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Could you ever grow enough crops on Earth to replace jet fuel at current usage, without starving everyone to death? I have no idea how to evaluate this. How rea

Could you ever grow enough crops on Earth to replace jet fuel at current usage, without starving everyone to death? I have no idea how to evaluate this. How realistic is it?

stephen_g 4y ago
I think it's a bad idea. But I saw a statistic saying the waste oil collected now could satisfy about 2% of the demand, and I think if we looked at thermal depolymerisation and hydroprocessing of other biodegradable waste we could possibly get up to a decent chunk, maybe 20-30%? If done with zero emissions energy that would be pretty carbon neutral. Not sure where we go after that for aviation, it's definitely one of the most tricky applications for alternate fuels. Maybe efuels would be next for some portion. Hopefully electric aircraft can eventually do regional short haul but I'm not holding my breath on energy densities getting competitive for that to take a huge chunk of aviation any time soon...
adrianN 4y ago
Since plants are very bad at converting sunlight to oil, I would assume that it will always be much more space efficient to use solar panels and synthesize the fuel. But there is waste biomass, including oils, that can supplement a small fraction of our energy demands with little extra effort.
sofixa 4y ago
I think the idea is to use waste cooling oil, meaning oil that was already used for cooking, then blended with whatever to make it more usable as jet fuel and reused. So it wouldn't be a waste of crops, but reuse of a waste product already manufactured and used for other things.
- rob74 4y ago
  That's nice in theory, but in practice most biofuels in use today are manufactured from food crops. So worries that producing kerosene from cooking oil might worsen the already existing food crisis are not completely unfounded. Related article from today: https://www.theguardian.com/environment/2022/jul/13/halt-use-of-biofuels-to-ease-food-crisis-says-green-group https://www.theguardian.com/environment/2022/jul/13/halt-use...
a-dub 4y ago
around fifteen years ago at the start of the synthetic biology boom, there was lots of talk of genetically engineered algae as a potential stand in for fossil fuels. i haven't heard much in a while so i'm guessing there were problems with it, but it always sounded like the most elegant of solutions to me....
- jabl 4y ago
  Algae fuels have been researched at least since the 1970'ies. In principle they are very promising, but it seems it's almost impossible to make these theoretical yield predictions work out in practice.

Could you ever grow enough crops on Earth to replace jet fuel at current usage, without starving everyone to death? I have no idea how to evaluate this. How realistic is it?

stephen_g 4y ago

I think it's a bad idea. But I saw a statistic saying the waste oil collected now could satisfy about 2% of the demand, and I think if we looked at thermal depolymerisation and hydroprocessing of other biodegradable waste we could possibly get up to a decent chunk, maybe 20-30%? If done with zero emissions energy that would be pretty carbon neutral. Not sure where we go after that for aviation, it's definitely one of the most tricky applications for alternate fuels. Maybe efuels would be next for some portion. Hopefully electric aircraft can eventually do regional short haul but I'm not holding my breath on energy densities getting competitive for that to take a huge chunk of aviation any time soon...

adrianN 4y ago

Since plants are very bad at converting sunlight to oil, I would assume that it will always be much more space efficient to use solar panels and synthesize the fuel. But there is waste biomass, including oils, that can supplement a small fraction of our energy demands with little extra effort.

sofixa 4y ago

I think the idea is to use waste cooling oil, meaning oil that was already used for cooking, then blended with whatever to make it more usable as jet fuel and reused. So it wouldn't be a waste of crops, but reuse of a waste product already manufactured and used for other things.

rob74 4y ago
That's nice in theory, but in practice most biofuels in use today are manufactured from food crops. So worries that producing kerosene from cooking oil might worsen the already existing food crisis are not completely unfounded. Related article from today: https://www.theguardian.com/environment/2022/jul/13/halt-use-of-biofuels-to-ease-food-crisis-says-green-group https://www.theguardian.com/environment/2022/jul/13/halt-use...

a-dub 4y ago

around fifteen years ago at the start of the synthetic biology boom, there was lots of talk of genetically engineered algae as a potential stand in for fossil fuels. i haven't heard much in a while so i'm guessing there were problems with it, but it always sounded like the most elegant of solutions to me....

jabl 4y ago
Algae fuels have been researched at least since the 1970'ies. In principle they are very promising, but it seems it's almost impossible to make these theoretical yield predictions work out in practice.