Eli Yablonovitch: Carbon Negative Technology to Solve the Climate Crisis
geometry and learned relationships and all that they don't really put a lot of good stuff you know the children go crazy about it when they're really cycling it's mathematics yeah so hopefully the next generation is a better happy to be too much Jeff I think it's one year yeah all right good afternoon everybody welcome to the first of our eecs Department colloquium uh every Wednesday or almost every Wednesday at this time and uh it's a great pleasure to kick off this semester with our own professor gabelanovic Eli uh is a uh an amazing guy he has made uh contributions to science and technology across across a wide range of uh disciplines and and areas that have all made uh amazing impact uh Eli is the uh um let's say father of uh the technology that's used in every Optical Communications laser today strained layer strained layers he is the inventor of photonic crystals which are seeing widespread use now in all kinds of Imaging and Optical Communications and all kinds of applications like that he has made incredible contributions in uh solar photovoltaics uh at one point held the record for the highest efficiency a solar cell has uh still and uh is responsible for uh teaching the whole field a number of really uh basic yet surprising to some facts about how to make efficient solar cells and a number of other things and and so he every once in a while he he just goes off in some random direction that seems random to most of us and makes a big impact and I think that's what we're going to hear about today is his latest uh foray into a completely different field uh namely that of um uh the climate climate crisis and uh carbon in the atmosphere and so I can't wait to hear about Eli's great idea about how to solve literally the entire uh problem of the climate crisis in an economical way and that's the title of his talk so I introduce uh Eli yabunovic [Applause] before I get started my co-author Harry Decker who Someone I used to work with uh 40 years ago and we've kept up our intellectuals oh I'm still muted okay okay you can hear me now it's okay all right so uh let me um say I think we've heard plenty about the climate crisis uh but and and we're trying to go carbon neutral but there are some things that are very difficult to uh to deal with and to correct uh for example uh their functions for which it's very difficult to replace a hydrocarbon fuel unfortunately so one example is international Aviation uh which depends very much upon the uh the uh Mega joules per kilogram of the fuel and it's very difficult to do better than jet fuel another problem that we haven't solved is summer winter energy storage which is um uh very challenging most energy storage they talk about batteries but now uh when you talk about summer and winter which is probably the most important type of energy storage uh it's it's something that has to be Rock Bottom keep and you'll use it only once a year so it's a problem and then another problem is there will always be countries that do not cooperate okay and so uh what it says is that carbon in the atmosphere will grow on unless we find a way to extract it and then there's a fourth thing to worry about and that is that there are some very credible models that suggest that positive feedback of CO2 from permafrost can lead to a thermal runaway which is to say that being carbon neutral will not help that we actually have to go back and pull that carbon dioxide the historical carbon dioxide out of the air to prevent that so it means we need carbon negative technology now uh this was a controversial up until about eight eight nine years ago and then people noticed that this was an issue so the various National academies all over the world came out with reports you know and uh basically saying okay here are some ways to do carbon dioxide removal and uh just to show that the Europeans are not far behind so they wrote a report about five years ago on negative emissions now now uh reached a point that people are realizing this this has to be done and carbon negativity has become a thing and uh here's an article in physics today but there are many examples I would say the conventional wisdom now is that we we do need to have uh carbon negative technology now one of the ways of doing that is to actually um well this is not a great way to do it you force the atmosphere essentially through a pipe and in the pipe you have amines which capture CO2 and you can imagine this is not going to be cheap essentially you solve the problem by passing the entire atmosphere through a pipe so that's not going to work in fact the most optimistic estimates say six hundred dollars a ton but the the things that are being funded now are more like thousand dollars a ton which is very expensive and I will calibrate because I don't I know you don't go to often to the supermarket to buy a ton of CO2 so I have to calibrate it in terms of uh things that you know about I think I'll do that in a couple of slides so um if you look at the European report they proposed a number of options controlling forestry reforestation Etc uh Land Management to increase carbon in soils bioenergy so you you burn biomass and then you capture the CO2 and then pump the CO2 Underground uh and then there there are certain rocks that actually absorb CO2 there are not very many but uh the the processes has very slow kinetics