What Food Sources Could Be Produced With Minimal Light?

[Weaver]

Say you have a large group of people living underground. The only light available is artifical and while it is possible to use to to grow some crops, due to the high energy requirements it is not possible to do so on a large enough scale to feed everyone that way. What food sources could be cultivated/raised with little to no light? I've already come up with mushrooms but man cannot live by mushrooms alone.

[Ethilrist]

Meat animals could eat the mushrooms...

[Joey P]

Since you mention things like high energy requirements of lights and not being able to use lights to make food on a large enough scale, but you want to be able to grow food with the lights for a large group I think you'll have to define a few things...
How large is the group and how much energy/electricity is available?
There are indoor greenhouses that rely totally on lights that make a wide variety of different vegetables as well as run pumps to keep a fish farm operational.
But you'll have to give us the specs so we have something to work with.

ETA here's short article on a place I took a tour of a few years ago. Vegetables (mainly leafy stuff) and fish, all indoors.

[appleciders]

Well, there are chemosynthetic organisms in the deep ocean that draw their power by breaking down chemicals in their environment, not from photosynthesis. Such organisms might form the basis of a food chain in an ecosystem if your hypothetical cave people had access to hydrothermal vents and the water from those vents were high enough in the necessary chemicals. Such a system would not be truly self-sustaining, as it depends on outside input in the form of chemicals.

[Weaver]

The population is between two hundred and four hundred. To be honest, I don't have any idea as to what sort of energy requirements an artifically lit greenhouse would have beyond 'a lot', so I'm going to be having a close look as the site that was linked. As for the rest of the specs, I'm still trying to figure them out (this is for a story idea I've had). Sorry for the vagueness.

Tech level and general resources are roughly level with what's available today and no, they don't have access to hydrothermal vents.

[chacoguy]

Can you run fiber optics to the surface?

[Weaver]

Originally Posted by chacoguy

Can you run fiber optics to the surface?

Not sure. Probably not though. *adds to list of things to figure out*

[biddee]

Could you have cracks in the rock that lets in daylight? How far underground are these people? Are they living in the subway under a city or in a cave system?

[Weaver]

Originally Posted by biddee

Could you have cracks in the rock that lets in daylight? How far underground are these people? Are they living in the subway under a city or in a cave system?

The group that my story focuses on are living in a old mine (said mine is rather large and free from flooding). There are others referred to who are living in everything from old bomb shelters (there's some impressive ones here in the UK) to subway systems to old RAF ammunition depots though.

[TriPolar]

Yeast would be a good source of food. It's a fungus, so that's covered in the mushroom category. But yeast grows fast, and has the side benefit of producing alcohol. Yeast and mushrooms need food themselves, and they seem to grow well on manure, something that ought to be available. Yeast can be grown in a liquid making effective use of limited underground space. Yeast can also be used to make something called Marmite, but that has only been found digestable by Australians. It is toxic to most other people. I think the drawback may be that yeast and other fungi don't get their carbon from the air like photosynthetic plants. Since the humans will be converting a lot of what they eat into CO2, you'll be losing a lot of carbon out of the system. Maybe there's fungus that feed directly off of coal?

[gazpacho]

I can't remember the book but there is an old sci fi series that talks about using oil as a food source for yeast which they use to feed an over populated earth. In it the main character lamented that 20th century man wasted so much oil dragging themselves and a few thousand extra pounds of metal over the surface of the earth instead of feeding the hungry.

[biddee]

Originally Posted by Weaver

The group that my story focuses on are living in a old mine (said mine is rather large and free from flooding). There are others referred to who are living in everything from old bomb shelters (there's some impressive ones here in the UK) to subway systems to old RAF ammunition depots though.

There have to be ventilation shafts in an old mine, possibly there could be a system of mirrors to reflect sunlight underground. Otherwise, yeast and other fungi would probably be your best bet.

Have you seen this?

[Shalmanese]

Originally Posted by TriPolar

Yeast can also be used to make something called Marmite, but that has only been found digestable by Australians.

Marmite is British and no self-respecting Aussie would be caught dead eating it.

