Environmental Engineering Reference
In-Depth Information
The industrial revolution drastically changed the conditions of human societies by making
available large amounts of energy from coal (and later oil, gas, and nuclear fuel) far exceeding that
available from the biofuel, wood. Some of this energy was directed to increasing the productivity
of agriculture, freeing up a large segment of the population for other beneficial activities. Urban
populations grew rapidly as energy-using activities, such as manufacturing and commerce, concen-
trated themselves in urban areas. Urban population and population density increased, while those
of rural areas decreased.
By the middle of the twentieth century, nearly all major cities of the industrialized world
experienced health-threatening episodes of air pollution, and today this type of degradation has
spread to the urban areas of developing countries as a consequence of the growing industrialization
of their economies. Predominantly, urban air pollution is a consequence of the burning of fossil fuels
within and beyond the urban region itself. This pollution can extend in significant concentrations
to rural areas at some distance from the pollutant sources so that polluted regions of continental
dimensions even include locations where there is an absence of local energy use.
Despite the severity of urban pollution, it is technically possible to reduce it to harmless levels
by limiting the emission of those chemical species that cause the atmospheric degradation. The
principal pollutants comprise only a very small fraction of the materials processed and can be made
even smaller, albeit at some economic cost. In industrialized countries, the cost of abating urban
air pollution is but a minor slice of a nation's economic pie.
While the industrialized nations grapple with urban and regional air pollution, with some
success, and developing nations lose ground to the intensifying levels of harmful urban air con-
tamination, the global atmosphere experiences an untempered increase in greenhouse gases, those
pollutants that are thought to cause the average surface air temperature to rise and climate to be
modified. Unlike the urban pollutants, most of which are precipitated from the atmosphere within
a few days of their emission, greenhouse gases accumulate in the atmosphere for years, even cen-
turies. The most common greenhouse gas is carbon dioxide, which is released when fossil fuels
are burned. As it is not possible to utilize the full energy of fossil fuels without forming carbon
dioxide, it will be very difficult to reduce the global emissions of carbon dioxide while still provid-
ing enough energy to the world's nations for the improvement of their economies. While there is
technology available or being developed that would make possible substantial reductions in global
carbon dioxide emissions, the cost of implementation of such control programs will be much larger
than that for curbing urban air pollution.
1.1.1
An Overview of This Text
This topic describes the technology and scientific understanding by which the world's nations could
ameliorate the growing urban, regional, and global environmental problems associated with energy
use while still providing sufficient energy to meet the needs of populations for a humane existence.
It focuses on the technology and science, the base on which any effective environmental control
program must be built. It does not prescribe control programs, because they must include social,
economic, and political factors that lie outside the scope of this topic. We do not delve deeply into
the science and technology, but do provide an adequate description of the fundamental principles
and their consequences to the topic at hand. We present a bibliography in each chapter for the use
of the reader who wants to pursue some aspects at greater depth.
The major sources of energy for modern nations are fossil fuels, nuclear fuels, and hydropower.
Non-hydro renewable energy sources, such as biomass, wind, geothermal, solar thermal, and
