http://www.thefarm.org/permaculture/ has one of David Holmgren's
essays which i find useful. It says we can use "energy" as the
currency to measure sustainability and also as part of the
definition.
Probably the biggest failure of modern technology is
connected to energy. Almost everything is driven by high
energy processes which assume energy will always be
available. With a large supply of energy we can undertake
massive construction projects, transport products anywhere,
use inefficient heating methods, win wars, convert raw
materials into many forms, and construct a society that could
not exist without high energy input. That is exactly what we
have today.
Holmgren points out that basic physics says this high energy
usage isn't sustainable. The two laws of thermodynamics
state:
Energy is neither created or destroyed. The energy entering
the system must be accounted for either as being stored there
or as flowing out.
In all processes some of the energy loses its ability to do
work and is degraded in quality. The tendency of potential
energy to be used up and degraded is described as entropy,
which is a measure of disorder which always increases in
real processes.
On earth almost all energy comes from the sun and a sustainable
usage level would be limited by how much is provided. Instead
we have decided to ignore this and use energy at a much higher
rate. This high rate of usage changes earth's balance slightly
and potentially might cause other problems such as climate
change.
At an individual these ideas become painful because much of
our life is dominated by high energy use. Our transport,
house construction, food supply, recreation, and just about
everything is energy related. When we try to reduce this
energy we tend to move in two directions at once. We move
back to low tech methods from the past and we move forward
into conservation and efficient methods/products.
At first these two directions may seem to be in conflict,
but not if viewed from an energy usage perspective. In fact
an ecologist "Odem" showed that we can view all life, the
earth, and even culture from an energy perspective and
clearly see ways to improve our world. In essence we
can use energy as the measure of sustainability.
----
jeff owens, [EMAIL PROTECTED], http://www.xprt.net/~jko
underground house, solar power, self-reliance, edible landscape
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