The Diet of Space Dwellers

Question

I've looked around the forum but didn't find an answer to this particular question. In short, what food could realistically be produced in a space station assuming current (or near future) technological constraints?

Let's assume that we want to build a space station that is entirely self-sufficient (at least in the realm of food and water production). The station will carry a commune of say 10,000 people. It rotates enough to mirror gravity on Earth.

Now we want to create farms or food factories to feed the populace, but what is the most viable crop/livestock in space?

Food pills, protein powders, or any other form of artificial supplements aren't considered, so disregard that as an option.

The way I see it, the food must meet some or all of the following criteria in order to work in such constrained settings:

• The food must be able to grow or be produced in as compact an area as possible (how much can be produced per square feet, for example)
• The food must be calorie or nutrient dense (more bang for the buck)
• The food must be energy efficient in its production (that is, not require as many resources such as light, fertilizer, water, etc.) OR take little time to produce
• The food must have a long shelf life (or require little energy for preservation)
• The food must be somewhat palatable (not tasteless or downright unappetizing, this would be subjective)

Given these criteria, I can think of a few food items that space dwellers could eat. I'll list them out to get the ball rolling.

For vegetables and fruits:

• Potatoes (they are nutrient dense, and have high calories per acre grown)
• Sweet Potatoes, Leeks, & Parsnips (high calories per acre grown)
• Quinoa (high protein concentration)
• Beans (low water intake needed)
• Blueberries (superfood, but may require lots of water)

Meats, Livestock:

• Salmon (very nutritious, but high water requirements)
• Sardines (very nutritious, but high water requirements)
• Chicken (decently high in protein, moderate calories, small livestock and less energy required versus pork and beef)
• Eggs (very nutritious, but somewhat energy intensive to produce)

Forms of Food Preservation:

• Salting (albeit obviously high in salt content)
• Pickling (possibly not efficient)
• Canning
• Drying or smoked (dried foods such as beans, pemmican, and jerky have long shelf lives and high nutrient content, also easy to store)
• Refrigeration (useful in the short run, but ultimately energy-intensive)
• Vacuum packaging (given correct packaging material, very viable option)
• Freeze-drying

Unconventional alternatives

• Seaweed (high nutrient content, necessary for thyroid health, possibly high on water content)
• Quorn/high-protein fungus

These are just a few I can come up with.

Does anyone have any thoughts on what they see a space station producing based on this criteria? Or are there any additional parts to the criteria I listed that should be considered?

Answer 1

To make food, you need nonfood raw materials and energy. Raw materials include a carbon source, a nitrogen source and trace minerals. Each trophic level you step through loses efficiency. Some protein sources are better than others at feed conversion - @CreedArcon's idea of using insects is reasonable as they have the best feed efficiency of any protein source (compared to other animals like fish, fowl, etc). A problem: feed for these animal protein sources is also potentially feed for humans, and putting the animals in between.

Better is a human food source that uses energy and nutrient sources that humans cannot use. Best of all would be a food source that could do double duty: process waste materials you have in abundance (from your humans) and turn these waste materials together with energy back into food.

I propose your space people eat bioengineered microorganisms.

This is being tried (although with regular bacteria for now): https://www.newsweek.com/astronauts-living-space-can-eat-bacteria-feed-human-waste-791883

The researchers tested three species of bacteria in a reactor built with aquarium parts that wound up with about the same volume as a basketball. Two species grew well in temperatures and pH levels that were high enough to kill off pathogens; another species grew in the kind of methane-rich environment created when bacteria munch on poop. Best of all, the bacteria could consume about half of the solid waste in less than a day. "That's why this might have potential for future space flight. It's faster than growing tomatoes or potatoes," House said.

A variety of bacteria could be used - those similar to the above linked article that subsist on waste, photosynthetic bacterial like spirulina (already marketed as a dietary supplement(. Yeasts are not bacteria but fit these requirements in that they can subsist on carbon sources that humans cannot use and can synthesize all their own amino acids - yeast has long been used as animal feed and nutritional yeast is in vogue right now among the vegan set.

In space your spirulina tanks would scrub CO2 from the air and be exposed to filtered sunlight. These are your primary producers. Humans could eat this and also carbohydrate fixed by the spirulina could be fed to the bacteria and yeast tanks. The bioengineering comes in to maximize nutritional yield but also flavor: there have been forays into making recombinant organisms that produce "beefy meaty peptide" (that is its real name). Your space folk have a variety of organisms which taste like different delicious real things - good for morale.

