Environmental Engineering Reference
In-Depth Information
not reducing the social utility of energy availability. By combination of all these methods, the rate
of rise of atmospheric carbon dioxide can be ameliorated at an economic and social cost that may
be acceptable.
The amelioration of environmental degradation caused by energy use is a responsibility of
national governments. By regulation and by providing economic incentives, governments induce
energy users to reduce pollutant emissions by changes in technology or use practices. Bilateral
or global treaties can bring about coordinated multinational actions to reduce regional or global
environmental problems, such as acid deposition, ozone destruction, and climate change. The role
of technology is to provide the necessary reduction in emissions while still making available energy
at the minimum increase in cost needed to attain that end.
1.2
ENERGY
There is a minimum amount of energy needed to sustain human life. The energy value of food is the
major component, but fuel energy is needed for cooking and, in some climates, for heating human
shelter. In an agricultural society, additional energy is expended in growing, reaping, and storing
food, making clothing, and constructing shelters. In modern industrial societies, much more energy
than this minimum is consumed in providing food, clothing, shelter, transportation, communication,
lighting, materials, and numerous services for the entire population.
It is a basic principle of physics that energy cannot be destroyed, but can be transformed from
one form to another. When a fuel is burned in air, the chemical energy released by the rearrangement
of fuel and oxygen atoms to form combustion products is transformed to the random energy of
the hot combustion product molecules. When food is digested in the human digestive tract, some
of the food energy is converted to energy of nutrient molecules and some warms the body. When
human societies “consume” energy, they transform it from one useful form to a less useful form,
in the process providing a good or service that is needed to maintain human life and societies.
A quantitative measure of the ongoing good that energy “consumption” provides to society is
the time rate of transformation of the useful energy content of energy-rich materials, such as fossil
and nuclear fuels. In 1995, this worldwide consumption rate amounted to 12.1 terawatts (TW)
1
,
or about 2 kilowatts (kW) per capita.
2
Of this world total, the United States consumed 2.9 TW, or
about 13 kW per capita, which is the largest of any nation. However unevenly distributed among
the world's population, the world energy consumption rate far exceeds the minimum required to
sustain human life.
The capacity to consume energy at this rate is a consequence of the technology developed in
industrialized nations to permit the efficient extraction and utilization of these fuels by only a small
fraction of the population.
3
But the earth's fossil and nuclear fuel resources are being depleted at
a rate that will render them very scarce in future centuries, even if they are used more efficiently
than in the past. The current cost of these fuels, however, has remained low for decades as recovery
technology has improved enough to offset the distant threat of scarcity.
1
One terawatt
=
1E(12) watts. See Appendix A for a specification of scientific notation for physical units.
2
This rate is 16 times the per capita food energy consumption of 120 W.
3
This situation is analogous to the industrialization of agriculture in advanced economies, whereby a few
percent of the population provides food for all.
