[qwanta]

I've often heard the claim that the usage of oil in the US is the equivalent of having hundreds of slaves working for each person... but I had never seen the numbers behind it.

Well, I just came across this article:

http://www.informationclearinghouse.inf ... e11213.htm

which sources back to:

http://www.lifeaftertheoilcrash.net/Res ... #anchor_71

1. How Much Human Energy Is Contained in One
Gallon of Gas?

From Dr. David Pimentel:

"That is, the 38,000 kcal in one gallon of gasoline can be transformed into 8.8 KWh, which is about 3 weeks of human work equivalent.(Human work output in agriculture = 0.1 HP, or 0.074 KW, times 120 hours.)"

He, of course, is accounting for the energy lost in the process of converting the gasoline into usable energy.

My calculations excluding the energy lost in the conversion process are as follows:
1 Gallon of Gas = 125,000 BTUs
Source: US Department of Energy

3,400 BTUs = 1 KWH
Source: US Department of Energy, Bonneville Power Mgt.

1 Gallon of Gas = 37 KWH
(125,000 BTUs in a gallon of gas divided by 3,400 BTUs in 1 KWH)

1 Gallon of Gas = 500 hours of human work output
(37 KWH in 1 gallon of gas divided by human work output in agriculture of .074 KW = 500)

2. How Much Human Energy Is Contained in One
Barrel of Oil?

1 Barrel of Oil = 5,800,000 BTUs
Source: Louisiana Oil and Gas Association

1 Gallon of Gas = 125,000 BTUs
Source: US Department of Energy

1 Barrel of Oil thus contains the energy contained in 46.4 gallons of gas
(5,800,000 divided by 125,000 = 46.4 )

1 Gallon of Gas = 500 hours of human work output
Source: Calculations Done Above.

1 Barrel of Oil = 23,200 Hours of Human Work Output
(Energy equivalent of 46.4 gallons of gas per barrel of oil x 500 hours of human work ouput per gallon of gas = 23,200 hours)

If you assume about 21 million barrels per day for the US, that's roughly 21million/300million = 0.071 barrels per day per person.

0.071 * 23,200 = 1647 man-hours per day per person.

Assuming 12 hour workdays: 1647/12=137 slaves per person.


It makes the "return to feudalism" scenario painted by S.M. Stirling in "Dies the Fire" all that much more plausible:
"There are only two ways to live now; farming, and running the farmers."

[anthem]

There are two major errors in your calculations. First, not considering the loss in heat of a gigantic portion of energy in the conversion of gasoline to work is disingenuous. Secondly, assuming that a human's work output in agriculture is only 0.1 horsepower. In agriculture, a significant amount of energy is gained in the task in the production of useable food.

0.1 horsepower is moving 3300 pounds 1 foot in 1 minute. This is assumed to be the maximum "sustainable" power a human can generate, but over what period of time?

Some research has indicated that for generating power by pedalling a generator, an average human can do about 0.2 horsepower, which is twice what you have in your calculation. A huge difference, I would say. That would halve the number of slaves I would need.

You also assume that in the feudal world you suggest (or even hope for?) we would have the desire to use the same amount of energy we do today. For example, it is easy for me to drive to the market twice a day because they have what I want, so it doesn't seem so much like a waste to drive a couple extra miles. However, if the market will not have what I want (and I know this up front) there is no reason for me to drive the second time. So in the feudal world, I just saved 50% of the energy I would have used to go to the market.

[qwanta]

well, I doubt you could get 0.2HP, 12 hours a day for 365 days a year out of anybody! Even 0.1HP is probably stretching it. In addition, the slaves must also produce food for their own consumption, which is time/energy unavailable for work. Also, fossil fuels are forms of energy that are much more convenient, concentrated, and flexible than human power. You cannot fly a jumbo jet or make fertilizers on an industrial scale using man power alone no matter how many 'units' you have. In fact running things on an industrial scale would become pretty much impossible, so I certainly don't think we could keep our industrial society running pretty much the same as now with a few elites and billions of slaves!

I was trying to be conservative in this number - I think the term 'hundreds' for slaves that I've seen bandied around is more probably accurate - but I admit it is a bit like comparing apples and mushrooms.

Still, I think it's an interesting statistic that underlines our dependence on fossil fuels

[AmericanEmpire]

Its calculations like the above which makes me realize just how screwed we are.

