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173 points rbanffy | 2 comments | | HN request time: 0.4s | source
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VyseofArcadia ◴[] No.42127346[source]
Time scale is also something I want to know about. "Can I remove CO2 from the air and turn it into something valuable in a way that is cost effective?" is one question. Another question is, "Can I remove CO2 from the air and turn it into something valuable faster than a tree?"
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danbruc ◴[] No.42128010[source]
I have not thought about this too carefully so I might be overlooking something. With that out of the way, a quick search indicates that we burn about 90 % of gas, oil, and coal for one purpose or another. Let's round this and pretend we burn it all. To undo this we will essentially need the same amount of energy again that we got out of it when we burned it, we would need to use all the energy coming from fossil fuels to undo burning them. Conservation of energy essentially.

Which makes it obvious that the entire idea is pretty pointless, burn fossil fuels to generate energy to then use it to unburn fossil fuels. To do it with renewable energy, we still need the same capacity as the fossil fuel capacity and when we have that - ignoring issues like fluctuations in renewable sources - it makes more sense to just use the renewable sources directly instead of using them to undo burning fossil fuels.

If you want to use the process to pull carbon out of the atmosphere, then you first have to replace all fossil fuels with renewable ones, then you can use additional renewable capacity to remove carbon. Add additional 10 % capacity to the world energy capacity to undo one year of carbon emissions every decade, at least to a first approximation.

To come back to the initial question, you essentially need an industry the same order of magnitude as the fossil fuel industry to have a meaningful impact. Not going to happen anytime soon.

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1. bryanlarsen ◴[] No.42135702[source]
If you can use the renewable energy directly, that's far better, but often you can't.

Synthetic hydrocarbons let you use renewable energy shifted in time, space, modality or avoid capital costs.

- applications that can't use batteries, like long distance plane flights

- applications where it's cheaper to spend 6X as much for fuel than it is to buy a new vehicle

- for storage more than a few days

etx

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2. danbruc ◴[] No.42137372[source]
Sure, if you capture carbon dioxide from the atmosphere to use it as a storage or transportation medium for renewable energy, that is perfectly fine. Trade some efficiency for overcoming some of the limitations of renewable sources like their variability or the difficulty to store electricity.

But that is not really carbon removal from the atmosphere, you take some out and later put it back. The article however frames the endeavor as removing carbon from the atmosphere, either the one we are currently burning or even the one we burnt in the past. Carbon removal by definition means we can not burn it later somewhere else, we have to permanently store it somewhere. There is no point in turning the carbon into some high quality product if we then just bury it somewhere, you want something cheap to make and easy to store.

As a non-fossile source for chemicals it makes sense but that is just a small fraction of our problem as we just burn most of the stuff.