This section covers emissions from peatlands undergoing active peat extraction. Use of peat is widely distributed: about half is used for energy; the remainder for horticultural, landscape, industrial waster water treatment, and other purposes (International Peat Society, 2004). Techniques for extracting the peat from deposits are similar, and all on-site sources of greenhouse gas emissions should be reported under this category regardless of the end-use of peat. Emissions from the off-site energy use of peat should be reported in the Energy Sector, and are not considered in this chapter.
18.104.22.168 CO2 EMISSIONS FROM PEATLANDS REMAINING Peatlands
Estimating CO2 emissions from lands undergoing peat extraction has two basic elements: on-site emissions from peat deposits during the extraction phase, and off-site emissions from the horticultural (non-energy) use of peat
(Equation 7.2). Peat extraction starts with vegetation clearing (Section7.1), which prevents further carbon sequestration, so only CO2 emissions are considered.
CO2 EMISSIONS IN PEATLANDS DURING PEAT EXTRACTION
CO2WWpeat = (CO2 -CWWIealojr_s,e + CO2 ^^«on-ste ^ ^ [ [4
CO2 WWpeat = CO2 emissions from land undergoing peat extraction, Gg CO2 yr-1
CO2-CWW peatoff site = off-site CO2-C emissions from peat removed for horticultural use, Gg C yr-1
CO2-CWWpeat on = on-site CO2-C emissions from drained peat deposits, Gg C yr-1
Off-site CO2-C emissions are associated to the horticultural (non-energy) use of peat extracted and removed. Off-site emissions from peat used for energy should be reported in the Energy Sector, and is therefore not included here.
Regardless of the end-use of peat, the choice of method, emission factors, and activity data for estimating the on-site emissions can be the same, so long as the data are disaggregated for type of peat, which is closely associated with nutrient level (rich and poor), and if appropriate climate zone.
CHOICE OF METHOD
Figure 7.1 presents the decision tree to estimate greenhouse gas emissions from peatlands. Tier 1
A default methodology is provided that covers on-site CO2 emissions (without distinction between the phases of peat production), and the horticultural use of peat (Equations 7.3 to 7.5).
CO2 -C2 EMISSIONS FROM MANAGED PEATLANDS (TIER 1)
2 WWpeat 2 WWpeat0jf -site 2 WWPeat<m-.site
CO2-CWWpeat = CO2 -C emissions from managed peatlands, Gg C yr-1
CO2-C WW peat on = on-site emissions from peat deposits (all production phases), Gg C yr-1
CO2-C WW peat off = off-site emissions from peat removed for horticultural use, Gg C yr-1
Equation 7.4 is applied to the total area of managed peatlands, including land being converted to peatlands and abandoned peatlands, unless abandoned peatlands were converted to another use, in which case emissions should be attributed to the new land use, e.g., Cropland or Forest Land.
The Tier 1 methodology considers only emissions from biomass clearing. When the total area of managed peatlands increases, conversion to peatland is occurring. The conversion of peatlands for peat extraction involves clearing and removal of vegetation. The term ACWW peat B of Equation 7.4 is estimated as ACconversion, using Equation 2.16 (Chapter 2 of this Volume). Other changes in C stocks in living biomass on managed peat lands are assumed to be zero.
CO2-C refers to carbon emitted as CO2
Figure 7.1 Decision tree to estimate CO2-C and N2O emissions from Peatlands
Figure 7.1 Decision tree to estimate CO2-C and N2O emissions from Peatlands
1: See Volume 1 Chapter 4, "Methodological Choice and Identification of Key Categories" (noting Section 4.1.2 on limited resources), for discussion of key categories and use of decision trees.
On-site soil CO2-C emissions from managed peatlands (Tier 1)
z " " peaton-sue
(■ApeatRich • EFCOipeaRich ) + (ApeatPoor • EFC02peliPm )
CO2-C ww peat t = on-site CO2—C emissions from peat deposits (all production phases), Gg C yr ApeatRich = area of nutrient-rich peat soils managed for peat extraction (all production phases), ha ApeatPoor = area of nutrient-poor peat soils managed for peat extraction (all production phases), ha EFCO2peatRich = CO2 emission factors for nutrient-rich peat soils managed for peat extraction or abandoned after peat extraction, tonnes C ha-1 yr-1
EFCo2peatPoor = CO2 emission factors for nutrient-poor peat soils managed for peat extraction or abandoned after peat extraction, tonnes C ha-1 yr-1
ACWW peat B = CO2-C emissions from change in carbon stocks in biomass due to vegetation clearing, Gg C
Off-site emission estimates are derived by converting the annual peat production data (either volume or air-dry weight) to the weight of carbon (Equation 7.5). All carbon in horticultural peat is assumed to be emitted during the extraction year. Countries may modify this assumption at higher tiers.
