Environmental Engineering Reference
In-Depth Information
2.0
Fossil fuel
CO
2
release
Net forest
uptake
Net non-forest
uptake
Net CO
2
release
1.5
1.0
0.5
0
Net Flux of Carbon as CO
2
FIGURE 9.2
Estimated annual net CO
2
emissions and uptake in the United States in 2003,
according to the U.S. Climate Change Science Program. U.S. fossil fuel CO
2
emissions
accounted for more than 20% of the global total in 2003. Net uptake fluxes (photosynthesis
minus oxidation) are shown for forest and non-forest areas. The largest net U.S. CO
2
uptake
was associated with regrowing forests and harvesting wood products. Non-forest net carbon
uptake—including accumulation in shrubs, agricultural soils, wetlands, rivers, and reser-
voirs—was smaller and more uncertain. (From USGS,
Carbon Sequestration to Mitigate
Climate Change
, U.S. Geological Survey, Washington, DC, 2008.)
TERRESTRIAL CARBON SEQUESTRATION
Terrestrial sequestration (sometimes termed
biological sequestration
) is the removal
of gaseous carbon dioxide from the atmosphere and binding it in living tissue by
plants. Terrestrial sequestration is typically accomplished through forest and soil
conservation practices that enhance the storage of carbon (such as restoring and
establishing new forests, wetlands, and grasslands) or reduce CO
2
emissions (such
as reducing agricultural tillage and suppressing wildfires). In the United States,
these practices are implemented to meet a variety of land-management objectives.
Although the net terrestrial uptake fluxes shown in Figure 9.2 offset about 30% of
U.S. fossil fuel CO
2
emissions, only a small fraction of this uptake results from
