Environmental Engineering Reference
Hydropower is a relatively clean source of electricity, but most of the high-gradient rivers and
streams that are near population centers have already been dammed up for powering the turboelectric
generators. Damming up more rivers is encountering increasing public resistance, because of the risk
to the watershed ecology and because it may entail massive population displacement. While several
new hydroelectric power generators are being built or planned, notably the 18-GW hydroelectric
station on the Yangtze River, hydropower is not expected to increase its share substantially among
other sources of electricity.
Other renewable energy sources, besides hydropower, hold the promise of occupying an in-
creasing share among electricity generators. Renewable sources are biomass, geothermal, wind,
solar thermal and thermal electric, photovoltaic, and ocean tidal energy. Biomass and geothermal
plants are able to supply electric power dependably on a daily and annual basis. The other sources
of renewable energy have diurnal and seasonal rhythms that do not necessarily match the demand
for electric power. Because electricity cannot be directly stored, the renewable generators usually
need to be backed up by conventional power sources. However, when producing electricity, the
renewable sources can displace fossil fuel consumption and reduce air pollutant emissions. Re-
newable electricity generators require a greater capital investment than fossil power plants and are
currently not economically competitive with these power plants.
REGULATING THE ENVIRONMENTAL EFFECTS OF
Mitigating the adverse environmental effects of energy use has been a chronic problem afflicting
nations worldwide, because national economies do not automatically respond to limit environmental
Economists label the release of pollutants into the environment as an externality, an activity
that does not enter into the cost of production of a good or supply of a service. The capacity of the
environment to tolerate the discharge of pollutants is considered a free good; the polluter pays no
price for its use. But the environmental capacity to endure pollution is finite, and the cumulative
effects of pollution from many sources degrades its quality, adversely affecting the interests of
society as a whole to a much greater extent than the interests of one or even all the polluters.
Although the total social cost of bearing the ill effects of pollution outweighs the cost of eliminating
the pollution, the polluters share of these social costs are too small to offset his abatement cost, so
that abatement is uneconomic for each polluter, both individually and collectively.
A common solution to this social and economic dilemma is government regulation of pollutant
producing activities. Most often this takes the form of a performance requirement, such as a standard
of maximum emissions per fuel input from energy using sources, or a requirement that certain
pollution reduction technologies be employed. Less often, economic incentives to abatement are
used, such as emission taxes, pollutant fines, or tax deductions and credits. Except for the case
of deductions and credits, the cost of abatement is borne by the polluter, thereby internalizing the
externality of pollution into the production process.
In almost all cases of pollution of air, water, or soil, the amounts of toxic pollutants emitted are
only a tiny fraction of the fuel burned or material processed. In general, the cost of reducing ordinary
pollutant emissions is only a small fraction of the economic value added to the production process,
but the cost per unit of pollution removed is often very high, inevitably higher than any possible