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> start from CO2 Why would that route even be taken though? Biofuel for jet engines is proven technology in limited use for many years now. Let plants deal w

> start from CO2 Why would that route even be taken though? Biofuel for jet engines is proven technology in limited use for many years now. Let plants deal with the CO2, since they're good at it, then process the resultant vegetable oils to produce a suitable diesel or jet fuel. https://en.wikipedia.org/wiki/Aviation_biofuel https://en.wikipedia.org/wiki/Aviation_biofuel

avmich 6y ago
> Let plants deal with the CO2, since they're good at it They aren't good with it at all. Convert CO2 slowly, take space to do that, take other resources like fertilizers, require some shielding from pests and herbs, can produce massive fires... They have advantages, but it's not a silver bullet, especially when you're in a hurry.
- liability 6y ago
  I believe popular proposals involve the use of algae. Regardless, farming in general is something modern civilization already has a strong competency in. Synthesizing jet fuel from scratch might make sense for the USN since they have nuclear reactors and all the water they want, but I think it's fair to say our civilization in the general case struggles with generating huge amounts of clean electricity. Plants do it with solar energy on a scale we should be jealous of. And so what of they take a few months to do it? They take that long to grow the food you eat too and it's not like you starve for months waiting for them.
  - jabl 6y ago
    Society uses absolutely mind-gobbling amounts of energy, mostly from fossil fuels. There's just not enough land available to produce even a significant fraction of that from biofuels. Never mind the ecological devastation that would be caused by converting the little wilderness left to intensive biofuel cultivation. That is not to say biofuel don't have a role to play. Agriculture and forestry wastes, municipal biowaste, etc. can all be used for energy. And yeah, it makes sense to use the available biofuel for sectors that are otherwise very hard to decarbonise, such as aviation. Algae, well, that has been researched for decades with very little to show for it. It has great potential, but it seems very difficult to make it actually work.
    - liability 6y ago
      But this is my point; biofuel makes a ton of sense for aviation. Biofuels would be used in cases where there is no realistic alternative, particularly with airplanes. It's more practical and likely to succeed in this domain than hydrogen, and isn't a total pipe dream like battery powered planes. In other domains, like grid power or automobiles, solar/wind/etc are the way to go (I never suggested we run power plants off biofuel!), but there is still a fuckton of coal and natural gas plants that need to be replaced. Trying to also replace jet fuel with synth fuel at the same time will only set back efforts to close coal and natural gas plants. If we already had a surplus of clean electrical energy then things would be different, but we don't. Every solar farm dedicated to the production of synth fuel is a solar farm that isn't replacing a coal plant. I just don't see any way that synthesis of jet fuel from atmospheric carbon makes any sense for anybody but a nuclear Navy.
      - Hypx 6y ago
        The problem is twofold: The first is that biofuel doesn't scale. Maybe if we shifted all biofuel production to aviation we could do it. But the market is growing over the long term. Which means biofuels will eventually stop being a solution. The other problem is that biofuel isn't actually all that green. It still needs lots of fertilizer, pesticides, farm equipment, etc., that ultimately gives it a relatively high GHG output. At some point, we need to bite the bullet and go with hydrogen or one of its derivative fuels (e.g. ammonia, methanol, etc.). People are constantly trying to imagine a solution that avoids this outcome, but no one has come up with anything that looks like a viable alternative.
- ncmncm 6y ago
  Maximum efficiency of 2%. Even the worst electrolysis driven by cheap solar does better.
  - liability 6y ago
    You've forgotten that we have a limited capacity for solar cell production and those solar cells are put to better use replacing coal plants than synthesizing something plants can synthesize.
    - ncmncm 6y ago
      Biofuel is just very, very expensive. The only reason it is used at all is heavy, heavy subsidies, often connected with corruption. (Cf. Archer-Daniels-Midland.)
      - liability 6y ago
        And hydrogen or synth fuel aren't expensive? If these alternatives weren't more expensive then the problem would be moot because the industry would be voluntarily using them already.
        ncmncm 6y ago
        They have always been more expensive than petroleum, and anyway would be made with power generated from petroleum or coal, or (in the case of hydrogen) from natural gas. But that was before solar and wind became substantially cheaper than petroleum.
ganafagol 6y ago
> Let plants deal with the CO2, since they're good at it, This is never going to happen at the necessary scale. Where do you want to put all those plants? The planet's land area that is suitable for agriculture is already being used for food production. Well, apart from a few areas with natural reserves but you really don't want to touch those if you care about the environment. And if you don't then the whole clean energy topic is not for you anyway. Sure some areas can be made a bit more efficient, but that's never going to be enough.
Symmetry 6y ago
Biomass fuel production averages 1 watt per square meter compared to the 100 watts per square meter that solar power gives. Before fossil fuels civilization was in many ways energy constrained, forced to make harsh tradeoffs in how much land was devoted to forests for heating/iron production and how much to farmland for food.
Qwertious 6y ago
Speaking generally about biofuel, it's a terrible idea - it's taking farming output and turning it into fuel, which is a bad idea because 1) it's unreliable and climate-dependent, and 2) we're basically just turning oil into plants and then turning the plants back into oil.

