Re: Alernative Energy Technologies

Thu, 2 Jul 1998 08:54:31 -1000
Jay Hanson (j@qmail.com)

>political, commercial, and social support, a cluster of renewable
>energy technologies actually surpasses petroleum in providing world
>commerical energy requirements by late in the next century.

This World Bank report is simply not believable. Undoubtedly,
they have concerned themselves with "economics" and failed to
consider either "net energy" or the availability of "arable land".

David Pimentel understands both net energy and arable land.

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[snip]
Several studies indicate that to enjoy a relatively high
standard of living, America's human population should be 200
million or less (Pimentel et al., 1994a).
[snip]
http://www.envirolink.org/orgs/gaia-pc/Pimentel2.html

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[snip]
The inevitable conclusion is that the availability of land will
be the major constraint to the expanded use of solar energy
systems because land is needed for solar energy, and this need
cannot encroach on that needed by agriculture, forestry, and
natural biota in the ecosystem. Our expanding human population
can be expected to put increasingly great pressure on land
availability and use.

The amount of land required to provide solar-based electricity
for a city of 100,000 people illustrates the land constraints. To
provide the needed 1 billion kWh/yr from wood biomass would
require maintaining 330,000 hectares of permanent forest (Table
3). Even hydropower is, in part, land based, because on average
it requires 13,000 hectares of land for an adequate size
reservoir. Then too, the land used for the reservoir is often
good, productive agricultural land (Pimentel et al., 1984). Thus,
solar energy and hydropower have serious land and environmental
limitations. Note that nuclear and coal-fired power plants,
including mining, require relatively small areas of land compared
to biomass and hydropower production.

Unfortunately, the conversion of biomass like corn into energy
such as liquid fuels requires enormous inputs of fossil energy.
For example, about 1.5 liters of oil equivalents are used to
produce 1 liter of ethanol equivalents (ERAB, 1981; Pimentel et
al., 1988). Thus, under optimal conditions only about one-third
of the biomass can be converted into valuable liquid fuels
(Pimentel et al., 1988). Even if we quadrupled the efficiency so
that 1 kcal of fossil energy produced 2 kcal of ethanol, about 10
acres of corn land would be required to fuel one U.S. automobile
per year (Pimentel et al., 1988).

If we make the optimistic assumption that the amount of solar
energy used today could be increased about 3- to 10-fold without
adversely affecting agriculture, forestry, or the environment,
then from 3 to 10 x 1015 kcal of solar energy would be available
(Pimentel et al., 1984; Ogden and Williams, 1989). This is
one-fifth to one-half the current level of energy consumption in
the United States, which is about 20 x 1015 kcal and averages
8,000 liters of oil equivalents per capita per year (USBC, 1988).
[snip]
http://dieoff.org/page136.htm
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Jay