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Sun Feb 10, 2019, 05:20 PM

A Discussion of Direct Air Capture of Carbon Dioxide.

The scientific paper that I will discuss in this post is this one: Moving Beyond Adsorption Capacity in Design of Adsorbents for CO2 Capture from Ultradilute Feeds: Kinetics of CO2 Adsorption in Materials with Stepped Isotherms (Christopher W. Jones et al Ind. Eng. Chem. Res., 2019, 58 (1), pp 366–377)

We have failed miserably at addressing climate change and the rate of degradation of the planetary atmosphere is now proceeding at the fastest rate ever observed. The popular approaches to doing anything about climate change - at least among bourgeois types with the time and resources to pick lint out of their navels and daydream - specifically drive around in electric Tesla cars and applaud endlessly and mindlessly for wind turbines and solar cells, have not worked, are not working and will not work.

The reason is physics.

Since we have irresponsibly and contemptuously dumped the consequences of our irresponsibility on future generations with an uninterrupted sequence of pie-in-the-sky pronouncements ("By 2035"..."By 2050"..."By 2100"... etc, etc...) of when the grand so called "renewable energy" nirvana will spontaneously arrive, the only avenue that these generations, from whom we have stolen the future, will have, should they hope to restore anything that can be restored, will be geoengineering.

After some decades of considering the issue, I have drawn the conclusion that the only type of geoengineering that makes any sense whatsoever is the removal of the carbon dioxide, the dangerous fossil fuel waste, that we and previous generations have dumped, again, with contempt for the future, into the planetary atmosphere, thus dangerously destabilizing it.

From my perspective, one of the things we've dumped is not only the chemical wastes themselves, including but hardly limited to carbon dioxide, but also entropy. Over coming entropy involves energy.

The entropic situation is some what less dire in seawater than it is in air, and I believe that the only realistic approach for solving this huge thermodynamic problem which translates into a vast engineering problems, is to process seawater, which besides removing carbon dioxide, may also solve and/or ameliorate several other major environmental problems involving entropy.

Nevertheless, after seeing him speak some years ago at a meeting of the American Chemical Society, I have been following the work of Dr. Christopher Jones at Georgia Tech, who has focused on the removal of carbon dioxide directly from air.

Thus, I was pleased to come across one of his papers some weeks ago in my general reading, the paper referenced above.

Here's the cartoon graphic of what the paper is about:

Note that the "feed" gas here has 400 ppm of carbon dioxide, which was the concentration of this dangerous fossil fuel waste in air a few years back. We are now at over 411 ppm as of this morning, and currently concentrations are rising at a rate of 2.3 ppm/per year, with no slow down in sight. (And no, sorry, the "Green New Deal" lead by Edward Markey, antinuke, won't cut it.) No one now living will ever again see a carbon dioxide concentration as low as 400 ppm again, although one hopes that future generations may be smarter than the dumb shits we apparently are, and find a way to geoengineer as described above. The magnitude of the engineering requirements are so high however, that I feel fully confident in saying "no one now living."

Nevertheless from the introduction to Dr. Jones's paper:

CO2 capture from ultradilute feeds is gaining attention as a key part of global and local carbon management programs.(1−3) Direct air capture (DAC) is one of the few carbon emission mitigation technologies that has the potential to be carbon negative. Amine-functionalized adsorbents such as mesoporous silica,(3−5) carbon,(6) and metal organic frameworks (MOFs)(7,8) have attracted attention for DAC because of their high CO2 capacities even at ultradilute CO2 concentrations. Much of the work in this field has focused on the development of materials with large equilibrium adsorption capacities.(9−11)

