this post was submitted on 16 Feb 2025
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Just checked the numbers, for those interested.
A gas power plant produces around. 200-300kWh per tonne of CO2.
Capture costs 300-900kWh per tonne captured.
So this is basically non viable using fossil fuel as the power. If you aren't, then storage of that power is likely a lot better.
It's also worth noting that it is still CO2 gas. Long term containment of a gas is far harder than a liquid or solid.
It's also way easier to just stop digging up coal instead of inefficiently trying to get the exhaust from burning it partially back underground.
Who says you power that thing with fossil fuels? The real way to do that is via giant nuclear reactors or reactor complexes.
Fission power can be made cheaper per MW by just making the reactors bigger. Economies of scale, the square cube law and all that. The problem with doing this in the commercial power sector is that line losses kill you on distribution. There just aren't enough customers within a reasonable distance to make monster 10 GW or 100 GW reactors viable, regardless of how cheap they might make energy.
But DACC is one of the few applications this might not be a problem for. Just build your monster reactors right next door to your monster DACC plants.
But then the power generated by those reactors is better used to power things that burn fossil fuel in a less efficient way or to simply replace the fossil fuel powered electricity generators...
Quebec transports its electricity over more than a thousand kilometers, surely distance from nuclear reactors isn't an issue if you build the infrastructure around it.
Only when the last carbon based power plant is close, we can see if there's energy left to waste on that capture carbon machine.
I'm sure the AI datacenters would have a few GW to spare if we put the LLMs on pause.
Solar and Wind are cheaper than nuclear now. The main problem is it's not sunny and/or windy every day. A carbon capture system doesn't need to be running 24/7 though.
If we build way more wind/solar than we use then the excess can dumped into things like this.
Sorry but the economics of nuclear just doesn't work for everything.
One of the interesting energy capture ideas I've seen with Solar and wind is based on kinetic potential energy in high-rise buildings. So you build a sort of heavy weight elevator that is elevated during windy and sunny hours and then it slowly gets released and gravity driven friction generating energy.
This coupled with solar windows and it's a pretty neat idea (not sure how viable though)
Edit: examples: https://spectrum.ieee.org/gravity-energy-storage-elevators-skyscrapers
This might work on the scale of a building to even out its own power usage throughout a day, but to make a difference on a city grid scale, you need an insane amount of height and/or weight.
Check out Pumped Water Energy Storage. It's the same concept but uses water as the weight. Doing the math on the Ludington Pumped Storage Power Plant's active capacity, it stores over 100 billion pounds of water.
There are 3 use cases I've seen.
Making fossil fuel power stations "clean".
CO2 recovery for long term storage.
CO2 for industrial use.
It's no good for the first, due to energy consumption. This is the main use I've seen it talked up for, as something that can be retrofitted to power plants.
It's poor for the second, since the result is a gas (hard to store long term). We would want it as a solid or liquid product, which this doesn't do.
The last has limited requirements. We only need so much CO2.
The only large scale use case I can see for this is as part of a carbon capture system. Capture and then react to solidify the carbon. However, plants are already extremely good at this, and can do it directly from atmospheric air, using sunlight.
Why wouldn't the device include or feed a compressor to liquidize the CO2? It takes just a little over 5 atm of pressure which is trivial.
You also need to sustain 5 atm, with no leaks for years. Where is it being stored, and who's paying for the maintenance? All it would take would be a bit of civil unrest, or corruption, and the work could be undone in mass.
The only DAC variant i could see working out is if it takes the CO2 from high-concentrated sources (such as portland cement factories) and transforms it into something practical, like liquid fuel or methane.
It could be leading to cheaper methane than from biological sources, because technological processes can have higher efficiency, and therefore lower prices.
Good luck building enough capacity in nuclear power to do that. Nuclear plants tend to be a lot more expensive and take a lot longer to build than anticipated.
Literally only in the US and Europe. Remove the profit motive and don't keep on inefficient construction companies and it's a quick process.
There's no profit motive for large scale carbon capture anyway, so big CC plants and big nuclear plants would need the same political will.
Can you point out a nuclear project that was a quick process? How would removing the profit motive make it quicker?
Sure, China. You can build a nuclear power plant from dirt to operation in 6 months. Not 10 years plus infinite overages, 6 months.
If there's not a perverse profit motive at every stage and instead people are rewarded for getting the job done and getting the job done right, you end up with high quality fast engineering.
Yes, it works as a "plan B" (along with many other things).
Don't loose hope. We can still win. Keep pushing for producing less CO2.
You would presumably capture the carbon using excess solar and wind power, which is also the cheapest power there is, sometimes going negative
Is your capture number including the cost of liquifying the CO2 for storage?
We already have solar powered carbon sequestration systems, that require almost no maintenance over a period of a couple of hundred of years of operational life...
Trees.
Until they burn or rot and release the carbon back into the air
Also trees only grow where trees grew in the past, so growing new forests will only capture the carbon that was released when the old forest there was burnt or cut
Decomp still sequesters carbon.
Sure, burning them releases a portion back, but not most of it..
What do you think comprises ash?
If you want to capture the most of the carbon, you cook the wood in an oxygen free environment turning it to charcoal and liberating volatile components (which could be used as carbon neutral fuel to run the furnaces)
Nothing can eat charcoal, so it could be stored cheaply
If you want to capture the CO2 from fossil fuel, it feels like it'd be easier to filter it out before dumping it in the atmosphere in the first place (apart from the obvious option of just not using fossil fuel)
It would, but it takes more energy that gets produced total. You're spending 300wKh to make 220kWh of electricity.
Is that using numbers for carbon capture from the atmosphere? Carbon capture directly on the exhaust of a fossil fuel power plant would probably be an order of magnitude more efficient. Obviously you can't sustain everything by only using fuel combustion, but you could probably reduce to total emissions per kWh quite a bit without even looking at renewables.
So power it with solar/wind?
You could just replace the power plant with solar/wind and it would be cheaper
What power plant? We're talking about powering a carbon capture plant. If you do that with close to zero emission power, what's the downside?
Worst case is that they realize that the carbon capture plant is inefficient and you still have wind power.
Right but the carbon capture uses more power to capture the co2 than the power plant uses to produce it. So if you replaced said power plant with renewable energy instead of using three times as much to capture the carbon from the original plant, it would net the same result.
Essentially carbon capture makes no sense until you’re at the point that carbon capture requires less energy to capture carbon than to produce it
Co2 is liquified before storage.
And how do you plan to keep it liquefied, on a large scale, for 100s of years? It's currently done using pressure vessels amd chillers, that require maintenance etc.