I,'ve been looking up some stuff about energy efficiency in agriculture and i found some remarkable things.
this is just about the production, not the packaging, distribution,... .
industrial agriculture focusing gets an energy efficiency of 1/8 for corn till 1/1,3 for potatoes. 1 kcal spent for 1 kcal harvested. i'm focusing here on crops with high energy in them, tomatoes for example give a total different picture.
organic agriculture has an efficiency which is about 25% higher (depending on the crop), mainly because they don't use synthetic fertilizers. and without reaching the same yield.
traditional corn production has an energy efficiency of 1/250, no synthetic fertilizer, no machinery, fuel. but a yield which is half of the industrial one.
Theoretically permaculture would get a higher energy efficiency than traditional, but if i look at my garden, and at projects close by or further away (hail internet), i'm doubting if i, the other projects get at the energy efficiency of industrial agriculture.
offcourse there are other factors, like biodiversity, carbon sequestration,... that speak in our advantage but it's something to think about.
for example: i get a lot of horsemanure on woodshavings from a neigbour, which is great to improve my soil fertility but i go and get them with a tractor of another neighbour( which is great that i can use it) and just this 1 day of driving back and forth with a tractor uses so much energy that it totally outcompetes my handwork in the garden for the "364" other days.
and i can see all these kind of things also in other projects.