Nonco2 Emissions

There are significant emissions of non-greenhouse gases from biomass burning, livestock and manure management, or soils. N2O emissions from soils are covered in Chapter 11, where guidance is given on methods that can be applied nationally (i.e., irrespective of land-use types) if a country chooses to use national scale activity data. The guidance on CH4 and N2O emissions from livestock and manure are addressed only in Chapter 10 because emissions do not depend on land characteristics. A generic approach to estimating greenhouse gas emissions from fire (both CO2 and non-CO2 gases) is described below, with land-use specific enhancements given in the Forest Land, Grassland and Cropland chapters. It is good practice to check for complete coverage of CO2 and non-CO2 emissions due to losses in carbon stocks and pools to avoid omissions or double counting.

Emissions from fire include not only CO2, but also other greenhouse gases, or precursors of greenhouse gases, that originate from incomplete combustion of the fuel. These include carbon monoxide (CO), methane (CH4), non-methane volatile organic compounds (NMVOC) and nitrogen (e.g., N2O, NOx) species (Levine, 1994). In the 1996IPCC Guidelines and GPG2000, non-CO2 greenhouse gas emissions from fire in savannas and burning of crop residues were addressed along with emissions from Forest Land and Grassland conversion. The methodology differed somewhat by vegetation type, and fires in Forest Land were not included. In the GPG-LULUCF, emissions (CO2 and non-CO2) from fires were addressed, particularly in the chapter covering Forest Land (losses of carbon resulting from disturbances). In the Cropland and Grassland chapters, only non-CO2 emissions were considered, with the assumption that the CO2 emissions would be counterbalanced by CO2 removals from the subsequent re-growth of the vegetation within one year. This assumption implies maintenance of soil fertility - an assumption which countries may ignore if they have evidence of fertility decline due to fire. In Forest Land, there is generally a lack of synchrony (non-equivalence of CO2 emissions and removals in the year of reporting).

These Guidelines provide a more generic approach for estimating emissions from fire. Fire is treated as a disturbance that affects not only the biomass (in particular, above-ground), but also the dead organic matter (litter and dead wood). The term 'biomass burning' is widely used and is retained in these Guidelines, but acknowledging that fuel components other than live biomass are often very significant, especially in forest systems. For Cropland and Grassland having little woody vegetation, reference is usually made to biomass burning, since biomass is the main pool affected by the fire.

Countries should apply the following principles when estimating greenhouse gas emissions resulting from fires in Forest Land, Cropland and Grassland:

• Coverage of reporting: Emissions (CO2 and non- CO2) need to be reported for all fires (prescribed fires and wildfires) on managed lands (the exception is CO2 from Grassland, as discussed below). Where there is a land-use change, any greenhouse gas emission from fire should be reported under the new land-use category (transitional category). Emissions from wildfires (and escaped prescribed fires) that occur on unmanaged lands do not need to be reported, unless those lands are followed by a land-use change (i.e., become managed land).

• Fire as a management tool (prescribed burning): greenhouse gas emissions from the area burnt are reported, and if the fire affects unmanaged land, greenhouse gas emissions should also be reported if the fire is followed by a land-use change.

• Equivalence (synchrony) of CO2 emissions and removals: CO2 net emissions should be reported where the CO2 emissions and removals for the biomass pool are not equivalent in the inventory year. For grassland biomass burning and burning of agriculture residues, the assumption of equivalence is generally reasonable. However, woody vegetation may also burn in these land categories, and greenhouse gas emissions from those sources should be reported using a higher Tier method. Further, in many parts of the world, grazing is the predominant land use in Forest Land that are regularly burnt (e.g., grazed woodlands and savannas), and care must be taken before assuming synchrony in such systems. For Forest Land, synchrony is unlikely if significant woody biomass is killed (i.e., losses represent several years of growth and C accumulation), and the net emissions should be reported. Examples include: clearing of native forest and conversion to agriculture and/or plantations and wildfires in Forest Land.

• Fuels available for combustion: Factors that reduce the amount of fuels available for combustion (e.g., from grazing, decay, removal of biofuels, livestock feed, etc.) should be accounted for. A mass balance approach should be adopted to account for residues, to avoid underestimation or double counting (refer to Section 2.3.2).

• Annual reporting: despite the large inherent spatial and temporal variability of fire (in particular that from wildfires), countries should estimate and report greenhouse gas emissions from fire on an annual basis.

