Methane

When peatlands are drained in preparation for peat extraction, the natural production of CH4 is largely reduced, but not entirely shut down (Strack et al, 2004), as the methanogen bacteria thrive only in anaerobic conditions. Under Tier 1, methane emissions are assumed to be insignificant in these drained peatlands. At higher tiers, countries are encouraged to examine the pattern of CH4 emissions from topographic lows and drainage ditches, which can contribute a significant proportion of the total greenhouse gas emissions from these managed peatlands (Sundh et al, 2000).

NITROUS OXIDE

Depending on site fertility, peat deposits may contain significant amounts of organic nitrogen in inactive form. Drainage allows bacteria to convert the nitrogen into nitrates, which then leach into the surface where they are reduced to N2O. In drained peatlands, the potential quantity of N2O emitted depends on the nitrogen content of the peat. At C:N ratios exceeding 25, the N2O emissions may be considered insignificant (Klemedtsson et al, 2005).

Currently, there are no estimation methods that would allow separation of N2O emissions from organic matter decay during the off-site use of horticultural peat. Nitrogen fertilizers are commonly added to horticultural peat before use, and this source would likely dominate N2O emission patterns. In order to avoid double-counting N2O emitted from the use of fertilizers, the default approach for estimating N2O emissions from lands managed for peat extraction excludes emissions from the decay of organic nitrogen in horticultural peat.

Choice of method

Use the decision tree of Figure 7.1 to determine the appropriate methodological tier for N2O emissions. Tier 1

The Tier 1 method for estimating N2O emissions from drained wetlands is similar to that described for drained organic soils for agriculture or forestry, but emission factors are generally lower. The default methodology only considers nutrient-rich peatlands.

Equation 7.7

N2O EMISSIONS FROM PEATLANDS DURING PEAT EXTRACTION

N2 OWWpeaExtraction = \ApeatRich • ^^O-Np^R^J * ' 10

Where:

N2OWWpeat Extactioii = direct N2O emissions from peatlands managed for peat extraction, Gg N2O yr-1

ApeatRich = area of nutrient-rich peat soils managed for peat extraction, including abandoned areas in which drainage is still present, ha

EFn o-n , = emission factor for drained nutrient-rich wetlands organic soils, kg N2O-N ha-1 yr-1

2 peat Rich

Tier 2

Under Tier 2, the activity data are disaggregated by additional factors such as peat type and fertility, phase of peat extraction, and time since the onset of drainage activities. The corresponding emission factors are country-specific and take into account conditions and practices of peat extraction, drainage depth, and changes in the C:N ratio down the peat profile.

Tier 3

Tier 3 methods involve a comprehensive understanding and representation of the dynamics of N2O emissions and removals on managed peatlands, including the effect of site characteristics, peat type and depth, extraction technology, and the phases of peat extraction as described at the beginning of Section 7.2. The methodology will include all the relevant sources of N2O. Both on-site and off-site emissions will be considered, and take into account the rate of peat decay under common extraction and utilization conditions. Methods should be consistent with the estimation procedures for CO2 emissions, e.g., the same off-site decay rates should be used. If process-based models are used, they should be calibrated and validated against independent measurements which are representative of the national conditions.

Choice of emission/removal factors

Tier 1

Default emission factors for the Tier 1 method are provided in Table 7.6. Tiers 2 and 3

Countries applying Tier 2 methods develop country-specific emission factors, which may be able to differentiate emission rates during land conversion to peat land and the ongoing emissions during peat extraction. Tiers 2 and 3 require country-specific emission data that account for site characteristics, peat type and depth, extraction technology, the phases of peat extraction or other relevant factor. Peat type is especially relevant to its decomposability and the ensuing N2O emissions. Emissions from the off-site use of horticultural peat should be included in Tier 3 methods. Currently, the literature is sparse and results are sometimes contrasting. Countries are encouraged to share comparable data, when environmental conditions and extraction practices are similar.

Table 7.6

Default emission factors for N2O emissions from managed peatlands

Climate zone

Emission factor efn2o

(kg N20-N ha-1 yr-1)

Uncertainty range (kg N20-N ha-1 yr-1)

Reference/ Comments

Boreal and Temperate Climate

Nutrient-poor organic Soil

negligible

negligible

Alm et al, 1999; Laine et al, 1996; Martikainen et al., 1995; Minkkinen et al, 2002; Regina et al, 1996

Nutrient-rich organic Soil

1.8

0.2 to 2.5

Tropical Climate

3.6

0.2 to 5.0

The value for tropical areas is twice that for northern climates, based on the relative difference between temperate and tropical N2O EF in Table 11.1, Chapter 11.

Most of the data are from European peatlands not necessarily under production. Climate zones are as described in Chapter 3.

Choice of activity data Tier 1

The same activity data should be used for estimating CO2 and N2O emissions from managed peatlands. Information on obtaining these data is provided in Section 7.2.1 above. For countries in boreal and temperate regions using the Tier 1 method, area data should be stratified by soil fertility, since only nutrient-rich peat soils are considered. If the available information does not allow stratification by peat fertility, countries may rely on expert judgment. Boreal climates tend to promote nutrient-poor raised bogs or fens, while temperate and oceanic climates tend to promote the formation of nutrient-rich peatlands. Low fertility peatlands are generally acidic (with low pH). Under Tier 1, additional uncertainty arises from the use of unique default CO2 and N2O emission factors, applied to both Land Being Converted for Peat Extraction and Peatlands Remaining Peatlands, as the nitrogen content and bioavailability of organic C and N may change with depth.

Tiers 2 and 3

Priorities for the development of country-specific activity data include areas of organic soils managed for peat extraction, disaggregated based on nutrient status if relevant, and annual peat production data. More sophisticated estimation methodologies will require the determination of areas in each of the three phases of the peat extraction cycle, including abandoned areas on which drainage or the effects of former peat extraction are still present; and if warranted, areas characterized by different peat extraction technology, peat types and extraction depths. If site restoration is underway, countries should report separately the areas of restored organic soils formerly managed for peat extraction and estimate emissions and removals from these lands. In addition, countries with a significant production of horticultural peat may develop data to monitor the off-site fate of extracted peat in order to develop time-sensitive decay curves (see also Section 7.2.1).

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