avmich 6y ago

> Let plants deal with the CO2, since they're good at it They aren't good with it at all. Convert CO2 slowly, take space to do that, take other resources like fertilizers, require some shielding from pests and herbs, can produce massive fires... They have advantages, but it's not a silver bullet, especially when you're in a hurry.

liability 6y ago
I believe popular proposals involve the use of algae. Regardless, farming in general is something modern civilization already has a strong competency in. Synthesizing jet fuel from scratch might make sense for the USN since they have nuclear reactors and all the water they want, but I think it's fair to say our civilization in the general case struggles with generating huge amounts of clean electricity. Plants do it with solar energy on a scale we should be jealous of. And so what of they take a few months to do it? They take that long to grow the food you eat too and it's not like you starve for months waiting for them.
- jabl 6y ago
  Society uses absolutely mind-gobbling amounts of energy, mostly from fossil fuels. There's just not enough land available to produce even a significant fraction of that from biofuels. Never mind the ecological devastation that would be caused by converting the little wilderness left to intensive biofuel cultivation. That is not to say biofuel don't have a role to play. Agriculture and forestry wastes, municipal biowaste, etc. can all be used for energy. And yeah, it makes sense to use the available biofuel for sectors that are otherwise very hard to decarbonise, such as aviation. Algae, well, that has been researched for decades with very little to show for it. It has great potential, but it seems very difficult to make it actually work.
  - liability 6y ago
    But this is my point; biofuel makes a ton of sense for aviation. Biofuels would be used in cases where there is no realistic alternative, particularly with airplanes. It's more practical and likely to succeed in this domain than hydrogen, and isn't a total pipe dream like battery powered planes. In other domains, like grid power or automobiles, solar/wind/etc are the way to go (I never suggested we run power plants off biofuel!), but there is still a fuckton of coal and natural gas plants that need to be replaced. Trying to also replace jet fuel with synth fuel at the same time will only set back efforts to close coal and natural gas plants. If we already had a surplus of clean electrical energy then things would be different, but we don't. Every solar farm dedicated to the production of synth fuel is a solar farm that isn't replacing a coal plant. I just don't see any way that synthesis of jet fuel from atmospheric carbon makes any sense for anybody but a nuclear Navy.
    - Hypx 6y ago
      The problem is twofold: The first is that biofuel doesn't scale. Maybe if we shifted all biofuel production to aviation we could do it. But the market is growing over the long term. Which means biofuels will eventually stop being a solution. The other problem is that biofuel isn't actually all that green. It still needs lots of fertilizer, pesticides, farm equipment, etc., that ultimately gives it a relatively high GHG output. At some point, we need to bite the bullet and go with hydrogen or one of its derivative fuels (e.g. ammonia, methanol, etc.). People are constantly trying to imagine a solution that avoids this outcome, but no one has come up with anything that looks like a viable alternative.
ncmncm 6y ago
Maximum efficiency of 2%. Even the worst electrolysis driven by cheap solar does better.
- liability 6y ago
  You've forgotten that we have a limited capacity for solar cell production and those solar cells are put to better use replacing coal plants than synthesizing something plants can synthesize.
  - ncmncm 6y ago
    Biofuel is just very, very expensive. The only reason it is used at all is heavy, heavy subsidies, often connected with corruption. (Cf. Archer-Daniels-Midland.)
    - liability 6y ago
      And hydrogen or synth fuel aren't expensive? If these alternatives weren't more expensive then the problem would be moot because the industry would be voluntarily using them already.
      - ncmncm 6y ago
        They have always been more expensive than petroleum, and anyway would be made with power generated from petroleum or coal, or (in the case of hydrogen) from natural gas. But that was before solar and wind became substantially cheaper than petroleum.

ganafagol 6y ago

> Let plants deal with the CO2, since they're good at it, This is never going to happen at the necessary scale. Where do you want to put all those plants? The planet's land area that is suitable for agriculture is already being used for food production. Well, apart from a few areas with natural reserves but you really don't want to touch those if you care about the environment. And if you don't then the whole clean energy topic is not for you anyway. Sure some areas can be made a bit more efficient, but that's never going to be enough.

Symmetry 6y ago

Biomass fuel production averages 1 watt per square meter compared to the 100 watts per square meter that solar power gives. Before fossil fuels civilization was in many ways energy constrained, forced to make harsh tradeoffs in how much land was devoted to forests for heating/iron production and how much to farmland for food.

Qwertious 6y ago

Speaking generally about biofuel, it's a terrible idea - it's taking farming output and turning it into fuel, which is a bad idea because 1) it's unreliable and climate-dependent, and 2) we're basically just turning oil into plants and then turning the plants back into oil.