These Guidelines provide a comprehensive approach for estimating carbon stock changes and non-CO2 emissions resulting from fire in the Forest Land (including those resulting from forest conversion), and non-CO2 emissions in the Cropland and Grassland. Non-CO2 emissions are addressed for the following five types of burning: (1) grassland burning (which includes perennial woody shrubland and savanna burning); (2) agricultural residues burning; (3) burning of litter, understory and harvest residues in Forest Land, (4) burning following forest clearing and conversion to agriculture; and (5) other types of burning (including those resulting from wildfires). Direct emissions of CO2 are also addressed for items (3) and (4) and (5). Since estimating emissions in these different categories have many elements in common, this section provides a generic approach to estimate CO2 and non-CO2 emissions from fire, to avoid repetition in specific land-use sections that address emissions from fire in these Guidelines.

Prescribed burning of savannas is included under the grassland biomass burning section (Chapter 6, Grassland, Section 6.3.4). It is important to avoid double counting when estimating greenhouse gas emissions from savannas that have a vegetation physiognomy characteristic of Forest Land. An example of this is the cerradao (dense woodland) formation in Brazil which, although being a type of savanna, is included under Forest Land, due to its biophysical characteristics.

In addition to the greenhouse gas emissions from combustion, fires may lead to the creation of an inert carbon stock (charcoal or char). Post-fire residues comprise unburned and partially burnt components, as well as a small amount of char that due to its chemical nature is highly resistant to decomposition. The knowledge of the rates of char formation under contrasting burning conditions and subsequent turnover rates is currently too limited (Forbes et al., 2006; Preston and Schmidt, 2006) to allow development of a reliable methodology for inventory purposes, and hence is not included in these Guidelines. A technical basis for further methodological development is included in Appendix 1.

Additionally, although emissions of NMVOC also occur as a result of fire, they are not addressed in the present Guidelines due to the paucity of the data and size of uncertainties in many of the key parameters needed for the estimation, which prevent the development of reliable emission estimates.

METHOD DESCRIPTION

Each relevant section in these Guidelines includes a three-tiered approach to address CO2 (where applicable) and non-CO2 greenhouse gas emissions from fire. The choice of Tier can be made following the steps in the decision tree presented in Figure 2.6. Under the Tier 1 approach, the formulation presented in Equation 2.27 can be applied to estimate CO2 and non-CO2 emissions from fire, using the default data provided in this chapter and in the relevant land-use sections of these Guidelines. Higher Tiers involve a more refined application of Equation 2.27.

Since Tier 1 methodology adopts a simplified approach to estimating the dead organic matter pool (see Section 2.3.2), certain assumptions must be made when estimating net greenhouse gas emissions from fire in those systems (e.g. Forest Land, and Forest Land converted to another land use), where dead organic matter can be a major component of the fuel burnt. Emissions of CO2 from dead organic matter are assumed to be zero in forests that are burnt, but not killed by fire. If the fire is of sufficient intensity to kill a portion of the forest stand, under Tier 1 methodology, the C contained in the killed biomass is assumed to be immediately released to the atmosphere. This Tier 1 simplification may result in an overestimation of actual emissions in the year of the fire, if the amount of biomass carbon killed by the fire is greater than the amount of dead wood and litter carbon consumed by the fire.

Non-CO2 greenhouse gas emissions are estimated for all fire situations. Under Tier 1, non-CO2 emissions are best estimated using the actual fuel consumption provided in Table 2.4, and appropriate emission factors (Table 2.5) (i.e., not including newly killed biomass as a component of the fuel consumed). Clearly, if fire in forests contributes significantly to net greenhouse gas emissions, countries are encouraged to develop a more complete methodology (higher tiers) which includes the dynamics of dead organic matter and improves the estimates of direct and post-fire emissions.

For Forest Land converted to another land uses, organic matter burnt is derived from both newly felled vegetation and existing dead organic matter, and CO2 emissions should be reported. In this situation, estimates of total fuel consumed (Table 2.4) can be used to estimate emissions of CO2 and non- greenhouse gases using Equation 2.27. Care must be taken, however, to ensure that dead organic matter carbon losses during the land-use conversion are not double counted in Equations 2.27 (as losses from burning) and Equation 2.23 (as losses from decay).

