MIT engineers make converting CO2 into useful products more practical

The writer appears to be under the impression that CO2 is not a valuable commodity.

In fact, it is, so long as it's under enough pressure, and in the right place. In Montezuma County, Colorado, sits the McElmo dome, an ancient underground CO2 well. They pump it out, down a 500 mile pipeline, to Denver City, Texas, where it gooses oil wells into pumping more crude out. Other than making more oil and making it cheaper, not really much in terms of greenhouse gas contributions- the CO2 starts underground and ends up underground.

Kinder Morgan won't just let you back up your truck and buy some (it's already spoken for), and even if they would, they'd expect you to pay a pretty penny for what we widely consider to be waste gas.

I think MIT is doing some good work. Just wanted everyone to be mindful of the massive scale under which CO2 is already getting bought and sold.

Isn't it also used as input to basically every e-fuel which can replace fossil hydrocarbons?

It's not that CO2 isn't valuable on its own, but that other carbon-containing molecules are even more valuable (especially when factoring in transportation costs). This helps prove out the technoeconomics of carbon capture.

Plus, if we wind down oil extraction, we'll need new processes to produce all the precursors we use for plastics. A cheap pathway to ethylene from captured CO2 and water would be huge.

No. The value of commercial co2 is its energy content -- what it takes to process it into useful form. There is no useful form of co2 for making fuel. The energy has already been extracted.

You're right (current state of the art), but also wrong (in the spirit of the question as I read it).

If energy prices go down, e.g., from continuing decline of solar, then it may be very cost effective to store energy as hydrocarbons which are synthesized from cheap energy + CO2. E.g., make natural gas from the air and sell it cheaper than it could be extracted and transported.

In this scenario, rather than paying exorbitant fees for CO2, the cheap energy could be used to extract it from the atmosphere where it is abundant.

Before anyone bites my head off - consider the tyranny-of-the-rocket-equation problem of burning gas to transport gas from source (wells, refineries, etc) to consumers. Then consider that the sun shines most places, and CO2 is effectively uniformly distributed. So Synthesis wouldn't have to be cheaper at the source if it can beat the price at the consumer via avoiding huge distribution costs.

Exactly right. FTA: "The electrochemical process that converts CO2 into ethylene involves a water-based solution and a catalyst material, which come into contact along with an electric current"

That "electric current" is the challenge. It takes energy to convert CO2 into other chemicals. If that energy isn't carbon-neutral, you're just spinning your wheels.

The application you mention does not rely on the gas being co2 at all. The gas is being used because it is in a high pressure reservoir. It could by any gas. The C02 itself is literally free because it is literally in the atmosphere all around us.

Yes but this is not relevant in context of climate change. It does not matter that we can bury some CO2 while more of it is added to atmosphere.

CO2 may be everywhere, but it is at a very low concentration. Efficiently isolating CO2 from the rest of the gases is a limiting factor.

So, capturing CO2 from the air can be used to put out even more CO2 into the air. Fantastic.

Well, netting ~95%¹ of the extracted carbon as new release on the atmosphere is technically better than 100%. They could be using nitrogen instead.

But yeah, it's quite underwhelming.

1 - Wild guess. But it's certainly less than 100%, and certainly not by a lot.

I'm not sure if we are talking past each other, but: https://en.wikipedia.org/wiki/Electrofuel

Electrofuels, also known as e-fuels, are a class of synthetic fuels which function as drop-in replacement fuels for internal combustion engines. They are manufactured using captured carbon dioxide or carbon monoxide, together with hydrogen obtained from water split.

It is my understanding that there is actually a shortage of concentrated co2 if we want to produce e-fuels as drop-in replacements in e.g. planes.

> If that energy isn't carbon-neutral, you're just spinning your wheels.

True, but the "long term" angle here would be to supply that energy from, say, excess solar generation during midday after the overnight storage batteries are refilled.

Pressure is only part of the equation. The pressure gets it to the field economically and does boos reservoir pressure, but co2 injection has more to do with miscibility with hydrocarbons at relatively low pressures. Miscibility yields viscosity reduction and swells the oil to improve displacement and mobility, particularly in heavier crude. Couple that with pressure and you can dramatically improve recovery factor.

It the example you give, CO2 gas is not really a valuable commodity. Pressure is the valuable commodity in that example, and so it's kind of irrelevant when discussing carbon sequestration solutions.

All ideas for "fuels" hinge on the future availability of an economical energy source, which would have to be either solar or nuclear.

> A cheap pathway to ethylene from captured CO2 and water would be huge.

Is it considered cheap if the marginal cost of a PV MWh is close to zero ?

