5 ms·

"All the food you need" is a bit of a stretch for me. Maybe I'm mistaken. A human needs around 2000 kcals per day, or a little less than 100 joules/second. Easy

by mabbo 10y ago

"All the food you need" is a bit of a stretch for me. Maybe I'm mistaken. A human needs around 2000 kcals per day, or a little less than 100 joules/second. Easy to remember: we use as much energy as a 100 watt incandescent light bulb. Solar energy has a maximum output of 1120 W/m2 at the surface of the earth. So theoretically, a square meter could support 10 people. But there are one or two efficiency losing steps that throw this all off. There's only light for half the day. Plants only are about 3-6% efficient at absorbing solar energy. The plants also are only taking up a fraction of the ground they're using, let's be liberal and say half. Then there's the whole 'how much of the energy the plant used was actually converted to edible calories' question, which is beyond my ability. Multiplying that together, the best I can imagine is around 12 m^2 per human. I'd love someone to show me a mistake in that logic, because I am super excited about things like this. I know I'm going to own one of these someday in the future.

officialjunk 10y ago
There is also all the molecules from the local environment that play a part as well. Sunlight energy is used by the plant to convert the available local resources into a different form. The total energy available isn't limited to sunlight energy, but includes plants' local environment.
mikekchar 10y ago
Has something changed? I don't see the string "All the food you need" in the article (or anything like it... possibly I missed it). Anyway, in Japan the amount of rice that one person historically has eaten for one year is 1 koku (which is about 150 kg). The yield for rice is about 0.41 kg per square meter. So you need well over 300 square meters to grow enough rice for one person for one year. That doesn't include other vegetables or fish (or whatever). In Walden, Thoreau describes self sustenance and living off the land. I believe he talked about farming a quarter of an acre, which is about 1000 square meters. Many people doubt he was able to rely completely on that quarter acre. You can get some extra efficiency if you build vertical grow systems, but even your 12 m^2 is a pipe dream. Their 3.5 m^2 system will provide snacks at best. So I think you are right to be skeptical.
- mabbo 10y ago
  "All the food you need" is in the video. The 12m^2 is a theoretical limit, like the minimum one could do without violating the law of physics. It's not practical.
underbluewaters 10y ago
For reference, I had a very productive set of raised beds for a while in sunny coastal California that represented about 7.5 square meters. I could produce more than enough vegetables for my wife and I for about 1/4 of the year. That did not include meat, and various carbohydrates like rice, pasta and bread. I felt very confident though, that a with a total of 8 8x4ft raised beds that I could feed us all the fruits and vegetables we needed. We ate quite a few vegetarian meals so when the garden was doing well it reduced our food budget enormously.
roel_v 10y ago
I do some work on crop modeling. A few years ago at a project meeting, in the evening in a bar, we did some rough calculations; there were agricultural engineers and agricultural economists in our group, so it wasn't completely amateur hour (but not scientifically robust either, of course). Anyway, the result was that in Western Europe you need about 100m2 per person to grow enough food to sustain oneself for a year. This took into account that you need to grow crops that keep a long time to last you through winter etc. It didn't particularly consider variety in crops (neither for taste not for soil management purposes), but it wasn't potatoes year round either. You need to be a competent farmer as well, but it didn't consider really high tech closed-greenhouse-like setups either. Still, that was a sobering number for many in the crowd - it completely undermines the whole 'self-sufficiency = sustainable' mantra.
- justin_vanw 10y ago
  100m^2 doesn't seem like so much to me at all, certainly not sobering. This would mean one acre of land would sustain about 40 people (or 100 per hectare). Taking wikipedia's number of 13,958,000 km^2 of arable land in the world, this would mean a maximum world population of 137,963,876,580, which is about 20x the current world population. Of course, this assumes equal quality of land to the land in your rough calculations, and I am guessing your number is assuming far more intensive cultivation than is typical (typical numbers I've seen are 1-2 acres / person).
  - TheSpiceIsLife 10y ago
    The full calculation would also need to take in to consideration wastage / spoilage; crop failure; loss to pests; nutrient density (probably can't thrive off potatoes and corn only); animal feed (pets as well as animals for food). Having said that, I'll now go on to say: with one inhabited planet there are limits to resources, but the limits to human resourcefulness are undefined.
    - rahkiin 10y ago
      Don't eat animals. One problem solved. Might want to have some cows for milk and using their waste as fertilizer Edit: the not eating animals is not in a vegatarian way. I love meat. But if you want to fully sustain yourself on the smallest area possible, animals do not aid your cause.

