One Trillion People!

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Based on my research on the purported output of aquaponics (potentially more than a half a pound per square foot per day of edible food) I decided to amuse myself by calculating how many people the world could sustain using these techniques. I found a web site that detailed yields from hydroponic and used that as a basis for my calculations, though aquaponics is supposed to be more productive overall. I came up with a rather amazing number that, based on my assumptions, seems to be by far the lower bound for the maximum human population. I did some what I feel are modest extrapolations and came up with even more amazing numbers, then decided to throw caution to the wind and put in a few more un-modest extrapolations and got some unbelievable numbers for what sorts of populations that could be sustained. I don't expect to convince anyone my numbers are realistic, plausible, etc., but what I hope to do is show that our current global food economy is seriously out of whack and people are only starving because no one wants to do something about it.

What will we all eat?

I use as a basis for my calculations the information here: (which I have copied here: in case something happens to the original site). This greenhouse facility reports that it is capable of turning out 10,000 lbs of produce per month from an 1,800 square foot greenhouse. According to my calculations (see that results in a bit more than 1 million calories per month or a bit less than 19 calories per square foot per day. Presuming people need 2,500 calories per day to survive, that means that the 1,800 sqft greenhouse can support more than 13 people, or around 132 square feet per person.

Something to note: the amount of calories I calculate is likely very far from the absolute maximum that could be captured per square foot of greenhouse space. At a minimum, the reported amounts of production are for the edible portions of the plants, the total biomass is much higher. Additionally, from a raw calorie perspective, duckweed (a nearly complete nutrition source, btw) is quite prolific and can probably produce on the order of 4 times more biomass per square foot. Then, of course, there is the use of algae, which grow faster still (and, in certain cases, are complete in nutrition, though I imagine quite boring to eat) and in general it is reported that algae can produce about 10 times more biomass than higher plants. As such, it should be practical to consider the calorie estimates above the rock bottom, worst-case scenario and expect that after just a few decades of selective breeding and process optimization that 5-10 times as many calories could be produced per square foot. For this paper, though, I will stick with the 18.8 calories per square foot as outlined.

Also, one needn't confine oneself to only vegetables; using the principles of aquaponics (the synergistic combination of aquaculture and hydroponics, where the 'waste' water from the fish is used as food for the plants, which in turn, purify the water for the fish) a rather staggering amount of fish can be produced in a very small amount of space (around 2.7 lbs/person/day on average, based on the 132 sqft figure above) and all of that can be underneath the plant surface, thus there would be no reduction in the total number of calories captured via photosynthesis. For variety chicken and rabbit could almost as easily be swapped in for fish with only minor modifications to the process. Also, if we are to presume that the least fortunate would get their calories from less appetizing sources like algae with their perhaps more than 10 times increase in calories/sqft, then the most fortunate could probably easily afford to 'waste' space and raw calories by feeding (and then consuming) such traditional calorie sources such as beef, pork, lamb, etc. The same principle would be true for diversity with regard to produce, for a higher price (in reduced overall efficiency in calories/sqft) other crops could be just as easily grown and I easily envisage a robust market place where a wide variety of food sources are commonly available, fresh daily.

Where will we all live?

While there are some minor exceptions in the very heart of cities, for the most part human living today is two dimensional. If we are to assume that people will only occupy the space needed to produce the calories they need (i.e., 132 square foot per person), that would result in a population density of a bit more than 211,000 people per square mile (or a bit more than 80,000 people per square kilometer). This is quite high when compared to today's population density (where the most populated city (Manila, Philippines) has 111,000 people per square mile and the average density of the 50 most populated cities is 62,000 people per square mile; see, but, I think, not out of the question when you consider that the average city is not built of 100 floor sky scrapers but is mostly filled with much shorter buildings and, of course, has a lot of space devoted roads.

If we go with the rather arbitrary designation of 7,500 square feet per person on average (for living, shopping, waste collection/processing, building supports, infrastructure, etc., etc.) then we require that the average number of levels below each square foot of greenhouse to be 57 (or, around 680 feet, presuming an average of 12 feet per level). Since we currently have many buildings well in excess of 57 floors, I presume it is quite plausible to expect this sort of density is not just possible, but probable without any serious difficulties. Indeed, when designing an entire city that is expected to be 700 feet 'tall' on average there are probably some simplifications that could be made as wind load would be averaged over the entire structure and there are probably some seismic simplifications that could be made as well.

(Regarding my rather arbitrary selection of 7,500 sqft per person, people can live in very small areas quite comfortably and for the long-term. A good friend of mine shared a 500 sqft apartment in Hong Kong for several years and that included bathroom, kitchen, living room and of course bedrooms, for a whopping total of 250 sqft per person. Another good friend raised 8 children in a 1,500 sqft house, for a grand total of 150 sqft per person (granted they had a full basement and lived on 10 acres). Most of the houses I have lived in, in my mostly middle class existence, have been less than 2,500 sqft and there were four of us, so for us a bit more than 600 sqft sufficed. I 'pad' the square footage up because each person has a certain amount of infrastructure dedicated to them and that infrastructure also takes up space. For instance, each person shares some grocery story, common area, waste processing, government, employment, etc. spaces and I wanted to attempt to capture that. I am sure there is some research somewhere that details the average amount of space a person needs in our industrialized society, but I didn't research it. If anyone does find that I would love to know about it.)