Metal organic frameworks (MOFs) are a class of hybrid organic–inorganic materials that have generated significant interest for CO2 capture. Several MOFs have been developed that strongly adsorb CO2 at ultradilute concentrations.(12−14) One example is the amine-functionalized Mg2(dobpdc) material reported by Long and co-workers.(13,15,16) The Mg2(dobpdc) framework, when functionalized with N,N′-dimethyl ethylene diamine (MMEN) and ethylene diamine (ED), has room temperature CO2 uptakes of 3 mmol/g(15) and 2.83 mmol/g,(17) respectively, in the presence of 0.4 mbar of CO2. The sigmoidal shape of the CO2 isotherm in these materials has been explained in terms of a cooperative insertion mechanism in which capture of one CO2 creates a facile pathway for capture of another CO2. This mechanism has led to the creation of a series of materials with a sharply stepped CO2 adsorption isotherm in which the variation in metal centers and diamines allows the pressure at which the step occurs to be tuned.(15) The existence of a sharp step in the CO2 isotherm suggests that a high working capacity for CO2 capture may be possible in a cyclic adsorption process using a relatively small change in pressure or temperature.(16,18) A key aim of this paper is to explore whether factors extending beyond this conceptual description of equilibrium adsorption may be critical in practical applications of these materials.

Keep in mind that even "small" changes in pressure and temperature dealing with carbon dioxide capture on a scale of trillions of metric tons of carbon dioxide - we have dumped the stuff on this scale - implies vast, incredibly vast, quantities of carbon free energy - this at a time when the proportion of fossil fuel energy is rising significantly as well as absolute quantities. In the year 2000, when energy demand was well under 400 exajoules per year, 80% of the world's energy came from dangerous fossil fuels, in 2017, when world energy demand was almost 200 exajoules higher, specifically 584 exajoules, dangerous fossil fuels represented 81% of the world's energy production.

Nevertheless, Dr. Jones goes bravely into defining what a practical process might look like, while confessing that little is actually known about such a process might involve:

Practical adsorption-based separations require that the adsorbent be deployed in a fixed-bed, immobilized on a practical substrate such as a monolith(22,23) or hollow fibers,(24,25) or deployed in a fluidized bed.(26) Ultradilute systems require special attention to the design of the gas–solid contactor, necessitating designs that offer very low pressure drops such as fiber and monolith contactors.(11,27) Mass transfer in these systems can potentially be affected by a range of competing heat and mass transfer effects, including film, macropore, or micropore resistances and adsorption/desorption/reaction. Film and macropore resistances are relatively well understood.(28,29) Nontrivial components of system design include the estimation of micropore diffusion, surface resistances, and reaction (or adsorption/desorption) kinetics. Usually, one or more of these are the controlling resistances, and limited studies exist for transport of CO2 in supported amine materials.(30−38) In the absence of precise microscopic techniques, macroscopic techniques such as gravimetric uptake or pressure decay can be used to measure the kinetics of CO2 adsorption.

He explores these issues with TGA, thermogravimetric analysis.

A well-designed experiment with a small bed can allow accurate predictions for larger beds if it can capture the dynamics of CO2 adsorption satisfactorily. Some of the parameters of interest are the CO2 concentration profile at the exit of the bed, the fractional bed usage, the overall CO2 capture fraction, the breakthrough time, the productivity, and the adsorption rate constant, kads. Mass transfer of CO2 in a packed bed can be modeled by eq 1,(46) which takes into account dispersive and mass transfer effects.

Equation 1 is this differential equation:

Appealing to earlier work related to the theory of chromatography (as well the use of metal organic frameworks he explores here) he offers us this equation describing "absorption waves."

In the absence of any dispersive and diffusive effects associated with diffusion of gas molecules, the actual velocity (w) of a particular adsorption wave can be related to the superficial velocity (ug) by eq 2


One of the references for this equation, this one, Applying the wave theory to fixed-bed dynamics of Metal-Organic Frameworks exhibiting stepped adsorption isotherms: Water/ethanol separation on ZIF-8 (Julien Cousin-Saint-Remi, Joeri F.M. Denayer, Chemical Engineering Journal 324 (2017) 313–323), is a paper apparently focused on another energetically expensive process, the separation of water from ethanol, commonly employed in an effort to get Iowa corn farmers to vote for specific Presidential candidates in elections.

