Is Capturing Carbon from the Air Practical? | Hacker News Reader

Is Capturing Carbon from the Air Practical?

technologyreview.com

30 pointsmrfusion60 comments

“Once capturing carbon from the air is profitable, people acting in their own self-interest will make it happen,” says Chichilnisky.

This is the key to the entire article.

The conversation shouldn't be around the practicality of capturing carbon from the air, the conversation should be what is the most profitable way to reduce carbon in our air either through not putting it in the air in the first place or removing it cheaply after the fact.

This demands a more robust marketplace beyond CO2 for soda and oil wells.

"The idea is to first sell carbon dioxide to niche markets, such as oil-well recovery, to eventually create bigger ones, like using catalysts to make fuels in processes that are driven by solar energy."

I'm a bit worried that, because of weird locally-smart but globally-dumb incentives, we might see people consuming 1 KWh to capture a unit of CO2, but the generation of 1 KWh puts more than 1 unit of CO2 into the atmosphere.

I'd like to see the numbers.

EDIT:

The worst coal emits 2.18 pounds of CO2 per KWh.[1] As little as 917Kwh of energy puts a ton of CO2 into the air.

They say that can do it for "$15 to $50 a ton". How much of that is energy costs? $50 buys 500KWh, so even if you used coal to operate it, it would net remove carbon from the air.

I'd still like to see a plant using nuclear energy to change CO2 into fossil fuel, though.

[1] http://www.eia.gov/tools/faqs/faq.cfm?id=74&t=11

That would be an effective way to arbitrage the cost of carbon which isn't externalized on the power plant. However I don't think it would come to that. I'm surprised the SRI effort isn't recovering the CO2 (they claim to be venting it). After all if they really do think they can get $100 a ton for it and make it at $50 a ton, that would at least offset some of their research costs.

The conversation shouldn't be around the practicality of capturing carbon from the air, the conversation should be what is the most profitable way [...]

No, money should play no role. It is obviously easier to reduce CO2 emissions if it is profitable but there is - at least in theory - nothing that prevents governments from just demanding the reduction even if it will increase the price of products or services. In practice you will of course have to deal with businesses just moving to where nobody cares and the like but that does still not mean that money should be an important factor.

Reducing carbon emissions does not affect profitability because emitters don't pay for them; they are 'externalities', if I remember my economics correctly. Put the cost on their balance sheets and reducing carbon emissions will become profitable.

If you dump a ton of solid toxic sludge in my back yard, ruining my back yard, and you will pay to clean it up. Dump a ton of gaseous toxic sludge in the atmosphere, contributing to a global catastrophe, and you don't pay a dime.

Ignoring the morality of it, it seems like simple responsibility: Why is everyone else suffering from and paying to clean up their mess? Sea walls, forest fires, water shortages, etc. etc. Taxpayers are paying to clean up the mess made by the emitters.

Because neither party wants to write off the coal states.

There is still a Coasean way out: offer those states money to not burn their coal.

"This demands a more robust marketplace beyond CO2 for soda and oil wells."

The only permanent solution is sequestering the carbon deep underground (depleted oil/gas fields or saline aquifers). Most CO2 "utilization" cases (including production of biofuels) merely delay the inevitable release of the gas into the atmosphere.

Sequestering CO2 for the sake of sequestering it does not pay though. In order for this to make sense, a carbon tax would likely have to be imposed (it worked in Norway, where Statoil has stored excess CO2 geologically for almost two decades now at the Sleipner field).

This statement from the article cautions us that the economic incentives (which are also reasonably well described in the article) so far aren't promoting technical fixes like the one proposed by the inventors: "None of the world’s thousands of coal plants have been outfitted for full-scale capture of their carbon pollution. And if it isn’t economical for use in power plants, with their concentrated source of carbon dioxide, the prospects of capturing it out of the air seem dim to many experts. 'There’s really little chance that you could capture CO2 from ambient air more cheaply than from a coal plant, where the flue gas is 300 times more concentrated,' says Robert Socolow, director of the Princeton Environment Institute and co-director of the university’s carbon mitigation initiative."

When I hear about plans to capture CO2, I wonder immediately about whether those plans will help enough if other gases (for example, methane) play a significant role in greenhouse effects. We may have to sequester more than one gas, in more than one way, to role back the accumulation of greenhouse gases already in the atmosphere, if that is considered a desirable worldwide goal.

That's true, I've heard that methane is much worse than CO2. I wonder if methane can be pull out of the air?

Since methane is worse than CO2, it's actually better WRT the greenhouse effect to burn it and produce CO2 + water. Water's also a potent greenhouse effect contributor, but the atmosphere's already saturated with it, so the excess will just rain back down.

Here's an interesting site found through Google:

http://www.bbc.co.uk/climate/evidence/methane.shtml

Wouldn't extra water vapor end up as clouds and reflect sunlight away from earth?

The atmosphere water content is self-regulating, since it works as a cycle (water evaporating, condensing and raining down, with the atmospheric content mainly regulated by how much vapor the air can hold). Not so with CO2. There is no similar "excess" threshold for CO2 after which it would "rain down".

As the poster above mentioned, Methane has a greater immediate impact, but it only stays in the atmosphere "for 11-12 years"[1], making it a relatively short term problem. CO2 stays in the atmosphere for "approximately 100 years"[2].

1: http://www.bbc.co.uk/climate/evidence/methane.shtml 2: http://www.bbc.co.uk/climate/evidence/carbon_dioxide.shtml

How about the idea of building a giant "freezer" in the coldest part of Antarctica and sublimating the CO2 out of the air? Some places already hit that temperature naturally [1]

[1] http://news.nationalgeographic.com/news/2013/12/131210-colde...

It isn't a high enough proportion of the atmosphere to be an effective strategy (also, you mean precipitate out of the air; sublimation is the process where a solid becomes a gas).

We talked about it before:

https://news.ycombinator.com/item?id=7174246

I linked this article, which discusses somebody actually testing the partial pressure explanation in a lab freezer capable of maintaining those low temperatures:

http://wattsupwiththat.com/2009/06/13/results-lab-experiment...

Wow, you're right. We already had this conversation :-)

Ok, so let's assume you're right about this. According to that chart, at a partial pressure of 0.0004 atmospheres the precipitation temperature would be around -140C. And nature is still doing a lot of the work of getting us to that point at -93C.

So the question becomes is cooling air from -93C to -140C an efficient means to capture CO2?

It surprising how little plans for fixing global warming are discussed. Most of the discussion deals with preventing global warming by reducing carbon dioxide emissions, which is of course something we need to do.

But if we agree that there's already too much CO2 in the air, why not figure out ways to remove it or otherwise prevent further damage?

The CO2 content of the exhaust from a coal-fired power plant is (fortunately) many orders of magnitude higher than what's found in the atmosphere. It would be much cheaper to capture it at the source. But even that is still considered too expensive, which is part of the reason we don't see many large-scale carbon capture and storage operations popping up.