8.4.2 Mitigation technologies and practices: per-area estimates of potential
As mitigation practices can affect more than one GHG, it is important to consider the impact of mitigation options on all GHGs (Robertson et al,. 2000; Smith et al., 2001; Gregorich et al., 2005). For non-livestock mitigation options, ranges for per-area mitigation potentials of each GHG are provided in Table 8.4 (tCO2-eq/ha/yr).
Mitigation potentials for CO2 represent the net change in soil carbon pools, reflecting the accumulated difference between carbon inputs to the soil after CO2 uptake by plants, and release of CO2 by decomposition in soil. Mitigation potentials for N2O and CH4 depend solely on emission reductions. Soil carbon stock changes were derived from about 200 studies, and the emission ranges for CH4 and N2O were derived using the DAYCENT and DNDC simulation models (IPCC, 2006; US-EPA, 2006b; Smith et al., 2007b; Ogle et al., 2004, 2005).
Table 8.5 presents the mitigation potentials in livestock (dairy cows, beef cattle, sheep, dairy buffalo and other buffalo) for reducing enteric methane emissions via improved feeding practices, specific agents and dietary additives, and longer term structural and management changes/animal breeding. These estimates were derived by Smith et al. (2007a) using a model similar to that described in US-EPA (2006b).
Some mitigation measures operate predominantly on one GHG (e.g., dietary management of ruminants to reduce CH4 emissions) while others have impacts on more than one GHG (e.g., rice management). Moreover, practices may benefit more than one gas (e.g., set-aside/headland management) while others involve a trade-off between gases (e.g., restoration of organic soils). The effectiveness of non-livestock mitigation options are variable across and within climate regions (see Table 8.4). Consequently, a practice that is highly effective in reducing emissions at one site may be less effective or even counter-productive elsewhere. Similarly, effectiveness of livestock options also varies regionally (Table 8.5). This means that there is no universally applicable list of mitigation practices, but that proposed practices will need to be evaluated for individual agricultural systems according to the specific climatic, edaphic, social settings, and historical land use and management. Assessments can be conducted to evaluate the effectiveness of practices in specific areas, building on findings from the global scale assessment reported here. In addition, such assessments could address GHG emissions associated with energy use and other inputs (e.g., fuel, fertilizers, and pesticides) in a full life cycle analysis for the production system.
Table 8.4: Annual mitigation potentials in each climate region for non-livestock mitigation options
Climate zone | Activity | Practice | CO2 (tCO2/ha/yr) | CH4 (tCO2-eq/ha/yr) | N2O (tCO2-eq/ha/yr) | All GHG (tCO2-eq/ha/yr) |
---|
Mean estimate | Low | High | Mean estimate | Low | High | Mean estimate | Low | High | Mean estimate | Low | High |
---|
Cool-dry | Croplands | Agronomy | 0.29 | 0.07 | 0.51 | 0.00 | 0.00 | 0.00 | 0.10 | 0.00 | 0.20 | 0.39 | 0.07 | 0.71 |
| Croplands | Nutrient management | 0.26 | -0.22 | 0.73 | 0.00 | 0.00 | 0.00 | 0.07 | 0.01 | 0.32 | 0.33 | -0.21 | 1.05 |
| Croplands | Tillage and residue management | 0.15 | -0.48 | 0.77 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.17 | -0.52 | 0.86 |
| Croplands | Water management | 1.14 | -0.55 | 2.82 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.14 | -0.55 | 2.82 |
| Croplands | Set-aside and LUC | 1.61 | -0.07 | 3.30 | 0.02 | 0.00 | 0.00 | 2.30 | 0.00 | 4.60 | 3.93 | -0.07 | 7.90 |
| Croplands | Agro-forestry | 0.15 | -0.48 | 0.77 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.17 | -0.52 | 0.86 |
| Grasslands | Grazing, fertilization, fire | 0.11 | -0.55 | 0.77 | 0.02 | 0.01 | 0.02 | 0.00 | 0.00 | 0.00 | 0.13 | -0.54 | 0.79 |
