Environmental Engineering Reference
In-Depth Information
temperature rise may cause associated climatic effects, such as change in precipitation patterns,
more frequent and extensive tropical storms, glacier and ice-sheet melting, ocean-atmosphere
interaction variability, and a rise in sea level.
Global warming could be ameliorated by slowing, or even reversing, the trend of GHG con-
centration increases in the atmosphere by reducing their emissions. In this chapter we discussed the
possible options for reducing CO
2
emissions, the gas that bears the bulk of the greenhouse effect.
The options include the following:
•
Demand-side conservation and efficiency improvements, including less space heating and
better insulation, less air conditioning, fluorescent lighting, more energy-efficient appliances,
process modification in industry, and, very importantly, more fuel-efficient automobiles.
Such measures may even incur a negative cost (i.e., consumer savings by using less energy)
or at least a rapid payback period for the investment in energy-saving devices.
•
Supply-side efficiency measures. Here we mean primarily increasing the efficiency of coal-
fired power plants. Coal gasification combined-cycle power plants have a thermal efficiency
in the 45-50% range, compared with single-cycle pulverized-coal plants in the 35-40%
range. However, coal gasification power plants are more expensive than single-cycle plants.
•
Capture of CO
2
from the flue gas of power plants and sequestration in terrestrial or deep
ocean reservoirs. This is an expensive option, and it will be exercised only if governments
mandate or subsidize it.
•
Utilization of the captured CO
2
. The utilization for enhanced oil and natural gas recovery is
economically attractive; the utilization of CO
2
as a raw material for the production of some
fuels and chemicals requires extra energy input and does not appear to be economical.
•
Shift to nonfossil energy sources. The choices here are agonizing, because the largest impact
could be made by shifting to nuclear electricity and hydroelectricity, both presently very
unpopular and fraught with environmental and health concerns. The shift to solar, wind,
geothermal, and ocean energy are popular, but because of their limited availability and
intermittency and because of their larger cost compared to fossil energy, a substantial shift
to these energy sources can not be expected in the near future.
•
Greater use of biomass, especially wood. The use of biomass is CO
2
neutral, because as
much CO
2
that evolves in burning biomass is reabsorbed in the growth of the next generation
of vegetation.
•
Afforestation without using the trees for 100-200 years, during which period the CO
2
concentrations in the atmosphere will decline because of exhaustion of fossil fuel resources
and shift to nonfossil energy sources.
•
Stopping slash and burning practices of forests, especially tropical forests, which are prodi-
gious absorbents of CO
2
, and the burning of which releases CO
2
.
None of these options can ameliorate global warming by itself. They have to be taken in
combination and on an incremental basis, starting with the least expensive ones and progressing
to the more expensive ones. Even if the predictions of global climate change were to turn out to
be exaggerated, the fact that fossil fuel usage entails many other adverse environmental and health
effects, and the certainty that fossil fuel resources are finite, makes it imperative that we curtail
fossil energy usage as soon as possible.