A generic methodology to estimate the emissions of individual greenhouse gases for any type of fire is summarized in Equation 2.27.

Equation 2.27 Estimation of greenhouse gas emissions from fire

Where:

Lfire = amount of greenhouse gas emissions from fire, tonnes of each GHG e.g., CH4, N2O, etc. A = area burnt, ha

MB = mass of fuel available for combustion, tonnes ha-1. This includes biomass, ground litter and dead wood. When Tier 1 methods are used then litter and dead wood pools are assumed zero, except where there is a land-use change (see Section 2.3.2.2).

Cf = combustion factor, dimensionless (default values in Table 2.6) Gef = emission factor, g kg-1 dry matter burnt (default values in Table 2.5)

Note: Where data for MB and Cf are not available, a default value for the amount of fuel actually burnt (the product of MB and Cf ) can be used (Table 2.4) under Tier 1 methodology.

For CO2 emissions, Equation 2.27 relates to Equation 2.14, which estimates the annual amount of live biomass loss from any type of disturbance.

The amount of fuel that can be burnt is given by the area burnt and the density of fuel present on that area. The fuel density can include biomass, dead wood and litter, which vary as a function of the type, age and condition of the vegetation. The type of fire also affects the amount of fuel available for combustion. For example, fuel available for low-intensity ground fires in forests will be largely restricted to litter and dead organic matter on the surface, while a higher-intensity 'crown fire' can also consume substantial amounts of tree biomass.

The combustion factor is a measure of the proportion of the fuel that is actually combusted, which varies as a function of the size and architecture of the fuel load (i.e., a smaller proportion of large, coarse fuel such as tree stems will be burnt compared to fine fuels, such as grass leaves), the moisture content of the fuel and the type of fire (i.e., intensity and rate of spread which is markedly affected by climatic variability and regional differences as reflected in Table 2.6). Finally, the emission factor gives the amount of a particular greenhouse gas emitted per unit of dry matter combusted, which can vary as a function of the carbon content of the biomass and the completeness of combustion. For species with high N concentrations, NOx and N2O emissions from fire can vary as a function of the N content of the fuel. A comprehensive review of emission factors was conducted by Andreae and Merlet (2001) and is summarized in Table 2.5.

Tier 2 methods employ the same general approach as Tier 1 but make use of more refined country-derived emission factors and/or more refined estimates of fuel densities and combustion factors than those provided in the default tables. Tier 3 methods are more comprehensive and include considerations of the dynamics of fuels (biomass and dead organic matter).

Figure 2.6 Generic decision tree for identification of appropriate tier to estimate greenhouse gas emissions from fire in a land-use category

Figure 2.6 Generic decision tree for identification of appropriate tier to estimate greenhouse gas emissions from fire in a land-use category

Note:

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.

Table 2.4

Fuel (dead organic matter plus live biomass) biomass consumption values (tonnes dry matter ha"1) FOR FIRES IN A RANGE OF VEGETATION TYPES

( To be used in Equation 2.27 , to estimate the product of quantities ' MB • Cf ' , i.e., an absolute amount)

Vegetation type

Subcategory

Mean

SE

References

Primary tropical forest (slash and burn)

Primary tropical forest

83.9

25.8

l, 15, 66, 3, 16, 1l, 45

Primary open tropical forest

163.6

52.1

21,

Primary tropical moist forest

160.4

11.8

3l, l3

Primary tropical dry forest

-

-

66

All primary tropical forests

119.6

50.7

Secondary tropical forest (slash and burn)

Young secondary tropical forest (3-5 yrs)

8.1

-

61

Intermediate secondary tropical forest (6-10 yrs)

41.1

2l.4

61, 35

Advanced secondary tropical forest (14-17 yrs)

46.4

8.0

61, l3

All secondary tropical forests

42.2

23.6

66, 30

All Tertiary tropical forest

54.1

-

66, 30

Boreal forest

Wildfire (general)

52.8

48.4

2, 33, 66

Crown fire

25.1

l.9

11, 43, 66, 41, 63, 64

Surface fire

21.6

25.1

43, 69, 66, 63, 64, 1

Post logging slash burn

69.6

44.8

49, 40, 66, 18

Land clearing fire

8l.5

35.0

10, 6l

All boreal forest

41.0

36.5

43, 45, 69, 4l

Eucalypt forests

Wildfire

53.0

53.6

66, 32, 9

Prescribed fire - (surface)

