1) If the sun is not completely blocked during a global catastrophe, the cooling of the upper layer of the ocean would cause overturning, bringing nutrients to the surface. Over a longer period of time, macronutrient (e.g. nitrogen) fertilization could allow the ramping up of fishing to feed the global population. This might even be economical now. Figuring out how to retrofit ships for fishing would be a good near-term project. We could also harvest deeper fish in a catastrophe that are not economical now.
2) Processes already demonstrated to convert natural gas to edible calories with bacteria are also technically viable. Work here would be figuring out how to retrofit existing breweries and chemical plants.
3) Extracting food from leaves: grinding leaves and extracting leaf protein concentrate: again, figuring out how to scale up quickly.
4) Mushrooms: again scale up investigation.
5) Current cellulosic biofuel techniques with agricultural residues as feedstock produce an intermediate product of sugar. Though there are currently few biofuel plants like this, it may be possible to quickly retrofit existing chemical production plants, as was done with automobile factories in the U.S. to produce airplanes for World War II.
Waste from mushrooms consuming wood could then be fed to:
6) ruminants (cattle, sheep, goats, etc.) (already been done),
7) cellulose-digesting beetles (needs more research because current insects raised for food are not cellulose-digesting), and
8) rats (needs more research).
Furthermore, bacteria can make fiber digestible by non-cellulose digesters, so this may work for:
9) chickens (needs more research) and
10) as a backup plan even humans (needs more research).
11) Leaves can be eaten directly by ruminants and rabbits (needs more research for common leaves.)
12) The tropics would generally stay unfrozen, but even though crops currently grown outside the tropics would be able to tolerate the lower light, precipitation, and temperature, they generally would not be adapted for the high UV levels. One exception is crops being grown on the Tibetan plateau because of the thin high-altitude atmosphere (more detail here). This needs experiments to confirm.
So basically, some of the alternate foods are already commercialized, but we need to figure out how to scale them up quickly. Other of the foods are more speculative, and would need research and development. I also have a paper (not yet published) that estimates current cost of alternate foods. The most promising ones from this perspective are fish, cellulosic sugar, leaf extract, natural gas digesting bacteria, and Tibetan wheat. Does that answer tractability?
Truly one of the most satiating interventions on the menu of causes!
Could you go more into the full list of what the food alternatives look like, and how tractable each of them are?
:) There is lots more detail here, but briefly:
1) If the sun is not completely blocked during a global catastrophe, the cooling of the upper layer of the ocean would cause overturning, bringing nutrients to the surface. Over a longer period of time, macronutrient (e.g. nitrogen) fertilization could allow the ramping up of fishing to feed the global population. This might even be economical now. Figuring out how to retrofit ships for fishing would be a good near-term project. We could also harvest deeper fish in a catastrophe that are not economical now.
2) Processes already demonstrated to convert natural gas to edible calories with bacteria are also technically viable. Work here would be figuring out how to retrofit existing breweries and chemical plants.
3) Extracting food from leaves: grinding leaves and extracting leaf protein concentrate: again, figuring out how to scale up quickly.
4) Mushrooms: again scale up investigation.
5) Current cellulosic biofuel techniques with agricultural residues as feedstock produce an intermediate product of sugar. Though there are currently few biofuel plants like this, it may be possible to quickly retrofit existing chemical production plants, as was done with automobile factories in the U.S. to produce airplanes for World War II. Waste from mushrooms consuming wood could then be fed to:
6) ruminants (cattle, sheep, goats, etc.) (already been done),
7) cellulose-digesting beetles (needs more research because current insects raised for food are not cellulose-digesting), and
8) rats (needs more research).
Furthermore, bacteria can make fiber digestible by non-cellulose digesters, so this may work for:
9) chickens (needs more research) and
10) as a backup plan even humans (needs more research).
11) Leaves can be eaten directly by ruminants and rabbits (needs more research for common leaves.)
12) The tropics would generally stay unfrozen, but even though crops currently grown outside the tropics would be able to tolerate the lower light, precipitation, and temperature, they generally would not be adapted for the high UV levels. One exception is crops being grown on the Tibetan plateau because of the thin high-altitude atmosphere (more detail here). This needs experiments to confirm.
So basically, some of the alternate foods are already commercialized, but we need to figure out how to scale them up quickly. Other of the foods are more speculative, and would need research and development. I also have a paper (not yet published) that estimates current cost of alternate foods. The most promising ones from this perspective are fish, cellulosic sugar, leaf extract, natural gas digesting bacteria, and Tibetan wheat. Does that answer tractability?