We can't get enough of the black stuff and look at all the energy it provides.

[turmoil]

well, I doubt you could get 0.2HP, 12 hours a day for 365 days a year out of anybody!

Especially me!

[frankthetank]

We do have plenty of electricity from hydro, wind, nuclear...So i guess we could have electric tractors or even steam tractors that burn wood...lots of wood! i have wood

I'll work the fields if i have to, just give me a cold beer and some sunscreen...May help if the women work topless....

[lorenzo]

Just a nasty nuance. These 23,200 man hours are only correct when you take a normal man, that is a fit, healthy, relatively smart, and slim person who can push his body to producing 0.1 hp per day.

Now the effect of petro-addiction is that it makes fat, unhealthy, relatively dumb whales out of people who sit on their bum all day and who can't even lift up their daily bucket of mayo without getting exhausted.

So the '23,200 man hours' are a bit skewed; we should at least quadruple that when you take the average oil-addicted obese man into account.

Thus, one barrel of oil contains 100,000 obese man hours!! Amazing!!

[KingM]

And? It's called using tools and it's something we've been doing ever since we used stones to crack the marrow from the bones of our prey. We make tools and thus extend our power beyond that of muscle alone. Oil is just the latest, greatest, but it's not the only way.

[AmericanEmpire]

Oil is just the latest, greatest, but it's not the only way.

In order to feed a population of 6.5 billion people it is.

[lorenzo]

And? It's called using tools and it's something we've been doing ever since we used stones to crack the marrow from the bones of our prey. We make tools and thus extend our power beyond that of muscle alone. Oil is just the latest, greatest, but it's not the only way.

Sure, but over-dependence on a single resource is lethal. People since the dawn of humanity have understood this basic idea.

[coyote]

And? It's called using tools and it's something we've been doing ever since we used stones to crack the marrow from the bones of our prey. We make tools and thus extend our power beyond that of muscle alone. Oil is just the latest, greatest, but it's not the only way.

Sure, but over-dependence on a single resource is lethal. People since the dawn of humanity have understood this basic idea.

We have? I think we have yet to learn it...

[qwanta]

OK, here's another way to look at it, with all the caveats that apply:

23,200 man hours per barrel * 21,000,000 barrels per day = 487.2 billion man hours per day done by oil in USA.

assume 12 hour days: 487.2billion/12 = 40.6 billion men ... it would take over 5x current world population just to match the energy work done by oil in the USA alone!

[Dukat_Reloaded]

I think this is an over reaction. Most likely 1% of everything we need done with oil is essential. Most of the oil is used for transport, and 23k hours per barrel of oil comes into play when 100 people have to haul a rig across country which would be energy inefficent anyway. The same could be said about silicon (we'll never run out) but the fact is, if someone calculated all the worlds total cpu time (playing computer games, web browsing, video editing, encoding/decoding) and someone claimed we don't have enough silicon to manufacture cpu chips anymore, they would say if people had to perform all the calculations that cpu's used to do by hand with pencil and paper, to keep the world running would require 10^122 trillion human hours per second and we could not possibly keep up and that we'll be doomed. Just trying to put some perspective on this, as I don't believe it's a fair conversion to say 1 barrel = 23,200 man hours, same as 1 cpu running for 1 day = 1 quadtrillion man hours.

[Keith_McClary]

The same could be said about silicon (we'll never run out) but the fact is, if someone calculated all the worlds total cpu time (playing computer games,..) and someone claimed we don't have enough silicon to manufacture cpu chips anymore, they would say if people had to perform all the calculations that cpu's used to do by hand with pencil and paper, to keep the world running would require 10^122 trillion human hours per second and we could not possibly keep up and that we'll be doomed. Just trying to put some perspective on this, as I don't believe it's a fair conversion to say 1 barrel = 23,200 man hours, same as 1 cpu running for 1 day = 1 quadtrillion man hours.

Fortunately computer game calculations can be simplified: GAME OVER

[pilferage]

Dukat hit the nail on the head. Even if a barrel of oil is ~22,300 man hours, the average ICE has an efficiency of ~30%. So we're only constructively using ~7000 man hours. On top of that, we use vehicles for personal transportation that are 10-15 times larger and have horrendous CoD's. So, we're using ~15 times more energy than we need to... so we're at what? ~450 man hours per barrel of oil.
Oh, and I left out the inefficiency of refining. So yeah... it's not that bad.