16.0

13.l

66, l2, 54, 60, 9

Post logging slash burn

168.4

168.8

25, 58, 46

Felled, wood removed, and burned (land-clearing fire)

132.6

-

62, 9

All Eucalypt forests

69.4

100.8

Other temperate forests

Wildfire

19.8

6.3

32, 66

Post logging slash burn

ll.5

65.0

55, 19, 14, 2l, 66

Felled and burned (landclearing fire)

48.4

62.l

53, 24, l1

All "other" temperate forests

50.4

53.7

43, 56

Table 2.4 (continued)

Fuel (dead organic matter plus live biomass) biomass consumption values (tonnes dry matter ha-1) for fires in a range of vegetation types ( To be used in Equation 2.27 , to estimate the product of quantities ' MB • Cf' , i.e., an absolute amount)

Vegetation type

Subcategory

Mean

SE

References

Shrublands

Shrubland (general)

26.l

4.2

43

Calluna heath

11.5

4.3

26, 39

Sagebrush

5.l

3.8

66

Fynbos

12.9

0.1

70, 66

All Shrublands

14.3

9.0

Savanna woodlands (early dry season burns)*

Savanna woodland

2.5

-

28

Savanna parkland

2.l

-

57

All savanna woodlands (early dry season burns)

2.6

0.1

Savanna woodlands (mid/late dry season burns)*

Savanna woodland

3.3

-

57

Savanna parkland

4.0

1.1

57, 6, 51

Tropical savanna

6

1.8

52, 73

Other savanna woodlands

5.3

i.l

59, 57, 31

All savanna woodlands (mid/late dry season burns)*

4.6

1.5

Savanna Grasslands/ Pastures (early dry season burns)*

Tropical/sub-tropical grassland

2.1

-

28

Grassland

-

-

48

All savanna grasslands (early dry season burns)*

2.1

-

Savanna Grasslands/ Pastures (mid/late dry season burns)*

Tropical/sub-tropical grassland

5.2

i.l

9, 73, 12, 57

Grassland

4.1

3.1

43, 9

Tropical pasture~

23.l

11.8

4, 23, 38, 66

Savanna

l.0

2.l

42, 50, 6, 45, 13, 65

All savanna grasslands (mid/late dry season burns)*

10.0

10.1

Other vegetation types

Peatland

41

1.4

68, 33

Tundra

10

-

33

Agricultural residues (post harvest field burning)

Wheat residues

4.0

see Note b

Maize residues

10.0

see Note b

Rice residues

5.5

see Note b

Sugarcane a

6.5

see Note b

* Surface layer combustion only

Derived from slashed tropical forest (includes unburned woody material) a For sugarcane, data refer to burning before harvest of the crop. b Expert assessment by authors.

Table 2.5

Emission factors (g kg"1 dry matter burnt) for various types of burning. Values are means ± SD and are based on the comprehensive review by Andreae and Merlet (2001) _(To be used as quantity 'Gef' in Equation 2.27)_

Table 2.5

Emission factors (g kg"1 dry matter burnt) for various types of burning. Values are means ± SD and are based on the comprehensive review by Andreae and Merlet (2001) _(To be used as quantity 'Gef' in Equation 2.27)_

Category

CO2

CO

CH,

N2O

NOx

Savanna and grassland

1613

65

2.3

0.21

3.9

± 95

± 20

± 0.9

± 0.10

± 2.4

Agricultural residues

1515

92

2.7

0.07

2.5

± 177

± 84

± 1.0

Tropical forest

1580

104

6.8

0.20

1.6

± 90

± 20

± 2.0

± 0.7

Extra tropical forest

1569

107

4.7

0.26

3.0

± 131

± 37

± 1.9

±0.07

± 1.4

Biofuel burning

1550

78

6.1

0.06

1.1

± 95

± 31

± 2.2

± 0.6

Note: The "extra tropical forest' category includes all other forest types.

Note: For combustion of non-woody biomass in Grassland and Cropland, CO2 emissions do not need to be estimated and reported, because it is assumed that annual CO2 removals (through growth) and emissions (whether by decay or fire) by biomass are in balance (see earlier discussion on synchrony in Section 2.4.

Note: The "extra tropical forest' category includes all other forest types.

