Re: Hydrogen economy

From: Joel Moore <joelmoore@psu.edu>
Date: Fri Apr 23 2004 - 10:27:17 EDT

> >>Soil is not an endless resource, either. It needs to be factored in
>these bio-energy budgets, too.>>
>
>Nothing is an endless resource, of course. At some point we will have
>used up all the earth's resources, each coming to an end at a different
>time. Coal, oil, humus, gas, you name it.
>
>What we are arguing about is HOW FAST this will happen. Do we have
>another 1000 or so years? If so, interplanetary exploration MAY be able
>to help push the day of reckoning forward some. Do we have 100 years? Do
>we have even 10 years?
> I am in agreement with Glenn that the only known possibility appears to
>be nuclear fusion if we are seriously to consider 1000 years rather than
>100.
>
>Just take topsoil. Each year some is made. Each year more is used up.
>Which do you think is the freater of these two? By how much?
>
>Burgy
>
>www.burgy.50megs.com/astory.htm (a story to tell)
>
>Ubi Caritas
>

The amount of topsoil created and how much is eroded is varies
greatly from location to location and depends on topography, bedrock
type, climate, etc. That said, when people talk about topsoil,
they're usually concerned with agricultural soils. Topsoil in most
agricultural regions is essentially being mined, i.e. rates of
erosion greatly exceed rates of soil creation (I'm guessing something
approaching an order of magnitude). Topsoil cannot be replaced on the
human time scale. The clearest example is in the prime
agricultural/former prairie soils of Illinois, Iowa, and the rest of
the Midwest. Even on relatively flat fields (< 5 degrees of slope),
tons of soil can be lost annually depending on the farming practices
employed.

Soil can be regenerated by humans but only in limited areas by
intensive labor (eg, numerous applications of compost/manure, growing
of nitrogen-fixing legumes, crop rotation, etc). And then the soil
must be maintained by those same processes in order for agriculture
to be sustainable. It seems likely that growing some crop as a
wholesale replacement for oil would involve the growing of a
monoculture year after year on large amounts of land, which is
unsustainable.

If anybody is really interested in learning about the history of
soil, agriculture, and society, I'd highly recommend Daniel Hillel's
Out of the Earth. He is a soil scientist at UMass-Amherst (though is
probably close to retirement) and well-known. I've seen numerous
references to his book Soil Physics in scientific papers. He spent
much of his early life in Israel where he was involved in irrigation
and agriculture projects in the Negev and other marginal agricultural
areas. He discusses how the Sumerians and many subsequent
civilizations have collapsed, in large part, because of their lack of
care for their soils. One of the issues he ran into in the Negev, the
Sumerians ran into, and parts of the American west (Central Valley of
CA, Arizona) ran into was the poisoning of soils by irrigation that
occurs in arid environments. In arid environments, much of the water
used for irrigation is lost through evapotranspiration. Eventually
salts build up in the soil and most plants, and certainly any plants
used for food, can no longer grow in the soil. The Egyptians escaped
this fate through most of their history because the annual flooding
of the Nile deposited new soil and flushed salts from the soil. The
Aswan dam has stopped the annual flooding and fields that have been
productively farmed for thousands of years are becoming or have
become infertile.

That was a long answer to a short question.

Joel

-- 
Joel Moore
315 Hosler Building
Department of Geosciences
Pennsylvania State University
University Park, PA 16802
(814) 863-8055
http://www.geosc.psu.edu/~jmoore/
Received on Fri Apr 23 10:17:33 2004

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