| Organic soils | Restoration | 36.67 | 3.67 | 69.67 | -3.32 | -0.05 | -15.30 | 0.16 | 0.05 | 0.28 | 33.51 | 3.67 | 54.65 |
| Degraded lands | Restoration | 3.45 | -0.37 | 7.26 | 0.08 | 0.04 | 0.14 | 0.00 | 0.00 | 0.00 | 3.53 | -0.33 | 7.40 |
| Manure/biosolids | Application | 1.54 | -3.19 | 6.27 | 0.00 | 0.00 | 0.00 | 0.00 | -0.17 | 1.30 | 1.54 | -3.36 | 7.57 |
| Bioenergy | Soils only | 0.15 | -0.48 | 0.77 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.17 | -0.52 | 0.86 |
Cool-moist | Croplands | Agronomy | 0.88 | 0.51 | 1.25 | 0.00 | 0.00 | 0.00 | 0.10 | 0.00 | 0.20 | 0.98 | 0.51 | 1.45 |
| Croplands | Nutrient management | 0.55 | 0.01 | 1.10 | 0.00 | 0.00 | 0.00 | 0.07 | 0.01 | 0.32 | 0.62 | 0.02 | 1.42 |
| Croplands | tillage and residue management | 0.51 | 0.00 | 1.03 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.53 | -0.04 | 1.12 |
| Croplands | Water management | 1.14 | -0.55 | 2.82 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.14 | -0.55 | 2.82 |
| Croplands | Set-aside and LUC | 3.04 | 1.17 | 4.91 | 0.02 | 0.00 | 0.00 | 2.30 | 0.00 | 4.60 | 5.36 | 1.17 | 9.51 |
| Croplands | Agro-forestry | 0.51 | 0.00 | 1.03 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.53 | -0.04 | 1.12 |
| Grasslands | Grazing, fertilization, fire | 0.81 | 0.11 | 1.50 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.80 | 0.11 | 1.50 |
| Organic soils | Restoration | 36.67 | 3.67 | 69.67 | -3.32 | -0.05 | -15.30 | 0.16 | 0.05 | 0.28 | 33.51 | 3.67 | 54.65 |
| Degraded lands | Restoration | 3.45 | -0.37 | 7.26 | 1.00 | 0.69 | 1.25 | 0.00 | 0.00 | 0.00 | 4.45 | 0.32 | 8.51 |
| Manure/biosolids | Application | 2.79 | -0.62 | 6.20 | 0.00 | 0.00 | 0.00 | 0.00 | -0.17 | 1.30 | 2.79 | -0.79 | 7.50 |
| Bioenergy | Soils only | 0.51 | 0.00 | 1.03 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.53 | -0.04 | 1.12 |
Warm-dry | Croplands | Agronomy | 0.29 | 0.07 | 0.51 | 0.00 | 0.00 | 0.00 | 0.10 | 0.00 | 0.20 | 0.39 | 0.07 | 0.71 |
| Croplands | Nutrient management | 0.26 | -0.22 | 0.73 | 0.00 | 0.00 | 0.00 | 0.07 | 0.01 | 0.32 | 0.33 | -0.21 | 1.05 |
| Croplands | Tillage and residue management | 0.33 | -0.73 | 1.39 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.35 | -0.77 | 1.48 |
| Croplands | Water management | 1.14 | -0.55 | 2.82 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.14 | -0.55 | 2.82 |
| Croplands | Set-aside and LUC | 1.61 | -0.07 | 3.30 | 0.02 | 0.00 | 0.00 | 2.30 | 0.00 | 4.60 | 3.93 | -0.07 | 7.90 |
| Croplands | Agro-forestry | 0.33 | -0.73 | 1.39 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.35 | -0.77 | 1.48 |
| Grasslands | Grazing, fertilization, fire | 0.11 | -0.55 | 0.77 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.11 | -0.55 | 0.77 |
| Organic soils | Restoration | 73.33 | 7.33 | 139.33 | -3.32 | -0.05 | -15.30 | 0.16 | 0.05 | 0.28 | 70.18 | 7.33 | 124.31 |
| Degraded lands | Restoration | 3.45 | -0.37 | 7.26 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 3.45 | -0.37 | 7.26 |
| Manure/biosolids | Application | 1.54 | -3.19 | 6.27 | 0.00 | 0.00 | 0.00 | 0.00 | -0.17 | 1.30 | 1.54 | -3.36 | 7.57 |
| Bioenergy | Soils only | 0.33 | -0.73 | 1.39 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.35 | -0.77 | 1.48 |
Warm-moist | Croplands | Agronomy | 0.88 | 0.51 | 1.25 | 0.00 | 0.00 | 0.00 | 0.10 | 0.00 | 0.20 | 0.98 | 0.51 | 1.45 |
| Croplands | Nutrient management | 0.55 | 0.01 | 1.10 | 0.00 | 0.00 | 0.00 | 0.07 | 0.01 | 0.32 | 0.62 | 0.02 | 1.42 |
| Croplands | Tillage and residue management | 0.70 | -0.40 | 1.80 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.72 | -0.44 | 1.89 |
| Croplands | Water management | 1.14 | -0.55 | 2.82 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.14 | -0.55 | 2.82 |
| Croplands | Set-aside and LUC | 3.04 | 1.17 | 4.91 | 0.02 | 0.00 | 0.00 | 2.30 | 0.00 | 4.60 | 5.36 | 1.17 | 9.51 |
