Direct Air Capture of CO₂ is Less than Net-Zero
Direct Air Capture of CO₂ is Less than Net-Zero
Part 1: a 101 Primer on the DAC debacle and a best use of CO₂ capture
Above: this basic direct air capture (DAC) cartoon shows that dilute CO₂ is “scrubbed” or captured by a “filter”, typically a chemical absorbant such as caustic soda or NaOH. Release of the CO₂ from the absorbant requires heat, followed by isolation, storage, maintenance, and injection of the captured CO₂ into the earth.
Above: energy intensive direct air capture (DAC) fans suck in air that contains only 400 ppm CO₂ (400 mg/1000 g). Scrubbing gases is an “Old School” technology typically used for corrosive industrial effluent gases, but now has been Shanghaied by the Carbon Capture Tax Credit Crowd.
Introduction
Let’s start with a simple Gedankenexperiment or thought experiment for myself and my valued readers with regards to the viability of direct air capture (DAC) :
Question: have you ever looked at a set of numbers or a spreadsheet and saw a number that stood out or didn’t make sense?
For example, which number stands out in the list below?
10
15
12
8
16
1000000
20
7
9
So common sense would suggest that one number shown above does not fit with rest of the numbers.
The same goes for objects that don’t match or are different, as illustrated in this classic Sesame Street video, “one of these things is not like the others”, a concept of which AOC apparently struggles with to this day:
Above: one of these things is not like the others.
Just like a big or small number that is out of place, or a blue balloon, DAC is an outlier; yet billions of dollars are being poured into DAC plants worldwide, such as the OXY-BlackRock venture in TX, which will supposedly remove 500,000 tons of CO₂/year. We also note that Occidental is a petroleum company and is happy to supply the hydrocarbons to run the DAC plant. Also, petrochemical companies use purified CO₂ as a feedstock in a number of chemical processes and in shale fracking. Ah, follow the “Inflation Reduction Act” money and tax breaks (IRS 45Q) and carbon credits!
Above: Larry Fink of BlackRock is the architect of the woke capitalism scam and is now involved with DAC.
In these confusing Fake News times, I have found it always best to revert to basic 101 concepts, to help cut through the BS; and think about the problem in terms of logic and reason, and then possibly in terms of energy flow and the Law's of Physics and Thermodynamics. To that end, what follows below are some basic 101 concepts to consider regarding the DAC Debacle.
The DAC Debacle
DAC Debacle 1: CO₂ Removed by DAC may be Replaced by CO₂ from Terrestrial and Oceanic Sources
Back to 101 chemical principles, this time Le Chatelier’s principle. But don’t go glassy eyed just yet, this is an important and intuitive concept, as follows:
Vast repositories for CO₂ include the land, plant biomass, ocean and plankton, in all their various forms. CO₂ is always traveling back and forth from the sea, land and the air. This is called the planetary CO₂ exchange, or carbon cycle and is illustrated below.
Above: planetary CO₂ movement or exchange is shown with arrows. CO₂ is shuttled back and forth from the sea, land and the air.
What could happen if CO₂ was removed from the air ? If some substantial amount of CO₂ was removed from the air via DAC or other methods, CO₂ might outgas from the land or ocean sinks to replace some fraction of CO₂ that was removed, per Le Chatelier’s principle.
Above: Henri Louis Le Chatelier
Drilling down, Le Chatelier’s principle can be interpreted as follows:
If CO₂ is removed from the air, CO₂ from the land and oceans may outgas to replace the removed CO₂, until some equilibrium is reached again, which may take a substantial amount of time.
The reverse is true as well: when CO₂ is increased in the air, the ocean and land will uptake more CO₂ until a new equilibrium state is possibly reached over time.
A recent paper published in Nature Climate Change discusses the possible effect of CO₂ removal on the global carbon cycle. The paper notes that removing tons of carbon dioxide from the atmosphere might not be effective, because the shifting atmospheric chemistry could, in turn, affect how readily land and oceans release their CO₂, aka Le Chatelier’s principle. Another reference discusses the same concepts, and it is noted that both rely on synthetic models, like most climate change theory.
Handwaving: like climate models, a general rule that has been propagated is that for every tonne that ends up being emitted from fossil fuels or “land use changes”, a quarter gets absorbed by trees, another quarter by the ocean and the remaining half gets left in the atmosphere. I have not seen any hard data that backs this up. It basically says half the CO₂ emitted by man is left over and can’t be absorbed or re-equilibrated. My take is how arrogant can “they” be to assume we truly understand the complex planetary CO₂ equilibria or exchanges occurring?
DAC Debacle 2: DAC is a Highly Inefficient Process
Above: looks simple, eh? From Ben James.
Lets get semi-nerdy for a minute, as what follows is important. The Second Law of Thermodynamics teaches us that things in our world tend irreversibly towards disorder, which may be interpreted as an increase in entropy.
