Enclosed Bio Systems (think biodome?)

[Momtoast]

Ok, so maybe this is more sci-fi than fantasy, but I was hoping you would all brainstorm with me anyway.

I have a plan for a novel where everyone lives in floating cities. Each city would basically be an enclosed ecosystem, possibly cycling in things from the atmosphere around them but that atmosphere is fairly toxic so it would have to be heavily filtered.

The catch? All of their technology is completely biological. They do not forge metals, though I suppose they could have plastics, since we do know you can make those from organic components.

All I know so far is they would have to have a lot of algae in there, as that would help with oxygen. But that's about it so far. How many people could live in one of those? How many animals if any could they have? What would they grow to eat? I know I don't have to be crazy precise about it, since it is fiction, but I'd like to make it believable.

What do you think?

 

[Orc Knight]

Why not make it a living ship of sorts? The space whale trope and those who live their form a symbiotic relationship with it. It could also have it's own living internal ecosystem, turtle island style but inside. As for the rest, no clue on populations and you can go crazy with what grows and what they eat. If you can suspend disbelief with what you have, that's probably what to aim for first.

 

[pmmg]

I think the answer would have a lot to do with how big the domed environments would be. The bigger, the more animals and all that.

In our own world there are actually people working on how to dome in cities, such as Houston to make it more protected from Hurricanes, and consideration for building floating platforms that could snap together and be separated for put cities together and to make them mobile.

I am a little dubious that this could be done without metals, and even plastics require oil, which has to be obtained somehow, but....stranger stuff has happened. Could a planet like Coruscant really exist and cities just be floating in the sky? Who knows. I also wonder at why it is important to hammer this down when I think the average reader will accept on its face that the domed city has a workable eco system.

Just a quick search, I found a website saying a person will eat about 7000 animals in their lifetime (which looks high to me, must be small animals). Using some math, and saying a person lives about 70 years (give or take), that's 100 animals a year. Supposing people were very conserving, lets say they eat 50 or 25 animals per year. Now how many people in your dome?

If these animals were goats, I see a website saying a goat eats about 3-4 pounds of food per day. That's 200 pounds per day for 50 animals, 73000 pounds of food per year for 50 goats, so one person can eat sparingly for a year.

How far would you want to carry that? If you are in SciFi realm anyway, why not just say they are managing it, and let the reader assume the details are figured out.


Here is a link to a page where I roughly did some math and figure it takes about 1 acre of hydroponics to feed 70 people.

space ship food production

 

[Prince of Spires]

The answer is: However many you need / want.

In the end, if you want animals then you can simply make your dome bigger. Any society evolved enough to build such a dome will be able to make it a bit bigger to fit in animals if they want.

It's interesting to think about, in that they are not the most efficient use of space if you look at it directly. However, with all the plants you're growing to feed people, you will end up with a lot of waste-products that are ideal to feed animals with. Think carrot-peels for rabbits and that sort of thing. So if you're going for efficiency, then there will be some animals around, but in low quantities and they will be small animals. A cow takes up an awful lot of space and food and time to grow to a size big enough before you eat it. But rabbits, chickens (or equivalent other small birds) and especially bugs will be around. Grasshoppers, beetles and the like are fast growing and require very little space per kilo (as compared to bigger animal).

The other option with a technologically advanced society of course is to go with synthetic meat products instead of real animals. Already in our world there are experiments with "printing" meat. It's not that far fetched to use that to feed a city.

 

[Yora]

Speaking about efficiency, they should not have any animals at all. Animals make sense when you have surplus land that can grow animal feed with little human intervention but is unsuitable for growing human food economically.
If you want to minimize use of space and energy, just grow plants for humans to eat. Everything else is extremely wasteful.

Another thing related to energy is heat. I don't think there are any bio-materials or plastics that can stand up to the heat of fire. They still probably want such comforts like computers, transportation, and various industries that all produce a lot of waste heat. Having the interior of the city not get baked or burst into flames would be a huge challenge. I don't think you could do this physically sound. It would always be fantasy.

