Efficient food production
Mar. 9th, 2005 02:11 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
I was noodling around on soc.history.what-if and made a calculation I'd never bothered with before: if a human needs enough food to produce N Watts, how many square meters are required to intercept that much sunlight? OF course I was too lazy to actually look up insolation for various latitudes but the BOTEC I committed seemed to show that it should be a few square meters.
Even Fairbanks, Alaska, gets from 90 to 350 watts/m^2. Say your mark 1 human needs at least 100 watts worth of food to keep functioning [1]: They'd need about one square meter dedicated to collecting solar powers, asssuming no losses. The entire population of North America should require a few hundred to a thousand square kilometers of converters to power themselves. Even a factor of ten losses should mean that we'd need about 300 square kilometers to feed all of Canada, assuming the lowest insolation in Alaska is what we have to work with, and about 3000 square kilometers to feed all of the USA. That's a square less than 20 kilometers on an edge for Canada and a bit over 50 kilometers on an edge for the USA. Feeding the entire planet should require about 60,000 square kilometers or a square about 250 km on an edge (or less, if we pick someplace sunnier than Fairbanks to grow food).
Clearly modern methods of coverting solar (and fossil) energy into human energy are criminally inefficient.
1: Googling says "at least 2500 kilocalories" per day so call it 4000 to be safe. That works out to about 50 watts, which I will double just because.
Even Fairbanks, Alaska, gets from 90 to 350 watts/m^2. Say your mark 1 human needs at least 100 watts worth of food to keep functioning [1]: They'd need about one square meter dedicated to collecting solar powers, asssuming no losses. The entire population of North America should require a few hundred to a thousand square kilometers of converters to power themselves. Even a factor of ten losses should mean that we'd need about 300 square kilometers to feed all of Canada, assuming the lowest insolation in Alaska is what we have to work with, and about 3000 square kilometers to feed all of the USA. That's a square less than 20 kilometers on an edge for Canada and a bit over 50 kilometers on an edge for the USA. Feeding the entire planet should require about 60,000 square kilometers or a square about 250 km on an edge (or less, if we pick someplace sunnier than Fairbanks to grow food).
Clearly modern methods of coverting solar (and fossil) energy into human energy are criminally inefficient.
1: Googling says "at least 2500 kilocalories" per day so call it 4000 to be safe. That works out to about 50 watts, which I will double just because.
no subject
Date: 2005-03-09 09:36 pm (UTC)Of course, because the stuff is meant to be et by humans, a crapload of other animals can also eat blackleaf plants. At a guess, about four times as many as can be fed by greeleaf plants. Those animals aren't going to just sit around, either. They are going to use that energy to do stuff and not all of it is going to please humans.
Oh, and if blackleaf is doing stuff like releasing O2 at four times the rate normal plants do, there could be short term side effects from that as well.
Blackleaf
Date: 2005-03-09 09:57 pm (UTC)Re: Blackleaf
Date: 2005-03-09 10:07 pm (UTC)I was thinking black leaves = lower albedo for the Earth = warmer in the immediate area of the plants.
Re: Blackleaf
Date: 2005-03-10 12:26 am (UTC)Now, if you happen to be in a large nation currently run by neocons, check out how much of their support comes from rural areas and imagine how those voters will react to a technical development that makes them as cutting edge as an 8-track.
Re: Blackleaf
Date: 2005-03-10 02:13 am (UTC)So if there were a doubling of yields on American farmland it would indeed mean a reduction in prices, but not all the way down. At current cost levels for oil prices would fall 17% and then stabilize at the level where it becomes practical to replace standard petroleum diesel with bio diesel. If world demand for energy increased it could actually increase crop prices depending upon the exact details of the transition with the usual caveats about this only being a very simple calculation and all.
Also after having done some more reading I've learned that the real losses in efficiently are due to oxygen. Higher amounts of the waste gas in the system mean that sometimes instead of doing the right reaction it does one termed photorespiration that produces junk. So if you found a way to more efficiently exclude and remove O2 from plant cells it would greatly increase yields. So the problem isn't that plants reflect green light or whatever, though that could bump up yields a bit.