# How many calories can a cubic meter produce?

In my Generic Dystopian Setting™, space inside the nuclear shelters is at a premium, and so people have had to come up with creative means of growing food inside them. This often includes thinking three-dimensionally. For instance, edible vine-based foods might be grown in the space above conventional agriculture, although this example is merely for the purposes of proving a point and shouldn't effect any answers to this question.

The question: how many kilocalories/large calories/food calories can be produced by growing plants/fungi/etc. in a single cubic meter of space?

The food in question can be prepared via microwaving, cooking, curing, or the like, but it cannot be something like algae where it's just biomass that can't be turned into a human-suitable meal with the facilities of a 21st-century kitchen.

Assume that all forms of modern 21st-century technology (including advanced aeroponics and hydroponics technologies) are available, as well as 1 kilowatt of power per cubic meter.

Variety doesn't matter. I'm fine if it's all rice.

A question similar to this has been asked, but not answered. I hope I covered the bases it missed.

• "kilowatt per hour" doesn't make sense. Kilowatts already have per hour in them. Commented Oct 16, 2021 at 10:57
• @JohnDvorak Will edit. Commented Oct 16, 2021 at 11:00
• Just converting the units, 1 kW = 860 kCal/h. I will leave it to someone else to pick a plant that provides the best conversion ratio, but with the right plants you should have plenty of power output. Commented Oct 16, 2021 at 11:10
• worldbuilding.stackexchange.com/questions/9582/… Relevant? Most plants will need a minimum height above and below ground for growth, plus some space for energy/water/nutrient provision. Commented Oct 16, 2021 at 11:20
• Volume is irrelevant. What matters is the amount of photosynthetic AREA exposed to light, and the light intensity. So it's kW per square meter. Commented Oct 16, 2021 at 16:57

You can look at work done for food for space exploration, and extrapolate. An example is this paper. It uses square metres rather than cubic for some reason, but looking at their diagram on page 9 the system is approximately 1 metre high so for simplicity's sake you could just assume 1 m square = 1 metre cube. That gives the numbers below. I am surprised that winter squash seems to produce the most at 54 Kcal/metre/day, but I guess they are well suited to the hydroponic conditions.

These are calculated to provide the nutritional requirements of the crew:

There is probably not a single answer.. there are quite some options ! I'm not familiar with calculations, but there exist certain types of food that allow very volume-effective production,

Growing food underground: peanuts

A very high yield, maybe a winner: peanuts. They grow underground, allowing for a high production per unit of volume. Same counts for potatoes and radish. High energy, large yield.

Bananas

My second place, sofar.. in terms of pure energy per volume,

.. but un practice, you'll need a lot of space to grow banana trees. I mension them because if you would calculate calories/m3 only, it would probably result in a very nice yield. I think genetic engineering is needed to allow large scale banana harvesting in greenhouses.

Growing food inside boxes

Fungus or mealworm may not be appropriate food (or appreciated food) for most humans. However, in times of great resource difficulties, it may become necessary. In times of need, insects and worms could be the answer to your question !

Fungus

Certain species are edible, they will fit in very small spaces and grow very fast, under certain conditions.

Mealworms

A very effective way to produce large amounts of "calories per volume" is insects, larvae and mealworms.

Chicken meat is definitely not an answer, but there will be demand for it as a supplement. Your small volume mealworm farm could feed many chicken. Consider modern bio-industrial techniques to raise your chicken in stacked cages, you could fit a lot of them in a cubic meter..

Chicken suffering from energy optimization decisions

Greenhouses

Chicken also produce high energy fertilizer, suitable for greenhouses. The advantage of using greenhouses is volume/density (your question) and energy use effectiveness.

Honey

Bees are able to produce healthy and very high energy food with lots of carbon hydrates. However, your natural surroundings should provide the bees with food, which would involve additional total "volume" used, of course.

Sources,

https://courses.lumenlearning.com/wm-nmbiology2/chapter/fungi-as-food/

https://www.instructables.com/Mealworm-Farm/

https://www.gardeningknowhow.com/composting/manures/chicken-manure-fertilizer.htm

https://www.rd.com/article/peanuts-real-definition/

• "Consider modern bio-industrial techniques to raise your chicken in stacked cages" - makes for a whole lot of very unhappy birds. Not good. Commented Oct 16, 2021 at 12:00
• Not good, agree.. but there are no tags requiring ethic considerations.. this question is about energy yield per volume. As said, there are many alternatives. There are no tags for culinair appreciation or culture, either. Insects/worms could be the actual answer. Suppose you'd want to produce food in a space ship, the crew would eat home grown pindas, mushrooms, insects and worms, and chicken for Christmas ? Commented Oct 16, 2021 at 12:07
• ... but I do agree with yout remark. I've added a horrendous picture with a suitable comment. Commented Oct 16, 2021 at 12:18

Grasshopper farming.

Grasshoppers have many benefits. They are already eaten by many people in the world, their dry protein weight after processing is high (70%, turned to powder it seems), they dont fatten as much, they are healthy to eat with lots of nutrients already in them (like iron, zinc, omega 3&6 and follic&amino acids), they are swarm insects so can be grown in large groups and they eat pretty much any biomatter (grasses, plant stems, flowers, fungi, moss, animal dung which might include human feces, rotting meat, and weakened/dead insects or spiders).

Since they are insects and dont need light, you can create beehive like boxes with space for them to sit on and food to be thrown in for them to eat and compared to other protein sources extremelt efficient. I cant verify the claim but apparently it reduces greenhouse gas emissions by 99%, water consumption 1,000-fold, and arable land usage 1,500-fold compared to other protein production methods.

Unfortunately I couldnt find any claim to the exact nutrients per cubic meter, but the 1500 fold less arable land required claim should be an indication that it is efficient.

The big "but" here is that you first need biomass. It means that grasshoppers would be a good way to deal with biowastes but that growing plants directly is more efficient overall. I still wanted you to have this option as a side-option, since you can turn the inedible parts of whatever plants you use as food for them.

https://www.foodnavigator-usa.com/Article/2019/04/12/Grasshoppers-not-crickets-will-drive-the-edible-insect-revolution-says-Hargol-Foodtech-at-Foodbytes