It features this cool cartoon graphic showing an MOF, metal organic framework:

Isn't that special? We're saved.

Just kidding...

The above equation is simplified by appeal to "Golden's Chord Rule" that allows determination of absorption waves in this fashion:

This graphic is offered to show geometrically how it works:

The caption:

Figure 1. Shapes of various types of isotherms (top), corresponding concentration fronts inside the bed (middle) and corresponding breakthrough curves (bottom) as predicted by the local equilibrium theory. Dashed red lines indicate the chords used in applying Golden’s String Method to describe the bed behavior from the initial state (I) to the feed point (F).

In any case, some experiments are set up to compare with theory.

Here's a schematic of the apparatus employed by the Jones Group:

The caption:

Figure 2. Packed bed adsorption system schematic

The IR detector - the strong absorbance of infrared energy by CO2 is why it's a climate gas - detects the "breakthrough" of carbon dioxide from the packed bed, when its capacity is full.

A model is constructed of the absorption:

Total adsorption is the sum of two adsorption mechanisms denoted by q1* and q2*. The equilibrium adsorbed quantity at the isotherm transition pressure, pstep, is denoted by qsat. Adsorption of CO2 below pstep is represented by a Sips isotherm with a temperature dependent surface heterogeneity factor (nL). A combination of Langmuir and Henry’s isotherm is used after the transition step.

A smooth function(w) is used to switch between the low pressure Sips and the high pressure Langmuir–Henry isotherms, shown here in eq 10. Parameters in the isotherm are listed in Table S1. Other details in the isotherm are given in eqs S1–S13 and Table S1.

Equation 10 is quite beautiful to look at:

Anyway, the model developed apparently works quite well when compared to experimental data points:

The caption:

Figure 3. Experimental data (symbols) and modeling fit (solid curves) at 25 °C (black), 49 °C (red), and 69 °C (blue) for CO2 adsorption in MMEN–Mg2(dobpdc). Parameters for the modeling fit are listed in Table S1.

Application of Golden's String Rule for CO2 breakthrough:

The caption:

Figure 4. Application of Golden’s string analysis to predict breakthrough curves resulting for the simulated CO2 isotherm in MMEN–Mg2(dobpdc) at 23 °C at conditions relevant to DAC. The overall partial pressure change between the initial state of the bed, I, and the feed concentration, F, in (a) is divided into two zones in (b) and (c).

Some more on breakthrough:

The caption:

Figure 5. Normalized breakthrough profiles for a packed bed of MMEN–Mg2(dobpdc) at 23 °C as a function of the partial pressure of CO2 in the gas entering the bed. Simulations (left) and experiments (right) were carried out at the flow rate of 17.2 N mL/min. The results are shown in terms of the normalized CO2 concentration at the exit of the bed.

Note that here we're talking in terms of milliters, and for the atmosphere, we're talking trillions of tons. Note too that some of the concentrations of carbon dioxide are multiple orders of magnitude of the current (disastrous) levels in our atmosphere, heading toward Venus, not that we show any reluctance to go there.

A graphic more appropriate to the real world in which we live:

The caption:

Figure 6. Breakthrough adsorption experiments performed at 23 °C with the feed containing CO2 at the partial pressure of 0.4 mbar and different flow rates of 17.2, 28.2, 48.6, and 100 N mL/min. The figure on the left shows the full breakthrough profile while the figure on the right shows breakthrough profiles for the first 3 h.

Some more about the model:

The caption:

Figure 7. CO2 uptake at 23 °C (black diamond) on TGA for a typical sample of MMEN–Mg2(dobpdc). As shown in the figure on the left, one single pseudo-first-order uptake model (red solid line) is not sufficient to model the entire uptake. As shown in the figure on the right, a hybrid model with pseudo-first-order model (red solid line) for the initial uptake and the Avrami model (blue solid line) for the subsequent uptake fits the data well.