CO2-C WW peat off = off-site CO2-C emissions from peat removed for horticultural use, Gg C yr-1
Wtdry_peat = air-dry weight of extracted peat, tonnes yr-1 Voldry_peat = volume of air-dry peat extracted, m3 yr-1
Cfractionwt_ peat = carbon fraction of air-dry peat by weight, tonnes C (tonne of air-dry peat)-1 Cfractionvoi_peat = carbon fraction of air-dry peat by volume, tonnes C (m3 of air-dry peat)-1
Tier 2 calculations use country-specific emission factors and parameters, spatially disaggregated to reflect regionally important practices and dominant ecological dynamics. It may be appropriate to subdivide activity data and emission factors according to extraction practices (e.g., the technology used to dry and extract peat), peat fertility and composition as influenced by previous vegetation cover, and the carbon fraction of air-dry peat under local climates. Generally, peatland drainage leads to peat compaction and subsidence as well as oxidation and carbon losses other than as CO2. The acrotelm (upper, oxic zone of the peat) is susceptible to seasonal variations in volumetric moisture content especially if the peat structure has been altered (Waddington & Price, 2000). Hence, measurements of carbon stock changes in peat soils are difficult to make and are unlikely to estimate correctly CO2 fluxes from these soils, and are therefore not recommended unless data are carefully calibrated.
Tier 2 methodologies involve separating peatlands being converted for peat extraction from those already producing commercial peat. Section 7.2.2 describes estimation methodologies for Land Being Converted for Peat Extraction. Care should be taken not to double-count CO2 emissions from biomass clearing.
A Tier 3 approach involves a comprehensive understanding and representation of the dynamics of CO2 emissions and removals on managed peatlands, including the effect of site characteristics, peat type and depth, extraction technology, and the phases of peat extraction described at the beginning of Section 7.2. The methodology will include all the known on-site sources of CO2 (Equation 7.6). The term C02—Cww peat of Equation 7.6
F conversion refers to emissions from the land conversion, including changes in biomass carbon stock and soil emissions. The term CO2-CWW peatextraction corresponds to on-site emissions to be reported under Tier 1 (less the biomass term, now included in CO2-CWW peat ). Emissions from stockpiles of drying peat (variable CO2-CWW peat , .,. )
conversion stockpiling are much more uncertain. Higher temperatures may cause stockpiles to release more CO2 than the excavation field, but data are not at present sufficient to provide guidance. CO2 emission patterns from abandoned peatlands (CO2-CWW peatpost) vary with restoration techniques and the rates of soil respiration and vegetation regrowth (Petrone et al., 2003; Waddington & McNeil, 2002; Komulainen et al, 1999); these patterns are therefore quite site-specific. As in Tier 2, direct measurements of soil C stock changes are not recommended. Countries with a significant peat extraction industry and restoration activities should undertake to document separately the three on-site sources of CO2 of Equation 7.6.
On-site CO2-C emissions from managed peatlands (Tiers 2 and 3)
CO 2 ~Cww peaton-site
C02—CWW peat = on-site CO2-C emissions from peat deposits, Gg C yr-
C02—CWW peat ^ = on-site CO2-C emissions from lands conversion for peat extraction, Gg C yr-C02—CWW peat ^ = CO2-C emissions from the surface of peat extraction area, Gg C yr-CO2-CWW peatstockpilmg= CO2-C emissions from peat stockpiles prior to off-site removal, Gg C yr-1 C02—CWW peat t = CO2-C emissions from soils of abandoned, cut-over peatlands, Gg C yr-
CHOICE OF EMISSION FACTORS Tier 1
Implementation of Tier 1 method requires the application of default on-site emission factors EFC02peatRich and
EFC02peatPoor , and default carbon fractions of peat by weight (Cfractionwt_peat ) or by volume (Cfractionvoi_peat,) to estimate off-site emissions from production data in weight or volume, respectively. Default values of EFC02peatRich and EFC02peatPoor are provided in Table 7.4. Default carbon fractions of peat are provided in Table 7.5.
