11.2.2 Mitigation Technologies
Agriculture is the main source of methane (CH4)
and nitrous oxide (N2O) emissions. CH4
emissions from domestic ruminants, animal waste and rice fields were estimated
to be 65-100 (IPCC, 1992; Hogan, 1993), 20-30 (Safley et al., 1992) and 25.4-54
(IPCC, 1996) Tg/yr. N2O is produced primarily by microbial processes in the
soil (Bouwman, 1990; Duxbury and Mosier, 1993). It was estimated that more than
75% of the anthropogenic N2O sources are derived
from agriculture, the total amount was 4.2Tg N2O-N/yr (Mosier et al., 1998b).
A significant fraction of the CH4 and N2O emitted from agricultural systems
could be avoided if some combination of agricultural management practices listed
in Table 11.2 were adopted worldwide (IPCC, 1996).
| Table 11.2 List of practices to
reduce CH4 and N2O emissions from agricultural systems (IPCC, 1996) |
| Mitigation practice |
Estimated decrease due to practice (Tg CH4 or N2O-N/yr) |
|
Ruminant livestock
- Improve diet quality and nutrient balance
- Increase feed digestibility
- Production-enhancing agents
- Improve animal genetics
- Improve reproduction efficiency
Livestock manure
- Covered lagoons
- Small digesters
- Large digesters
Flooded rice
- Irrigation management
- Nutrient managemen
- New cultivars and other cultural practices
Biomass burning
- Incorporate crop residues into soil
- Increase the productivity of lands
- Lengthen the rotation time
Agricultural soil
- Match N supply with crop demand
- Tighten N flow cycles
- Use advanced fertiliser techniques
- Optimise tillage, irrigation and drainage
|
29(12-44)
25(10-35)
2(1-3)
2(1-3)
-
-
5.1(2.6-8.7)
3.4(2-6.8)
1.7(0.6-1.9)
-
20(8-35)
5(3.3-9.9)
10(2.5-15)
5(2.5-10)
6(3-9)
-
-
-
0.68
0.24
0.14
0.15
0.15
|
Beyond the use of biomass fuels to displace fossil fuels, the management of
forests, agricultural lands and rangelands can play an important role in reducing
current emissions of CO2, CH4
and N2O, and in enhancing carbon sinks. A number
of measures could conserve and sequester substantial amounts of methane (approximately
24-92 Tg/yr, 15-65% of current levels) over the next century (Mosier et al.,
1998a). A total potential reduction of global N2O
emissions from agricultural soils is thus 0.7 (0.36 to 1.1) Tg N2O-N/yr or 9-26%
of current emissions from agriculture (Mosier et al., 1998b).
|