so it's not very practical and then I already mentioned the direct air capture which is very expensive and another idea that's out there is ocean fertilization and then they hope that they will promote the algae growth and the algae will fall to the Bottom of the Sea but it's uh people say very little of it falls so the of all these I think they have ignored the most obvious candidate which is to grow biomass and instead of making biofuel out of it just to bury it so how do you do the safe burial of agricultural biomass and we call that aggro sequestration that's what I'm going to talk about now what was the first one who came up with this and so this is why it's uh this talk maybe uh does belong here in at least among the electrical engineers is Freeman Dyson uh one of the most famous physicists and uh surprisingly uh he uh he was truly maybe Jeff gave me too much credit for being attack of all trades but he was truly a Renaissance Man and he he covered everything and he already proposed this exact idea in 1976 so this kind of amazing and uh what he said is we we grow uh some kind of tree and we bury the tree and uh and that and he says and that solves the problem okay so uh well you didn't hear much about it uh perhaps we should have heard more um here's uh another example of carbon removal that has become uh very big now is that the X prize committee is in the middle of a competition to find the best way to remove carbon and the 100 million dollar prize and they're going to the first prize is going to be 50 million dollars uh but you have to remove a thousand tons now let me mention one scientific one fundamental scientific thing that makes it difficult to pull carbon out of the air the concentration is very low and when the concentration is very low uh you see the carbon dioxide can be here it can be there you're not sure where it is because there's so little of it and so there's entropy associated with the dilute concentration of carbon and you do K log of the dilutus and you end up with a certain amount of entropy and that converts to free energy which is not enormous but still very difficult to deal with and so you to pull carbon out of the air you have to supply some form of energy of course if you pull it out in the form of biomass the plants will will through their photosynthesis will provide the free energy so this is one of the difficulties of pulling carbon out of the air now so which plants so I'm relying very heavily on the biofuel people who've already studied this in great detail starting about 15 years ago so the here at Berkeley biofuel became kind of a big thing and in every region there's an ideal crop in the Midwest of the United States it's something called miscanthus but they have other crops for example that are more adapted to the Caribbean and so this has been worked out and the agricultural stuff has been worked out the cost of the agriculture by the way every country publishes agricultural statistics and because it's it's so important so what happens then is that we have these different crops and now these crops not something you can eat it's cellulose is it's not really a very good food and so the insects don't like it and and so it's easier to grow these types of crops than it is to grow something like corn and of course I gave this talk in Europe so I had to use Maize so they wouldn't get confused about corn and um uh if you if you grow these non-food crops you get greater productivity about three times more than a major food crop like corn so and then you you pull out 44 Way by weight carbon and you in one acre you can extract five tons in every growing season and then it would take a certain a large number of acres to extract the annual fossil fuel from the atmosphere so that's sort of the plan so let me mention this gentleman so there was a time as and Jeff was kind enough to mention that I had done some work on solar energy and in fact my mentor at that time is a gentleman who should be famous uh he's probably not very famous but he should be he he graduated from Cornell in 1938 and went to work at RCA and invented the vidicon camera which is the camera that all of Television used until the charge couple device so uh from 1940 to 1980 television if you watch television you were watching Through The Eyes of a vidic on camera so he was a very distinguished scientist in that regard but he in his later life when I got to know him he became very interested in solar energy and I was working on solar energy he was kind of like a consultant at the company I was working on and he told me one day Eli uh you know on your way to work you passed some gas stations and the price this was 1979 and the price of gasoline wasn't one one of its energy crises and the price of gasoline had gone very high and he said why don't you figure out the cost of gasoline not per gallon but you figure out per Joule per 100 Mega joules actually decent unit 100 megajoules and then go look up on in the Wall Street Journal lookup on the Chicago Board of Trade what is the price of corn per bushel and of course the challenge in that calculation is to convert bushels into metric units okay so I I did do that and uh I was very shocked that in fact the price of gasoline at that time was pretty much the same as the price of corn and you think the corners of food is valuable and so on and so it was rather surprised that agriculture could be so efficient well