Which meat animals can survive on only mushrooms?
Just start raising a large population of the ones you want. Evolutionary stress will leave some of each species that can live on only mushrooms.
As has been pointed out, humans get energy from the food they eat. That energy has to come from somewhere. If you eat a plant, the energy comes from sunlight. If you eat mushrooms or yeast, the energy comes from breaking down organic material. If you eat animals, the energy comes from the plants the animal eats.
So you can’t have a mushroom farm underground unless you have continous inputs of organic materials. Mushroom farms bring in tons of compost, grow mushrooms on them, then the compost is spent and won’t support any more mushrooms, so it becomes a soil amendment.
You can use yeast, bacteria or fungi to extract a bit more food energy out of waste materials that aren’t edible for humans, but you don’t get anything for free. Mushrooms and such are the equivalent of animals. They can convert food that is inedible to humans into edible food, but they need food of their own. You couldn’t run a dairy farm underground without continous inputs of grass for the cows to eat, and you can’t run a mushroom farm underground without continous inputs of compost.
Are you serious?
Rhubarb grows well in the dark. In fact the tenderest and sweetest examples are grown that way:-
Except it’s not really being “grown”, it’s being sprouted from roots. You can sprout potatoes the same way in a dark closet, but sprouting doesn’t increase the amount of energy in the potatoes. Likewise, you can grow bean sprouts in complete darkness. The only problem is that you need to grow the bean seeds first, or the potatoes, or the rhubarb roots. It’s certainly possible to use sprouting to change the amount of usable nutrients in a given root or seed, but you have to have the roots or seeds to begin with, which means plants grown under sunlight or reasonable facsimile thereof.
Bottom line, if you have a limited amount of energy to run lights for an underground greenhouse, that’s the amount of energy that can be turned into food, minus whatever thermodynamic inefficiencies there are in the production chain. Maybe the best use of the light is some kind of fast growing but inedible plant which is composted and fed to mushrooms or yeast, which is processed and turned into human edible food. But the more steps in the process the greater the energy loss.
95% sure you are thinking of Gateway, first book of the Heechee Saga by Frederik Pohl. The protagonist starts off as a shale miner, where the shale is used to create food.
Reverse-engineer an electric eel so that it uses electricity to form nutrients instead of the other way around.
Could the lower levels of the mine connect to a large body of water through perhaps a cave or even a quarry that has since flooded? That opens up a potential large source of nutrients and abandoned mines normally are damp and many are flooded so it it reasonable. A flow of water through the lower sections of the mine could be a major score.
Depends what you mean by ‘nutrients’ - plant nutrients (nitrates, phospates, etc) are no use unless the plants have light (plants eat light - ‘plant nutrients’ are more like vitamins for them).
If you mean actual food suspended in the water flowing through (invertebrates, digestible biological debris, algae, etc), that could be a food source, but it would only be sustainable if it’s plugged into some external source of energy - i.e. the sun.
There is a external energy source, the sun, which stores energy in the form of plant and animals that die at shallow depths and sink and take that energy to the bottom. There is life below the level that sunlight can penetrate water that is not dependent on hydrothermal vents, but lives on what rains down from above.
That could work, depending on the availability of suitable food chains based on the input - but it’s not really an isolated system (dont know if that matters to the OP, but if this is a post-nuclear story, it might).
One slight problem…
The organisms die at the surface if a deep lake, then sink to great depth, then somehow flow into the cave where the people live… why isn’t the cave completely flooded?
The cave/mine water level reaches a equilibrium just like a well. The entrance of the mine could be above the lake level. You could also have a situation where water enters the mine through the cave at a certain rate but it’s drainage capacity is greater. This is common in caves with underground streams.
Okay, after being made aware of certain fridge logic issues and putting some thought into things, I think that I may have come up with a solution with regards to the story I’m writing. Given that the reason that people are hiding underground is that there are things on the surface that find them crunchy and good with ketchup, rather then anything wrong with the environment, it’s possible for people to go out on the surfece provided that they are very careful, very stealthy, and don’t hang around. So while the protein sources and a couple of other things are produced underground, there would be a variety of easily camoflauged, low maintance crops that can be largely left to their own devices grown above ground. Now I just have to work out what they are.
If that were the case, farming today would be a doddle - and it’s not. I mean, there are some crops that require less maintenance than others once planted, but planting and harvesting annual crops is always going to be a bit time consuming.
Perennial crops such as tree fruit and nuts can be left alone, but will only produce high yields if they’re properly tended - if you just let them go, harvesting them is more like foraging from the wild.
I didn’t mean that they’d be left alone altogether, I just meant crops that only needed tending every so often rather then ones that need constant attention and/or elaborate protection from rabbits, wood pigeons and other pests. Bonus points if it’s possible to get a high yield from relatively little space.
I would say that hunting or raiding parties would be more effective then trying to farm in this method.
Except that there’s nothing worth hunting and there’s no one to raid since everyone is in the same position and/or a long way away.
As long as they can get to the surface they can drag down any vegetation they find to feed animals and grow yeast and mushrooms. But it’s more efficient for the people to eat fresh vegetables taken from the surface if they can find them or cultivate them.
Nukes and hydroponic farms come to mind, but I suppose that’s disallowed. If you want to pursue the fiber optic route, consider this proposed underground park in downtown New York City. It is supposed to be able to support plants and trees.