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While you are right that capturing the carbon dioxide can be done with relatively little energy, that is not what the article is about. If you capture it, you e

While you are right that capturing the carbon dioxide can be done with relatively little energy, that is not what the article is about. If you capture it, you end up with tons and tons of waste, essentially as much as the fuel you burned, what are you going to do with it? The article is about [...] converting CO2 into useful products [...] so that you do not end up with waste but useful products and the requires as much energy as you got from burning the stuff, at least to a first approximation, you would of course not try to recreate the exact same stuff you just burned. If you capture the carbon dioxide, then for every supertanker full of oil you burn you need to permanently get rid of a supertanker full of liquid carbon dioxide. This is of course a project of insane scope given that we burn billions of tons every year. So in order to not have to deal with the waste, what if we just turn it into something useful that people will pay for? Because that costs a lot of energy, the energy we just extract. And now you want to put it back in? To get back what you just burned or at least something similar that you could almost certainly produce more efficiently directly from the oil?

toss1 2y ago
OK, yes, building larger-molecule more-useful-stuff will take more energy, and I'll go with the first approximation that it's a similar quantity of energy re-input (some useful things less, some more). And yes, all that product will take substantial volume. Thx for clarifying. That said, it still seems an extremely useful measure, even if we keep using only single-digit percentages for long-use plastics instead of hydrocarbon fuels. Let's assume that for the next century or so a bunch of applications will continue to require the convenience and energy-density of liquid hydrocarbons. In order to avoid extracting more and further increasing CO2 levels, we'll have to input significant energy to reconstitute them from CO2. Obviously, inputting that energy from more fossil fuels defeats the purpose, but using renewables will work; and now they are even cheaper energy inputs. The result would be a cycle of newly fabricated hydrocarbon fuels, which can be custom-optimised for each application. No new CO2 would enter the atmosphere and the existing levels would be reduced by the amount of hydrocarbon fuels (and plastics, etc.) fabricated and in existence throughout the entire chain of existence, fabrication, storage, distribution, transport, in-vehicle, right up to the moment it is burned. With cheaper renewable energy inputs and optimized custom fabrication, it would likely get cheaper than the existing drill/pump/transport/refine process. And, it's permanently sustainable, and as liquid hydrocarbon fuel use declines, custom production can be converted to storable materials.
- danbruc 2y ago
  Totally agree, it makes sense to use renewable sources to produce hydrocarbons from the air, whether to burn them or for chemical products. But to significantly remove carbon from the atmosphere as suggested in the article it makes no sense.

toss1 2y ago

OK, yes, building larger-molecule more-useful-stuff will take more energy, and I'll go with the first approximation that it's a similar quantity of energy re-input (some useful things less, some more). And yes, all that product will take substantial volume. Thx for clarifying. That said, it still seems an extremely useful measure, even if we keep using only single-digit percentages for long-use plastics instead of hydrocarbon fuels. Let's assume that for the next century or so a bunch of applications will continue to require the convenience and energy-density of liquid hydrocarbons. In order to avoid extracting more and further increasing CO2 levels, we'll have to input significant energy to reconstitute them from CO2. Obviously, inputting that energy from more fossil fuels defeats the purpose, but using renewables will work; and now they are even cheaper energy inputs. The result would be a cycle of newly fabricated hydrocarbon fuels, which can be custom-optimised for each application. No new CO2 would enter the atmosphere and the existing levels would be reduced by the amount of hydrocarbon fuels (and plastics, etc.) fabricated and in existence throughout the entire chain of existence, fabrication, storage, distribution, transport, in-vehicle, right up to the moment it is burned. With cheaper renewable energy inputs and optimized custom fabrication, it would likely get cheaper than the existing drill/pump/transport/refine process. And, it's permanently sustainable, and as liquid hydrocarbon fuel use declines, custom production can be converted to storable materials.

danbruc 2y ago
Totally agree, it makes sense to use renewable sources to produce hydrocarbons from the air, whether to burn them or for chemical products. But to significantly remove carbon from the atmosphere as suggested in the article it makes no sense.