 

[CupofJoe]

If by animals we are thinking of cows, goats, sheep [let alone pets], then I agree. They are too inefficient unless you can use some handwavium to make them work. But if we go smaller to insects, plankton and those strange things might be plants or animals or something in-between, then they can definitely be in the mix.
It depends on what you mean by fire, but there are a few woods that don't burn unless an accelerate is used. If you put them to heat or something like a camp-fire they will char, but not burn on their own.

 

[Maker of Things Not Kings]

Yes, the idea of what animals or, even better, "pets" might be in such an environment is interesting. Small, newt like creatures? Winged wombats? Or a whole other species coming from another dimension (it IS sci-fi). As a short story to listen to for a bit of inspiration, I might recommend, "Mongoose" by Sarah Monette. It takes place on space freighters far into the future but that is similar enough to have created the environmental collapse and the grounds for new species. You can listen to it on the Drabblecast site. Episodes 170 and 171.

 

[Momtoast]

Why not make it a living ship of sorts? The space whale trope and those who live their form a symbiotic relationship with it. It could also have it's own living internal ecosystem, turtle island style but inside. As for the rest, no clue on populations and you can go crazy with what grows and what they eat. If you can suspend disbelief with what you have, that's probably what to aim for first.

That was my other plan. But I thought people would think it a bit gross if my whole city was basically inside a giant bladder.

 

[Momtoast]

Thanks for all the details. I like to have a few numbers to make it a little believable. I know it will still be a stretch, but the less the reader has to stretch I think the better.

 

[Prince of Spires]

There is another side to the discussion to consider as well. If your society has any capitalist tendencies and your people like eating meat then it is actually very likely that there will be a source of meat. It will be expensive and not something for everyday. But someone will figure out that people are willing to pay a lot of money for a steak and therefore they will supply that, given a high enough price. People might use it to impress neighbors or on special occasions, but it should be around.

Another thing related to energy is heat. I don't think there are any bio-materials or plastics that can stand up to the heat of fire.

Teflon is a plastic. The space-shuttle nose-cone was made of something called Reinforced Carbon-Carbon, which is made from a resin which you turn into graphite. It's stable up to temperatures above 2.000 C. So, as long as carbon based materials are "allowed" then you can probably find some human made substance that does what you need it to do. For instance, besides the above two that stand heat pretty well, you also have completely organic semiconductor microprocessors.

The challenge I think to making this world believable is explaining how they got to this point. You can make organic substitutes for most things. But they're harder to create (and as a consequence more expensive as well) then their non-organic counterpart. The only reason we could come up with organic semi-conductors was that we first learned how to do it with non-organic materials that were easier to work with.

 

[Momtoast]

The challenge I think to making this world believable is explaining how they got to this point. You can make organic substitutes for most things. But they're harder to create (and as a consequence more expensive as well) then their non-organic counterpart. The only reason we could come up with organic semi-conductors was that we first learned how to do it with non-organic materials that were easier to work with.

The idea is that they are in these cities around this planet to make it habitable, which is taking a long time. They are there because their own planet was ruined in some kind of ecological disaster, so they are dedicated to doing as much organically as they can. I imagine there will have to be some metallic or non-organic components, but I'm hoping to avoid them if possible.

I am playing also with the idea that this civilization evolved differently than ours, and discovered biological technology before things like steam power or smelting metals. I'm only just starting that idea. So to them, because of which discoveries they made when, biological technology is easier. Not just non-metal based things, but focusing on living cells to do stuff like store solar energy and such.

 

[Prince of Spires]

That sounds like a plausible enough reason to me. The main thing is that you need some kind of justification, because that's what people will be wondering about. What the actual justification is matters less, as long as it's deeply integrated in the world and it sounds plausible enough.

Two concepts you could look in to for some more inspiration are circular economy (the idea that all waste of a process is the input for a next process) and urban mining (extracting metals from waste, which can currently have a higher gold particle count than you find in a gold mine).

 

[enoch driscoll]

People have already found ways of growing food very very compact spaces. A great example of that is in Square Root farms, who uses trailers as fields to harvest a whole lot of food from a very small space. To me this seems ideal for a floating city with limited farming area.