Note the time scale and the flow rates.

The caption:

Figure 8. Experimental (scatter) and simulated (solid lines) breakthrough profiles for CO2 adsorption with the CO2 partial pressure of 0.4 mbar in the feed. Simulated profiles were obtained at a flow rate of 17.2, 28.2 N, 48.6, and 100 N mL/min at 23 °C. The Avrami model was used in this analysis to account for the cooperative CO2

I'm not entirely sure how "practical" any of this really is, since the volume of the atmosphere is huge, but offer the following caveat.

I am, in general, hostile to the idea of energy storage since generally it wastes energy and the idea is bandied about in popular culture to further squander money and resources to overcome the biggest drag on so called "renewable energy," its inherent reliance on the weather, such reliance being a factor on why so called "renewable energy" was abandoned by humanity beginning at the outset of the 19th century. (We often forget that the idea of so called "renewable energy" is reactionary and is in no way new, particularly where wind energy is involved.)

A caveat to this statement is the general feeling that one form of energy storage might be capable of avoiding the worst of this waste of energy by the application of waste heat: Compressed air storage. This has the potential to convert energy storage into energy recovery by considering a system that converts the compression into, effectively, a Brayton cycle, by which jet engines and combined cycle dangerous natural gas plants operate.

One can imagine a system where the necessary flows of air so involved might utilize these MOF systems Dr. Jones's Group describes.

From the conclusion of the paper:

The MOF MMEN–Mg2(dobpdc) has shown unprecedented, high adsorption capacities and high amine efficiencies at ultralow partial pressures of CO2 in equilibrium isotherm studies. This system shows a stepped isotherm that is tunable, and it has been suggested previously that such a system may be ideally suited for direct air capture (DAC) applications. In this work, CO2 adsorption in MMEN–Mg2(dobpdc) was studied under ultradilute conditions using a breakthrough adsorption setup as a proxy for practical flow systems. Dynamic CO2 adsorption experiments were carried out at various flow rates, temperatures, and concentrations. The resultant breakthrough profiles were analyzed using local equilibrium theory. Local equilibrium theory suggested either a shock wave–dispersive wave–shock wave or a shock wave breakthrough, depending on the feed concentration. This was confirmed through experiments where a shock wave–dispersive wave–shock wave breakthrough was observed in experiments simulating DAC conditions. A shock breakthrough was observed for CO2 concentrations above 1%. A higher wave concentration was observed in adsorption experiments at higher flow rates using the feed concentration of 400 ppm, corresponding to DAC

It's a very nice paper, a wonderful paper, and I hope to continue to monitor the Jones Lab's work for as long as I can.

I trust you're having a pleasant Sunday afternoon.

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Reply A Discussion of Direct Air Capture of Carbon Dioxide. (Original post)
NNadir Feb 10 OP
Botany Feb 10 #1
NNadir Feb 11 #2
John ONeill Feb 11 #3
NNadir Feb 11 #4
John ONeill Feb 12 #5
NNadir Feb 13 #6
John ONeill Feb 15 #7
John ONeill Feb 15 #8
NNadir Feb 16 #9

Response to NNadir (Original post)

Sun Feb 10, 2019, 05:31 PM

1. Thanx for posting


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Response to Botany (Reply #1)

Mon Feb 11, 2019, 04:18 AM

2. My pleasure. Thanks for reading. n/t

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Response to NNadir (Original post)