Example: take a mixture of 5 blue marbles and 5 red marbles, and separate them by color. You have to do some work to do that, and entropy decreases because you have ordered the objects, but entropy must increase somewhere else per The Conservation Law's. I am betting that you have never seen a mixture of 5 blue marbles and 5 red marbles spontaneously order themselves by color, size, or shape.
Then, in a fit of rage over climate change, you sweep those ordered marbles off a table onto the floor, and the question is: will they spontaneously order? Unlikely.
One has to do work to order things in our modern world, and there is an energy expense for doing that, usually by burning fossil fuels, with a concomitant and irreversible increase of disorder or entropy somewhere else. We hope to do efficient work, but there are many inefficiencies in reality. DAC is the Poster Child for inefficiency, as we will show.
Airing it Out with Trace CO₂. Air comprises nitrogen, oxygen, CO₂, and other trace gases which have a tendency to mix and disorder, which is commonly referred to as the entropy of mixing.
We note that thermal energy or heat creates disorder and imparts kinetic energy in gases. Gas and air molecules are always in motion and vibrating, except at absolute zero Kelvin. Gas molecules do not spontaneously order themselves into neat piles or lumps, unless one does work on them such as energy intensive liquification via cooling, freezing and/or pressurization. Gas molecules prefer to stay well mixed and bounce around as illustrated in the air mixture below, with trace CO2 in red (from Aatish Bhatia):
Above: normal state of well mixed CO₂ (red) in air, bouncing around with thermal energy and vibrating.
Above: red CO₂ molecules segregated from other air molecules. Work has to be done on the mixture to lower it’s entropy. That requires lots of energy, especially with a dilute gas such as CO₂ at 400 ppm.
DAC Debacle 3: Separating the Dilute from the Plenty
Keying off the concept of entropy of mixing, most of us have an intuitive feel that one has to do alot of work to find a needle in a haystack and isolate it.
Mining industry: one may also imagine that it is “worth it” to separate a trace amount of a valuable substance, such as 3 ppm gold (Au) from a pile of dirt and rocks. That is the basis for the mining industry and refined metals. And it takes a heck of alot of energy to isolate that gold, as Tuco can attest.
Chemical and pharmaceutical industries: one has to refine a mixture to isolate a desired substance. This is what chemists do typically.
Separating the Dilute from the Plenty is Plenty Costly. In 1959, Thomas K. Sherwood, a legendary chemical engineer, developed the concept that the cost to separate a given substance from a mixture scales inversely with the initial concentration of that substance.
Sherwood published the original version of what is now commonly referred to as a Sherwood plot, which graphically illustrates that the cost to separate a given substance from a mixture scales inversely with the initial concentration of that substance. This means that the more dilute the stuff is that you want, the more costly it will be to isolate it.
An updated Sherwood plot, shown below, reveals an empirical relationship between the market price of materials and their concentrations using mature separation technologies.
Note that the dilute materials include pollutants, valuable organic compounds, metals, and the heinous toxic gas CO₂.
Above: an updated Sherwood plot from Grübler, includes three categories of materials to be refined or separated: metals, organics, and pollutants. The Sherwood plot shows the relationship between the concentration of a target material in a feed stream and the cost of removing the target material. The heinous toxic CO₂ gas, directly from a coal-fired power plant exhaust stack, is shown left and at the bottom. Note that on this plot this is 0.1 mole fraction of CO₂ or about about 12%, much much more concentrated than CO₂ in the air, which is 0.04 %.
Aatish Bhatia has conveniently calculated and plotted the theoretical versus real world energy costs of DAC in his Substack, which are reproduced below, and further illustrate Sherwood’s concept.
Above: the graph shows the theoretical minimum energy needed to extract 1 tonne metric of CO₂ from the air, plotted versus the fraction of CO₂ in the air. Dilute CO₂ is much harder to remove than more concentrated CO₂, and that is why the plot goes ballistic vertical at low CO₂ concentrations.
To make it more easy to visualize where we are with that 400 ppm of CO₂ and the theoretical energy needed for capturing 1 tonne metric of it, we can make the graph more useful by switching the y-axis to a logarithmic scale, which straightens out the curve. Each step of the x-axis represents a 10 fold increase in CO₂ concentration.
Above: log graph shows crossover point of 400 ppm or 0.0004 CO₂ fraction with energy needed to isolate 1 tonne of CO₂. Dilute CO₂ is costly to remove from air as shown.
Bottom Line DAC Numbers: Reality ain't too Kind.
The calculated theoretical minimum energy cost to extract 1 tonne of CO₂ from air is approximately:
500 Megajoules (MJ) or 140 kWh
The 500 Megajoules (MJ) or 140 kWh numbers are within most published estimates. This number also tells us what is theoretically possible, but not what’s technologically feasible.
However, reality ain't too kind. Any real-world DAC process has significant energy losses or inefficiencies which cause it to consume more energy than the 140 kWh.
