Environmental Engineering Reference
In-Depth Information
Mechanical
energy
(moving,
thinking,
living)
Chemical
energy
(food)
Solar
energy
Chemical energy
(photosynthesis)
Waste
heat
Waste
heat
Waste
heat
Waste
heat
Active Figure 2-11
The second law of thermodynamics in action in living systems. Each time energy changes from
one form to another, some of the initial input of high-quality energy is degraded, usually to low-quality heat that is
dispersed into the environment.
See an animation based on this figure and take a short quiz on the concept.
efficiency. Scientists estimate that only 16% of the en-
ergy used in the United States ends up performing
useful work. The remaining 84% is either unavoidably
wasted because of the second law of thermodynamics
(41%) or unnecessarily wasted (43%).
Thermodynamics teaches us an important lesson:
The cheapest and quickest way to get more energy is to
stop wasting almost half of the energy we use. We can
do so by not driving gas-guzzling motor vehicles and
by not living in poorly insulated and leaky houses.
What are you doing to reduce your unnecessary waste
of energy?
waste) economies
that attempt to boost economic
growth by increasing the one-way flow of matter and
energy resources through their economic systems
(Figure 2-12). These resources flow through their
economies into planetary
sinks
(air, water, soil, organ-
isms), where pollutants and wastes can accumulate to
harmful levels.
What happens if more people continue to use and
waste more energy and matter resources at an increas-
ing rate? In other words, what happens if most of the
world's people become infected with the affluenza
virus?
The law of conservation of matter and the two laws
of thermodynamics discussed in this chapter tell us
that eventually this resource consumption will exceed
the capacity of the environment to dilute and degrade
waste matter and absorb waste heat. However, they do
not tell us how close we are to reaching such limits.
See examples of how the first and second laws of
thermodynamics apply in our world at Environmental
ScienceNow.
2-4 MATTER AND ENERGY CHANGE
LAWS AND SUSTAINABILITY
Matter-Recycling-and-Reuse Economies
Recycling and reusing more of the earth's matter
resources slow down depletion of nonrenewable
matter resources and reduce our environmental
impact.
There is a way to slow down the resource use and re-
duce our environmental impact in a high-throughput
economy. We can convert this linear economy into a cir-
cular
matter-recycling-and-reuse economy,
which
mimics nature by recycling and reusing most of our
matter outputs instead of dumping them into the
environment.
Unsustainable High-Throughput Economies
Most nations increase their economic growth by
converting the world's resources to goods and
services in ways that add large amounts of waste,
pollution, and low-quality heat to the environment.
As a result of the law of conservation of matter and the
second law of thermodynamics, individual resource
use automatically adds some waste heat and waste mat-
ter to the environment. Most of today's advanced in-
dustrialized countries feature
high-throughput (high-