[Mangetout]

Yeasts and fungi need feeding - and the things they feed on are part of a food chain that includes the conversion of sunlight to food energy - so those are only going to be sustainable as long as there is a stockpile of something to feed them on.

And you can't feed them on the wastes of the organisms consuming them - that's a closed system, which will run out of energy.

[Weaver]

Originally Posted by Mangetout

Yeasts and fungi need feeding - and the things they feed on are part of a food chain that includes the conversion of sunlight to food energy - so those are only going to be sustainable as long as there is a stockpile of something to feed them on.

And you can't feed them on the wastes of the organisms consuming them - that's a closed system, which will run out of energy.

Out of curiousity, how long would it take for the energy to run out? Also, would a relatively small quantity of plants grown under artifical light combined with occasional runs to the surface to grab plant matter (the question is story research and the setting does allow brief trips to the surface but it's very risky) be enough to keep things going?

[Mangetout]

It would run out pretty much straight away. Even if it was possible to live on yeast alone, there's nothing much in human excreta that is of interest to yeast as their food. The same goes for amy closed cycle - you can't just keep extracting energy out of a substance and expect it to remain valuable as food - for anything.

And a small amount of artificially-grown plant would contribute a small amount - no more than their intrinsic value as food themselves.

[TriPolar]

Originally Posted by Mangetout

It would run out pretty much straight away. Even if it was possible to live on yeast alone, there's nothing much in human excreta that is of interest to yeast as their food. The same goes for amy closed cycle - you can't just keep extracting energy out of a substance and expect it to remain valuable as food - for anything.

And a small amount of artificially-grown plant would contribute a small amount - no more than their intrinsic value as food themselves.

Fungi can't extract carbon dioxide from the air. And a lot of the carbon we consume ends up getting exhaled as carbon dioxide. It's a closed cycle with an enormous hole in it leaking carbon. Now if fungi can extract carbon directly from coal or oil, or it can be fixed through some other method, there's a means of keeping things going.

[psychonaut]

What do blind cave fish eat? Perhaps those could be cultivated; the lack of light wouldn't bother them.

[Mangetout]

Small invertebrates, which will probably be variously grazing on bacterial films, and/or feeding on other invertebrates or single celled organisms - anything that's edible and has food value, really - it's the food chain below the fish that's going to limit the scalability of that.

[Lumpy]

There are plants which don't need as much light to grow, but then the question is how quickly do they grow? If they need half as much light but take twice as long to double their mass, you haven't gained anything. If energy is the limiting factor than the question is what plant does the most efficient job of converting light into humanly edible biomass? My guess would be probably some form of algae.

[John Mace]

Originally Posted by Ethilrist

Meat animals could eat the mushrooms...

Which meat animals can survive on only mushrooms?

[bup]

Originally Posted by John Mace

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.

[Lemur866]

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.

[John Mace]

Originally Posted by bup

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.

Are you serious?

[Rayne Man]

Rhubarb grows well in the dark. In fact the tenderest and sweetest examples are grown that way:-

http://www.youtube.com/watch?v=R_A4GaFCEG0

[Lemur866]

Originally Posted by Rayne Man

Rhubarb grows well in the dark. In fact the tenderest and sweetest examples are grown that way:-

http://www.youtube.com/watch?v=R_A4GaFCEG0

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.

[awldune]

Originally Posted by gazpacho

I can't remember the book but there is an old sci fi series that talks about using oil as a food source for yeast which they use to feed an over populated earth. In it the main character lamented that 20th century man wasted so much oil dragging themselves and a few thousand extra pounds of metal over the surface of the earth instead of feeding the hungry.

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.

[Lumpy]

Reverse-engineer an electric eel so that it uses electricity to form nutrients instead of the other way around.

[kanicbird]

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.

[Mangetout]

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.

[kanicbird]

Originally Posted by Mangetout

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.

[Mangetout]

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?

[kanicbird]

Originally Posted by Mangetout

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.

[Weaver]

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.

[Mangetout]

Originally Posted by Weaver

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.

