CO2 "magic bullet"

It is easy to scrub CO2 out of air. What is hard is to do it in such a fashion that it is worth while doing it. Lord knows how much energy it takes to separate the CO2 from the calcium carbonate each time around.

It sounds like an April 1st joke that has run a little late to me.

Very possibly. The only way it makes any sense is if the process uses a lot of off-peak electricity (from nuclear for example) that's otherwise difficult to store.

Why not justs use nuclear power instead?

There is an existing cycle used in at least one carbon capture and recovery pilot, IIRC it involves amines. And it will certainly need significant energy input for "regeneration", but I haven't seen the figures.

They talk about "hydroxide", since they claim scrubbing the CO2 results in chalk, I had assumed calcium hydroxide, but it seems they use sodium hydroxide, so how do they get to chalk?

I assume the full process under discussion is:

1. burn gas to make electricity
2. use the chemical process powered by nuclear power to mop up the CO2 created by stage 1

I think we can both see that some simplification is possible. :)

Wikipedia

The BBC seems to have a 2nd page on the magic bullet, gives a bit more detail, and comes up with a price of $100/tonne for CO2 removed

Try this:

Na3Co3 + Ca(OH)2 --> CaCO3 + 2NaOH

CaCO3 + heat --> CaO + CO2

CaO + H2O --> Ca(OH)2

Air containing the CO2 is scrubbed with sodium hydroxide solution, to give a solution of sodium carbonate. The sodium carbonate solution is then reacted with slaked lime in water to precipitate calcium carbonate (chalk) and regenerate the sodium hydroxide solution, which is used again. The calcium carbonate is then heated to about 900 -

Presumably some of the heat used to calcine the calcium carbonate can be recovered from the slaking process.

Presumably it works on the pilot scale set-up they have. All you need is energy to make up the difference between that used to calcine the calcium carbonate and that recovered in the slaking process. How much energy, and where it comes from, is another matter.

If it's so good, why hasn't this process been adopted for CCS of CO2 from coal-fired power stations, rather than pratting about with amines? Possible answer - it isn't that good?

For Co3 read CO3. It's not using cobalt!

Back of envelope sum suggests coal thermal energy content is about 6 MWhr/tonne. So electrical content a little over 2 MWhr/tonne. With wholesale electricity prices around £50 / MWhr this means turning coal into electricity gives a revenue of around £100 per tonne, ignoring plant costs. (ISTR from CEGB days that 90% of the cost of electricity was the fuel).

So if you get your CC energy from coal you get little net benefit even if their "cost" figure is right. I realise that gas gives you a bit more thermal energy per tonne of carbon, and you get higher conversion efficiency with CCGT.

But it still illustrates the point that carbon sequestration is going to be *very* expensive. Thank goodness renewable energy is cheap.

odd that so many don't realise it's fundamentally pointless at best.

The heat from the slaking process might just about give you 150C, far short of the calcining temperature. Second law rules.

I am pretty sure this is where the amine process scores. I did see a description of the chemistry some time ago, but I couldn't find details from a quick look. My vague recollection was that they released the carbon dioxide at something like 250 C.

Drax has a system that can capture a ton of carbon a day from the biomass burners. In the good old days the 2000 MW coal fired stations were burning the best part of a ton of coal a second.

Big Oil & Big Coal are to invest $68M in the process

Virue signall;ing crap.

They know perfectly well that it will never be a practical solution.

It will reduce the net energy outpout of power strains to about zero

Yes a couple of years ago somebody was supposed to have made paving and road material that absorbed co2 and major pollutants. However if it were that good one might imagine it would be in use widely by now. I think the drawback as with most of these ideas was that laying a new set of paving every five years and then finding a way to dispose of the toxic waste of the old ones might make it a bit of a non starter. Add to that apparently they were only made in Yellow and turned a dirty grey when no longer doing their job.

Its a bit like all those wonderful inventions we used to see in Tomorrows World, like the spray which meant you could safely use power tools underwater. Brian

Yes indeed but one thing is for certain, it would be, I reckon possible to engineer plants to produce a lot of growth and give out oxygen. That would work, but then what do you do with all that plant growth. If you uses it as fuel then its putting co2 back surely? Been a lot of science fiction stories written about genetically engineered plants that do this getting away and taking over from all our food crops. Brian

Seems like that's about pumping the captured and driven-off CO2 into nearly depleted oil wells to get the dregs out ...

One option is to put right the mistakes that nature made in classic photosynthesis (which evolved in a reducing atmosphere) so that it goes well beyond C4 efficiency. Laboratory specimens have already been done where the biomass accumulation is way better ~40% than natural plants.

Another group independently have got a 15% improvement using a different approach.

The technology is most likely to get used in food crops or forestry.

If you could cycle the same carbon through biomass again and again using sunlight and plants to make fuel then you would be onto a winner.

The article looks to me like a magic boulder of the sort that used to fall on Captain Kirk on Star Trek. No substance and made of polystyrene.