Two papers on direct air capture of CO2 and the energy cost of overcoming the entropy of mixing.

[NNadir]

In this post I will briefly refer to two papers, which appear one after the other in the current issue of Industrial and Engineering Chemistry Research, a publication of the American Chemical Society, on the remediation future generations might take to clean up the vast waste dump we have made of the planetary atmosphere, if, as is doubtful, they will be left with any resources to do so.

The papers are:

Optimal Design and Operation of Solid Sorbent Direct Air Capture Processes at Varying Ambient Conditions
Jan F. Wiegner, Alexa Grimm, Lukas Weimann, and Matteo Gazzani, Industrial & Engineering Chemistry Research 2022 61 (34), 12649-12667

...and...

Modeling, Optimization, and Techno-Economic Analysis of Bipolar Membrane Electrodialysis for Direct Air Capture Processes, Francesco Sabatino, Matteo Gazzani, Fausto Gallucci, and Martin van Sint Annaland, Industrial & Engineering Chemistry Research 2022 61 (34), 12668-12679

Both of these papers are "author's choice" papers, meaning that they are open for reading by the public; no subscription is required. Therefore there is no need for me to excerpt very much or anything from them, and I refer to them merely to make a few points but let me, for convenience, excerpt a bit from the introduction to the second paper:

As a consequence of COVID-19, global CO2 emissions fell by 6.4% in 2020, when many countries underwent a lockdown. While this decrease is remarkable, it is still well below the needed cut of 7.6% per year in the next decade to prevent global warming above 1.5 °C. (1) Within this context, artificial removal of CO2 from the atmosphere, that is direct air capture (DAC), is to be expected to become a pivotal technology to tackle hard-to-avoid emissions.

I added the bold to ask the question, "expected by whom?"

The first point, I wish to make is that the energy requirements described in these papers is merely to overcome with a very subtle, very expensive, and very difficult legacy with which we have left all future generations: Entropy.

It is a well known, but perhaps little acknowledged even as it cannot be escaped, law of physics that the disorder in the universe increases. This is entropy. While the topic can seem arcane (which is why people often pretend it's not real by hyping things like batteries to fix the appalling lack of reliability associated with so called "renewable energy), one can perhaps think of it in less abstract terms by simply considering a lump of coal, which is primarily carbon with quantities of inert, but sometimes toxic, impurities, like mercury, lead, and other minerals.

No work, no expenditure of energy or effort is required to locate the carbon atoms in a lump of coal. If the lump of coal is crushed, the containment is a little more difficult. One would need to do work to clean up and organize the chunks of coal, and the dust. One might actually lose some of the carbon; the atoms would be still there somewhere but not easy to collect in one lump. The original lump will never spontaneously reassemble without the expenditure of energy. If one burns the coal, then collecting the carbon atoms would involve enormous amounts of work. Although the laws of conservation of mass hold - every carbon atom would still exist - they would now be bound to oxygen and be in gaseous form (along with some of the volatile toxic impurities). To separate the same number of atoms of coal, one would need to do enormous amounts of work to separate them from other molecules in which they were not contained. In other words, we would need to overcome the entropy of mixing, the entropy obtained by making the formerly ordered atoms of coal formerly in a continuous molecular structure into a vast and widely distributed and highly randomized gas which might - and does - diffuse across the planet's matrices.

Since our generation has taken vast quantities of fairly organized carbon atoms in highly concentrated form, dangerous coal, dangerous petroleum, and even dangerous natural gas, since the latter is not mixed with air in geological formations, and burned them, we have left all future generations with entropy.

I happen to believe that direct air capture of carbon dioxide, possibly via the related matrix with which air interacts, seawater, may just be at the edge of feasibility. This said, future generations will be required to produce all the energy released to put carbon dioxide into the atmosphere in the first place - PLUS - all the energy required to overcome the entropy of mixing.

Both papers cited at the outset were produced by Dutch scientists. Let's consider the Netherlands.

For centuries, the pumps that kept "The Netherlands" - i.e. the Lowlands - relatively dry used wind powered pumps, the famous pastoral images that appear on Delft plates and the like.

Now all the pumps are electrical. In other words, the Dutch abandoned reliance on the wind to use the more flexible, but thermodynamically degraded form of energy, electricity, and in some cases, diesel engines powered by dangerous fossil fuels. Despite much delusional hype and magical thinking, electricity is not a form of primary energy. It is a derived form of energy and its production leads to entropy both in the form of molecular disorder and, more subtly, heat. If, with considerable simplification, we can consider the wind to be primary energy in a sense, that is, in a higher thermodynamic state than electricity produced by it, how is that the Dutch abandoned wind pumps and replaced them with electrical (or directly driven diesel) pumps?

There had to be a reason. We ignore consideration of the reason at our peril.

The following two graphics show the 5 year electrical energy generations profile of the Netherlands showing the primary energy source as of this writing:




Energy Map, Netherlands (Accessed 9/4/2022).