[Weaver]

Originally Posted by Mangetout

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.

[kanicbird]

I would say that hunting or raiding parties would be more effective then trying to farm in this method.

[Weaver]

Originally Posted by kanicbird

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.

[TriPolar]

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.

[Measure for Measure]

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.

[Autolycus]

You could maybe domesticate moles?

[Mangetout]

Originally Posted by Weaver

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.

Yes, but we'd be farming like that now if it were possible. Best bet might be some crop that is toxic until processed -bitter cassava for example.

[Phnord Prephect]

How about a system whereby the survivors make foraging trips to the surface and gather... basically, whatever organic materials they possibly can. They then take these materials underground, and use them in the most efficient possible manner, whatever that might be, to provide a food supply for the colony.

I'm thinking specifically about using the ant colony farming methods nature has proven viable here. The ants carry leaves underground, which they compost and use to grow fungi, which they eat.

Humans might, let's say for example, have an underground farm of some sort. Animals include cows, chickens, and pigs. Cows eat grass, chickens eat grain, pigs eat pretty much anything. This would provide a basic diet of milk, eggs, and meat.

Light is minimal, so... Let's start there. Hydroponics. Obviously there's not enough power to grow everything belowground, so reserve the hydroponic systems to low-mass-high-value plants. Herbs and spices, medicinal plants, and 'luxury' goods when possible, ie: tomatoes and such. Nutrients for the plant will come from processing of the colony's wastes, water supply (grey water possibly), and whatever electric sources you might let your colony have.

More food is needed, so let's work in the fungus. Bonus is that you don't need the electric lighting, but you still need water and nutrients. You can grow a LOT of mushrooms off just a couple cubic meters of 'soil', and the nice part of this is that the soil will be constantly resupplied by the wastes from the rest of the colony. Some of these mushrooms feed the colonists; the rest go to feeding the farm animals. I'm sure pigs will eat mushrooms quite happily; chickens might? Don't think cows would, but I'm a city boy so I'm guessing here anyway. Perhaps there are other valuable food animals that can be fed primarily by mushrooms?

Pigs eat mushrooms, mushrooms eat pigshit. Stable loop? Not quite. Thanks to entropy, you need to add something here that grows in sunlight, which is the point that's been made over and over previously in this thread. That's where the surface-gatherers come in.

You say it's possible to occasionally visit the surface, and if so it's possible to gather something usable on each trip. Ideally this would be things like gasoline and venison, but don't forget about the massive resources that exist in the form of wild plants, even those not directly edible by humans. Make a rule whereby each person returning to the colony has to bring in SOMEthing organic, if they don't have anything more valuable this can be leafy branches from nearby trees, or just a few bucketfuls of nice loamy soil, preferably with earthworms. Of course, you'd want fruit and vegetables when available, so depending on the situation small orchards and gardens could be planted. Perhaps there are berry bushes nearby as well, or a fish pond, river, lake, or even the ocean. Basically, if there's any environment better than a desert on the surface, you've got a potential source of raw materials. In a survival situation, you'd do well to get the most value possible from it.

I think, depending on the ratio of underground survivors to foragers, a stable or at least semi-stable colony could survive this way. You're still getting most of your energy from sunlight, but all the real 'farming' is taking place underground, converting the most basic of resources through your farm animals into usable people-food, in whatever the most efficient manner might be. I envision the cycle looking something like grass-fed to cow-turned to cheese-turned to poop-fed to mushrooms-fed to pigs-turned to bacon-turned to poop-turned to mushrooms-turned to pigs-turned to bacon, and so on until all the valuable nutrients are used up, at which point the depleted 'soil' you end up with goes into an incinerator to generate electricity, and the ashes buried somewhere. Or something like that.

The nice part of this setup is that the balance is key. The more efficient the imput of raw materials, the more efficient the recycling system underground, the less foraging that needs to be done on the surface. If the colony can forage a lot, then it can grow a lot. If they can barely meet their needs, you've got a balance. If they can't quite sustain this for the long-term, you've got an excellent source of tension with which to spur adventure on the surface for your characters. If they can't sustain it anymore at all, then you have an exodus story or a nice depressing end-of-it-all story.

