A Hydroponics-based Agriculture System

[voidbeetles]

Hi!

One of my current writing projects is set in a civilization that has, for thousands of years, lived in a sort of large scifi underground bunker. They have easy access to water, very little access to soil (they're able to compost biomass, add minerals, etc, but that will only get you so far), and no access to sunlight (grow lights will have to suffice) - for these reasons, I imagine that their agriculture system is mostly hydroponics-based. Though I've done a little research on hydroponics, I'm having difficulty extrapolating this information to my worldbuilding, mostly because a lot of the info I've found relates to singular plants without giving a good sense of what fares better/worse compared to others. And also just because I have a hard time wrapping my head around plant cultivation in general, I think. I was wondering if anyone here had any insights! (Or suggestions of topics/resources to look into more!)

The big questions I'm thinking most about are:

• Compared to, say, the modern Western world, would certain foods/food groups be underrepresented or over-represented in this fictional world's cuisine? (for example, I imagine that rice might be the main staple, as flooding rice fields is pretty important to cultivating it... and that potatoes might not be such a good choice, as their "main thing" is growing beneath the soil?)
• What effect would this have on the plant fibers that are most commonly used for making clothes (and other fiber technology like rope)? That is: how would cotton, linen, hemp, etc fare? Would a certain one of these plants be more common? More expensive? Quicker/easier to grow/harvest on large scales? (This question is especially relevant because my protagonist has an interest in textiles.)

Comments

[conuly]

You don't need to flood rice fields. You can flood rice fields, which makes it convenient to grow rice in wet places where you can't grow other crops (and which also helps keep away pests and weeds - plus, your paddies can double as fish farms!) - but rice can grow just fine on dry land.

You also don't need to grow potatoes under soil. Potatoes will grow very happily in a basket with a little bit of soil, and then you can keep dumping straw or leaves or compost or whatever over the lowermost leaves whenever they pop up.

[winterbird]

So, you're going to have a few things to consider:

* Thousands of years means a genetic bottlenecking, most likely, were there any extinctions of entire groups of plants? Similar to the Gros Michel banana? (The Gros Michel still exists but is no longer a commercial variety, and our current Cavendish is at risk of mass extinction due to genetic bottlenecking).

* Hydroponics also means potential susceptibility to mass infection at once. If a fungal infection gets into a crop, or is in say, a badly stored seed, the spores in the enclosed space can wreak massive havoc, and are likely to grow quickly due to like, the humidity that hydroponics creates unfortunately.

* If they're composting biomass (say, faeces, dead people, dead animal companions if there are any) as well as all vegetable scraps, and paper/cardboard (though this is probably in diminishing supply) and possibly hay, this will actually get you VERY far. Plants like pigeon pea, for example, grow very quickly on very little, are nitrogen fixing (meaning they can be very useful chop/drop mulch for future plants who need nitrogen - which is most edible plants), and will great a lot of 'bulk' that makes a great mulch, compost. It's actually *far* more realistic to have a dual 'soil + hydroponics' system where certain plants are grown in soil - potentially in pot environments (which would allow for trees, fruit crops etc.) - and hydroponics. This also means all dead / dying / pruned hydroponics plants further are useful as a mulch / compost. (Provided there's no spores in the mix).

People produce a lot of waste through living and eating. And while we can eat much more of many plants than we actually do, the reality is that you will have a surprising amount of biomass. It's actually a common problem for people who live in a two-person home, for example, to start composting and realise *very quickly* that they are making far far more compost than they could ever need or use, certainly enough to support a lot of food for more than two people over time. (Although you do need dry matter for compost to work, but grow lights or ovens used to dry out leaves and branches would help with this).

TL;DR do not rule out soil, because biomass really doesn't 'only go so far.' Biomass is going to overwhelm your underground bunker if they don't find a way to recycle literally all their food waste / faeces / etc. In fact most science fiction stories I've read that feature underground bunkers that have been sustaining themselves for a long time will both mention a) genetic bottlenecks making plants more susceptible to disease and b) be using soil from their own waste + plants + food not eaten etc. Hydroponics isn't as common as you'd think in these scenarios! This is largely because clean and fresh water is usually not as abundant as...well...biowaste / plant waste / bodily waste. So you may want to look at a split approach.

*

As for plant fibres, you're probably going to be relying on hemp an awful lot from everything from paper, to clothing, to rope etc. (Hemp does pretty well hydroponically). Cotton can also grow very well hydroponically though it usually has to be developed specifically for the process. But it often has higher yields and needs less water proportionately.