it turned out I looked it up and he had already figured the whole thing out he was he was maybe he was testing me but he had just published it about a year earlier before he asked me that little riddle so this the purpose of this slide is to have some respect for agriculture that is actually very efficient and that you could grow you could grow the biomass which is not food which is cellulose a very efficient form of Agriculture and you throw it into the ground in the Modern Landfill so what's a Modern Landfill when you had breakfast this morning you undoubtedly generated some garbage that garbage ended up in a landfill and the modern landfills and I don't doubt that California has the most modern landfills they are sealed off with four millimeters of polyethylene and that's important to us of course the reason they're sealing it in polyethylene they don't want the garbage to contaminate the groundwater and what I'll show you is that we actually we draw we will grow some biomass we have to keep it dry and now so we have to do in Reverse we don't want the groundwater to come in and mess up the dry biomass because to preserve it for a long time you need to keep the biomass dry so I wrote a paper on this with my co-author Harry deckman and was published a few months ago in the proceedings and National Academy of Sciences now uh the if you go back to what uh what we heard from Freeman Dyson he was just going to throw blogs in the ground that doesn't really work because if you just throw things in the ground they it decomposes and you get back your carbon dioxide and worse you you get back some methane with it so so that's not very good so you think well if I have it anaerobic maybe that'll help actually you know there's plenty of microbes fungi and anaerobic things that will will decompose even when there's no Oxygen present and uh so uh the uh that's a problem you end up producing CO2 and you end up also producing methane which is sort of worse than what you started with and so we have to correct Freeman Dyson a little bit on that and so the simple burial is still very attractive and I thought of it a long time ago I've been thinking about this for 40 years and uh but I ran into a roadblock simple burial doesn't work if you make it anaerobic it still doesn't work and so what do you do and so it was only a couple of years ago that my co-author came to realize that there is a a way of making burial work and that is to keep the biomass dry and I'll show you some slides on that but here's what happens in decomposition you get back your CO2 and you get methane now what people like to do is to bury wood and uh so sometimes and I don't know if anyone has been digging in their backyard uh maybe you're doing some Horticulture and you're trying to plan something and you dig up a board that the contractor left their decades ago when the house was built and you dig up the board and uh you hold it and it looks like a board it has all the appearance of a board but it's very lightweight it weighs almost nothing well it weighs a lot less than expected and the reason is that wood is composed of has two major components uh you have cellulose and you have lignin now lignin is the part of the wood that makes the grain of the wood and it's um it's present it's fairly High concentration 30 lignin so what happens is that all of the cellulose decomposes very quickly but the lignin turns out to be a very very difficult material to deal with it for example the biofuel people they were always troubled by lignin it's so stable they could not convert it to biofuel and so what happens is that that board that you picked up that had only like incomplete weight it didn't weigh what a board should have weighed is the cellulose was gone but the shape of the board was was still there and so you see this in in museums they will dig up some some old thing and uh what it still looks like it's there so maybe some old ship I remember once in Stockholm they dug up an old ship from the harbor and the lignin is still there but you've given up 70 of your biomass so uh yes you've got some benefit you've you've managed to store the lignin but you're sort of inefficient because only 30 of the wood ends up being sequestered so this is something that uh the it is uh maybe a little controversial among my colleagues because I can point to seven startups they're just going to bury wood and and I and it's kind of tough to explain it I'm sorry uh that doesn't work so I'll have to explain to them now uh so now we get a little scientific and so I mentioned that the solution to the problem of decomposition is dryness so now we have to sort of Define what is dryness I think everybody here knows what relative humidity is so I have here a picture of a steak and uh if I asked you well what is the dampness of how you know what's the humidity of the steak and so well it's it's air has a relative United States do not have relative humidity so how do you know the stake is dry so they uh the chemists have introduced a concept called water activity so water activity is the uh the equivalent to relative humidity in air so if you have uh 60 relative humidity in air then if you let the state dry it will end up with 60 water activity and all biomass has water activity and if the biomass is very dry it might have a low water activity and and why do I bring up the water activity is that metabolism the the decomposition requires