For the last 5 years, the power output of the gas plants was roughly 8 GW, this in a small country. The people who produce the Energy Map website, report the carbon intensity of dangerous natural gas power plants at 490 gCO2/kWh. This is more or less consistent with the figures I've seen elsewhere, some higher, a few lower, varying with the efficiency of the dangerous natural gas as well as ambient conditions of pressure and temperature. For the purpose of calculation, I'm going to use 500 gCO2/kwh.

Between 09/05/17 and 09/05/22, there have been 1826 days, or 43,824 hours. There are a 1,000,000 kWh in a GWh. At 500 gCO2/kwh, this suggests that the Netherlands dumped around 175,000,000 tons of carbon dioxide into the planetary atmosphere to produce electricity with dangerous natural gas in their country over 5 years to produce about 1.26 EJ of electricity after entropy losses. Some, but obviously not all, of the electricity went to replacing the activity of the windmills that appear on Delft plates showing historical scenes.

For convenience, I'll reproduce a graphic from one of the papers cited at the outset, Figure 4 from the Gazzani paper, Industrial & Engineering Chemistry Research 2022 61 (34), 12668-12679.



The caption:

Figure 4. Productivity and specific energy requirements for maximal productivity optimization.

For convenience, some commentary from the paper related to Figure 4.

...Figure 4 shows the interpolation of the results in the investigated range of ambient conditions. As expected, the CO2 capacity of the sorbent decreases with temperature, and therefore, the productivity is higher at low ambient temperature. In addition, the capacity increases with increasing humidity, especially for low temperatures. However, for temperatures above 30 °C, the productivity decreases with humidity. The reason is found in the trade-off between the two competing objectives of optimization. When having a higher humidity in the feed stream, more water has to be heated up during the regeneration; while for lower feed temperature, this is compensated by the sorbent capacity, for higher feed temperature, the capacity of the sorbent is low, and the heat required to heat up the water has a high effect on the overall energy consumption. Therefore, the process optimization keeps the energy requirement limited by allowing a loss in productivity...

We have seen extreme temperatures all over the world in this Northern Summer, notably in Europe, which would place the energy requirements in figure 4b, irrespective of humidity and the closeness to fatal wet bulb temperatures, in the range of 8000 kWh/ton of CO2 captured from the air. (I note that much of the European summer involved low wind conditions, meaning Germany and other countries had to burn more dangerous fossil fuels, in Germany the fossil fuel use has been dominated by coal.)

Of course, depending on the season, the energy requirements in the scheme presented in this paper would be more favorable. In the pharmaceutical industry, we speak of "ICH conditions" for stability testing - the shelf life of drug formulations - and the "standard" condition is 25°C/60% humidity. Looking at this and assuming that ambient conditions average pit to "ICH standard" conditions, we can estimate from the heat map scale at the right that the energy requirement to capture all a ton of carbon dioxide would be somewhere around 5000 kWh/ton. Thus to remove the carbon dioxide from the dangerous natural gas waste dumped by the Netherlands into the atmosphere, we would require 876 billion kWh, about 3.16 Exajoules, roughly 2.5 times as much electrical energy produced by burning dangerous natural gas and dumping the waste directly in the atmosphere.

Further down in the paper - which is about optimization - lower energy costs are given for various "scenarios" for direct air capture, estimating costs. For convenience, the relevant figure is presented here:



The caption:

Figure 8. Cost and energy results for the stand-alone model for all operational configurations for (a, b) OC1, (c d) OC2, and (e, f) OC3.

The authors modeled their optimized systems on conditions in three different geographical areas:

To study the effect of different climatic conditions on the DAC process with plausible humidity and temperature profiles, we selected three representative locations: Schiphol (The Netherlands), Barcelona (Spain), and Lancaster (US).

They normalized the cost to $300 (US)/ton.

The best of these optimized scenarios (Option 3, at Schiphol, Netherlands) indicates and energy cost of 926 kWh/ton. At this energy cost, capturing all the dangerous natural gas waste dumped by the Dutch over 5 years would require 0.845 Exajoules, or in the "percent talk" utilized by anti-nukes, 43.6% of the electrical energy generated by dumping the dangerous natural cost in the first place. More sobering is the cost, 1.21 of the normalized cost of $300 (US)/ton ($363/ton). According to these figures, the cost would be around $63 billion dollars.

I've been interacting with an anti-nuke in this space who complained that the cost of the two Vogtle reactors that will soon operate in Georgia ballooned to $30 billion dollars, almost certainly because the US lacked nuclear manufacturing infrastructure, the destruction of which anti-nukes have been cheering for half a century. Of course, the Vogtle reactors will still be operating after every wind turbine blade on this planet will have been in a landfill for half a century, but no matter. The reality is simply this, a small European country has dumped dangerous fossil fuel waste into the atmosphere which under optimal conditions - conditions unlikely to prevail for extended periods - would require $63 billion dollars to "clean up" assuming it can be cleaned up, and frankly, although I think it may be possible, there is nothing suggested by the behavior of humanity to suggest to me, at least, that it will be possible.