OK, so if we are going to stick with the idea that each person is going to occupy no more than horizontal space needed to produce the food to survive, what population could our globe support? The current amount of arable land (that land which is generally accepted to be suitable for farming, but might not actually be in use; see is a bit more than 5.3 million square miles (13,805,153 kmĀ², or around 10% of the land surface area, leaving plenty of elbow room for the rest of nature on land and leaving the sea totally untouched). With that surface area, we can thus support a bit more than 1.1 trillion people. Given the number of quite conservative assumptions I have been making (yes, I see you rolling your eyes when I just mentioned a trillion), later I will extrapolate a bit and show that the earth could probably support more than 400 trillion people if we were to use the entire surface area and dedicate the exclusive purpose of the planet to sustaining the maximum human population.

CO2 and Global Warming?

People are CO2 emitting machines (like essentially all non-photosynthetic organisms) and with such a huge population density there would be lots of people contributing. However, plants grow more robustly in an environment with higher levels of CO2, so given that we can assume that the city's ventilation system would cycle the air in living spaces through the growth areas. Indeed, I would expect it is plausible to make arguments that a trillion people living as described herein could have a dramatically lower impact on the natural ecosystem since except for the direct impact of the living space everything else is recycled and thus no on-going impact to the remaining 90% of the land or any of the ocean.

Economics and Eployment

I will be addressing this elsewhere and when I have it written I will edit this to have a link to it, but basically it is about a pure virtual economy where almost all physical tasks have been automated and people are basically paid to consume.


Really, this isn't an issue at all. For success at this level 100% of 'waste' would have to be recycled as all the plants to is convert CO2 and water (and nitrogen and some minerals, which are recycled also) into complex molecules using the sun's energy, which is already happening all over the globe and has been for billions of years.

Living like Troglodytes

For those of you who can't imagine living underground all your life, what would be more valuable to you? A window that allows too much heat in during the summer and lets out too much heat during the winter and in all cases looks out on the exact same scene or a 'window' that is full programmable and capable of displaying anything you desire, anywhere in the world and even produce recorded views. If all of our walls were essentially video screens then we could easily have any view we want irrespective of whether we were at the penthouse suite or not. Indeed, we could have virtual crowds with the joy of knowing a bathroom always remains just a few steps away and you can 'magically' return home in an instant at any time. I can easily imagine such a virtual life would be worlds better than what we have today, though there will always be those who stubbornly refuse to go with the flow.


I am sure one major complaint many people would have is how can we possibly support a trillion people when we are already undergoing an energy crisis. Well, the easiest response is to reveal that the 'crisis' is limited to crude oil supplies (and it is quite arguable we are indeed having a crisis, but that is for another post: In any case, and certainly for the long term, fossil fuel is not capable of sustaining our current population levels for more than a dozen centuries at best and this post is about long-term sustainable population. Clearly nuclear energy will be the way to go, but not the messy, expensive and inefficient methods we have today, but way better, way more effective and way more efficient means such as molten salt core reactor ( So what is the maximum number our planet could sustain?

So what is the maximum number our planet could sustain?

If we presume that substantial increases in efficiency are to be expected as the system is optimized and plants and animals are bred for the conditions, we can probably safely assume that we can increase caloric output by at least an order of magnitude. Thus, each square foot could produce as much as 200 calories per square foot, per day, so each person would only need 12.5 square feet of surface area. With the total surface area of the planet being almost 200 million square miles (510,072,000 km2, see, if we used 100% of the surface to produce food we could support over 400 trillion people (this assumes that the average productivity at the poles is the same as at the equator). Then the average population density becomes the rather staggering 2.1 million people per square mile. If we go with the same 7,500 sqft per person, then the average depth of the global city becomes 600 levels, or (at 12 ft per level) 7,200 feet or about a mile and a third. Clearly there would be no room left for anything except what was necessary to sustain human life, so no nature, no visions of the sea, nothing (but all that could have been recorded, so our virtual lives might go on in ignorance of the total destruction of nature).

Even more possible?

Have we reached the maximum yet? Only if we presume we are totally reliant on the sun to provide the energy necessary to produce calories to sustain our population and limit ourselves to the planet. If we presume some rather modest extrapolations on (nuclear) energy production, it seems conceivable that we could have multiple levels of light emitting surfaces other than the sun which then would enable us to grow yet higher populations. Indeed, it might prove possible to preserve some semblance of natural ecosystems even with 400 trillion people if we were to posit leaving the actual surface of the planet natural and provided our own light energy.

Things get really amazing if we are to assume a space-based population using the same calorie production techniques. How many people could our solar system sustain? Given that the earth's surface represents a nearly infinitesimal amount of the area capturing the sun's output, if we were to capture the entirety of the sun's output to produce calories we could support an additional 550 million times higher population (see Actually, if you consider that the surface of the earth is dark half the time, we could support an additional 1.1 billion times higher population or a rather difficult to imagine 440,000,000,000,000,000,000 or (if my research is correct) 440 quintillion people. This is only looking at the output of the sun, if we add in our own nuclear energy we have tripped off into further increases. Clearly at some point the material mass of the solar system can no longer support the infrastructure, but given that any such population density would be 100% devoted to 100% recycling long before it gets to these truly astronomical levels, 400 quintillion people might not even be the maximum our solar system could sustain.

Don't even get me started on other solar systems!