Agriculture Reference
In-Depth Information
tAble 18.8
world Primary energy supply in 2004
source
% of total energy
Oil
34
Coal
24
Gas
21
Combustible renewable & waste
11
Nuclear
7
Hydro
2
Others
1
Source:
Adapted from EIA, 2004; EPA 2005.
erosion (Lal 2005a) and leaching, and increase in frequency and intensity of
extreme events may exacerbate the problem of soil degradation.
4. Increase in the future energy demand may accentuate soil degrada-
tion directly and indirectly. Presently, only 11% of the world's primary
energy supply is met through combustible renewable and other biosolids
(Table 18.8). There is a strong emphasis on increasing the use of biofuels.
Toward this strategy, the goal is to procure 1 billion Mg (Megagram, one
metric ton) of cellulosic biomass in the United States and 4 to 5 billion Mg
in the world (Lal 2005b; Somerville 2006). Harvesting crop residues for
biofuel production (ethanol) may increase the risk of erosion, compaction,
depletion of the SOC pool, and so on.
Indirectly, the severity and extent of soil degradation may be affected by the
rapid change in land use, especially conversion of forest/woodlands and grasslands
to cropland and pastures. Presently, 19 to 20% of the total annual emissions (CO
2
equivalent) are attributed to land use change and deforestation (Table 18.9). The
effect of land use, land use change, and soil cultivation on the radiative forcing may
tAble 18.9
sources of global emissions in 2000
source
% of total Pgc equivalent
Fossil fuel combustion
53.0
Cement manufacture
2.0
Land use change and forestry
19.0
Methane emission
16.0
Nitrous oxide
9.0
High GWP gases
1.0
Source:
DOE, 2006.