metabolism and the metabolism requires water to move the chemicals around inside the cell and so surprisingly maybe not so surprisingly metabolic activity stops if the water activity is less than 60 percent so this is kind of an interesting fact so it's sort of the scientific part so you ask well uh what about how dry does it have to be so here's an interesting factoid when farmers are selling corn on the Chicago Board of Trade they have to drive a corn because they the Chicago Board trade will not accept corn that has more than 14 moisture in it so 14 moisture by weight would come out about here and that would come out to be maybe around 60 percent water activity so in order to get down to 60 water activity you have to um you have to dry the corn to 14 that's actually not that difficult to do because they've been selling corn in the in the Midwest for 150 years and the farmers used to dry the crop they just leave it out and it was dry enough and they put protection against rain and so forth and the one and would be dry enough of course today the farmers don't do that what the farmers do these days is they use propane or something of that sort to dry the crop so this is uh this drawing of food is an ancient principle for food preservation so this is from the Indians in the northwest drawing salmon these are little hunks of salmon they would dry it and say well how dry does it have to be so that it doesn't decompose and uh so uh yeah as soon as you make it dry it gets hard so already many bacteria give up at 95 percent yeasts mildews and so forth and you go down and fewer and fewer living things can survive if it's uh very very dry and who has studied this as NASA has studied this because you want to discover life on other planets you need to know well how much moisture does life need and so it needs 60 percent water activity and the other government agency that has studied is in great detail is the Food and Drug Administration because let's say you have some type of food you wrap it into dry and you wrap it in cellophane are you allowed to put on the Shelf how do you know it's not going to spoil on the Shelf so the Food and Drug Administration checks the water activities it's always dry enough you can leave it on the Shelf in the supermarket and so this has been studied both by NASA and the Food and Drug Administration so six percent sixty percent is water activity is the boundary now there are a couple ways of doing it you can dry it very thoroughly and that that works another thing you can do is add a little bit of salt uh so to get down to 60 in terms of sodium chloride doesn't quite do it but magnesium chloride does it and there are other salts that will get you below the 60 water activity of course uh this has been known uh since Biblical times that salt acts as a food preservative and was extremely valuable in the Roman Empire for that reason so this is a little bit of scientific part which is the fraction of water in the food on this axis fraction of water and the water activity and so that's kind of interesting so why the salt help because salt displaces water gets into solution displaces water molecules if you have fewer water molecules you have floor vapor pressure and that gives you a lower water activity and if you have a divalent salt it's even more effective because then the salt molecules cluster around the divalent salt and it works even better so these are some options and but you can just do some more aggressive drawing but calcium chloride is a famous salt that is used for these purposes and you if you have lived on the East Coast during the winter uh the salt that they throw on the highway is not sodium chlorine it's calcium chloride it's a relatively benign salt and so they can just throw it on the ground and not worry about it and but it has this great great property is that you can easily drop below 0.6 water activity with calcium chloride or you can just dry it more thoroughly so if you build one of these landfills how big does it have to be it would occupy about 1 10 000 the area of the land that is used for the agriculture itself and then when you're you're done with it you just throw dirt back on top of it and it's good for agriculture again now what is the key thing is that you you do need to seal it off but this is an existing technology for landfills it is uh rather thick it's four millimeters of polyethylene polyethylene doesn't like water so the diffusion is very slow the diffusion of four millimeters of polyethylene to water is equivalent to 1.7 microns of water every year and so for that reason it lasts a very long time thousands of years okay so that gives you some idea of what the solution is that we're proposing now what is the size of the problem I have a whole bunch of calculations here but it comes out to be that you've got to pull every year you have to pull 20 gigatons of CO2 out of the atmosphere so it's a lot but it has already been studied thoroughly by the biofuel people and so these are some of the papers that they wrote on this and here's a department of energy report how do you how to get to the gigaton level and so from those you can put them together and figure out how much land how much agriculture are you going to need and so you can look up the availability of agricultural land and um of course there's the polls that are covered in ice and those other land that is completely hopeless but there's also