Mon Feb 11, 2019, 06:38 AM

3. CO2 sequestration

Have you looked at CO2 sequestration by artificial weathering ? The theory is that in nature, weathering of hydrocarbon-bearing rocks is counteracted, during times of active mountain building, by the weathering of ultramafic rocks, which absorb CO2. We've artificially ' weathered' coal and gas deposits which should still be safe from the atmosphere, thousands of feet below the surface. However, by selective 'weathering' of oceanic rocks such as olivine, high in magnesium, we can restore the balance. To match current fossil fuel use, mining and grinding up of such rocks would have to become the world's third largest earthmoving industry, after building materials and coal. Since coal will have to be taken out of the picture anyway, there should be excess capacity left over.
An objection raised is the energy that would be needed, mostly for grinding the rock. However, as you know, there is plenty of nuclear energy available, and grinding rock would be an ideal use for off-peak power, unlike, for example, aluminium smelters or factories. I think the author of the link I'll attach claimed that to get back to pre-industrial levels of CO2, we'd have to grind down a mass of olivine about equal to Kauai Island in Hawaii - it's about 40 x 50 km, and up to 1500 m high. In practice, tropical countries with cheap labour would be ideal - the reaction would happen faster, it would cost less, and it would transfer money to people who need it. http://www.innovationconcepts.eu/res/literatuurSchuiling/olivineagainstclimatechange23.pdf
Kind regards, John ONeill

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Response to John ONeill (Reply #3)

Mon Feb 11, 2019, 07:20 AM

4. Of course, the question is, once it's removed what do we do with it?

Last edited Mon Feb 11, 2019, 12:31 PM - Edit history (1)

I strongly oppose geologic sequestration, but favor carbon dioxide use. (I generally oppose all dumping schemes.)

I am very fond of carbon dioxide splitting, followed possibly by disproportionation of carbon monoxide into carbon and carbon dioxide, with the latter recycled for splitting.

This can only be economically and environmentally sustainable with nuclear heat.

With this type of approach the carbon can be "sequestered" as an alloying agent (or reduction tool) for metals, for incorporation into other carbon based materials, silicon carbide, MAX phases, carbon fibers, and polymers. This kind of use is economically positive and eliminates the need for metallurgic coal and in electrochemical settings, dangerous fossil fuel derived anodes.

One very big criticism, among many, I have of so called "renewable energy" is that because of its low energy to mass ratio it has high material intensity, particularly with respect to steel and aluminum. The latter two require significant dangerous fossil fuels, steel for coal based coke, and petroleum coke for anodes in aluminium reduction. The FFC metallurgic process also requires carbon anodes.

I most recently wrote about carbon dioxide splitting here: Cerium Requirements to Split One Billion Tons of Carbon Dioxide, the Nuclear v Solar Thermal cases.

I wrote about anodes in this space, here:

Can Biocoke Address the Anode CO2 Problem (Owing to Petroleum Coke) for Aluminum Production?

...and here:

Another Discussion of Biomass Derived Anodes to Replace Petroleum Coke in Aluminum Production.

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Response to NNadir (Reply #4)

Tue Feb 12, 2019, 10:52 PM

5. CO2 sequestration

The Earth's stock of carbon includes about 810 gigatonnes in the atmosphere, ~36,000 gigatonnes in the oceans, and around 1,900 gigatonnes in the biosphere. The quantity in hydrocarbon deposits, mostly coal, is about 19,000 Gt. These are all dwarfed, however, by the quantities bound up in carbonate rocks. If we need to reduce the amount in the atmosphere to pre-industrial levels, which may be necessary to keep the ice caps, we'd need to take over 300 Gt out of the atmosphere. If you're only turning that into useful stuff, that would be around forty tonnes of it for every man, woman and child alive, and it would involve endothermic reactions, and so fantastic amounts of energy. Absorbing it into carbonate rocks like limestone is exothermic, under easily realised conditions, and so much more easily done. The olivine rocks required are available in profusion, in readily available deposits all over the world. Some have already been ground up as mine waste, and are already absorbing millions of tonnes of CO2 through leaching.
Weathering is the main natural method of controlling excess levels of CO2 in the atmosphere - increased weathering after the uplift of the Tibetan plateau and Himalayas is believed to have lead to the glaciation of Antarctica and Greenland. It's just too slow for us.
Your distaste for 'dumping' is shared by, among others, Greenpeace, which sued to halt the German/Indian Lohafex experiment, which put a mere twenty tonnes of iron sulfate into the southern ocean in 2009. The results of that were inconclusive - although there was a brief flush of phytoplankton, normally constrained by lack of iron, there was not enough silica present to allow diatoms to build their little armoured shells, so they were rapidly gobbled up. Olivine dust, as well as helping reduce acidity and adding iron, would also provide silicates. Diatoms which live out their little lives uneaten, die and sink to the sea floor, taking their carbon with them.

