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.
As you have alluded to, there are a lot of factors when you consider "energy efficiency".
I have a small 25 hp Kubota tractor that honestly sips fuel. With good going, a short haul and a good work day; I can pull out 6 cord of tree length wood and make up a "load" for the log truck in two days time. In that time I might burn 7 gallons of fuel. A skidder on the other hand will get the same amount of wood out in a single day, but burn 5 gallons an HOUR doing so, or in other words, 40 gallons roughly to get out the same amount of wood!! Still, if the haul is long from the landing to the stump, and there is difficult areas in between, a skidder might be the only option. On good going however; oh yes I am making more money per cord, per day with the small Kubota tractor.
When you get into agriculture though, things get a lot more complicated because you must factor in efficiency of scale, horsepower, drawbar pull and tractive effort and so the efficiency starts tipping drastically for the bigger equipment.
A few years ago I took my Kubota and plowed up a 2 acre field with a two bottom plow and it took me all day and burned 7 gallons of fuel doing so. That seems good until you realize that my family has a few dairy farms and when using a 180 hp tractor with a 7 bottom plow, in the same amount of time a 12 acre field could be plowed on about 30 gallons of fuel. Yet when we scaled up to 450 hp tractor we could till that 12 acre field in twenty minutes. In the end, with the 450 hp tractor, we are only burning 3/4 of a gallon of fuel per acre and that is pretty sweet considering we have high manganese soil so tillage really matters.
I kind of feel for the organic dairy farmers because they were drawn in by the prospect of large payouts for their milk, but that has yet to happen. While their production has remained the same, conventional dairy farms have doubled their production per cow and are predicted to go much higher. It is the same with crops; just ten years ago we were happy to get 30 tons to the acre but now we are nearing 50 tons to the acre and all the while spending less on fuel due to a variety of factors. (Better corn seed, better management practices, cover cropping, etc).
With my own sheep farm, an already low energy input type of farm commodity, I can increase efficiency simply by growing. It takes X-amount of fuel to feed my sheep every winter day, and that extra scoop of silage to feed more of them is not going to cost that much more. My overhead is not going to double either such as my lights, insurance, equipment costs, etc. Without question the three sisters way of growing veggies is going to produce more food per given acre, however it cannot be harvested in a timely enough fashion to festoon acreages with that method. The limiting factor is what the worker can harvest in a given time frame before the crop rots in the field.
The USDA says 1% of the nation are farmers, but they include restaurant workers and a host of other quasi-farm related jobs in that. The real percentage is like one half of one percent. If a half a percent is feeding 99-1/2 percent, by gosh I would call that pretty darn efficient.
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