More realistic estimates suggest that the best we can achieve is 10 times the theoretical estimate (aka 10% thermodynamic efficiency), which are the number(s) shown below:
5000 Megajoules (MJ) or 1400 kWh to remove 1 tonne of CO₂ at 10 % efficiency
Another DAC Reality Check: efficiency is less than 10 %, requiring roughly 2000 kWh to remove 1 tonne of CO₂ per data graphed below:
Above: graph illustrates the differences between capturing CO₂ from more concentrated CO₂ streams vs. DAC which sucks in air that comprises only 400 ppm CO₂. From Ben James.
Another DAC Reality Check Key Points
Current processes use roughly 2000 kWh of energy to capture one tonne of CO2.
This means that capturing one year of global CO2e emissions would require ~120,000 TWh of energy.
120,000 TWh is about the same amount of energy that the world uses per year. So we’d have to double the world’s energy supply just to power our giant hoover!!
Super Ultra-Distilled Take Home on DAC
Capturing CO2 emissions using DAC requires almost as much energy as that contained in the fossil fuels that produced the carbon dioxide in the first place, per Keynumbers:
In 2020, the world used 462 exajoules (EJ) of energy from fossil fuels, which resulted in 32 billion tonnes of CO2 emissions. Capturing that carbon dioxide through DAC — which sucks the greenhouse gas out of the air — would require 448EJ, according to calculations by Australian maths-as-a-service company Keynumbers.
That 448EJ is the equivalent of 124,444TWh — more than five times the annual global electricity consumption in 2020 (23,177TWh, according to Enerdata). And that doesn’t even include the energy that would be required to then transport and store the captured CO2.
“The world would need just as much energy to clean up the energy it made a mess with in the first place,” said Keynumbers founder John Poljak. “Not quite what the circular economy had in mind.”
Moving on - DAC Debacle 4: CO₂ Does Not Cause Climate Change, so Why Bother ?
Well, this is the most obvious reason that DAC is a debacle. If I may be so bold, I propose here that man made CO₂ is not the cause of climate change, and has no significant effect on normal earth temperature variations.
Fact one: geological research observes that the amount of CO₂ in our atmosphere does not lead to temperature change, it follows it.
Fact two: global temperature is driven predominantly by two factors, the amount of cloud cover in our atmosphere, (clouds reflect the sun's heat back out into space) Cloud cover amounts are determined by our own weather patterns (Albedo) and cosmic ray activity. The other major factor is the angle of the earth on its axis (GM Angle) as we orbit the sun, and as our solar system orbits around our universe. Our orbits are not a perfect circle as depicted in so many pictures, it is elliptical and over thousands years that ellipse changes, we get slightly closer or farther from the sun.
Fact three: the climate models that are being used to predict our imminent destruction use two factors that are completely wrong. The first is that they cannot account for color, so they use radiative color black. The earth is not a black body in space. Nor are the other planets in our solar system. The other mistake is that they needed a constant to make the models work, and for some reason they picked a number that was not prime and they used it twice. Constants are prime and even ‘ol Albert who tried proved you cannot use a constant the same way twice in a formula or algorithm.
Blasphemy! However, I will leave most of this to the experts, such as John Clauser the 2022 Nobel Prize Winner in Physics and other common sense scientists, some of which are members of the CO2 coalition and the others featured in the excellent video below.
Best Use of CO₂ Scrubbing - No Bubbles Bonus Section
In addition to our astronauts, our Special Operators need CO₂ scrubbing for their Special Super Secret Diving Excursions
Badass CO₂ Scrubbers: SpecOps guys use Draeger rebreather units that scrub CO₂ from their respiration, allowing no bubbles low detection diving excursions !
Substack SEAL CO₂ Scrubber
Our own Concierge Special Operator Sam Alaimo writes Original Stoic Essays on his Substack and is a former Navy SEAL. His article below is a great read, and notice the use of Draeger rebreather units. Sam is also heading up a new start-up called ZEROEYES, featuring Automated Optical AI Firearm Detection.
ChemNerd Section
Chemistry of CO₂ scrubbing by caustic soda or caustic lime: transform CO₂ to the carbonate form
(1) CO2 + H2O ⇌ H2CO3
(2) H2CO3 + 2NaOH (or KOH) ⇌ Na2CO3 (or K2CO3) + 2H2O + Heat
(3) Na2CO3 (or K2CO3) + Ca(OH)2 ⇌ CaCO3 + 2NaOH (or KOH)
Thank you for reading Tuco’s Child’ Newsletter. Please subscribe and restack like crazy, we need more gold.
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Thanks for a nice overview of the physics problems with DAC! This is one to save!
What a great article! Thanks for the chemistry lesson. I was quite convinced of the futility of CC, now I’m certain. If we get too good at pulling CO2 out of the air…won’t we kill all the little plants?