normal agriculture there's Forest uh the shrubs and so on and so forth so let's look at the normal agriculture most of it is used for pasture only 11 percent of the earth's surface is used for row crops which is kind of interesting and what is the land needed to pull the carbon dioxide out of the air so the land is represented by this blue rectangle so it's a a fraction of the Agricultural Lansing and in this analysis from the Department of energy they split it between pasture Forest shrubland and um other forms of of land that are underutilized well I'm going to show you a slide very shortly that agricultural land surprisingly is underutilized and this is sort of an indication of that you've all heard about the Green Revolution the Agricultural Revolution and certainly in terms of Labor the human labor we become way efficient by over 100 times since Malthus predicted very pessimistically that the Industrial Revolution wouldn't help because people would still have too many children there would never be enough food for them but it he was wrong in fact you can see here on this graph that the productivity of land in the least developed countries has improved about about 2x over a 50-year period in fact I went we searched and we found some data that started in England in the 1700s of the productivity of land for growing wheat and this is a rather interesting data because then you have uh you know they didn't have hectors back then they uh they had very strange rooms of land in in that in that era of British history but let's start the graph at 1800 Malthus makes his very pessimistic prediction but between 1800 and 1900 the productivity of land doubled this is the reason why uh his prediction of overpopulation didn't work out and then something happened at the beginning of the 1900s the Haber process and the Hebrew process a method of producing artificial fertilizer and so it fell onto a faster curve so every 50 years this say in the first half of the 20th century doubled and then second half doubled again so since the 1800 since moth has made his negative prediction you had a an exponential increase in the productivity of land and this is in real human so it's it's tons of wheat per hectare of land and so likewise the United States followed the same track and so the current situation for the productivity of land is that there is a Moore's law for agriculture the Moore's Law is way slower than the Moore's law that we are accustomed to but it's it has been doubling every 50 years now I say well it's saturating we've gone as far as we can with fertilizer but wait a minute we have crispr now and and many other technologies that are going to improve the productivity of the land that is a very good question and the reason is uh there the land is so much cheaper in the U.S than in Britain that rather than putting more inputs into the land to get more productivity out uh they they yeah they just use more land and in in the European Union of course they're trying to be self-sufficient in food and so they subsidize all the farmers and they put a lot of info a lot of effort in and they in Britain they have higher productivity and throughout the European Union that's the case but I expect that might continue now here's a graph showing you a similar fact is that um to grow a fixed amount of food the amount of land needed has gone down and it's gone down by roughly one over it's uh 68 less land after 50 years starting the Baseline was 1961.
um 68 less land to produce the same amount of food so it's giving you some idea of the agriculture is is doing very well and actually I can uh as a solar cell person myself I can calibrate how far we can go with agriculture so if you grow corn the efficiency is two percent but it's food and nobody complains and it's and it's gotten better over the years and so on and so forth now uh if you um if you get the record-breaking solar panel is 29.1 percent so what what has nature done wrong after a hundred million years of evolution the solar the the uh the agriculture is nowhere near as good as the solar panels and by the way the process is very similar uh in a uh in a solar panel or in a solar cell you have separation of quasi-fermi levels and uh they sometimes we call it a chemical potential of course this was invented by chemists not by physicists and uh if you have an energy rich molecule present let's say in uh in a crop or in your body uh we can talk about the chemical potential just the same as we would in the solar cell so the physics of photosynthesis is very similar to the physics inside solar cells so what that suggests is that great improvements are possible so let's say we do a factor two and well that only gets us to four percent efficiency long way to go another factor to gets us eight percent efficiency and and so on and if of course if we had started with the uh that's starting with corn let's start with something more efficient like the bio the biofuel plants and uh they'll it suggests that three more factors of two are possible and it's going to take crisper and other forms of kinetic manipulation to give us the strains of of both food and of biofuel that are much more efficient and indeed we the efficiency arises from experience so Humanity has had about 10 000 years of experience with agriculture and have made it more and more efficient and um so also we can figure out what it costs what agriculture costs and if you're