Comment by semi-extrinsic | Hacker News Reader

Comment by semi-extrinsic | Hacker News Reader

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> Capturing carbon is a valuable step, but only as part of a process that net removes it from the atmosphere.

The IPCC, the IEA, and a boatload of scientists disagree. We cannot prevent catastrophic global warming without doing the type of CCS you describe as useless. Sure, we also want to be doing stuff that's net carbon negative, but that's a long way into the future.

And CCS from power generation is only one aspect. CCS from cement plants, steel furnaces etc. is another thing we need - those processes will inherently emit large amounts of CO2 even if electric power is 100% renewable.

Finally, when it comes to capture from air, I think stuff like "biomass -> syngas -> water shift -> separation of CO2 captured and stored, H2 produced for energy" is much more likely to be successful, because you can make it net CO2 negative and it produces something valuable as a byproduct. Capture from air is a whole 'nother matter, starting from a very low CO2 partial pressure and thus very inefficient.

(I work in CCS, happy to answer questions.)

> Sure, we also want to be doing stuff that's net carbon negative, but that's a long way into the future.

Isn't refusing emitted carbon (net negative) the entire point? That wouldn't be an "also" then, and newfangled ideas that don't give such a result are nothing to be excited about.

Seems to me capturing from the air is a wholly separate matter, whereas capturing at the source (i.e. power plant) should be the focus.

I guess "net negative" can be interpreted different ways. I was thinking of "net negative" to mean "capturing CO2 that's already been emitted", as opposed to "capturing CO2 before it is emitted in the future".

I agree any CCS scheme must be "net negative" in the sense that it doesn't produce more CO2 than it captures. But all the technologies in the pipeline today fulfill this.

How effective is carbon capture? Are we talking 30% less carbon? 99% less carbon? somewhere in the middle?

How much cost does it add to a typical coal plant? How does that compare to new solar installations?

Is carbon capture tech renewable? I.e. does it depend on some finite chemical material?

Is carbon capture feasible in smaller scales? E.g. can we stick a carbon capture system on a car?

> How effective is carbon capture? Are we talking 30% less carbon? 99% less carbon? somewhere in the middle?

Usually this is something you can tune to optimize your total system and the cost of capture. But typical requirements are >90% CO2 captured, often you see >95% or even 99%.

> How much cost does it add to a typical coal plant? How does that compare to new solar installations?

IIRC the target for something like a coal plant is getting below $100 total cost per ton of CO2 captured, transported and stored. Usually that's calculated summing up CAPEX paid down over some time span, plus OPEX, plus the price you pay someone else for taking the CO2 and storing it. To put that into perspective, if you pass this cost directly on to the consumer, it would correspond to almost doubling the price of electricity. Usually some form of government subsidy accounts for this price increase.

> Is carbon capture tech renewable? I.e. does it depend on some finite chemical material?

Depends very much on the tech. Broadly, we can split into four categories: solvent-based, adsorbent-based, membrane-based and liquefaction-based. E.g. for membranes for H2/CO2 separation, palladium is a key ingredient, which is hardly renewable (but we're not exactly running out tomorrow).

> Is carbon capture feasible in smaller scales? E.g. can we stick a carbon capture system on a car?

On a car? No. I've heard it discussed for diesel locomotives, anything smaller than that your CAPEX and OPEX are so high it makes much more sense to either go electric, or do "pre-combustion" capture, such as converting natural gas into CO2/H2 in a big plant and separating out CO2 while distributing H2 for use in cars.

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