Linen (flax) is less viable.

A big thing to consider overall is that long-season crops invariably do not do great in indoor hydroponics, so you need to look at short season crops - herbs, leafy greens like lettuce, sometimes beans etc. Anything that's longer season will struggle indoors. This is a huge consideration, there's a reason so much of successful hydroponics is done outside, grow lights can only do so much.

As an example, if I were contemplating something like this, I'd grow all green short season crops in hydroponics, and everything else indoors in recycled/composted soil, with an interest in using textiles for both the hydroponics (it helps), and also as dry matter in the compost (it helps), which would open me up to more options and introduce interesting dynamics like...experiments in what grows better in hydro or soil, or arguments over what 'deserves' soil more if it's in smaller quantities or alternative what 'deserves' hydroponics more.

Make sure when you're searching that you're restricting your searches to 'what grows best in indoor hydroponics' and not just 'hydroponics.' Because the word "indoor" takes so many plants out of the equation. Presumably some science developments would help with some things, but disease vectors are rough.

Anyway it's a huge subject! With many different theories etc. there's no single 'this is definitely what always grows best in hydroponics' (like, do you have hard or soft water, can they chemically treat the water, does it have an excess of calcium or lime, how are they dealing with build up, etc.) Water from different places in the same country can impact hydroponics systems very differently!! And obviously some water with some minerals is going to be better for some plants and worse for others (plants usually like a very specific Ph to grow in, and not all plants share that same Ph).

[mecurtin]

Wet-field rice basically *is* a type of hydroponics/aquaculture. It's *incredibly* productive, a lot of the nitrogen-fixing is done by algae growing in the wet fields. There can also be seasonal fish and ducks in the fields, so you can get more protein than you might expect. So: think food of south China/southeast Asia: rice, fish, duck, shrimp, bok choy and other oriental cabbage, lemongrass, cilantro & other herbs. Growing the rice productively, enough to feed people, would mean that the rice "fields" should be really bright, hot, and humid: think Java or Bangladesh.

Atomic Rockets discusses this

[ilzolende]

There’s an in depth discussion of these issues on Atomic Rockets! Aquaponics might be worth a look, perhaps? With enough space, bamboo could also be relevant.

[hamatebones]

In re clothing fibers, it's worth considering that all plant and animal fibers require processing after harvest. However hard it is to raise the fiber, the labor (and potentially danger) of the processing is another factor that would constrict supply. Flax processing is back-breaking stuff: whacking the stems to break them open, lots of yanking and pounding, etc. etc. Even WITH slavery in its cultivation, cotton wasn't really a profitable crop until after they automated removal of the seeds from the bolls. There used to be like 10 different professions in processing wool: shearer, washer, carder, spinner, dyer, weaver, fuller, etc. Rayon can be made from all kinds of plant fibers, including bamboo, but there's chemical processing required, like big vats over huge burners.

Is this a high-tech civilization, i.e. have they been able to automate some/all processing tasks? Or a very low one, where each task is done manually? Somewhere in between?

Once you have the processed fibers, of course, you have to make them into clothes, tools, rope. If the fabric can be gotten cheaply/automatically, then there's enough of it kicking around to sew complex garment styles with waste leftover. If fabric is dear, then the clothing styles will be much simpler: squares and rectangles belted together rather than curved seams and buttons. Even if there are sewing machines, you don't want to waste fabric by cutting fitted styles! Fabric would be recycled regularly downward (Sunday best to everyday clothes to scullery clothes to rags), and then maybe pulped and turned into paper, especially if you're in a civilization without trees. Yes, paper used to be made out of fabric rags, and is now made out of wood pulp.

[lilacsigil]

Hemp is relatively easy to grow and process manually compared to cotton or linen, which is why you see it used on a wide scale for the clothing of very poor people across eastern Asia (it was also used by wealthier people but not so much when they had other choices, it can be quite rough). It is also extremely durable and really good for rope. As a bonus, it takes dye particularly well.

[fred_mouse]

I'd be betting that fungus would be an important foodstuff. I've seen one fiction novel that addressed this well, which was one of Dave Luckett's Tenebran Trllogy (Dark Winter, I think, but it might have been one of the others). Luckett talked about getting really grumpy reading fantasy with troglodyte communities where the story made assumptions that all the food was coming from above ground.