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46 comments on A Net Energy Parable Revisited
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46 comments on A Net Energy Parable Revisited
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Pitt can you substantiate that statement. What are the caloric needs of a human cutting 8 tons of cane a day. You also have to count the calories to feed the family just as a hunter gather has to kill enough prey to feed his family. Housing and transportation are energy needs of that human too, as well as medical care. In a complete system you also have to count the calories needed to raise that child from an infant...some figure apportioned out over the years of their life.
You said that one person in Brazil can harvest 8 tons cane per day. Let's assume that this hard worker consumes 5000 cal/day and let's put 250 cal per BTU. That amounts to 2.5 BTU/ton harvested. This seems very low.
Because in the US we use about 8.4 gallons of diesel to mechanically harvest an acre. Let's say that acres is 35 tons of cane and a gallon diesel is 139000 BTU. Then the amount of BTUs required is 33000BTU/ton.