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Comment by simonblack | Hacker News Reader

And where do you put it? A billion tons of CO2 doesn't convert to nothing. A ton of CO2 will convert to several tons of non-gaseous product like (say) calcium carbonate.

For the sake of illustration:

    CO2 -> CaCO3
    44  -> 100     (molar numbers)

so one ton of CO2 gives you just over 2 tons of calcium carbonate. Extrapolating that to roughly 35 gigatons of CO2 per year means that we would have to find somewhere to put about 80 gigatons of calcium carbonate per year.

That's a mountain range per decade. :)

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I like converting it to soil and wood. Forests and grasslands store hundreds of gigatons of carbon. It can't just be planting trees, it has to be cultivating rich ecosystems: the more living things the better.

I've been converted by Charles Eisenstein's book "Climate: a new story" - he makes a strong case that we're only obsessed with carbon because we don't have good ways of measuring anything else, and that while of course the greenhouse effect is real, the negative effects of climate change including unpredictable weather and stronger storms can be mitigated by restoring forests, coral reefs, marshes, barrier islands, anything that lives will act as a buffer to fast changes in weather.

There's some good stuff in there too explaining the feedback loops between life and the weather, such as forests releasing aerosols that act as cloud seeds that bring moisture toward the forest.

Wood is carbon neutral, not carbon negative. Trees take carbon out of the air and produce wood. When they die and decompose or burn, the carbon is released back into the atmosphere. Oil in the ground was produced during a time that wood was so abundant it almost suffocated the surface of the earth because nothing could decompose it. Somehow, brining all that oil back to the surface and turning it back into wood doesn’t seem like a good idea.

if you build with the wood then it doesn’t burn or decompose (yes, eventually, it will burn or decompose, but the more buildings on earth made of wood at any one time is carbon that isnt in the air.)

Eh if you keep it dry, it can hold it for a few hundred years. Permanent sequestration is ideal, but we’re really trying to minimize the area under the excess carbon curve in the near future to buy some time, so even shorter term stuff can be helpful. Reduction of excess carbon-ton-years is the way to think of it, IMO.

If the wood is converted to syngas and biochar through gasification, the biochar is chemically inactive in the soil for thousands of years. The syngas can be used as an energy source.

Bogs are actually great sinks of carbon, all of the biomass created in the bog will sink below the waters surface and remain inert.

> during a time that wood was so abundant it almost suffocated the surface of the earth because nothing could decompose it

I believe this is no longer the consensus for the large coal deposits of the Carboniferous: https://www.pnas.org/content/113/9/2442

Honestly, you can do a similar calculation for things like trees and algae. But the thing is that we didn't get that carbon from thin air in the first place. We dug it out of the ground. I'm not sure how much we mine every year, but I wouldn't be surprised if we mined a "mountain range" per decade.

Also I think your mountain estimate is off. Mt Everest is 158.76 gigatons (~350e12 lbs). I don't think this detracts from your point (that's a TON of mass each year) but I thought I'd make the correction. I mean we're still talking half an Everest every year.

For reference, I did also find a source that says we mine between 32 and 50 billion tonnes of aggregate (sand and gravel) every year. So maybe 80 isn't that bad?

Ideally in the ocean, solving the acidification problem at the same time.

This is a weird argument because it’s not like CO2 is being produced from thin air (heh). Most of the CO2 we produce comes from fossil fuels stored deep inside the earth or inside literal mountain ranges. We can put it back there. Mountain top addition instead of mountain top removal.

Naïve take, just use it? Even if it ends up back there by escaping as a gas, better that it was 'used' in carbonation or for some other purpose than merely converted to something storable?

Or do the quantities just not work out, and (to the non-naïfs) that's too obvious for words?

Quantities do in fact not work out.

Hundreds of gigatons of carbon require removal from the atmosphere and/or oceans.

Ok. Obviously 1e11 tonnes is 'a lot', I just have no handle on how much is used in food production etc.

As a very rough first approximation, a person consumes 1 million food calories (kilocalories) per year. As carbohydrate, that's 4 cal/gram. Total population is about 8 billion.

8 billion cal * 1 million / (4 cal/g) / 1 million g / tonne = 2 billion tonnes net carbohydrate

That's a rough estimate (carbohydrate is neither pure carbon nor CO2, there is a humidity content) and undercounts total ag production (animal protein consumes a large amount of input feed for a much smaller amount of protein) , but gives a rough order-of-magnitude sense: 1e9 tonnes food vs. 1e11 tonnes net emissions.

FWIW, Our World in Data gives 2.7 billion tonnes net cereal production in 2018:

https://ourworldindata.org/agricultural-production

Total global live biomass is on the order of 550 billion tonnes:

http://www.pnas.org/content/early/2018/05/15/1711842115.full...

(via: https://en.wikipedia.org/wiki/Biomass_(ecology))

That does put it into perspective, thanks. To be clear though I meant CO2 used as gas in (for example) food processing, rather than somehow converting it back into other carbon forms and ultimately carbohydrates in the foods themselves.

Keep in mind that a gas is roughly 1000x larger than an equivalent solid mass.

So take all the food grown on Earth in a year, multiply it 100x, and multiply that 1,000x, to come up with the volume of gas you'd be dealing with sequestering somehow.

Gas doesn't like being sequestered, less so for hundreds or thousands of years. (Natural gas formations are interesting accidents of geological history in which sufficient source material, methane conversion of that material, and a geological substrate in which that gas is trapped in the earth, all coincide.) There's also the fact that eventually re-introducing that gas to the biosphere is probably beneficial (on the order of tens to hundreds of millions of years), as biologically-active carbon is weathered out of the system (though solar irradiance will also be increasing over this period, and by various accounts, the happy music stops in about 800 million to 1 billion years).

It really is difficult to convey the volumes of resources humans use on an annual basis. Vaclav Smil's books on the topics of energy and material resource uilisation are highly recommended, especially Making the Modern World:

https://www.worldcat.org/title/making-the-modern-world-mater...

You'd want to reduce it and convert it to some organic solid. When that becomes remotely economical it will likely compete with crypto mining as a use for spare electrical power and won't need further incentives.

Vegetative growth and forests are long-term carbon sinks, even though they reach a carbon neutral equilibrium once matured.

I'm not convinced that forests are carbon neutral, once they are mature they can continue to support ecosystem growth where more and larger animals can exist: keystone species are made out of carbon too ;)

Australia.

Put it in Diet Coke. I usually drink a can or two every day.

I mean, to me this seems like a minor concern. There are tons of places on earth that are essentially a whole lotta nothing. I mean, have you ever driven east-to-west across Texas?

We don't need to put it anywhere though? Trees can live for a long time.

If we did plant a hundred trees and the average age of a tree is even 50 years. It gives us 50 years to workout what to do next.

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