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Response to John ONeill (Reply #5)

Wed Feb 13, 2019, 12:08 AM

6. Forty tons for every man woman and child is actually not all that much.

The average American family consumes about 28 tons of oil equivalent each year, according to the IEA.

I certainly realize that the reduction of carbon dioxide would require fantastic amounts of energy, but that said, to the extent that this energy is provided as heat at very high temperatures, much of the energy might well be recovered in one form or another.

If we split carbon dioxide by a thermochemical method, we have effectively stored energy. If we capture waste heat from this process, we have increased efficiency. If Jevon's paradox applies, this will cause us to split even more carbon dioxide. If we take the oxygen side product and utilize it under oxyflame conditions in closed combustion chambers containing for example, waste biomass, there is in fact a route to fairly clean carbon dioxide with additional heat for use. (This sort of approach is often explored in the modern chemical literature in various incarnations of "chemical looping." )

I note that any effort to "sequester" carbon dioxide removed from air is an energy intensive process, a point I make all the time. This said, it may be possible to do remove some from air, for example in the process of using compressed air Brayton engines driven by nuclear heat. Because of the chemical pollution of air with long lived pollutants, the fluorochlorocarbons (which are still here), fluorohydrocarbons, SF6, N2O, and a host of other such species, there is good reason to irradiate air in processes, and while doing so, capture carbon dioxide as well.

Future generations are going to absolutely need to reprocess stuff from very dilute streams, and that will require energy, tremendous amounts of it - you are correct - quantities of energy that must be obtained using matter with high energy density, effectively only practically available from uranium and thorium, and perhaps, in some distant time, from tritium and deuterium in fusion systems.

However the removal of carbon dioxide from the air is best driven by processing seawater, which as you correctly note, contains the bulk of the world's carbon dioxide.

I personally view seawater as the ultimate source of carbon, and, for that matter, the uranium to drive the processes.

Let's be clear on something though, we will absolutely, positively need endothermic reactions to restore whatever can be restored

As for Greenpeace:

While I have a a profound distaste for Greenpeace, it does not follow that if Greenpeace says x, y or z then I must argue not x, not y, not z. Mostly I regard the membership of that puerile panty party as bourgeois morons with poor or non-existent science educations, but it is not impossible for a bourgeois moron to be right about something. If Donald Trump announces that the sky is blue, I am not required to claim its green. If Greenpeace insists that we process billions of tons of steel and aluminum to make stupid bird grinders in the sky, they are clearly wrong and clueless. If however, they argue for closed matter cycles, they are not wrong; they are just too technically ignorant to know how it might be practically be done and stupid enough to oppose the technical approaches by which it might be done. Greenpeace has no effect on my thinking in any way, positive or negative. The fact that they are asses does not preclude me from agreeing with them on a few points.

Nevertheless, the ecosystem sustains itself by reprocessing waste materials. Flies eat shit, and birds eat flies, people eat birds and people shit.

Stuart Kaufmann beautifully described life as "an eddy in thermodynamics." Life is, overall, an endothermic, low entropy system. You need energy to make a sugar, or for that matter a lipid, or a protein or a nucleic acid from carbon dioxide and water and (in some cases, nitrogen gas.) The problem is not whether low entropy systems made by endothermic reactions can exist or not, clearly they do. I am a low entropy system made by endothermic reactions. So are you.