| Croplands | Agro-forestry | 0.70 | -0.40 | 1.80 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.72 | -0.44 | 1.89 |
| Grasslands | Grazing, fertilization, fire | 0.81 | 0.11 | 1.50 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.81 | 0.11 | 1.50 |
| Organic soils | Restoration | 73.33 | 7.33 | 139.33 | -3.32 | -0.05 | -15.30 | 0.16 | 0.05 | 0.28 | 70.18 | 7.33 | 124.31 |
| Degraded lands | Restoration | 3.45 | -0.37 | 7.26 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 3.45 | -0.37 | 7.26 |
| Manure/biosolids | Application | 2.79 | -0.62 | 6.20 | 0.00 | 0.00 | 0.00 | 0.00 | -0.17 | 1.30 | 2.79 | -0.79 | 7.50 |
| Bioenergy | Soils only | 0.70 | -0.40 | 1.80 | 0.00 | 0.00 | 0.00 | 0.02 | -0.04 | 0.09 | 0.72 | -0.44 | 1.89 |
|
Table 8.5: Technical reduction potential (proportion of an animal’s enteric methane production) for enteric methane emissions due to (i) improved feeding practices, (ii) specific agents and dietary additives and (iii) longer term structural/management change and animal breedinga
| Improved feeding practicesb | Specific agents and dietary additivesc | Longer term structural/management change and animal breedingd |
---|
AEZ regions | Dairy cows | Beef cattle | Sheep | Dairy buffalo | Non-dairy buffalo | Dairy cows | Beef cattle | Sheep | Dairy buffalo | Non-dairy buffalo | Dairy cows | Beef cattle | Sheep | Dairy buffalo | Non-dairy buffalo |
---|
Northern Europe | 0.18 | 0.12 | 0.04 | | | 0.08 | 0.04 | 0.004 | | | 0.04 | 0.03 | 0.003 | | |
Southern. Europe | 0.18 | 0.12 | 0.04 | | | 0.08 | 0.04 | 0.004 | | | 0.04 | 0.03 | 0.003 | | |
Western Europe | 0.18 | 0.12 | 0.04 | | | 0.08 | 0.04 | 0.004 | | | 0.04 | 0.03 | 0.003 | | |
Eastern. Europe | 0.11 | 0.06 | 0.03 | | | 0.04 | 0.01 | 0.002 | | | 0.03 | 0.07 | 0.003 | | |
Russian Federation | 0.10 | 0.05 | 0.03 | | | 0.03 | 0.04 | 0.002 | | | 0.03 | 0.06 | 0.003 | | |
Japan | 0.17 | 0.11 | 0.04 | | | 0.08 | 0.09 | 0.004 | | | 0.03 | 0.03 | 0.003 | | |
South Asia | 0.04 | 0.02 | 0.02 | 0.04 | 0.02 | 0.01 | 0.01 | 0.0005 | 0.01 | 0.002 | 0.01 | 0.01 | 0.001 | 0.01 | 0.02 |
East Asia | 0.10 | 0.05 | 0.03 | 0.10 | 0.05 | 0.03 | 0.05 | 0.002 | 0.03 | 0.012 | 0.03 | 0.06 | 0.003 | 0.03 | 0.07 |
West Asia | 0.06 | 0.03 | 0.02 | 0.06 | 0.03 | 0.01 | 0.02 | 0.001 | 0.01 | 0.004 | 0.01 | 0.02 | 0.001 | 0.02 | 0.03 |
Southeast Asia | 0.06 | 0.03 | 0.02 | 0.06 | 0.03 | 0.01 | 0.02 | 0.001 | 0.01 | 0.004 | 0.01 | 0.02 | 0.001 | 0.02 | 0.03 |
Central Asia | 0.06 | 0.03 | 0.02 | 0.06 | 0.03 | 0.01 | 0.02 | 0.001 | 0.01 | 0.004 | 0.01 | 0.02 | 0.001 | 0.02 | 0.03 |
Oceania | 0.22 | 0.14 | 0.06 | | | 0.08 | 0.08 | 0.004 | | | 0.05 | 0.03 | 0.004 | | |
North America | 0.16 | 0.11 | 0.04 | | | 0.11 | 0.09 | 0.004 | | | 0.03 | 0.03 | 0.003 | | |
South America | 0.06 | 0.03 | 0.02 | | | 0.03 | 0.02 | 0.001 | | | 0.02 | 0.03 | 0.002 | | |
Central America | 0.03 | 0.02 | 0.02 | | | 0.02 | 0.01 | 0.001 | | | 0.01 | 0.02 | 0.002 | | |
East Africa | 0.01 | 0.01 | 0.01 | | | 0.003 | 0.004 | 0.0002 | | | 0.004 | 0.006 | 0.0004 | | |
West Africa | 0.01 | 0.01 | 0.01 | | | 0.003 | 0.004 | 0.0002 | | | 0.004 | 0.006 | 0.0004 | | |
North Africa | 0.01 | 0.01 | 0.01 | | | 0.003 | 0.004 | 0.0002 | | | 0.004 | 0.006 | 0.0004 | | |
South Africa | 0.01 | 0.01 | 0.01 | | | 0.003 | 0.004 | 0.0002 | | | 0.004 | 0.006 | 0.0004 | | |
Middle Africa | 0.01 | 0.01 | 0.01 | | | 0.003 | 0.004 | 0.0002 | | | 0.004 | 0.006 | 0.0004 | | |
|
The effectiveness of mitigation strategies also changes with time. Some practices, like those which elicit soil carbon gain, have diminishing effectiveness after several decades; others such as methods that reduce energy use may reduce emissions indefinitely. For example, Six et al. (2004) found a strong time dependency of emissions from no-till agriculture, in part because of changing influence of tillage on N2O emissions.