not sure you can look up on the Chicago Board of Trade you can look up the productivity of the land and look up the cost on the Chicago Board of Trade It costs about 500 an acre to conduct Agriculture and so you can get an idea of what the biofuel product will cost or you can do it the hard way and just add up all the inputs and you get the same answer and so here's what it costs so if you convert to the biofuel or the biomass to um tons of CO2 the price is about 30. I'm not going to look at the fine differences between the pine trees and the switchgrass and so forth it costs about thirty dollars a ton to grow the biomass and then you say well what are the landfill well we know how to build landfills and we we're continually building them because we're always grading garbage and so the landfill also costs about thirty dollars a ton uh so if you combine them it ends up as sixty dollars a ton and that's the projected cost so sixty dollars a ton now I'm going to convert it to units that uh you're we're more accustomed to so this is uh somebody sent me an email a professor sent me an email and he said oh this is such a great idea I have to teach it to my students I'll give them a problem and I said oh my God some of these are hard Concepts but this is one that's suitable for college students if you if you're paying 60 a ton of CO2 what is that going to cost for something that you're familiar with paying for which is a gallon of gasoline so that's a conversion essentially conversion of units and works out to be 53 cents a gallon so this process would add 53 cents a gallon to gasoline and we're trying to get rid of 20 gigatons and the world gross national product is 100 Giga gig you know Terra dollars yeah these are Terra dollars thank you so uh okay we're gonna pull all that all every year we're going to pull the carbon dioxide out of the air at this price at 600 a ton what is it going to cost it's um well it's 1.2
teradolars I mean it's it's a lot but it's like 1.2 percent of the world economy so it's doable so we sent the paper off to be published and the referee came back and said uh okay uh reasonable paper but you have to find some natural experiment that proves that this is really going to work that that you can point to and so we uh we we actually figured it out before we should have included in the in the paper and so I'm going to show you it's not exactly a natural experiment but it's an experiment that was created or started two thousand years ago so I'm going to tell you that story it's a very interesting story so in Israel there is a very famous Mesa uh that is uh famous for the last it was the massacre uh not the massacre of actually the suicide of the last holdouts against the Romans and so they laid seed to this Mesa and the they were up here but I'm not it's kind of interesting that's why tourists go there but there's something else there that's of great importance to us I should mention something about this Mesa is it's adjacent to the Dead Sea the Dead Sea used to come right up to the uh shores of erected up to the edge of the Mesa and the top of the Mesa is roughly at sea level and the bottom of the Mesa is about 1200 feet below sea level so it's very steep walls but what happens is that they had a king in Israel King Herod and like most Kings he was afraid of being overthrown and and so he built a palace it's not exactly a palace more of a fortress he built it up here and he left it there and it had been abandoned for thousands of years and then so this is King Herod this is a story King Herod builds his Fortress up there never uses it it gets sort of abandoned and then there's this guy an Israeli he was actually an appointment in the armed forces but he was really an archaeologist so in 1965 he excavates the the palace and he found our Fortress whatever you want to call it and then he finds some seeds of the date palm tree and these seeds are big like pecans they're about that big and uh and he he's an archaeologist he doesn't know what to do with him he leaves them in a drawer and then he passes away and a doctor an actual medical doctor at at the hospital in Jerusalem years about this and she sweet talks whoever's in charge of of the uh this archaeologist's records to give her some of these seeds and then she sends the seeds out to be carbon dated they are indeed two thousand years old and then she gives the seeds to this woman who is a horticulturalist and who germinates the seeds and the seeds germinate these are the seeds they germinate they give you a little little plant especially give you a bigger plant and and a bigger plant and then eventually becomes this plant and this plant is this picture is actually figure five of our paper so we have to revise our paper to include this to show that there is an example that if you keep things very dry that the biomass will be preserved for thousands of years so that satisfied the referee we managed to get this published this tree is is 18 years old and it's uh it's surrounded by a fence because it's of historical importance but there are are between half a dozen to a dozen of these trees in that have been germinated and are historical Curiosities so what it shows is the DNA was preserved for thousands of years and the so okay I need to tell you one more thing about biomass that I forgot to mention let me use a little white space here if you grow biomass and you convert it to biofuel so what