Carbon dioxide in the air, relative to coal is a high entropy result; we are leaving future generations not only chemical waste, but entropy as well. This will necessarily involve vast amounts of energy to achieve remediation, amounts of energy that are only accessible from uranium, unless someday someone actually builds a fusion device that meets the very challenging materials science and heat transfer engineering that involves.

Even were one to put carbon dioxide in solid phase dumps, one still needs to isolate it, and that is itself an energy intensive process.

The requirement that every man woman and child consume 40 MT of carbon is really not all that absurd. In the last 40 years or so the inorganic chemistry of carbon has exploded. I can certainly imagine a world where MAX phases like Ti3SiC2 are common place materials, where silicon carbide is a major building material and where graphite, for all its uses, is prepared from seawater and/or air.

There are all sorts of other options besides dumps. For example, there are amusing little projects that can make concrete, one of the major contributors to climate gases quite the opposite, a carbon sink. I took my son when he was in high school to a lecture by Richard Riman on this topic, and it had a lot to do with him majoring in and loving materials science. We look at structures all the time when we're out and wonder what the world would be if all that concrete one sees were "Riman Concrete."

Riman Concrete

I've thought a long time about closed systems for all of the elements in the periodic table, not merely limited to the fission products. I'm not going to change my mind. Dumps are exercises in consumption, the are economic drags on prosperity. Flies deal with shit much better than landfills, and somehow, on some level, I think flies find their lives rewarding.

Thanks for your comment.

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Response to NNadir (Reply #6)

Fri Feb 15, 2019, 03:38 AM

7. CO2 sequestration

One of the positive feedbacks of the glacial/interglacial cycle involves glacial advance and ocean retreat. Nothing grinds rock like a glacier, and the barren, windswept plains, left behind as the sea retreats down the continental shelf, allow great quantities of the rock flour to be swept into the oceans. That fertilises algae, which draw even more CO2 from the air, reducing average temperatures yet further. We can't recreate that scale, but we can select only the most CO2-philic rocks, just as our prospecting, till now, has zeroed in on high-carbon rocks from Saudi to the Powder River Basin.
Locking carbon in useful materials is good, though some of the links I followed for Riman concrete only claimed a 5% reduction from standard, with 70% hoped for in future, rather than actually being carbon negative. Looped fuel cycles, air >nuclear heat >fuel, would also be far better than the current one way route from mine to air, but wouldn't really reduce the current surplus of free CO2, only stop increasing it.
Another example of natural dust fertilisation is the ~180 thousand tonnes blown across the Atlantic from the Sahara each year, and deposited over the Amazon basin. The phosphorus in this dust comes from diatoms laid down, millennia back, on the bed of a now dry lake in Chad. It is about enough to replace the phosphorus leached out to the Atlantic. Similar layers of diatoms can be found on the sea floor, hundreds of metres deep. We may have sabotaged this natural sequestration mechanism by massacring most of the whales - some believe that modern oceans are deserts compared to the recent past, with overfishing and loss of whale poo attacking the top and the base of the food chain.
I don't think 'dumping' is a fair term for something which is not a disregarded harm, but an intentional good. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL063040?campaign=wlytk-41855.6211458333

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Response to NNadir (Original post)

Fri Feb 15, 2019, 05:34 AM

8. CO2 sequestration

Current cement production worldwide is about four billion tonnes, and steel production is 1.6 billion tonnes ( 86% of this is actually recycled steel.) As a thought experiment, replace all the cement with a pure carbon analogue of similar mass, and all the steel with Ti3SiC2 in like quantity, both produced by nuclear heat from atmospheric CO2, with no extra emissions. Then double consumption, to allow for increased population and greater average wealth.
The MAX phase cited is only about 15% carbon by mass, so you'd be taking about 8.5 billion tonnes of carbon out of the atmosphere each year, as compared to the post-Industrial Revolution excess of about 500 billion tonnes. So 35 years to knock that back by 300B tonnes C. That's pretty good. Still, I don't think any promising solution should be rejected out of hand.
Regards, John ONeill

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Response to John ONeill (Reply #8)

Sat Feb 16, 2019, 09:58 AM

9. It would be interesting, with respect to waste, if dangerous fossil fuel companies...

...were required to meet de facto nuclear standards for the containment of "waste."