by mabbo 10y ago

officialjunk 10y ago

There is also all the molecules from the local environment that play a part as well. Sunlight energy is used by the plant to convert the available local resources into a different form. The total energy available isn't limited to sunlight energy, but includes plants' local environment.

mikekchar 10y ago

Has something changed? I don't see the string "All the food you need" in the article (or anything like it... possibly I missed it). Anyway, in Japan the amount of rice that one person historically has eaten for one year is 1 koku (which is about 150 kg). The yield for rice is about 0.41 kg per square meter. So you need well over 300 square meters to grow enough rice for one person for one year. That doesn't include other vegetables or fish (or whatever). In Walden, Thoreau describes self sustenance and living off the land. I believe he talked about farming a quarter of an acre, which is about 1000 square meters. Many people doubt he was able to rely completely on that quarter acre. You can get some extra efficiency if you build vertical grow systems, but even your 12 m^2 is a pipe dream. Their 3.5 m^2 system will provide snacks at best. So I think you are right to be skeptical.

mabbo 10y ago
"All the food you need" is in the video. The 12m^2 is a theoretical limit, like the minimum one could do without violating the law of physics. It's not practical.

underbluewaters 10y ago

For reference, I had a very productive set of raised beds for a while in sunny coastal California that represented about 7.5 square meters. I could produce more than enough vegetables for my wife and I for about 1/4 of the year. That did not include meat, and various carbohydrates like rice, pasta and bread. I felt very confident though, that a with a total of 8 8x4ft raised beds that I could feed us all the fruits and vegetables we needed. We ate quite a few vegetarian meals so when the garden was doing well it reduced our food budget enormously.

roel_v 10y ago

I do some work on crop modeling. A few years ago at a project meeting, in the evening in a bar, we did some rough calculations; there were agricultural engineers and agricultural economists in our group, so it wasn't completely amateur hour (but not scientifically robust either, of course). Anyway, the result was that in Western Europe you need about 100m2 per person to grow enough food to sustain oneself for a year. This took into account that you need to grow crops that keep a long time to last you through winter etc. It didn't particularly consider variety in crops (neither for taste not for soil management purposes), but it wasn't potatoes year round either. You need to be a competent farmer as well, but it didn't consider really high tech closed-greenhouse-like setups either. Still, that was a sobering number for many in the crowd - it completely undermines the whole 'self-sufficiency = sustainable' mantra.

justin_vanw 10y ago
100m^2 doesn't seem like so much to me at all, certainly not sobering. This would mean one acre of land would sustain about 40 people (or 100 per hectare). Taking wikipedia's number of 13,958,000 km^2 of arable land in the world, this would mean a maximum world population of 137,963,876,580, which is about 20x the current world population. Of course, this assumes equal quality of land to the land in your rough calculations, and I am guessing your number is assuming far more intensive cultivation than is typical (typical numbers I've seen are 1-2 acres / person).
- TheSpiceIsLife 10y ago
  The full calculation would also need to take in to consideration wastage / spoilage; crop failure; loss to pests; nutrient density (probably can't thrive off potatoes and corn only); animal feed (pets as well as animals for food). Having said that, I'll now go on to say: with one inhabited planet there are limits to resources, but the limits to human resourcefulness are undefined.
  - rahkiin 10y ago
    Don't eat animals. One problem solved. Might want to have some cows for milk and using their waste as fertilizer Edit: the not eating animals is not in a vegatarian way. I love meat. But if you want to fully sustain yourself on the smallest area possible, animals do not aid your cause.