That sounds like a lot of it ends bound to, and thus comes up with, the oil/crude.

It absolutely does and has to be stripped out in processing. It typically gets compressed and reinjected over and over again

It can be way worse than 100% if the reduced oil extraction costs (or greenwashed accounting from earning carbon credits for sequestration) results in more net oil being extracted, than there would have been without access to CO2.

Not to mention the energy costs of actually pulling carbon out of the air. Often, getting 1kg of CO2 out of the air ends up costing so much energy that you end up emitting more than 1kg of it.

If sequestration weren't a fairy tale that will keep us distracted for another few decades while we continue to ruin our environment, people would be doing it, not talk about doing it.

That's not correct. If pressure was all that mattered, we'd just run compressors on nitrogen (or formation gas). CO2 has properties that make it especially favorable for flooding.

https://en.wikipedia.org/wiki/Carbon_dioxide_flooding

Has to be both. A random gas might interact with the oil being pumped. Why don't they just use compressed air? There must be a reason why CO2 is desirable for that application.

Exactly. And getting back to the original poster's comment "the CO2 starts underground and ends up underground"... that assumes there are no leaks anywhere in the process.

I wonder what happened to the Navy's attempts at synthesize aviation fuel in aircraft carriers. They have plenty of power (newer carriers have even more) and reducing or eliminating the need of support craft for fueling would be a massive bonus.

They've been looking at that for a while, I don't know what issues they encountered.

> The C02 itself is literally free because it is literally in the atmosphere all around us.

Not exactly.

> The concentration of carbon dioxide (CO 2) in the atmosphere reach 427 ppm (0.04%) in 2024.

Any process that tries to unmix something is not going to be 'literally' free. And given the relative trace amounts we're talking here...

So CO2 is magical here or would a reservoir of highly pressurized atmosphere be just as valuable? I think you are missing where the value is in this situation.

They couldn't get it to be efficient enough.

Strongly suspect you don't want pressurised oxygen-containing-atmosphere in that situation.

Liquefying air and separating O2 and N2 isn't that hard to do, particularly if your end desired state is a high pressure gas.

Yes of course, I am not claiming otherwise.

My point was just about the scarcity of concentrated co2.

But that point drives right into this one: compressed CO2 is valuable. So the value of your carbon capture process is already very substantial after you've extracted the CO2 from the atmosphere. I mean I have a cylinder of CO2 under my kitchen counter right now for this reason.

So the question is, is this so valuable that it outweighs just selling that CO2 once you've pulled it out of the atmosphere?

The energy costs are only part of the equation, though. Especially if your plan is to use excess renewable energy, the cost of your plant is a much bigger concern, because you can't run it all the time.

Yes, but if you don't have to do it, why bother?

Marginal cost. And one might reasonably expect fixed costs too to keep dropping, altho not as spectacularly quickly.

It's the opposite actually; CO2 interacts with petroleum in controllable ways via pressure, so engineers can change the properties of the oil and end up extracting more oil more quickly.

That was exactly my point. What makes the co2 referred valuable is not that it is co2. We literally (not metaphorically, or hyperbolically, but literally) are surrounded by the stuff every day of our lives.

What makes it valuable is that the co2 is concentrated and under pressure. But pretty much any gas would fit the bill.

And let's not forget, the original article was about MIT scientists making extracting co2 from the atmosphere "more efficient". Which, as you point out, is a rather hopeless quest---in order to get the co2 back out of the atmosphere, you'd need more energy than you got from burning whatever put it there in the first place.

So making any meaningful dent in the atmospheric co2 by extraction/converting a mug's game. You'd need on the order of the entire amount of energy used by the human race during the entire industrial age.

Exactly my point. The original comment claimed that the co2 itself was valuable. It is not. What is valuable is that it is concentrated and under pressure.

How close to zero? 1 MWh at 100% efficiency is enough to convert 180 kg of CO2 to ethylene (note this only produces 51 kg ethylene). Annual excess carbon emissions are 36.8 trillion kg of CO2. At a cost of $0.10 per MWh, which is about 3-4 orders of magnitude lower than it currently is, that's still $20 Billion per year. A cheaper pathway is still going to save an incredible amount of money even if solar power got ridiculously cheap.

$20 Billion per year worldwide is chump change. But that's 3 or 4 orders of magnitude away eh ?

Turning CO2 into a stable feed-stock seems to be an important part of it, given that as the article says, we need to be processing gigatons per year.

If we’re just using our captured CO2 to extract more fossil fuels to burn, thats not nearly as big a reduction in atmospheric CO2.