Environmental Engineering Reference
In-Depth Information
x
H
OW
W
OULD
Y
OU
V
OTE
?
Should we phase out the use of
fossil fuels over the next 50 years? Cast your vote online at
http://biology.brookscole.com/miller11.
Solutions
Global Warming
Prevention
Cleanup
Science: Removing and Storing CO
2
We can prevent some of the CO
2
we produce from
circulating in the troposphere, but the costs may be
high and the effectiveness of various approaches
remains unknown.
Figure 16-14 (p. 380) shows several techniques to re-
move CO
2
from the troposphere or from smokestacks,
and store (sequester) it in other parts of the environ-
ment. One possible way to remove more CO
2
from the
troposphere is to plant trees that store it in biomass.
However, this approach works only temporarily, be-
cause trees release their stored CO
2
back into the at-
mosphere when they die and decompose or if they
are burned (for example, by forest fires or to clear
land for crops).
A second approach is
soil sequestration
in which
plants such as switchgrass are used to remove CO
2
from the air and store it in the soil. But warmer tem-
peratures can increase decomposition in soils and re-
turn some of this stored CO
2
to the atmosphere.
A third strategy is to
reduce the release of carbon
dioxide and nitrous oxide from soil.
Ways to do so include
no-till cultivation
and setting aside depleted crop fields
as conservation reserves.
A fourth approach is to remove CO
2
from smoke-
stacks and
inject it into the deep ocean
or
pump it deep un-
derground
into coal seams that are too deep to mine,
depleted oil fields and natural gas reservoirs, and un-
derground pockets of saltwater (called
saline aquifers
),
as shown in Figure 16-14. Scientists are concerned that
placing vast amounts of CO
2
into the ocean will create
acidic plumes, which can disrupt deep-water ocean
ecosystems.
Many scientists see capturing CO
2
and pumping it
deep underground as the best sequestration strategy.
Oil companies have been piping CO
2
underground for
decades as a way to help extract more oil from wells. Re-
cent studies indicate that this CO
2
has remained under-
ground. In 2004, Ronald Oxburgh, Shell's CEO in the
United Kingdom, called underground sequestration es-
sentially the last hope to slow the rate of climate change:
“If we don't have sequestration, then I see very little
hope for the world.”
This strategy is costly because current methods
can remove only about 30% of the CO
2
from smoke-
stack emissions and using them would double or triple
the cost of producing electricity by burning coal. In
addition, the U.S. Department of Energy estimates that
the cost of sequestering carbon dioxide in various
underground and deep-ocean repositories must be re-
Cut fossil fuel
use (especially
coal)
Remove CO
2
from smokestack
and vehicle
emissions
Shift from coal
to natural gas
Improve energy
efficiency
Store (sequester)
CO
2
by planting
trees
Shift to
renewable
energy resources
Sequester
CO
2
deep
underground
Transfer energy
efficiency and
renewable energy
technologies
to developing
countries
Reduce
deforestation
Sequester CO
2
in soil by using
no-till cultivation
and taking crop
land out of
production
Sequester CO
2
in the deep ocean
Use more
sustainable
agriculture
Repair leaky natural
gas pipelines and
facilities
Limit urban
sprawl
Use animal feeds
that reduce CH
4
emissions by
belching cows
Reduce poverty
Slow population
growth
Figure 16-13
Solutions:
methods for slowing atmospheric
warming during this century.
Critical thinking: which five of
these solutions do you believe are the most important?
Figure 16-13 presents a variety of prevention and
cleanup solutions that climate analysts have suggested
for slowing the rate and degree of global warming.
Most of these suggestions are based on what we know
about how the earth's climate system works (Fig-
ure 16-7, p. 372) and how the earth sustains itself
(Figure 6-19, p. 126).
The solutions come down to three major strate-
gies:
improve energy efficiency to reduce fossil fuel use, shift
from carbon-based fossil fuels to carbon-free renewable en-
ergy resources,
and
sequester or store as much CO
2
as pos-
sible in soil, vegetation, the underground, and the deep
ocean.
The effectiveness of these strategies would be
enhanced by
reducing population,
which would de-
crease the number of fossil fuel consumers and CO
2
emitters, and by
reducing poverty,
which would de-
crease the need of the poor to clear more land for crops
and fuelwood.
