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Re: Ecological Economics and Entropy



George Antony Ph 93818 wrote:
 
> Ethanol is not the only motor fuel.  Various vegetable oils can be used
> as diesel fuel.

Were going to have to eat everything, probably the diesel fuel
 and tires too. <G>       ^^^^^^^^^^

Mike sent me a note and asked for more on Ethanol from Odum:

------------------------------------------------------------

WHAT IS EMERGY?

"The literature on evaluation of nature is extensive, much of it
 reporting ways of estimating market values of the storehouses and
 flows in environmental systems. In recent approaches to
 environmental evaluation (Repetto 1992), monetary measures were
 sought for the storages of nature. Others have used the simple
 physical measures of stored resources, especially energy.

"Shown in Figure 12.1 a is a storage of environmentally generated
 resources. Energy sources from the left are indicated with the
 circular symbol. Energies from sources are used in energy
 transformation processes to produce the quantities stored in the
 tank. Following the second law, some of the energy is degraded in
 the process and is shown as 'used energy' leaving through the
 heat sink, incapable of further work. Also due to the second law
 the stored quantity tends to disperse, losing its concentration.
 It depreciates, with some of its energy passing down the
 depreciation pathway and out through the used energy heat sink. 

"To build and maintain the storage of available resources, work
 requiring energy use and transformation has to be done. Work is
 measured by the energy that is used up, but energy of one kind
 cannot be regarded as equivalent to energy of another kind. For
 example, one joule of solar energy has a smaller ability to do
 work then one joule of energy contained in coal, since the coal
 energy is more concentrated than the solar energy. A relationship
 between solar and coal energy could be calculated by determining
 the number of joules of solar energy required to produce one
 joule of coal energy. The different kinds of energy on earth are
 hierarchically organized with many joules of energy of one kind
 required to generate one joule of another type. To evaluate all
 flows and storages on a common basis, we use solar emergy (Odum
 1986; Scienceman 1987) defined as follows:

"Solar emergy is the solar energy availability used up directly
 and indirectly to make a service or product. Its unit is the
 solar emjoule. 

"Although energy is conserved according to the first law,
 according to the second law, the ability of energy to do work is
 used up and cannot be reused. By definition, solar emergy is only
 conserved along a pathway of transformations until the ability to
 do work of the final energy remaining from its sources is used up
 (usually in interactive feedbacks). 

"Solar transformity is defined as follows: 

"Solar transformity is the solar emergy required to make one
 joule of a service or product. Its unit is solar emjoules per
 joule." [p.p. 201-203]

INVESTING IN NATURAL CAPITAL, ISBN 1-55963-316-6
published by The International Society for Ecological Economics
and Island Press, 1994. Phone: 800-828-1302 or 707-983-6432;
FAX: 707-983-6164

=================================================================

Some selected table entries:

Net emergy for Imported Oil: 13.6 to 1
Net emergy for Methanol from Gas: 4 to 1
Net emergy for Ethanol from Corn: 1.2 to 1,
  for Ethanol from Sugarcane 1.1 to 1


SECTION VI: Conclusions

>From  this study we would generally draw the conclusion that
natural gas and fuels produced from natural gas are likely to
play an increasing role in the economy generally. In addition, it
would appear that compressed natural gas and methanol made from
natural gas have the greatest near-term potential for use in the
transportation sector. On the other hand, cheap sources of
foreign oil prevent natural gas and methanol from having a
greater market impact now. Unless a major change in current trade
practices affects this fact, it is likely that oil-based fuels,
perhaps fuels reformulated to improve their direct emissions
qualities, will dominate the transportation sector for some time
to come.

The largest barriers to the use of natural gas-based
transportation fuels is the required investment in
infrastructure. There is a huge emergy investment in the
gasoline/diesel fuel oriented transportation sector, and this
represents a significant amount of momentum in the system. The
investment is not only in filling stations and existing
automobiles; it is also in the psyche of the car buyer, in the
education of automotive engineers, even in the regulatory
institutions that control various aspects of transportation.
These are difficult to measure, but the relatively high net
emergy value of natural gas suggests that these will slowly be
overcome, and current trends indicate this is already happening.

In addition to the alternatives we have considered for methanol,
it seems likely that it will find other markets through which to
expand. In fact, the rapid rise in its production is actually due
largely to its immediate market as methyl-tertiary-butyl-ether
(MTBE), a methanol derivative. MTBE is being used to replace
other, more toxic additives in reformulated gasoline fuels, and
this should continue because its net emergy is higher than the
petroleum components and the basic gasoline it replaces, to the
extent these come from domestic sources. Even cheap sources of
methanol made from remote sources of natural gas seem to have the
potential in the relatively near future for replacing sources of
foreign oil and diversifying our fuels mix or, at least, of
effectively putting a ceiling on oil prices.

Regarding ethanol, it must be said that there really would appear
to be no benefit to the country at this point in turning toward
ethanol production from energy crops. The value of corn, for
example, is much too high and net emergy value too low to justify
putting it into automobile fuel tanks when other alternatives
exist. Because the net emergy of the feedstock is so low relative
to other sources available, potential improvements in conversion
technology are irrelevant. An investment in construction and
operation of a farming and industrial ethanol production system
of 60 million gal/yr would cost the overall economy about $20
million annually in lost opportunities in investments with higher
net emergy. In addition, given the current nature of agriculture
and the economy generally, there is really no economy-wide
benefit in air quality when indirect impacts are considered.

At the same time, it must also be recognized that although a
major commitment to ethanol may not make sense today, it may have
a market niche. Spoiled corn or other crops that are lost to
their original purpose may well be better used if they are
converted to alcohol than wasted altogether, although we would
want to investigate the relative value of this periodic waste as
compost, as well. It should also be noted that ethanol or its
near derivative, ethyl-tertiary-butyl-ether (ETBE), in mixture
with gasoline, offers some potential benefits. But these benefits
are largely offered by methanol and MTBE at less total energy
cost. It is unlikely that the market would demand as much as is
being produced today without major federal and state subsidies.

There is insufficient land in this country to produce enough
ethanol to have a major impact on the transportation sector in
any event. And this situation will no doubt worsen, because
declining net emergy of the fuels available to the economy
generally are also forcing all farmers to decrease the energy
intensity of their operations. Ultimately, more land will be
needed to produce the same amount of food for human consumption,
and it is unlikely, therefore, that more land would become
available for energy crops. Although it is true that more land is
available for the production of lignocellulosic crops, such as
trees and grasses, we also calculated the net emergy of ethanol
production from these sources. Although the feedstock represents
less energy intensity, the greater energy demand of the
conversion process overwhelms any benefit achieved. This same
drawback would apply to municipal waste as a source for cellulose
as well.

[p. 299]

MAXIMUM POWER: The Ideas and Applications of H. T. Odum,
Charles A. S. Hall, Editor, Univ. Press Colorado 303-530-5337