Efficient food production

[james_davis_nicoll]

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.

Comments

[james-nicoll.livejournal.com]

Which sounds fine, if you aren't one of those "mass extinctions are bad" extremists. The blackleaf takes over and less favoured races become extinct. It's no worse than kudzu in the South and probably won't have effects any more dramatic than the whole flower/insect thing 125 million years ago.

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

[mishalak.livejournal.com]

Well it won't grow everywhere. Being a crop plant it will only disrupt life in areas where it gets enough water and such like and it isn't too cold. So we're not looking at a new ice age (thank our lucky stars we didn't do this to phytoplankton or we would). But it will definitely be a weed control problem because it grows so darn fast. Also thank our lucky stars it wasn't mustard seed for biodiesel. Those darn seeds are small...

Re: Blackleaf

[james-nicoll.livejournal.com]

Ice age? Oh, from the reduced CO2?

I was thinking black leaves = lower albedo for the Earth = warmer in the immediate area of the plants.

Re: Blackleaf

[james-nicoll.livejournal.com]

This has consequences even if the [whatever] is containable and never leaves the food-factory. Cheaper food isn't a good thing for people at the production end of the food business, because demand is inelastic. It's great for consumers, though, and most people are consumers.

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

[mishalak.livejournal.com]

Currently it is sustainable, though more expensive, to grow crops like mustard and soybean for oil to be converted into biodiesel. You get out roughly 200% of the energy you put into the farming and the conversion. But this is expensive relative to drilling for oil and refining it.

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.