How to feed interplanetary humanity?

Question

2175: humanity has expanded to the other planets, has found the ninth planet by observing slight gravitational disturbances from one direction (it turns out to have many habitable-ish moons that, if dark, are perfect for setting up colonies and space stations on), and population growth has since exploded. This instant massive expansion was kind of the ultimate land rush: instead of the government starting to sell the population land, an efficient cold-fusion torch drive was discovered that allowed for very fast travel to other planets - a few days at most to Jupiter and back, if the positions were favorable. The result is that everyone started moving to other planets, and with so much empty space and opportunities and whatnot, the population grew exponentially.

At first this was fine: countries of Earth just sent what supplies couldn't be made on other worlds out into space, and everything was fine. But exponential growth being exponential growth, by 2100 the carrying capacity of the entire Solar System was exceeded. Because of societal factors and random chance, the population hadn't the chance to level off into a logistic curve like regular demographics suggests, but instead rocketed into the range where all the combined farms of Europa, Titan, Mars, and Earth couldn't produce enough food to feed every mouth.

Obviously, people died. Riots broke out over food distribution, piracy skyrocketed even though there isn't anywhere to hide in space, and five hundred million people died before a solution was found.

The issue that I'm having is that I can't figure out what that solution is. By the time the food reserves and the backup plans are through, there are 80 billion living humans while the world-spanning farms of Europa and Mars and Titan can only sustain around ~40 billion; most of the excess are young adults born in the time of the Interplanetary Land Rush. In a less-extreme circumstance, the death rate would just increase a little bit and the population would level off, but obviously it won't level off by 50% without causing catastrophic damage to society.

I found I had this problem elsewhere, too, when designing supermassive galaxy-spanning alien empires: it fundamentally takes a large area of land per person to farm enough food to feed everyone, and there simply aren't enough planets whose conditions are perfect enough for any species to create enough farms to feed everyone without the population density being very low.

So: is there a way to circumvent the "carrying capacity" of planets for very advanced civilizations?

---

I feel like this question is a duplicate since it's so simple and seemingly basic, but I've searched the site a few times and found nothing. Sorry if this is a duplicate.

Answer 1

Fix your politics.

Production is limited by technology problems, infrastructure problems, and political economy problems.

Technology problems don't fit your core scenario of a sudden crisis. Parents aren't idiots: if they're having trouble affording to feed the children that they have, they tend to not have more. Businessmen aren't idiots: if the rising price of food means that they can reliably make bazillions of space dollars by shifting resources into food production, or by getting the rights to a technology that lets them produce more food with the same resources, they tend to do that. There's every reason for supply and demand to meet in the middle if technology is the limiting factor.

Infrastructure problems can fit your core scenario if there's a sudden calamity like a war or a natural disaster which destroys or disrupts the food-producing infrastructure, resulting in a famine. But your detailed scenario doesn't have any. Without a disaster, supply and demand meet in the middle as above.

Political economy problems fit both your core scenario and your detailed scenario, and have the added advantage of being common in real life. As you note: "Because of societal factors."

The typical inference is that "shortage" means "there just isn't enough of X". The meaning in economics is different: "less X is produced at the existing prices than is demanded at those prices". In the real world, unless there has been a disaster, a shortage almost always occurs because somebody, usually a government, has prevented the price from rising in one or more sectors, hindered investment in more supply, or both.

(For a real-world example involving water instead of food, when the government of a desert region uses price controlled contracts to set the price of water low enough that farmers can make a larger profit by growing high-rainfall plants in a desert than by growing low-rainfall plants, there just isn't enough water. And as long as the political support of farmers is needed to win the next election, it's likely to stay that way until the water starts to run out.)

If this is the case, our non-idiot parents and non-idiot businessmen will not change their behavior. The parents can afford to feed their children right up until the stockpiles run out, so they have more children. The businessmen don't see dollar signs blinking in front of their eyes when they consider diverting resources to food production, so they produce widgets instead, even as food stockpiles are running dry.

Fix the politics. Non-idiot parents and non-idiot businessmen will take care of the rest, whether it's by !aeroponics in space!, by converting buildings that used to manufacture widgets or manipulate information into terrestrial aeroponics, or by high tech chemical synthesis using your civilization's ultra-cheap fusion energy.

---

clarifying note: Businessmen (working for a particular well-established cartel which either influences the government or has in certain sectors become the de-facto government) can be the thing about the government that you have to fix. In that case it's usually "hindering investment in supply" (protectionism), since price ceilings on finished goods don't go together with charging as much as possible. Although it's conceivable if the government is captured by a group which uses food as an intermediate good (like water in the above example).

Answer 2

Farming in space!!!, the long and the short of it is that there are a lot of resources in space that can be used for food production and in the habitable zone, or even closer to the star, abundant energy. Eventually you'll end up running into a wall with Phosphorus, the issue of Phosphorous Abundance is probably going to be an eternal bottleneck on universal populations, but otherwise there's plenty of everything you need floating around once you're into full blown space industry. If you're out in the dark then nuclear power is your friend, particularly Thorium for abundance, and safety, and/or, if possible, fusion for energy density. Current technological trends suggest that antimatter is going to be non-competitive for a number of reasons and never particularly safe compared to other systems. You can also run with non-photosynthetic methods, using mycoculture. The major issue becomes one of enclosing, shielding, and supplying atmosphere to sufficient growth space volumes.

