Recently headlines announced a $68 million dollar investment in a company that is building air-carbon capture technology. Headlines claimed it could scoop CO2 from the air we breath economically. Hyperbole, like ‘magic bullet’, was spread liberally around. The threshold number of $100 per ton of CO2 was bandied about.
This of course leads to the requirement for assessment. After all, $68 million looks like a lot of money. Magic bullets don’t grow on trees. CO2 is spread extremely thinly through the atmosphere. And what exactly are those multi-billion dollar companies getting for their money?
The total CO2 load for the energy required for capture, processing, compression, storage, distribution and sequestration is almost certain to be greater than the CO2 removed from the atmosphere.
This isn’t a one-article drive-by, but a five-piece assessment. The first piece summarizes the technology and the challenges, and does a bottoms-up assessment to give context for what Carbon Engineering is actually doing. The second piece steps through Carbon Engineering’s actual solution in detail. The third piece returns to the insurmountable problem of scale and deals with the sheer volume of air that must be moved and the scale of machinery they have designed for the purpose. The fourth article looks at the market for air carbon capture CO2 and assesses why three fossil fuel majors might be interested. The final article addresses the key person behind this technology and the expert opinions of third parties such as Dr. Mark Jacobson of Stanford.
What is the magic bullet?
The magic bullet in question is an air-carbon capture solution from a company called Carbon Engineering. It’s based in Squamish, BC and just received $68 million in funding from three fossil fuel majors. One of the company’s principals is a seriously intelligent engineer who accepts the science of global warming, but likes geoengineering, burns fossil fuels to capture CO2 from the atmosphere, and doesn’t like wind generation. Bright, but not wise.
Carbon Engineering’s solution burns natural gas sufficient to create half a ton of CO2 in order to capture a single ton of CO2 from the air. They assert that they capture about 90% of the natural gas upstream and in-process CO2 emissions. They actually have three separate CO2 extraction technologies running in order to just take CO2 from the air with one of them. The technology won’t scale to anywhere near the size of the problem. The only potential use case for it is enhanced oil recovery, pulling more carbon from underground in tapped out oil wells.
At the heart of its technology is a clever re-use of existing technology, contactors. Like sorbents, another technology used in air carbon capture, a contactor is a filter for atmospheric CO2. It has a honey-comb of material that is wetted with a solution which captures CO2. The CO2 is then precipitated out of the solution into a solid, which is then baked at 900 degrees Celsius to capture the CO2.
To scale to a million tons of CO2 a year, the company would need 2,000 two-meter fans blowing air into contactors in an array 20 meters high, 8 meters thick, and two kilometers long (broken up into 10 slabs) surrounding a central gas-fired CO2-processing plant which also generates the electricity for the fans in the primary model. The company currently has a single fan working with a portion of its solution and isn’t achieving the efficiencies required for its goals, although it has an explanation for that. As the problem is gigatonnes of CO2, the company is four orders of magnitude off of a real solution, and the price tag to make this type of technology absorb useful amounts of CO2 would be in the trillions annually.
CleanTechnica has published several articles I’ve written about the fundamental scale problem of carbon capture and sequestration a few times, so I wasn’t surprised to find that the magic bullet was more of a lead balloon.
All of these carbon capture technologies like to talk up the price of capture, which Carbon Engineering puts at $100 per ton, but they neglect to count in storage, distribution, and sequestrations, easily half of the cost.
I reached out to Professor Mark Z. Jacobson of Stanford for a comment on the technology. He’d already assessed it of course:
SDACCS (synthetic direct air carbon capture and storage) is not recommended in a 100% renewable energy world. SDACCS is basically a cost, or tax, added to the cost of fossil fuel generation, so it raises the cost of using fossil fuels while reducing no air pollution and providing no energy security. To the contrary, it permits the fossil fuel industry to expand its devastation of the environment and human health by allowing mining and air pollution to continue at an even higher cost to consumers than with no carbon capture.
The $68 million is a fig leaf. It’s 0.03% of the three fossil fuel companies’ combined annual revenue. It’s change they found in the couch. It gives them a nice slurry of green paint to pour over their tarnished images and is cheap at twice the price.
The process is energy intensive
For the sake of this assessment, let’s do a bottoms-up assessment of likely energy needs and potential energy supplies and CO2 implications, and then contrast it to Carbon Engineering’s technology and claims per its published papers in a couple of academic journals. The contrast will be illuminating.