The problem in space is obligate loss - even with near perfect recycling it is not perfect you will gradually lose carbon and nitrogen over time just as a energetic process has obligate losses to heat. For the very long term you will need a stash of this stuff (not to mention water and oxygen). Maybe you could keep it outside as frozen CO2 and anhydrous ammonia. Wrap it up in reflective plastic.

Answer 2

Entirely vegan diet.

As has been noted below, each tropic level is a massive loss in potential calories. Animals don't put all of the calories they eat into building mass; most calories consumed are burned just being alive. It takes approximately 10 calories of grain to produce 1 calorie of beef. Meat is a hugely wasteful food source.

The claim that net calories could be increased by feeding crops through insects, who can often eat more of a plant than humans can, is poorly substantiated. Although there are many insect "ranches" in the world today, mostly raising crickets and meal worms for the pet industry, none of them feed their livestock on 100% food waste. Instead, they use grain and legumes as feedstocks - things that humans could otherwise be eating. Does this improve net calories? It's debatable, and at best a narrow margin, and at what cost? Keeping humans alive in space is already a massive, expensive, treacherous endeavor: high-density rearing of livestock, and all of the diseases they bring with them, would be a massive technical challenge. A colony would want to keep things as simple as possible, considering how many other challenges they would have to face.

And really, it doesn't get you anything. The only essential amino acid that is lacking in a vegan diet is vitamin B12. B12 is required in only very ver minuscule quantities, in doses as infrequent as once a week. 1.5 pounds of B12 could supply 100 humans for 800 years. If you really prefer true self-sufficiency, B12 is easily synthesized by bacteria that might be reared in a lab on site.

Synthesis can be good for micronutrients, but might be difficult to use for bulk food production. Your question asks for current technology to the extent possible, and engineering bacteria to produce large quantities of food is not proven technology. Many of spirulina's nutrients aren't biologically available. Nutrient yeast isn't much of a nutrient source -the B12 content is fortified- and is used by vegans as seasoning, not for health benefits.

So in the end it's down to traditional crops, grown hydroponically in nutrient slurries of water mixed perhaps with human waste. Lettuce, tomatoes, and strawberries have already been grown on the ISS, but these are low-calorie luxury garden crops, not the sort of plants you can live on. Grains are probably not a good route to go because they require milling, and keeping weight down is usually a priority in space. To that extent, Mark Watney was fortunate to have potatoes: a mix of root vegetables would be a good, reliable source of bulk calories for your colonists. Legumes would be great for protein. Soy has a huge yield and very high protein content. If you are concerned about excessive soy intake, there are many other beans to choose from. Lentils and cowpeas, for example, require a lower energy input to cook in comparison to other beans.

Answer 3

Aquaponics is your friend

Similar to Hydroponics, Aquaponics is the science of growing plants in a liquid medium (no soil), combined with aquaculture. They don't have to be water-borne plants, pretty much any green and leafy is very well suited for this, and with a bit of careful managing, other plants such as cucumber, tomato and peppers will work as well.

Combine these plants with edible, crowd friendly fish such as Tilapia or certain species of cod and perch. Finally, you will need nitrification bacteria to convert the ammonia produced by the fish into nitrates to be used by the plants. These can grow on any surface within the system.

After the water has passed through the hydroponics system, where nutrients, nitrates/nitrites and ammonia is taken in by the plants, is is cleaned and oxygenated then passed to the aquaculture system, before looping back around.

Yield is variable, but we will assume upper end as your world will likely have researched further into this. Thus per US gallon of water in the system, you will gain 1 square foot of farmland and 1 lb of fish stock. Lets say half of that stock goes towards rearing young fish, to ensure we get half a pound per gallon per day.

A quick google says 0.5 lb of Tilapia is 292.5 calories. According to this site, sweet potatoes can be grown in hydroponic conditions, and this other site says they provide 70,000 kcal/ha/day, or 650 calories per square foot. Thus you will need approximately 2.5 gallons of Aquaponics per person.

The five main inputs to the system are water, oxygen, light, feed given to the aquatic animals, and electricity to pump, filter, and oxygenate the water. You will likely have to manage separate tanks for breeding fish, but they can all be connected into the same water cycle.

