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Comment by gigatexal | Hacker News Reader

Could you “clean the air” by creating many such breaks and having it pull co2 out of the air?

Technically yes, but practically no.

It'd be a very inefficient and slow way to "clean the air. The materials still need to be invested with whatever energy (e.g. glucose) is going to be consumed by the process, and once it finishes you're stuck with some hardened inert lumps which may not be cheaply recycle-able.

Pound of cure, ounce of prevention -- the cheapest and easiest way to clean the air is top stop putting schmutz in it.

That said, if you're really interested in using biotech to pull carbon out of the air, probably the best approach involves reusing existing plant or algae species. and simply harvesting them to bury in such a way that they won't be uncovered for a couple hundred million years.

After all, they're far more robust, feature-packed, and battle-tested than any grey-goo we can make for ourselves in the near future.

> probably the best approach involves reusing existing plant or algae species. and simply harvesting them to bury in such a way that they won't be uncovered for a couple hundred million years.

As a bonus, you're helping out a future civilization by seeding their oil reserves. Talk about paying it forward...

Maybe that's what happened last time.

As far as I’m aware, plants are fairly inefficient at absorbing carbon from the atmosphere.

It’s conceivable a process could be created that pulls carbon from the atmosphere more efficiently while not hsving to deal with all the other mess biological live entails.

It’s also possible you’re right, this isn’t possible, and biological life is the best we’ve got.

As a thought experiment, we release 40 billion tons of co2 per year. An average skyscraper weights around 250,000 tons. So that would be the equivalent of 160,000 skyscrapers worth of this stuff. Hong Kong has the most skyscrapers current at 317. So it would be the equivalent of building the skyscrapers for a city that is 500 x the size of Hong Kong every year.

Not that you'd have to build skyscrapers with the material, but just to put this idea in some sort of perspective.

Skyscrapers are mostly empty space inside. The Great Pyramid of Giza weighs about 6 million tons, so we’d be producing about 7000 of them annually. Maybe we could just plop them all in the ocean? ;)

I'd probably mess up the arithmetic, but I wonder how many skyscrapers or Great Pyramids could be packed in a volume of 1 cubic mile. That's how much oil we use per year.[0] (All sources combined are equivalent to about 3 cubic miles of oil.)

It would be nice to find a way to bump that up a couple orders of magnitude without actually pulling that much oil/equivalent out of the ground, since there literally isn't enough there.

[0] https://en.wikipedia.org/wiki/Cubic_mile_of_oil

Start with a Great Pyramid of Giza, or locally sourced substitute following the traditional recipe [1]:

  * 5.5 million tonnes of limestone
  * 8,000 tonnes of granite
  * 500,000 tonnes of mortar

For a simple approximation, we ignore ingredients that are not limestone.

mass of limestone in great pyramid of giza

  = 5.5 * 1e8 kg of limestone

Volume of limestone in one great pyramid of giza, assuming medium-high density limestone at 2500 kg / m^3 [2]

  = 5.5 * 1e8 kg / (2500 kg / m^3)
  = 2.2 * 1e5 m^3

allegedly there are 4.168e+9 m^3 cubic metres per cubic mile. That gives about 19,000 great pyramids of giza per cubic mile.

[1] https://en.wikipedia.org/wiki/Great_Pyramid_of_Giza#Material... [2] http://www.natural-stone.com/limestone.html

edit: when i try to estimate by geometry from the pyramid dimensions, instead of by density, i end up with about 2,000 great pyramids of giza, but that's without trying to understand what the volume of a pyramid actually is, because i am not clever enough to do that.

Intuitively, isn't the volume of a pyramid going to be 1/3 of that of a prism with the same width/length/height?

Pass 1: culture a huge amount of spinachs that pull co2 out of the air

Pass 2: distroy this plants releasing co2 again in the air to obtain chloroplasts from the upper half of the creature. Set free again the co2 saved in roots. (Alternatively pick only leaves from the spinach).

Pass 3: use this chloroplasts to recover a part of the co2 released in the pass 2

Pass 4: ... D'oh!

> In ongoing and future work, the chloroplast is being replaced by catalysts that are nonbiological in origin

The next question is how much CO2 will be released during the manufacturing process for these catalysts.

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