Note: For combustion of non-woody biomass in Grassland and Cropland, CO2 emissions do not need to be estimated and reported, because it is assumed that annual CO2 removals (through growth) and emissions (whether by decay or fire) by biomass are in balance (see earlier discussion on synchrony in Section 2.4.

Table 2.6

Combustion factor values (proportion of prefire fuel biomass consumed) for fires in a range of

VEGETATION TYPES

(Values in column 'mean' are to be used for quantity Cf

in Equation 2.27 )

Vegetation type

Subcategory

Mean

SD

References

Primary tropical forest

0.32

0.12

7, 8, 15, 56, 66, 3, 16, 53, 17, 45,

Primary tropical forest (slash and burn)

Primary open tropical forest

0.45

0.09

21

Primary tropical moist forest

0.50

0.03

37, 73

Primary tropical dry forest

-

-

66

All primary tropical forests

0.36

0.13

Young secondary tropical forest (3-5 yrs)

0.46

-

61

Secondary tropical forest (slash and burn)

Intermediate secondary tropical forest (6-10 yrs)

0.67

0.21

61, 35

Advanced secondary tropical forest (14-17 yrs)

0.50

0.10

61, 73

All secondary tropical forests

0.55

0.06

56, 66, 34, 30

All tertiary tropical forest

0.59

-

66, 30

Wildfire (general)

0.40

0.06

33

Crown fire

0.43

0..21

66, 41, 64, 63

Boreal forest

surface fire

0.15

0.08

64, 63

Post logging slash burn

0.33

0.13

49, 40, 18

Land clearing fire

0.59

-

67

All boreal forest

0.34

0.17

45, 47

Wildfire

-

-

Prescribed fire - (surface)

0.61

0.11

72, 54, 60, 9

Eucalyptus forests

Post logging slash burn

0.68

0.14

25, 58, 46

Felled and burned (land-clearing fire)

0.49

-

62

All Eucalyptus forests

0.63

0.13

Post logging slash burn

0.62

0.12

55, 19, 27, 14

Other temperate forests

Felled and burned (land-clearing fire)

0.51

-

53, 24, 71

All "other" temperate forests

0.45

0.16

53, 56

Table 2.6 (continued)

Combustion factor values (proportion of prefire fuel biomass consumed) for fires in a range

OF VEGETATION TYPES

(Values in column 'mean' are to be used for quantity Cf in Equation 2.27 )

Vegetation type

Subcategory

Mean

SD

References

Shrublands

Shrubland (general)

0.95

-

44

Calluna heath

0.71

0.30

26, 56, 39

Fynbos

0.61

0.16

70, 44

All shrublands

0.72

0.25

Savanna woodlands (early dry season burns)*

Savanna woodland

0.22

-

28

Savanna parkland

0.73

-

57

Other savanna woodlands

0.37

0.19

22, 29

All savanna woodlands (early dry season burns)

0.40

0.22

Savanna woodlands (mid/late dry season burns)*

Savanna woodland

0.72

-

66, 57

Savanna parkland

0.82

0.07

57, 6, 51

Tropical savanna

0.73

0.04

52, 73, 66, 12

Other savanna woodlands

0.68

0.19

22, 29, 44, 31, 57

All savanna woodlands (mid/late dry season burns)*

0.74

0.14

Savanna Grasslands/ Pastures (early dry season burns)*

Tropical/sub-tropical grassland

0.74

-

28

Grassland

-

-

48

All savanna grasslands (early dry season burns)*

0.74

-

Savanna Grasslands/ Pastures (mid/late dry season burns)*

Tropical/sub-tropical grassland

0.92

0.11

44, 73, 66, 12, 57

Tropical pasture~

0.35

0.21

4, 23, 38, 66

Savanna

0.86

0.12

53, 5, 56, 42, 50, 6, 45, 13, 44, 65, 66

All savanna grasslands (mid/late dry season burns)*

0.77

0.26

Other vegetation types

Peatland

0.50

-

20, 44

Tropical Wetlands

0.70

-

44

Agricultural residues (Post harvest field burning)

Wheat residues

0.90

-

see Note b

Maize residues

0.80

-

see Note b

Rice residues

0.80

-

see Note b

Sugarcane a

0.80

-

see Note b

* Surface layer combustion only

~ Derived from slashed tropical forest (includes unburned woody material) a For sugarcane, data refer to burning before harvest of the crop. b Expert assessment by authors.

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