Who knows how long a system like this could last?

[Mangetout]

Originally Posted by Phnord Prephect

I'm thinking specifically about using the ant colony farming methods nature has proven viable here. The ants carry leaves underground, which they compost and use to grow fungi, which they eat.

Significant nitpick: it's been proven viable at that scale, but I suspect it would not be viable for humans due to a number of factors that increase cubically rather than linearly (load carrying capacity per individual, energy requirement to move about, etc)

[Mangetout]

Also, mushrooms just aren't a wonderful source of nutrition. 100g of mushrooms contains about 40 calories. An active adult male would have to eat about 6 kilos of mushrooms a day (which I think would cause digestive problems for various reasons).

And mushrooms generally don't live on shit. Can we just put that misconception to bed? They generally feed on decaying organic matter - cultivated mushrooms are grown on composted stable manure - comprising mostly sawdust or straw - animal dung provides some important nutrients for both the mushrooms and the other organisms that break down the straw, but mushrooms don't live on shit (well, some species do, but not the ones you're interested in farming).

[Jesta]

How about growing potatoes (or similar) on the surface, utilizing the sunlight and low maintenance aspects, but harvesting them from below ground, with either some careful shallow mining, or brutal methods along the lines of preparing an underground pit below the crop, then collapsing the crop into it, caving in the ground above, but leaving the crop accessible for below ground retrieval?...

[Lemur866]

The trouble with "occasionally grabbing anything organic" is that people have to eat every day. So, every day (on average) every human would have to bring in enough organic material to grow enough food to live on for that day.

This is not easy, which is why subsistence farming is backbreaking constant work. If it was easy to grab a handful of leaves and dirt and grow mushrooms on it, that's what peasants would be doing instead of growing wheat, rice, or corn.

So if you're going to the surface once a month, you have to bring back on that trip enough to last you for a whole month, as well as enough to support for a month the other people who weren't part of the gathering party. This is a lot of food.

Even if there was a gigantic field of wheat growing outside the cave, how much could you bring back if you sneaked out one night? If you could drive a combine out into the field at night it might be a lot. If you're out there with a sickle trying to gather wheat ears by hand, not very much.

[Darth Panda]

For occasional surface harvesting - how about sunflower seeds?

They're pretty nutrient dense - 204 calories / 35 grams / 1/4 cup. So 1 days worth of food is only weights about 350 grams and takes up 2.5 cups - not bad for carrying. Plus they're pretty healthy in general. http://www.whfoods.com/genpage.php?t...dspice&dbid=57

As far as growing them without much work - well, they're basically a weed.

[Lemur866]

Is there a sunflower seed vault up on the surface?

That cite is for the kernels, not the whole seeds. If there's a field of sunflowers on the surface, you have to harvest the flowers, separate the seeds, then crack the shells to get the kernels.

Food crops generally are only harvestable for a few weeks out of the year. This is why farmers plant, then tend, then harvest the crops rather than every day wander out into the field, gather enough food for the day, then go home.

You have to realize that what is being proposed is a system of farming where the farmers must live in caves, and can only come out to plow, plant, tend, and harvest the crops a few nights out of the year. How much food do you imagine farmers could produce this way?

Subsistence farming means year-round endless backbreaking labor caring for your tools, your land, your crops, and your animals. A system where you sneak out in the spring, scatter a few seeds, then sneak out in the fall to harvest the crops isn't going to produce enough food.

[Darth Panda]

Originally Posted by Lemur866

A system where you sneak out in the spring, scatter a few seeds, then sneak out in the fall to harvest the crops isn't going to produce enough food.

Well, not with that attitude it isn't

Seriously though, I didn't say it was a great idea - but surely, if you had to use that system, some foods would be better than others. I proposed sunflower seeds as that - better than other options, without necessarily commenting on the plausability of the idea in general.

I also think it depends on the size of the group we're talking about. For an underground city - not gonna happen. For 20 or 30 people, some occasional ground harvesting combined with some other ideas could be somewhat workable.