Answer 3

I agree with the @Ash. Farming in space is probably your best option. In the right conditions anything can be grown. I think of the film " The Martian" and how he was able to survive. Also it doesn't have to be pretty. Real life is stranger than fiction. I say that as I think of Rice patty Fields.

Answer 4

is there a way to circumvent the "carrying capacity" of planets for very advanced civilizations?

Planets do not have a carrying capacity.

The basic malthusian mistake is that output relates to "resources".

In fact resources are irrelevant, and output is caused by human brainwpower, and hence is totally unlimited.

Hence, we are always hearing for example that "the oil will 'run out' and we'll be screwed". Of course, if oil runs out humans will very simply make oil. In your scifi vision we have cold fusion for goodness sake, which can apparently generate almost incomprehensible amounts of power, so anything is possible.

Hence for example you mention a land shortage,

it fundamentally takes a large area of land per person

at the tech level you describe, they could trivially build (say) large flat "farm plates", ie planet-sized, that float around near a population-planet and provide all the 1800s -style organic cutesy farmland needed!

Answer 5

A solution I saw in another story is manufactured food. The solution here could be the invention of a synthetic food, which can be produced from metals, ice, and other stuff that can be easily extracted, and turned into something edible enough to sustain people long-term. Due to the shortage, it's likely a lot of capacity would be diverted into making as much of this synthetic food as possible, quickly solving the shortage.

Answer 6

Farming requires Light, Carbon, Water and trace elements of various kinds. And maybe a bit of gravity to help things out, at least until we bio-engineer or select stuff to grow in zero gravity.

Earth (or planets in general) is far from unique as being a source of any of those.

As it happens, this is also a way to convert CO2 back into O2.

So any large habitat will probably have huge bioreactors/farms to scrub CO2 out of the air and produce O2. That process produces plant matter, which can be feed stock for animals or food itself (or used as fertilizer).

You'll have ice mines (which is used to provide O2 to increase the total biosphere size). Carbon is crazy common, but maybe you'll have people mining hydrocarbons out of Hyperion or Titan some other moon.

With the energy needed to fly around the solar system, the energy to feed people isn't going to be hard. Just use the fusion drive as a "light bulb". Then build large hydroponic farms. Import raw hydrocarbons and water, crack some of the water, fuse the hydrogen, use the O2+hydrocarbons to make CO2, grow plants in the water+CO2+light and export food.

You can also move this closer to the sun and use solar power to grow food in a kind of "Dyson Swarm" of food production. That removes the need to have a fusion power source.

Biologicals self reproduce from extremely common raw elements. They are among the easiest things to build factories that produce them. It isn't plausible we'd have an industrial civilization capable of building things like spaceships and not be able to make food.

The food can be expensive - planets provide a huge amount of area to grow food without having to build a structure and support. This is why we grow food in fields instead of hydroponics today.

But our society is significantly poorer than a space faring one. We don't want to pay more than 10% of our economy for food in the industrialized world; an economy 10x larger could afford "vertical farms" to make food and not run short.

It would take extreme inequality to not be able to afford to feed people in space. Colonies whose standard of living has collapsed.

Answer 7

Welcome to Terra!

The Empire of Mankind is vast, and full of hiveworlds, but there is one planet that is much more populated than any other Hive: HOLY TERRA. And in contrast to Necromunda or other Hives, it produces nothing, not even its own food, but devours people... But how is it fed?

• Corpse Starch! Did you die? Great! Now you get fed to maggots that also consume your excrement in the vast cleaning vats. Don't mind that and those maggots are also harvested to be turned into food-paste.
• Agriworlds! There are whole planets that produce food material on a planetary scale, and those are shipped across the void. Often enough, the goods are perfectly conserved by just being exposed to vacuum and the cold of space: grain doesn't spoil that way! Also, the beauty of that is, that you could send the ships at sublight speed, they will feed future generations once they arrive.

Answer 8

If food variety and quality is not the issue, and we just focus on feeding for survival, this is not a major problem. Breeding algae in biotanks is by far the most energy/resource efficient way to produce calories. Couple this with full recycling of biomatter, and mass mining of H2O, CO2, nitrates and frozen hydrocarbons, and we are set.

Well, as long as everyone is ok with artificially flavored algae goop/tofu/humus/paste.

Algae-based agriculture can then be enhanced by adding fungi-producing mycocultures, and if there is some surplus, aquaponics, cultured tissue tanks, and even aquacultures to help recycle biomatter into food (or at least more palatable food.)

On interesting option too, is using methanotroph bacteria to convert methane into biomatter. There are plenty of sources of frozen or liquid methane out there, including Titan. Have the bacteria convert it to biomass, and the resulting spare CO2, and H20 could be funneled towards the algae. Now you have two types of bio-goop!

So at the very least, you can feed entire humanity with such exciting meals as algae derived greenish sludge, bacteria derived beige sludge, and (for variety) the luxurious grey sludge made of fungi. It should be possible to engineer some of those to produce capsaicin as flavor, and add salt recycled from human urine.

As long as you make sure to recycle compostable matter (including human waste and corpses) the system would be easily self-sustaining.

This assumes that there are no further gains in the technology of artificial food synthesis. Synthesizing sugars, oils, or even proteins out of inorganic matter is just a problem of computational complexity: once we cross the threshold of being able to produce those, we can just skip farming altogether. At which point will that be economical, is for your to decide.