. He said, well, are you going to pay a little extra? Maybe set back the economy by 1.2%. Well, the world economy improves by roughly 2% a year due to productivity. So one year of the productivity might be a little less, and then you'd carry on from that. So it's quite reasonable. But then, oh yeah, I got to tell you what happened. So then we send the paper off to be published. And one of the referees comes back and says, you need to find an example in nature where something was kept dry for thousands of years, and it did not decompose. So Wekli knew an example, but we didn't include it in the paper, but we changed the paper. So the example comes from Israel, a very famous mesa adjacent to the Dead Sea. Well, it used to be adjacent to the Dead Sea. The Dead Sea has gone down a little bit back here. It was famous as the last holdout against the Romans. However, before the Romans came, there was a king Herod who appears in the Bible. And King Herod, like all kings, he's afraid of being overthrown. So he built a castle, and this is the castle that he built. It's a very remote location, very hostile environment, and was abandoned for 2,000 years. And then in 1965, an archaeologist went and excavated King Herod's palace or castle, and he found a lot of things, and he wrote a lot of papers that archaeologists read. But one of the things he found was some seeds for the date palm tree, and these seeds are the size of pecans. And so the story is told in pictures. Here's a likeness of King Herod, some carving from 2,000 years ago. This is the archaeologist mid 1960s. He digs it up. He finds lots of treasures. One of the treasures are the seeds, but he doesn't know what to do with them. And then this woman, who is a medical doctor at a hospital in Jerusalem, but she was sort of a creative person, she heard about this, and she sweet talks the archaeologists into releasing some seeds to her. And then he sweet talks some carbon dating people into carbon dating the seeds, and the seeds are indeed 2,000 years old. And then she persuades this woman, who is a horticulturalist, I have these seeds. Can you check to see if they germinate? And they indeed germinated and started with a little tiny plant and grew to a bigger plant and had to change pots. And then ends up as a tree, 18 years later, this 18 year old tree. It is somewhat protected by this wrought iron fence because it is a historical and scientific relic. It was a tree that's 18 years old, but germinated from a seed that was kept in relatively dry conditions for 2,000 years, and the DNA was preserved, and if the DNA is preserved, the cellulose is preserved. So it's kind of famous, and we put this as figure five of our paper, and the referee accepted it. And so that part is known. I have to share with you a few more facts about agriculture. That are worth noting, and that is that there is a Moore's law for agriculture. So here's a graph showing that in relatively, I think this applies to least developed countries, nonetheless the productivity of agriculture doubled over a 50-year period. So this is the Moore's law for agriculture, and it doesn't just apply to underdeveloped countries. It applies to other countries. For example, I found data for the productivity of wheat in England, and dating back to the 1700s, but I started to graph it 1800, which was around the time that Malthus told us that the industrial revolution was useless because we wouldn't have enough food to feed everybody. And during the 1800s, the productivity of the land doubled, and this is true for anything that human beings do, that we're always getting better at. The more we do it, it's called the learning curve, and it's actually taught in business school. So then from 1900, the Haber process came along to pull nitrogen out of the air. So we had artificial fertilizer, and the agricultural productivity doubled again until 1950. From 1950 to 2000, it doubles again. So the Moore's law for agriculture is doubling. It's not as fast as the regular Moore's law for transistors, but it doubles every 50 years and really adds up. And the growing wheat, even in Great Britain, it's eight times more yield per acre than was the case when Malthus warned us there wouldn't be enough food. Of course, this is terrific for people to eat food. It's not so good for the farmers because the overproduction causes the prices to go down. But the area around Lafayette, this is among the most productive farmland in the world, largely because the glaciers pushed all this dirt down below the Great Lakes and the topsoil in places like Lafayette. I don't know your exact topsoil here, but in central Illinois, which is similar, the topsoil is 18 feet thick, and it's extremely productive for that reason. But whatever productivity it had, it went up by factor eight. And this is all the agricultural land that has gone out of production because we have too much agricultural land. So I know this is true back east. There are farms in New England that are just woodlots now. So this is the amount of agricultural land. This is the amount of land being used for agriculture. A lot of it has fallen out of production because of this increase in productivity. But the conclusions I arrived at do not rely upon future increases in productivity. I put in the numbers for today. So what I have described is it's a scalable industry. Agriculture is one of mankind's largest industries, also the oldest industry. That the cost is reasonable equivalent to 53 cents a gallon of gasoline and 1% of the world GMP, but spread over 100 years. The stability, I think, we are the only scheme. This is the only scheme that has experimental data going back 2000 years. There are a lot of ideas out there, but come back in a few hundred years, let's see how it works. We need predictability. We