is the biomass the chemical formula for the biomass is roughly this so the biomass is already partially oxidized so if you want to convert it into fuel you really need two of these molecules so that you can get rid of one of them as CO2 and then maybe sequester the CO2 but then you'd have a some fuel left over so these the sequestration is twice as efficient as making a biofuel because you've got to grow two acres to get one acre of biofuel and so this is just a little factoid to keep in mind okay so what are the prerequisites for solving the climate crisis is well you need scalability as to say is it big enough to deal with the problem and agriculture is one of Mankind's largest Industries so what about the cost well the cost I don't know this doesn't sound so bad to me 53 cents a gallon I'm willing to pay that and stability and so we have a proven sequestration over 2000 years and uh there are a lot of schemes out there that are interesting exotic and might work but they are uh Curiosities that you say okay if this is going to be a huge investment it's going to affect the future of mankind um maybe you can come back in 2000 years after you've proven it out and and this is something that essentially has been proven of so the predictability and so we don't need to do further experiments because the experiment has been done and we can validate it and the other thing is we know there is a crisis and we keep postponing Akron this is something agriculture is something you can Implement with the next growing season and so we can start pulling carbon dioxide out of the air starting in April coming coming up so what are the next steps certain scientific things we still need to study for example how low does the water activity really have to be and for example if instead of 0.6 we can get by with 0.75 which is kind of nice because then you can use ordinary salt for that and then how do we deal with the transition from dry biomass to very dry is always a danger what if there's a rain storm Etc and so um here there's questions of how to sequence the construction Etc of the bio landfill and and what is the outfit limit it looks like it's 0.61 but really really need to firm this up with mass uh spectroscopic measurements of tiny amounts of decomposition I think it matters for the future if it's 0.6 or 0.62 or down in that range I think that's relevant but this doesn't mean to suggest that we should stop conservation Abandon All alternative animal we need to do all these things we still need to do them and we need an all of the above approach so where where are we today well amazingly 40 percent of U.S corn is used
for ethanol and the process is far from carbon neutral so it's not very good so the actionable recommendations is the government instead of subsidizing the farmers to grow excess corn how about them growing this canthus and to build up some research test beds that would get this going of course this would be very good because the farmers would be happy because you're creating a new cash crop for the farmers so it's very politically acceptable to the farmers so I would say at this point the aggro sequestration appears to be the lowest cost scalable carbon negative technology and in fact in an emergency it could remove historical carbon emissions and that's part of being carbon negative is you can actually go back decades and pull look at that old carbon dioxide out of the air but we have to be careful of the moral hazard to say okay we've got it all figured out be I would say we need to continue a research in new forms of energy and new ways of dealing with this problem in fact right now where as you all know we're living in Uncharted Territory a very high carbon concentration that we haven't seen before and carbon neutral is not good enough we need to be carbon negative and that aggro sequestration can actually do this at a uh an acceptable cost so that's my conclusion let me invite questions thank you very much for listening okay questions before you get started on the questions let me put a little advertising slide uh we are trying to commercialize this I think it's uh it's part of uh turning it into reality so we're recruiting at all levels from a member of technical staff all the way to cos so please please email me CVS okay all right you can't beat that okay yeah great delay so actually I didn't know that uh process of I mean that it was so I mean the efficiency was so low compared to photovoltaic so that really surprised to me yes agriculture is amazingly inefficient and we could spend the whole talk on why yeah I wanted to ask the way so um so what is a photo synthesis optimizing so you suggested that crispr may be used to improve it but will that cause of our issues okay so uh I'm glad I stimulated it's a very interesting scientific question we can only speculate uh why it is that agriculture is so inefficient compared to solar panels and so I've thought about this a long time I know I I learned this 40 years ago from uh Al Rose my mentor and the I would say that one way to think about it is that the vegetation does not necessarily optimize for efficiency it optimizes for survival in fact all living things optimize for survival and if the uh if the Earth was very peaceful maybe it could just advertise or optimize for uh efficiency but in fact every plant that we see around us survived the asteroid Collision of 70 million years ago and so what