The Oil Drum

Not really. Exactly the same argument can be made on the labour side. How much energy has gone into the infrastructure of the steel mill where someone is a labourer, and the energy used getting the labourers to work, and the calories burnt while they're at home watching TV or sleeping, and so on...?

Wow - millions of man hours? I would guess billions... but at a few hundred barrels per million hours of labour, that's not much in return for the energy we've got from a trillion + barrels...

I think waht you are trying to get to is the term EMERGY or EMbodied enERGY as proposed by Howard T Odum.

http://www.greatchange.org/footnotes-emergy.html

Ywish I can see at least 1 basic error in your calculations:

"Vicki", in your reference, is supplying the calories consumed by the person doing the activity.

Assuming the numbers are right [big assumption - but they sound OK], this IS NOT the energy applied to the load, but the metabolic calories.

I have heard figures of 25% max efficiency for striated muscle eg 25% work 75% heat loss. Add in unfavourable leverages and other losses [eg friction] and 10% useful work sounds about right

How does a layperson factor in an 11-fold discrepancy...

You already explained 1/2 of the 11 fold discrepancy in your first post:

One hour of “hard human labor” like general forestry, or work in a steel mill requires about 636.3 Calories for a person weighing about 175lb. [The same person doing computer work needs 119.3 Cals/hr.]

636.3/119.3=5.33. The rest can be explained by the fact that people currently only work 8-10 hours a day in modern society - though they still burn calories during the other 14-16. They work 5 days per week and 50 weeks per year. The number quoted was 12.5 years, which working 40 hours per week equates to 25,000 hours. This becomes very conservative if we change total energy use into barrel of oil equivalents, because then we (an average american) use 57 boe (2005). This calculation is not a precise number and never can be, due to the higher energy quality of fossil fuels (how could you run a city like New York on a human labor with its current energy dense infrastructure?)

I don't know where the original quote came from, but since I have used this number myself, I've looked into it and am comfortable that 12.5 years/ 25,000 hours is in the ballpark. Even if that is off by a factor of 2, does it change anything?

I will write a short post on this in the future and you can add whatever calculations you wish into the comments. The point is we have moved up the energy quality and quantity ladder like a rocket compared to a few centuries ago. 99.9% of our past history we dealt directly with solar flows - now we are burning very valuable, in dollar and energy terms, fossil stocks.

ThatsItMount said:
'This brings up what could be an interesting challenge/test: I and others on TOD often talk about solar or electric....it would be interesting to attempt to build a hay handling "system" using only electric power and or solar and see how much be required to bring a hayfield of X number of acres!'
This would be a truly interesting and informative test, and if I might suggest a variant would also be interesting - using pyrolysis to produce charcoal and biofuel, and using the agrichar to enrich the soil and the biofuel to power the farm machinery.
this sort of data would give real insight into how easy/difficult it would be to maintain agriculture in a more ofssil fuel constrained world.
Theories are OK, but the whole pile of them don't add up to one case of jumping in and finding out!

Interesting question. I have a recently purchased small (38 acre) farm in NE Iowa. We raise organic chickens, and we're adding a small number of grass fed Dexter cattle. I think we might well abandon the notion of "bringing hay in." Even with round bales, many farmers concerned with sustainability prefer to feed the hay where it was harvested so that minimal nutrients are removed from the soil, and the cattle's rumen bacteria contribute to enriching the soil; organic matter is added to the soil. Of course, phosphorous and potassium and sulfur and calcium are largely returned to the soil.

I plan to use management intensive rotational grazing, which maximizes the grass production and enriches the soil. MIRG moves the cattle frequently (sometimes several times per day) and allows the grass time to recover before being grazed again.

I will need some hay for the winter months when the cattle can no longer break through the snow, though some kinds of grasses and legumes stand up well in the snow (e.g., yellow sweet clover) and even become more palatable as the snow softens them.

I want to experiment with re-learning the art of making hay stacks. One experienced man can mow one acre per day with a scythe. That's a lever that makes good use of human energy, and one cutting on an acre might be enough hay for two of my miniature (Dexter) cattle for the winter. (Sorry, I don't have accurate numbers immediately available. Depends on grass productivity, the winter's severity, and the cattle's size.) One Dexter per year (three years to mature on grass) produces roughly 400# net (healthy) grass fed beef, and the process sequesters carbon while enriching the soil.

Anyway, I want only to suggest that we don't want to imitate the way we do it with tractors and combines, but to find ways that suit the soil and our energy resources.

In general, running tools on the tractor's PTO sucks Diesel. A baler running on a PTO is a merry-go-round of flywheels, rams, belts, knotters, and other moving parts.

In thinking about this and as mentioned by other posters, modern farm equipment changed the way, in this case, hay is farmed and used; making the process far more energy intensive than it used to be but allowing hay to be easily stored and transported. What the baler does is make it possible to store and transport large amounts of hay at a cost of enormous amounts of energy. Without the baler its just a pile that must be consumed at the place where it is grown. I'm guessing that farms will have to become more self sufficient with growing their own animal feed. Just transporting hay a couple of miles down the road is significant considering it has to be baled.

Let us not forget the windmill needed to power irrigation pumps and cost of fertilizer which is made from natural gas.

My neighbor uses four horse drawn sickle mowers to cut his hay. I could do the same and that would save me about a third of the Diesel I use; however, those horses will themselves consume a significant part of my harvest! So probably the energy use equation horses vs. tractor is somehow balanced by the hay that the horses would consume out of my crop.

The other thing that comes out of this is that tiny hobby ranches with recreational horseback riding, pet llamas, miniature goats, horses, and donkeys will become very expensive.