Agriculture Reference
In-Depth Information
2 Emission of Greenhouse Gases (GHGs) from Agriculture
According to the Inter-governmental Panel on Climate Change-Assessment Report
4 (IPCC-AR4
2007
), the agriculture sector had contributed 10-12 % of the total
anthropogenic GHG emissions in the year 2005. Since 1990, CH
4
and NO
2
emis-
sions from agriculture sector are rising at the alarming rate of 58 Mt CO
2
equiva-
lent/yr (US-EPA
2006a
). Agriculture sector's contribution is more significant when
emissions from individual sources are considered separately. The agriculture sector
contributed 58 % of the total N
2
O and 47 % of the total CH
4
emissions in the year
2005 (IPCC-AR4
2007
). Emission from enteric fermentation and submerged rice
fields constitutes the major source of CH
4
whereas emission from soil constitutes
the single largest source worldwide (US-EPA
2006a
). Biomass burning and manure
management also account for a significant amount of global GHG emission. Net
CO
2
emission from agriculture sector is less than 1 % of the global anthropogenic
emission (US-EPA
2006b
). Terrestrial plants also emit methane, global flux 62-
263 Tg/yr, contributing 10-45 % of total global methane emissions (Keppler et al.
2006
). Terrestrial plants emit methane through detached leaves as well as whole
plant (Keppler et al.
2006
; Whiticar and Ednie
2007
). Transpiration is the dominant
mechanism helping such emission pathway through leaves via xylem. Stiehl-Braun
et al. (
2011
) studied the spatial distribution of methane-oxidizing bacteria (MOB)
and proved that methane consumer bacteria can escape the effect of nitrogen (N)
fertilization by shifting their zone of activity into deeper soil layers. Nitrogen fer-
tilization and global methane cycling are interdependent and interlinked in both
wetland conditions as well as in upland situations. Methanogenic archaea in wet-
lands is one of the major sources of methane whereas upland soil is a major C sink
(Bodelier et al.
2011
).
Developing countries contributed around 97 and 92 % of total global emissions
from rice production and burning of biomass while developed countries contributed
52 % of total GHG emission from manure management (US-EPA
2006a
). South and
East Asian nations contributed 82 % of the total CH
4
emissions while countries from
Sub-Saharan Africa and Latin America and the Caribbean have contributed about
74 % of total emissions from biomass burning. Yan et al. used the Tier-1 method
as described in IPCC (Eggleston et al.
2006
) guidelines for estimating global meth-
ane emissions and Monte Carlo simulation for estimating the uncertainty range.
They have estimated that the total global CH
4
emission in the year 2000 was about
25.4 Tg/yr. They have further calculated that if all of the continuously flooded rice
fields were drained at least once during the growing season, a reduction of 4.1 Tg
CH
4
/yr could be possible (Table
3.1
).
Jiang et al. (
2000
) used The Asian-Pacific Integrated Model for analyzing the long-
term Greenhouse gas (GHG) emission scenarios depending on alternative develop-
ment paths in the developing countries of the Asia-Pacific region. They have taken
into account four differeknt scenarios, namely Catch-Up Scenario ( Scenario C),
Domestic Supply Scenario (Scenario D), Short-cut Scenario (Scenario S) and Re-
gional Equity Scenario (Scenario E). They have estimated that the growth rate of
GHG emissions in the Asia-Pacific region is significantly higher than the overall
