The laws of thermodynamics govern the flow of energy in the universe,
and in our everyday lives. These laws arenıt like campaign-finance
laws or speed limits; the laws of thermodynamics canıt be broken.
Government and business leaders who talk about energy use and the
global climate treaty seem especially ignorant of the second law of
thermodynamics, and of the guidance it provides in choosing ways to
satisfy our needs.
The first law states that energy is neither created nor destroyed; it
can only be transformed - changed, for example, from fuel into
motion. Efficiency according to the first law is computed by
comparing the amount of energy that goes into a system with the amount
of work that results. A car which gets 40 miles per gallon of gas is
more efficient at converting gasolineıs energy into distance traveled
than a car that gets 15 miles per gallon.
The second law states essentially, that energy transformation goes in
one direction only. A carıs waste heat and motion canıt be converted
back to gasolineıs original, concentrated, high-quality energy. And,
this one-way energy conversion creates disorder or entropy which tends
to accumulate. If more energy is transformed, more entropy is
created. Air pollution and climate change are just two of the forms
that the entropy (from the conversion of gasoline to motion) takes.
To measure efficiency according to the second law of thermodynamics,
the energy that we do use is compared to the minimum energy required
to accomplish the same work. In effect, the question is, ³How can we
produce less disorder and still satisfy our needs?²
A head of iceberg lettuce provides a good lesson. With the help of
the educators in a workshop I presented at the ³Connecticut Energy
Council for Teachers Conference,² I compared the energy conversions
required and the resulting entropy for several ways of satisfying a
single need. In this case, the need for crunchy green plant material
for salads and sandwiches.
But first, a little background information. Lettuce is over 95
percent water. This head of iceberg lettuce, like more than 90
percent of the lettuce eaten in this country, was grown in the far
west, on the California coastal plain or in the California or Arizona
desert. I bought this lettuce at a neighborhood market in Derby. It
was the first lettuce Iıve bought in many years. Before I could get
the money out my pocket, the owner put the plastic wrapped head into
another plastic bag.
The teachers and I brainstormed the numerous ways that energy was
transformed to produce and deliver that lettuce. The resulting list,
just for that one head of lettuce, filled two full blackboards.
Of course, each time energy is transformed, entropy is created. Truck
exhaust, hazardous wastes from pesticide and plastics factories, the
plastic wrapper and empty bag as well as the ecological changes caused
by large-scale irrigation are just a few examples of the entropy
created by this one head of lettuce.
Each of these transformations can be made more efficient according to
the first law of thermodynamics. Making pesticides could require
fewer kilowatt hours of electricity, trucks may get more miles per
gallon, store coolers may use less energy, and on and on through all
However, it is second-law efficiency that we need to understand. For
that, we compare the energy used in all of those steps to the minimum
energy required to provide us with crunchy greens. One teacher
quickly suggested that growing lettuce in a home garden which is
hand-tended and fertilized with compost uses very little energy. This
is possible here for six to eight months of the year. I suggested
sprouting seeds on the kitchen counter for the winter months. Sprouts
provide crunchy greens with additional nutritional benefits.
Compared to garden lettuce or sprouts, the second-law efficiency of
California iceberg is nearly zero. Stated another way, despite
first-law efficiency improvements, the California lettuce is almost
absolutely inefficient according to the important second law.
If we really want to slow down climate change and still satisfy our
needs, the second law of thermodynamics provides clear guidance.
While globalization increases the energy transformations and entropy
produced in satisfying our needs, the second law points to the
importance of simple, local solutions.
This is Bill Duesing, Living on the Earth
İ1997, Bill Duesing, Solar Farm Education, Box 135, Stevenson, CT
Bill and Suzanne Duesing operate the Old Solar Farm (raising NOFA/CT
certified organic vegetables) and Solar Farm Education (working on
urban agriculture projects in New Haven, Bridgeport, Hartford and
Norwalk, CT). Their collection of essays Living on the Earth:
Eclectic Essays for a Sustainable and Joyful Future is available from
Bill Duesing, Box 135, Stevenson, CT 06491 for $14 postpaid. These
essays first appeared on WSHU, public radio from Fairfield, CT. New
essays are posted weekly at http://www.wshu.org/duesing and those
since November 1995 are available there.
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