don't need to do experiments in weight. We can predict and validate the approach right away. And as far as implementation is concerned, it can be implemented at the next growing season, which is this month, actually. So to offer apologies, I'm a high-tech guy offering a low-tech solution. But I would say the reason this is correct is that the world cannot take a chance on some weird ideas. And this is one of the simplest dumbest things. And we can't try to predict what will happen hundreds of years from now. So this has been proven for 2000 years. Now, with regard to the land, especially in Europe, they're very concerned about converting agricultural land for biofuel uses. And it's actually illegal in Europe to do this. However, in the United States, we've made that decision. So for example, 40% of U.S. corn is already going into ethanol, into biofuel. And can you imagine a state the size of Iowa, which is a very large state, and take 40% of that state? And that's already being used for biofuel. And of course, the ethanol is extremely inefficient. They could be growing miscanthus, and probably should be. So I have here a bunch of conclusions. One of the conclusions is that by its nature, such a technology can overshoot in the sense that it can pull out carbon dioxide that has been put there decades ago. So it can remove not only this year's emissions, but also historical carbon emissions. That's what it means to be carbon negative. But we have to be aware of complacency in the moral hazard. We have to continue research in new forms of energy. And we still need to do everything else. We still need conservation, efficiency improvements, alternative energy, decarbonization, and other forms of sequestration. There are many forms of sequestration. And we need an all of the above approach. So it turns out that in this field, the recent recognition is agriculture can actually do it. And there are some companies that have gone along this way. So one of the companies is from Silicon Valley called Charm. And they want to take agricultural products, process the carbohydrate into this thing which kind of looks like tar. Doesn't that look awful? Process it as tar and pump it back into the ground. And they have received huge amounts of venture capital and a contract for $53 million to take carbon dioxide out of the air. But I can tell you this is nowhere, it's the right idea, but the efficiency is not there. When you have to move the biomass some distance to an industrial plant, and then you have to move somewhere else, the cost is, the transportation cost is very important. When we bury the biomass in our scheme, it's right underneath the agricultural area. And so, and also to, because I know this question will come up, is that one acre of, let's say, let's call it an underground environmental chamber, one acre can accept the biomass from 10,000 acres of agriculture. So there's another company here. So this one is founded at least financially backed by Bill Gates. It's called Graphite. And the thing about Graphite is if you look at their webpage and their scheme, it is very similar to preprint that we had before we wrote our final manuscript. And it has a lot of inefficiencies that they did not take out. So for example, in that preprint, we talked about these bricks, and these bricks are not the most efficient way of doing it. And a lot of other strange things that we put into our preprint ended up in their business plan. So I'm not going to comment on who's copying whom, but the preprint was supposed to be confidential for the referees, but somehow I think they got hold of it. In any case, they're projecting also extremely low cost just like we are, but not quite as low because they don't have all of the improvements that we eventually put in. So $100 a ton. Why is the government paying $1,000 a ton? That's crazy. Okay. But they have been successful. They're very well backed. A lot of publicity. They have a contract with American Airlines. So you buy a ticket on American Airlines, and after you buy the ticket, do you want to buy travel insurance? Does the press know? The next page is would you like to offset your carbon? And the money goes to graphite. So it's a going thing right now, and it's very well financed, so it's going to happen. And of course, being a company, they don't do acknowledgments or citations. So we don't get mentioned. Okay. So let me summarize. The idea is that being carbon neutral is not enough. It leaves humanity exposed to danger. That's why people are worried about their grandchildren, but now carbon dioxide removal is a thing, and it's a developing thing, and agro sequestration can do this. And so let me finish with that. Thank you for listening. Thank you. Perfect timing. Perfect timing. Well, thank you so much. Well, hopefully politicians would be very receptive to the ideas, like venture capitalists and the companies. Questions? Rather commonplace. I would like to put your number of 1.2 percent into history rather than economics perspective. A few years back, if you remember, there was a major push by President Trump of forcing European economies to invest that agreed upon amount of 2 percent into their military expenditure. They were about 1.5. They did not succeed. 