happened light became very dim it became very difficult to survive and so the plants adapted to a very harsh conditions and they survived the asteroid Collision but they adapted his conditions by adapting to relatively weak sunlight this is just a theory of why this happens and indeed uh the people who do the algae the biggest problem with algae is they cannot withstand full sunlight and and so algae is actually one of the big disappointments of the past 10 or 20 years uh is that they never really resolved the issue of how do you use full sunlight algae it doesn't accept full sunlight and most crops do not and or do it with great difficulty they have a a channel to just dissipate the excited molecules dissipate the energy is heat and uh so but I think that sort of uh a kind of a hypothetical question so it's just a speculative answer anybody else any other questions why grow uh switch grass or some uh specific uh kind of uh uh biomass when half of most of wheat barley corn is not edible and you could use that as biomass yes so in fact this procedure that I described is sort of it's um it doesn't really care it's agnostic about the source of the biomass there is quite a bit of agricultural sort of waste that's available it's it's not that easy to do it economically though and the farmers like to leave that on the soil to help to help enrich the soil so what we have in mind is crops that are dedicated to pulling carbon dioxide out of the air yeah but the the cost of of uh convincing the farmers to sell you the waste has to be competitive at least with the cost of growing it fresh you would think so but the the farmers are very hard to deal with but uh we're we're sort of agnostic uh yes some of that will happen I mean undoubtedly any other questions okay I have one the the historical experiment that you cited about the 2000 year old date palms is it's kind of cute it's kind of uh impressive uh sure if the if you store seeds in Israel near the Dead Sea where it's dry as a bone uh then okay it doesn't decompose but you're proposing that that's not what you want to do you want to bury the biomass underground where it's somewhat moist and you can use salt to help reduce the amount of decomposition so my question is we have all this switch grass or whatever it is somehow you have to mix it and get the salt right to diffuse all throughout the biomass in order for this to work isn't that right and what about the cost for that okay so uh the the salt is merely an example and an option if you drive a crop sufficiently then it has uh by uh just because the crop is dry it can tolerate quite a bit of humidity before it goes up to 60 percent water activity so the I think uh that that's the way to analyze that is that to some extent maybe I should not have mentioned the salt although it is kind of interesting uh that it works out you made another point though no that was my point was that in order to use the salt to suppress the decomposition how do you actually yeah in practice you do that with these tons and tons of biomass you don't need the salt to prevent decomposition what you need is a way to keep the crop dry so the way it works out is you dry the crop and you dry out a little extra normal than normal and then you put that into a landfill the landfill is protected by four millimeters of polyethylene which is not an unusual thing because that's what the landfills do today and uh the four millimeters of polyethylene allow so little water diffusion that that's good enough according to the ability of the dry plant to safely take up tiny amounts of moisture and and still be below the 60 threshold so you spent a lot of time kind of teaching us about the the role of salt but you're actually not proposing to you actually uh the uh the one of the problems you bring up is uh the cost of the salt because you can't use sodium chloride is very cheap calcium chloride which is the road salt is the right kind of salt to use but the the they produce enough for uh for the icing the roads but we're talking about maybe expanding that industry so we don't want to get into too deep a discussion about salt it'll depend upon whether we can get continue getting the calcium chloride at very low cost right now the cost is very low but we would have to expand the industry if we were to use it what I'm bringing up is that it's not just the cost of creating or forming the calcium chloride I'm wondering what the cost is of effectively using it somehow get it uniformly distributed right all throughout the biomass and I'm saying that uh we maybe we haven't completely thought that through and uh but we don't have to think it through right now because we have uh the option of not using salt all right thanks close to the uh if you said that the algae or disappointment what about kelp is that something that you can throw in the seat yeah it's it's all uh this one actually kelp is a little bit better but the problem is that you need to diffuse the carbon dioxide through the surface of the of the sea and so the this is not as good as growing plants on land where you have the surface area of the leaves is much greater than the land area that it covers and so the uh the agricultural production in the ocean is doesn't compete that well with the agricultural production on land all right I think with that we'll uh close and thank Eli again for a really thought provoking [Applause] foreign
2023-09-11 12:35
