I am sure someone has done the sums. There is a lot of land that does not have agriculture on it.
What is the real limit of expanding solar+wind power?
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Farm Boy
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I'm curious as to how he accounts for the energy used in food production, since that seemed to be the bent of the article. The current global food supply is not sustainable without fertilizers, so the replacement needs accounted. As does all the horsepower for turning over arable land. He's, I assume, accounted for it somehow.
I mean, if he's assuming that you can just... reorient* so that suddenly we don't need 75% of agriculture, that would probably help.
*no meat diets for the orient!
I mean, if he's assuming that you can just... reorient* so that suddenly we don't need 75% of agriculture, that would probably help.
*no meat diets for the orient!
I did see if I could see the book easily, and failed so I cannot really comment. For fertilizers it is about getting the hydrogen for the Haber process? Electricity should be suitable for that, shouldn't it? It will take a lot of it, but I am sure he is accounting for it. I really do wonder what he says about agricultural vehicles. It has to be doable. It seems like it could be easier to make battery powered tractors than suck the CO2 that diesel tractors pump out with carbon capture.
Farm Boy
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I'm betting, like your chart, he's paring down an enormous estimate on protein consumption to balance the numbers combined with an army of solar powered robots that are supposed to be able to replace, or magically not need, currently used tillage and weed control to maintain productivity. Possibly with our without fertilizer. Somehow, again. But, call me jaded. 
Agriculture, food product manufacturing and basic chemical manufacturing energy consumption aren't a particularly predominant component of total energy consumption.
Here's global electricity shares (agriculture is in "other" in most of these, food products and chemicals are part of Industry)
Here's gas:
Here's oil:
And here's coal:
As shares of the above "Industry" sectors, primary chemicals production is about 10 EJ of energy use, nearly all gas and coal, and that's all chemicals so is a lot broader than just ammonia (mostly made from the hydrogen in natural gas) and other fertiliser production. Food product manufacturing (ie processing, packaging etc) is closer to about 5 EJ, a mix of electricity and the various fuel sources that go into direct heat generation for boiling, steaming, drying etc.
At the end of the day though, most of this energy use with some well known key exceptions (especially the portion used as non-energy feedstocks) can be electrified, and therefore met by renewables just as easily as any other source of electricity. Also worth noting that as other demands on things like natural gas and coal and oil recede, those feedstock uses where they're needed for the hydrocarbons, not the energy, will surely become cheaper due to a surplus of supply.
Here's global electricity shares (agriculture is in "other" in most of these, food products and chemicals are part of Industry)
Here's gas:
Here's oil:
And here's coal:
As shares of the above "Industry" sectors, primary chemicals production is about 10 EJ of energy use, nearly all gas and coal, and that's all chemicals so is a lot broader than just ammonia (mostly made from the hydrogen in natural gas) and other fertiliser production. Food product manufacturing (ie processing, packaging etc) is closer to about 5 EJ, a mix of electricity and the various fuel sources that go into direct heat generation for boiling, steaming, drying etc.
At the end of the day though, most of this energy use with some well known key exceptions (especially the portion used as non-energy feedstocks) can be electrified, and therefore met by renewables just as easily as any other source of electricity. Also worth noting that as other demands on things like natural gas and coal and oil recede, those feedstock uses where they're needed for the hydrocarbons, not the energy, will surely become cheaper due to a surplus of supply.
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