the 40 Factor

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Damnthematrix's picture
Damnthematrix
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the 40 Factor

Demographic Significance of the 40 Factor

http://sinkinglifeboat.blogspot.com/2009/08/demographic-significance-of-...

Human survival depends on there being enough food and drink to support life. Fresh water is easily obtained in many parts of the world. Food, on the other hand, has to be grown, raised or hunted. Producing enough of it, by agriculture, is serious work. Before about 1750, when the Industrial Revolution began, farmers depended on human and animal muscle. Now, in all but backward societies, diesel-powered tractors and mains electricity have taken over. The increase in efficiency is colossal.

Over the hedge from my garden is a hay meadow 7 acres (2.8 hectares) in area. Mowing it by tractor takes about 1.5 hours. This compares to the full day, including breaks for food and cider, that a man with a scythe traditionally took to cut one acre. The tractor is roughly 40 times more efficient in terms of man-hours.

The next two procedures in modern haymaking, tedding the cut grass to dry it, and then baling it, each take the tractor about 1.5 hours. Before 1750 the farm workers, men and women, used rakes to aerate and dry the hay, then loaded it into carts with pitchforks. Again the efficiency ratio is something like 40:1.

A giant combine harvester with its satellite tractors and trailers may be 100 times as effective as the peasants with their sickles and threshing floors in recovering the grain from large acreages of cereals.

Medieval woodcutters harvested energy with sharp axes. Several of them would have taken a day to load their cart with logs and haul it from the forest to the village. Thanks to my chain saw I can fill my car with logs cut to size and bring them home, a mile from the wood, in two hours.

Only 60 years ago, before piped water reached the streamless limestone plateau of the Mendip Hills, my neighbour’s cattle were supplied in summer by a horse and cart that carried a few large churns of water up the hill from the farm to a tank on the plateau 150 metres higher. The horse managed 2 journeys a day to water the little herd of about 10 animals. Now there is no limit to the number of cattle that can be watered.

Picture the dairymaid on her three-legged stool, milking about 5 cows every hour by hand a century ago. Now, only the capacity of the milking parlour limits the size of the herd, sometimes as many as 400, that can be processed in two or three hours.

Whether it be ploughing the fields, hedging and ditching, clearing out ponds, or raising livestock, few modern agricultural procedures are less than 40 times as efficient, in terms of food produced, as they were when the work was done by humans, with or without farm animals.

The significance of this “40 Factor” cannot be exaggerated. How long do we have before fossil fuels are so scarce that global food production begins its shrinkage to about one fortieth of present capacity?

According to the prestigious Association for the Study of Peak Oil and Gas (ASPO), annual production of conventional oil peaked in 2005 at 24 Gb (billion barrels) and total oils (including heavy oil, tar sands, oil shales, deepwater, polar and gas condensates) are expected to peak in 2011 at 33 Gb. All hydrocarbons including gas will peak about 2012. The world’s large coal reserves are fairly irrelevant because they are slow and expensive to mine and process into liquid fuels.

So the downhill slide in fossil fuel production, food availability and world population may well begin around 2012, or sooner if war breaks out in the Middle East or other oil-rich region. Depending on a host of variables it could end around 2150. The journey will be eventful, to say the least, and we must hope that our descendants will have learned from it as they try to survive in the hard world of non-fossil energy.

Dr William Stanton

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johnbryson
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Re: the 40 Factor

While I do think there will be a pinch in the food supply as a result of peak oil, I believe that people will eventually need to start taking food security seriously and turn their backyards into productive sources of food. This family in Pasadena managed to produce 6000lbs of food in a backyard - 66x66 feet (

).

John

 

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Damnthematrix
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Posts: 3998
Re: the 40 Factor

Renewable energy limits; A new estimate.

Ted Trainer

The full 17 pp. paper is at http://ssis.arts.unsw.edu.au/tsw/CANRE.html

I have attempted to roughly estimate the amount of generating plant and the
dollar cost involved in meeting a world energy budget of 1000EJ/y by 2050,
within ³safe² CO2 emission limits. Obviously confident conclusions are not
possible but the magnitude of the figures arrived is the important point. I
would appreciate critical feedback.

After making several assumptions re plausible/reasonable future efficiency,
losses, costs etc., the general conclusion is that the amount of PV, Wind
and Solar Thermal plant we would need would require annual global energy
investment 32 times as great as it is now.

When about 8 of the assumptions are all set at high levels the combined
effect is to reduce the multiple to 4.

The contributions of biomass, nuclear, hydro and geo-sequestration
electricity assumed are 50 EJ/y (1 billion ha), 8 EJ/y (as at present), 19
EJ/y (double the present), and 51 EJ/y (corresponding to 3 GT/y CO2
release.)

Note that if all 9 billion people expected by 2050 were to have the per
capita energy consumption Australians are heading for the supply would have
to be about 4 times as big as assumed in this exercise.

Why is the multiple so high? The main factors are:

* Capacity factors for renewables are low. A coal fired power station can
deliver .8 of peak rating, averaged over time. A solar thermal plant today
might deliver .1 - .14 (.19 assumed here.)

* The capital cost of renewables per kW delivered (not per peak kW as is
usually stated) is therefore high.

* The variability of renewable sources means there must be much redundancy
in plant available. In fact in the budget derived the amount of wind, PV
and solar thermal plant (measured in terms of peak generating capacity)
required to enable a constant winter demand to be met would have to be 7.3
times the amount of coal or nuclear plant required. (Stern, Garnaut and the
IPCC fail to recognise this issue.)

* Energy conversion: Advocates of renewables typically fail to take into
account the fact that almost all renewables produce only electricity but
this corresponds to only 20% of rich world primary energy consumption. Even
if transport was heavily electrified about half of all energy would be
needed in non-electrical forms. Converting from electricity is
energy-inefficient; .5 has been assumed in this budget.

* There are considerable energy and dollar costs in addition to those at the
generating site, including long distance transmission, embodied energy costs
of plant, operations and management. This analysis includes a few
quantifiable items but there are several large items not included, such as
ammonia storage plant for solar thermal heat, 3-4000 km HVDC transmission
lines from the Sahara to NW Europe, conversion and storage equipment (e.g.,
for hydrogen production and distribution), and the coal or nuclear plant
capable of meeting demand when wind and sun are low.

* Winter is the big problem. Renewable optimists tend to focus only on
performance in ideal conditions. What matters is how much plant would be
needed to meet demand when solar sources are at their weakest and the
attempted budget focuses on this task. Winds are at their best in winter,
but in this analysis the contribution from solar thermal systems in Central
Australia is estimated as corresponding to perhaps less than a 20 W/m
constant flow if all losses and costs could be taken into account. That
would mean a collection area of 50 million square metres would be needed to
equate to a 1000 MW coal plant, and at the present estimated cost ($1,100/m)
the solar thermal plant would cost $55 billion.

I think an approach of this kind based on better data would confirm my
general belief that renewable energy can¹t sustain an energy-affluent
society. The solution to the global sustainability problem has to be sought
in terms of vast and radical change away from the basic structures and ways,
and culture, of consumer-capitalist society. In my view workable and
attractive alternatives are available, but are not likely to be taken. (For
the detailed argument see The Simpler Way website,
http://ssis.arts.unsw.edu.au/tsw/ )

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