Nutrient-poor bogs predominate in boreal regions, while in temperate regions, nutrient-rich fens and mires are more common. Types of peatlands can be inferred from the end-use of peat: sphagnum peat, dominant in oligotrophic (nutrient-poor) bogs, is preferred for horticultural uses, while sedge peat, more common in minerotrophic (nutrient rich) fens, is more suitable for energy generation. Boreal countries that do not have information on areas of nutrient-rich and nutrient-poor peatlands should use the emission factor for nutrient-poor peatlands. Temperate countries that do not have such data should use the emission factor for nutrient-rich peatlands. Only one default factor is provided for tropical regions, so disaggregating peatland area by soil fertility is not necessary for tropical countries using the Tier 1 method.
Tiers 2 and 3
The uncertainty of emission factors can be reduced by measuring the moisture content and carbon fraction of extracted peat under local climates and extraction practices, taking into account interannual climate variability. Spatially disaggregated CO2 flux measurements should be used to develop more precise on-site emission factors, correcting for carbon losses through leaching of dissolved organic carbon or runoff. In boreal zones, winter emissions can account for 10-30% of net annual emissions (Alm et al, 1999); and should be estimated. Disaggregated CO2 flux measurements from peat stockpiles, abandoned and restored peat excavation sites would assist in reducing further estimate of uncertainties. The literature is sparse and countries are encouraged to share data, when peat quality, environmental conditions and extraction practices are similar.
CHOICE OF ACTIVITY DATA
All Tiers require data on areas of peatlands managed for peat extraction (ApeatRich and/or ApeatPoor) and peat production data by weight or volume of air-dry peat (Wtdry_peat or Voldry_peat).
The default methodology assumes that a country has estimates of the total area on which peat is currently and was extracted, including former commercial peatlands that have not been converted to other uses. In temperate and boreal regions, this area should, where possible, be separated into nutrient-rich and nutrient-poor with the default assumption consistent with the advice above on selection of emission factors. In addition, the quantity (by dry weight or volume) or peat extracted annually must be known to estimate off-site CO2 emissions.
International data sets on peat extraction sites and production vary in quality and consistency. The sources of production and area data may not be the same and different definitions and years between sources and countries will likely introduce inconsistencies. Because peat extraction methods rely on dry and sunny days for drying peat, the annual production varies depending on suitable summer weather. For the purpose of estimating off-site emissions, peat production data should be separated according to end-use, i.e., horticultural peat and combustion peat, since the estimation methods of this Chapter only require the production of horticultural peat. If it is impossible to separate the quantity of peat produced by end-use, emissions from peat consumption should be accounted under the inventory sector corresponding to the predominant end-use of domestically produced peat. Useful area data can be found in Joosten (2004); Joosten & Clarke (2002); Sirin & Minayeva (2001); Lappalainen (1996); and inventories published by Wetlands International (http://www.wetlands.org/). Data on peat production are available from World Energy Council (2004) (for combustion peat) and the United States Geological Survey (http://minerals.usgs.gov/minerals/pubs/commodity/peat/). Additional information may be obtained from the International Peat Society (http://www.peatsociety.org/) or the International Mire Conservation Group (http://www.imcg.net/).
When either areas or production data are missing, it may be possible to derive one from the other by using a default conversion factor equal to an average production rate provided by the local industry. In a mature, industrialized peat industry, block-cut methods can yield up to 1750 tonnes of air-dry peat per hectare annually, while the vacuum method can extract up to 100 tonnes per hectare per year (Cleary, 2005). Air-dry peat contains between 35% and 55% moisture (World Energy Council, 2004).
Tiers 2 and 3
Countries using higher Tiers should obtain national peat production data and the corresponding peatland areas. In boreal and temperate regions, these area data need to be disaggregated by soil fertility to correspond to appropriate emission factors. Possible sources of such data are national energy statistics, peat extraction firms, peat industry associations, landscaping industry associations, and government ministries responsible for land use or geological surveys. If it is not possible to stratify by peat fertility, countries may rely on expert judgment. Boreal climates tend to promote nutrient-poor raised bogs, while temperate and oceanic climates tend to promote the formation of nutrient-rich peatlands. Priorities for the development of country-specific activity data include: i) areas of organic soils currently and formerly managed for peat extraction and disaggregated based on nutrient status if relevant; ii) peat production data; iii) local moisture content that will reflect ambient conditions at the time of peat extraction; and iv) country-specific carbon content, preferably by peat type.
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 are encouraged to 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.
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