A graphic from the paper that I find delusional, indicating where the energy for this clean up should come:



The caption:

Figure 11. Energy system topology.

Who's kidding whom? The energy topology of the Netherlands is shown in the graphic produced above for the last 5 years of Dutch electricity from the Electricity Map.

The wind industry in the country where wind power was most widely used before the industrial revolution - a "revolution" driven by the Faustian bargain of consuming fossil fuels first to make steam and then to make electricity from (largely) steam - has produced 1/4th the electrical energy of dangerous natural gas in that country, the solar fantasy even less than coal produced in the same country.

Is it even remotely sane to say that what does not exist does exist, that people believing that a renewable energy nirvana will break out even though after 50 years of cheering, it hasn't come and isn't here?

The supposition made by advocates of wind and solar energy is that there will be so much of it, that we can divert from things like say, running air conditioners, computers, refrigerators, and more recently cars, among other things, that we can divert it to other things, like cleaning up the mess we created by running air conditioners, computers, refrigerators, and cars using dangerous fossil fuels. This, I'm sorry to report to whomever is living in an alternate universe, is a lie, a lie on a Trumpian scale.

The Electricity Map website gives the electricity profile of most of the industrialized countries on this planet. I defy anyone to produce a five year record of any country with a large wind or solar infrastructure that isn't burning dangerous fossil fuels and dumping the waste directly into the planetary atmosphere on an industrial scale..

As they used to say in California when I lived there, "Go for it."

Here is the temperature profile (in °C) of Lancaster, CA yesterday, September 4, 2022, one of the model cities described in this paper:



Weather History Dashboard for Lancaster, CA . Yesterday, Lancaster hit 40°C (104°F), with much higher temperatures being recorded elsewhere in California.

Working with the data downloaded from the CAISO website as CSV files for September 4, 2022, combining them into an Excel file, and calculating averages, highs, lows, and standard deviations, here is how the entire State of California produced electricity yesterday.



The last row is the difference between how much energy the lone nuclear facility in California, the Diablo Canyon plant on a 12 acre footprint, and all of the wind turbines in the State, spread across more 1500 square miles of wilderness converted to industrial parks.

(The California legislature, after years of anti-nuke delusion, voted last week overwhelmingly to save from ignorance, because California's climate back is against the wall. It's about time there is a trace of energy rationality there.)

On average, yesterday, a day marked by extreme temperatures all over the State, potentially fatal temperatures, the nuclear plant produced 1248 MW more power than all the wind turbines in California. At no point, during a time when the CAISO system was on alerts and Californians were being asked to conserve power, was there left over so called "renewable energy" to cleaning up the dangerous fossil fuel waste California is currently dumping to prevent its citizens from dying from exposure to extreme heat. The occasional curtailments for so called "renewable energy" which advocates of this absurd system like to pretend are common and providing oodles of energy are rare and tiny in reality, and in any case, building a standalone carbon capture plant infrastructure that can run only on rare occasions is - there's no other way to put it - environmentally and economically stupid, abysmally stupid, downright dangerous.

The interested reader is invited to use the energy figures in the other paper interesting paper referenced, that referring to "Bipolar Membrane Electrodialysis" to do similar calculations to these as an exercise.

Let's be clear, cleaning up the atmosphere to an acceptable state, somewhere far below the 420 ppm we've been seeing recently, is not an undertaking that can be addressed with glib handwaving. It's an enormous undertaking and the remark that anyone can expect success is absurd.

I have personally thought a great deal about direct air capture. To my mind it borders on feasible. I'm not sure, but I think it might be. To run different kinds of nuclear plants than those we commonly run now, to increase thermodynamic efficiency from the poor (but common) Rankine efficiency of nuclear plants like Diablo Canyon, roughly 33 to 35% to figures that might be realized of close to 80% (with some exergy recovered as carbon fuels) there may be good reasons to compress air and utilize air flows in operations, both to clean the air and to increase efficiency. In these cases, direct air capture of carbon dioxide would be a side product not a production goal. This would maximize environmental efficiency.

This said, the most important point of all of the above is that all of the energy described above is merely to overcome the entropy of mixing and NOT reducing the carbon dioxide to stable forms of carbon available for use. Far more energy, and in fact entropy, will be required address to reduce the carbon dioxide to a usable form, for example fuels and materials.

Sorry, the fantasies about wind and solar energy simply won't cut it. On reflection, after half a century of cheering for them, and the expenditure of trillions of dollars on them, there is no evidence that they can even stop the dumping of dangerous fossil fuel waste, never mind clean it up.

I trust you're having a pleasant holiday weekend.