0.5 percent was impossible. And when you talk about wealthy countries, it's easier for them to do than to increase, than to put in comparable amount of resources for not so wealthy country. The only way it could happen, and it did happen as a result of the major woe was hundreds of thousands of casualties. That's how it was in the entire human history. So there are two possibilities for this to happen. If the humanity doesn't change, option one, it is the result of a major war. Option two, it's 1.2 percent of profit, not expense. Or option three, humanity somehow changes momentarily. Historically, there was not a single violation of that rule. 1.2 percent is impossibility according to the previous history. Well, let me make a comment on that. It's very difficult to get every country to agree because it does cost money. However, if you get three countries to agree, then they're big enough countries. So the three countries are the United States, China, and Brazil. They have enough agricultural potential. They could do this. And of course, other countries, they said they'll want some of the money too. So they'll probably do some of this as well. And so I'm a little bit more optimistic about carbon sequestration. But with you, I'm less optimistic about world peace. I like this idea of drying plants and store on... Can you hear me? Yes. Drying plants and store them on the ground with a polyethylene shell so they won't go bad. But how about turning them into alcohol, which can also last a long time? Did you say alcohol? Yeah. Alcohol. So we already have that. That's the gaseous hull. It's extremely inefficient. It produces a lot of emissions. I just want everybody agrees that the gaseous hull is not a good idea. But I don't quite see how you would store such large amounts, where it's much easier to see how you would just store the biomass. You don't have to process it. Okay, the next one please. Yeah. I did try to understand the concept from conservation of mass, energy, elemental mass, energy, and transport processes, and so forth. But if you wear your professorial hat and tell us about how many of those... Or just using one control volume, what physical and chemical processes are important and if the balances have been worked out in terms of diffusion resistance? So this paper here, yeah, it's a good question. This paper here is within the length limitation of papers in that journal. But then we added 86 pages of supplementary information to deal with some of those questions. The easiest one to understand is we introduced a term, carbon efficiency. So let's say you sequester 100 tons of carbon, but you had to run the agricultural tractors. You had to run the transportation. You had to produce the fertilizer and so on and so forth. So how many tons of carbon dioxide did you emit in the course of all of those other things? And so because these plants are very efficient at pulling carbon dioxide out of the air, the carbon efficiency is 95% for these plants, approximately 95%. And that takes into account all of those factors that I mentioned that people are very worried about that even when you put nitrogen compounds into the soil, they eventually decompose and they give you nitrous oxide. We took that into account as well. So taking all of those factors into account, you sequester 100 tons, but net net, you're sequestering 95 tons. Thank you. Thank you, Professor. My question is, what happens after 2000 years to the biomass that is sequestered? And in the process, are we trying to avoid the crisis now and delaying it for a later stage? That's a very good question. I think it comes up in the following context. At some point, let's say, who knows what the future holds? Maybe some vandal will come along and they would have to dig through 20 meters of soil and make a hole in the polyethylene. Now, the environmental chambers are modular, so they would wreck one environmental chamber. And maybe that would happen before 10,000 years. So let's deal with that problem. So what would happen then is that you would not be an immediate disaster because it takes decades for the biomass to decompose. So you have decades to solve the problem. And the solution to the problem is you excavate it, dry the biomass, now that it's been made wet, dry it, and then store it. Again, just put it back into one of these underground environmental chambers. But what about after 10,000 years? So the reason that sort of is an important number, it is thought that the carbon dioxide drops out of the atmosphere very slowly. Part of it goes very quickly, but part of it goes slowly. And the part that goes slowly could take 900 years. And so for that reason we thought several thousand years was a good indication. Now, what will the technology, energy technology look like 10,000 years from now? I don't even know what it's going to look like 50 years from now. But there will be improvements. There have always been improvements. The solar is becoming very big. So I got into this through my work in solar cells. So I think with 10,000 years we kick the can down the road, fine enough that we can be pretty respectable. The XPRIZ competition requires only 100 years. And I think that's really insufficient. So that's more of a judgment call, is how long do you want to wait? And how much security for how many centuries do you want? Before we all move to Mars or something. The last one. Okay, so this is kind of a simple question, but I was wondering if the land above the buried biomass is able to be utilized in any way? Yes, that's the point. The calculations we've done include the cost of burying the environmental chamber under 20 meters of soil. Now why 20 meters? It's expected that tree roots will not go down 20 meters. And so the tree roots will not cause problems. The animals will not go down 20 meters, etc. But in case we need to go a little further, that would add slightly to the costs. But absolutely the land on top becomes agricultural land. So if you imagine that if humanity does this long enough, eventually the land around West Lafayette might go up by 30 meters. And maybe Lafayette would be higher by 30 meters. So that is a very important question. People are very concerned about that. You retain your farmland. Well, with that, I guess let's thank our fantastic speaker one more time today. Thank you so much.