The headline of one of those assessments I published, triggered in part by a previous glowing article about Carbon Engineering, is Air Carbon Capture’s Scale Problem: 1.1 Astrodomes For A Ton Of CO2. You have to push a lot of air through a small and resistant space for absurd amounts of time to get a ton of CO2 with a perfect capture method. I estimated that with close to 100% efficiency and several other conservative assumptions, it would take about 0.44 MWh just for moving the air to capture 1 ton of CO2. This used standard 1-meter diameter industrial fans, not the most efficient choice, but the specifications were at hand. I excluded back pressure, heating, cooling, movement of physical components, and the like.
For much of this assessment, I’ll posit a device which captures a ton of CO2 an hour, then later extrapolate to a million tons a year of capture, which is Carbon Engineering’s reported per plant target.
In addition to the large job of just moving sufficient air, Carbon Engineering’s technology has another major energy concern, the 900 degree Celsius heating process which bakes the CO2 out of the precipitate. Let’s consider that a more reasonable number with a minimum air flow through the contactor technology, a processing cycle, a cleaning cycle, and then pressurization and storage. That is probably in the range of 4.4 MWh of electricity for a ton of CO2.
Let’s model this out with electricity as the primary energy source to start, as it seems eminently sensible to use a primary energy source which can be carbon-neutral itself to extract CO2 from the air. What’s the carbon load of 4.4 MWh of electricity? Carbon Engineering is based in BC, which has a lot of hydro, and as a result, very low grams of CO2e per kWh : 15.1 grams CO2e / kWh.
That doesn’t seem like a lot, but there are 4,400 kWh in 4.4 MWh. A little math and it’s apparent that in order to capture the ton of CO2, you end up with electricity that emits about 66 kilograms. If Carbon Engineering were using electricity as the primary energy source and the demand were 4.4 MWh, this would be reasonable.
What does 4.4 MWh of electricity cost in BC? It’s running ~6 cents CAD per kWh for large customers and Carbon Engineering would definitely qualify if it were using electricity. At BC rates, 4.4 MWh would cost about $265 CAD or $200 USD. Running it for a year with 5% maintenance downtime would be an electricity cost of about $2.1 million CAD or about $1.6 million USD, and would only capture 8,300 tons.
Carbon Engineering is claiming $100 per ton USD according to the BBC article, or about $133 per ton CAD. That’s a big gap from $265. That means that its claimed process would only consume about 2.2 MWh per ton of CO2 if the company was running it off electricity as a primary energy source.
Could it really be 50% cheaper? Well, it’s hard to see how. And Carbon Engineering doesn’t actually claim that in its underlying peer-reviewed publication. The paper that triggered the latest round of headlines was published in Joule, a brand new cross-disciplinary journal focusing on energy at all scales, which has no impact factor yet. (Yes, the lack of an impact factor and the vagueness of Joule’s mandate is a red flag, implying challenges with getting the right peer reviewers on submissions. A bit more on this later.)
Here’s what is actually said in that paper (dollars in USD):
Levelized costs of $94 to $232 per ton CO2 from the atmosphere
Well, that’s not $100 per ton. The company has just built its first prototype and its current range barely includes the claimed $100. In Canadian dollars, it’s $125 – $310 per ton, nicely bracketing the bottoms-up electricity-only model of $265 CAD. Okay, we have some hyperbole from the press and a paper published in a brand new and weak (so far at least) journal which is more realistic. But the bottoms-up numbers are in the ballpark and probably more realistic than the $100 claim.
The paper also claims moving the air only takes 61 kWh per ton of CO2. My modeling with lower scale fans (hence less effective and efficient) suggested 440 kWh per ton of CO2. That’s a very large gap, especially as the 440 kWh I modeled doesn’t include back pressure. We’ll return to that.
What if Carbon Engineering set up right next door in Alberta and ran this off electricity from the grid? Well, Alberta’s electricity is at 820 grams of CO2e per kWh. That’s over 50 times worse than BC. The required 4.4 MWh of electricity would produce 3.6 tons of CO2e to capture one ton of CO2e. And the bottom end of 2.2 MWh? That’s still 1.8 tons of CO2e emissions. Even at its own claimed energy intensity, in Alberta the company would be significant net emitters.
The solution is energy intensive, would be a net carbon emitter in many jurisdictions if it used electricity, and has some already dubious claims. Experts such as Mark Jacobson rightly point out that just building wind and solar generation with the money instead would lead to much better emissions and pollution outcomes. But that’s not the end of the story.
The next article in the five-part series steps through Carbon Engineering’s solution in more detail, comparing and contrasting it to the bottoms-up model to see where there are gaps and where there might be issues.
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