Water will be a mostly closed loop, no worse than any other system on your station. light can be rolled into electricity costs and oxygen will be provided in part by your plants, although you will likely need additional oxygen systems.

Producing the feed for your fish is amusingly similar to the rocket problem. You need plants and fish meal for your fish, the fish meal is made from fish. You need feed to produce those fish... This site says the average feed contains approx 25% protein (a mix of fish and meat meal, plus oils), 70% plant meal and 5% minerals. This other site says you need 360~ grams of feed per 100 talipia (found by averaging the feed requirements of a newborn and adult).

Earlier, we worked out our population are each eating 1.5 Talipia per day (at 1lb per fish), which means we are harvesting 15,000 fish per day. The feeding plan recommended will bring newborns to 1lb in 194 days, meaning we will have 291,000 fish at any given moment. Thus we will need just 1,047.6kg of feed per day. I don't know how much fishmeal you get per Talipia, but we need 261.9kg of it from 15000lb (6804kg) of fish. Thus we will need to reserve 4% of each fish for fishmeal. I think that's easily doable.

Further we need 733.32kg of plant meal per day. Google says that 1kg of sweet potato has 860 calories, and we get 650 calories per square foot. Thus, we will need an additional 870 square feet of space for growing plant meal. This will come to 870 US Gallons of Aquaponics.

At 45,400 lb of Talipia in our system, we'll need 45,400 US Gallons of Aquaponics, providing 45,400 square feet of growing area. This is almost double what out population of 10,000 actually needs in crop yield. By picking a more suitable crop for plant meal (as I haven't found potato being suggested anywhere) we should be able to cut that down some. Or we could use the excess space to grow utility plants, such as textiles, or less efficient, more interesting food.

This amounts to 170 m3 of Aquaponics. Let's double that to 340 m3 to take support systems, access areas etc, and you can fit the whole thing into about 5 shipping containers, or 13.6% of an Olympic swimming pool.

So, we've proven that you can sustain your population with only 9 US gallons (0.034m3) per person and it is very efficient, as the only real input is power. You could stagger your yields to allow daily production, meaning preservation is not an issue, and finally it is real plants and real fish. What could be more palatable?

Answer 4

Insects lots and lots of Insects

Insects would be one of the best choices for your Space Dwellers to eat. The HIGHEST in protein and can adapt very well in space (better than the humans anyway) they could also be used to combo with other foods to help in production. if you have ever grown your own food before; you would know that even if you get all the right stuff (soil, lighting, nutrients) if you don't have an ecosystem to go along with it your plants will not thrive.

some examples:

Ants: some of the most amazing little creatures around (look them up) https://www.youtube.com/watch?v=Hc1hrvWjRQs they can be very useful to you and not just in "meat" they also can maintain your crops and get rid of your "green waste".

Cockroaches: yes they can be of use, if they get the right species even if its plan "meat volume".

Grubs and Worms: the best friends for any garden and the most reliable in "meat volume".

So pick insects, they will help you, they will feed you, and will cost almost nothing to produce

Answer 5

I got some great recommendations and ideas, so I can't really pick the "right answer" as they're all very good ones.

I'll post the summary and credit the authors:

Willik had the most upvoted answer, proposing that space dwellers eat edible bacteria (spirulina) and use microorganisms as micro food factories to create something called "beefy meaty peptides". Look up Willik's post for the links and sources, it's interesting stuff.

Creed Arcon proposed cultivating insects for both consumption and creating bio-diversity in space farmlands. A great idea, especially since insects are protein-dense.

Pink Sweetener argued that insects might not be sustainable as they too require food to be farmed and proposed an entirely vegan diet. He argues its entirely possible to adequately feed humans in space with a healthy diet of potatoes, legumes, soy, other such beans (as they are protein-dense and have high crop yields), in addition to veggies.

Kyyshak is the most math heavy, and is therefore more convincing then other posts. Kyyshak argues for aquaponics in which crops are grown in nutrient rich slurries that pump past these plants to enrich them as they grow, then are filtered and treated to farm fish such as Tilapia before looping back around to feed the plants again. Kyyshak has the hard math to back up his claims, and its pretty convincing stuff!

Thanks to everyone who posted, you've given me a lot to sink my teeth into! If anyone feels I didn't clarify or summarize their post correctly, please let me know and I'll edit accordingly. Thanks again!