That is, the standard that all of their wastes be contained forever in such a way that no one can even imagine anyone at anytime suffering injury.

As I repeat many times, the solution for the definition of used nuclear fuel as so called "nuclear waste," is simply a popular but frankly dullard definition that need not, and should not, be even remotely intellectually respectable, but somehow is.

In the last 30 years, I've been able to conceive a use - often marvelous uses - for every damned fission product one can find in used nuclear fuels, even obscure ones like, say, Ag-108, a very minor fission product.

Now personally, I would have no problem with dangerous fossil fuel waste if it met nuclear standards, since by definition, it would be harmless. It isn't however. As I also point out frequently, dangerous fossil fuel waste, along with dangerous biomass combustion waste, is killing seven million people per year.

I make a distinction between "waste" and "raw material" by the simple expedient of stating that if you have to pay to get rid of something, it's waste, and if you by contrast can make a product you can sell, it isn't.

All waste schemes for carbon reduce the energy to mass ratio of carbon products, and if they are not banned, this requires that more energy be utilized.

Suppose we embraced the dubious (in my view) scheme of seeding the ocean with iron to increase photosynthetic species. We have to dig the iron, truck it, put it on a ship powered by dangerous fossil fuels - since we are too stupid to build nuclear powered commercial ships - and dump the stuff. All of this takes energy and money. Someone has to pay.

There are many carbon products, they surround us, almost every human being on earth, as products and/or as waste.

Ti3SiC2 is only one of many, many MAX phases, probably the most famous, but one of many. (Some contain nitrogen, but there are hundreds of carbon types.) There are also many carbides. Many steels are carbon alloys, as are many other metals in common use.

There are many other types of carbides, silicon carbide is an example.

Some types of carbon products require the use of carbon oxides to effectively manufacture them. Tons and tons of work is being done around graphene - which is not yet really much of a commercial product - but if it becomes one, it seems to me that it will certainly involve Boudouard type chemistry, this disproportionation of carbon monoxide into carbon (in this case graphene) and carbon monoxide.

Finally, there's a lot of work being done on using carbon dioxide as a solvent, since it has a low temperature supercritical state.

As for carbon dioxide injection into geological formulations, even this need not be an economic loser. Right now, expressing our deep hatred of and contempt for all future generations, we are fracking the shit out rocks on the Marcellus shale in Pennsylvania. The rocks being fracked are uranium ores, and its well known that flowback water is rich in radium, not the shit for brains who whitewash fracking as "transitional" until they make giant toxic batteries for their useless "renewable energy" fantasy, care about this radioactive waste. Future generations will need to deal with the fact that the permeable rock, pierced with thousands of abandoned holes to bring that crap to the surface, will be leaching radon gas forever unless the uranium is removed. It happens that one can inject supercritical carbon dioxide into rock formations under certain conditions, and solvate uranium. In this process, if some carbonate rock forms are spontaneously created, so much the better.

If the uranium so removed is fissioned in breed and burn reactors, so much the better. It will prevent the formation of all of uranium's radioactive daughters, including radon, and its ultimate decay product, lead.

That may be an option to clean up the other form of dangerous fossil fuel waste, the fractured geology of formations like this all around the world, being built at a breakneck pace while we all wait for the grand renewable future that never came, is not here, and never will come.

Thanks again for your comments.

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