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Annex 1: Key categories

A1.1 Methodology used for identifying key categories

The key categories in the New Zealand inventory have been assessed according to the methodologies provided in good practice guidance (IPCC, 2000). The methodology applied was determined using the decision tree shown in Figure A1.1.

Figure A1.1 Decision tree to identify key source categories (Figure 7.1 (IPCC, 2000))

For the 2006 inventory the Tier 1 level and trend assessment were applied including the LULUCF sector and excluding the LULUCF sector (IPCC 2000, 2003). The “including LULUCF” level and trend assessments are calculated as per equations 5.4.1 and 5.4.2 of GPG-LULUCF. The “excluding LULUCF” level and trend assessments are calculated as per equations 7.1 and 7.2 of good practice guidance (IPCC, 2000). Key categories are defined as those categories whose cumulative percentages, when summed in decreasing order of magnitude, contributed 95 per cent of the total level or trend.

A1.2 Disaggregation

The classification of categories follows the classification outlined in Table 7.1 of good practice guidance (IPCC, 2000) by:

  • Identifying categories at the level of IPCC categories using CO2 equivalent emissions and considering each greenhouse gas from each category separately.

  • Aggregating categories that use the same emission factors.

  • Including LULUCF categories at the level shown in GPG-ULUCF Table 5.4.1.

There was one modification to the suggested categories to reflect New Zealand’s national circumstances. The “fugitive emissions from fuels–oil and natural gas” category was divided into two categories: “fugitive emissions from oil and gas operations” and “fugitive emissions from geothermal operations”. This is to reflect that New Zealand generates a significant amount of energy from geothermal sources that cannot be included as oil or gas operations.

A1.3 Tables 7.A1–7.A3 of the IPCC Good Practice Guidance

Table A1.1 Results of the key category level analysis for 99 per cent of the total emissions and removals for New Zealand in 2006. Key categories are those that comprise 95 per cent of the total.

(a) Tier 1 Category Level Assessment – including LULUCF
IPCC Categories Gas 2006 Level Cumulative
Forestland remaining forest land CO2 25859.65 23.9 23.9
Emissions from enteric fermentation in domestic livestock CH4 24110.67 22.3 46.2
Mobile combustion – road vehicles CO2 12606.68 11.7 57.8
Emissions from stationary combustion – gas CO2 7938.09 7.3 65.2
Emissions from agricultural soils – animal production N2O 7609.13 7.0 72.2
Emissions from stationary combustion – solid CO2 6754.95 6.2 78.5
Indirect emissions from nitrogen used in agriculture N2O 3387.22 3.1 81.6
Emissions from stationary combustion – liquid CO2 3008.08 2.8 84.4
Conversion to forest land CO2 2127.72 2.0 86.3
Direct emissions from agricultural soils N2O 1736.81 1.6 87.9
Emissions from iron and steel industry CO2 1622.36 1.5 89.4
Emissions from solid waste disposal sites CH4 1475.39 1.4 90.8
Mobile combustion – aviation CO2 1114.18 1.0 91.8
Emissions from manure management CH4 743.13 0.7 92.5
Cropland remaining cropland CO2 679.95 0.6 93.1
Other-emissions from liming CO2 676.11 0.6 93.8
Conversion to grassland CO2 661.04 0.6 94.4
Fugitive emissions from oil and gas operations CO2 657.47 0.6 95.0
Emissions from substitutes from ozone depleting substances HFCs & PFCs 601.35 0.6 95.5
Emissions from cement production CO2 560.66 0.5 96.1
Emissions from aluminium production CO2 552.76 0.5 96.6
Fugitive emissions from coal mining and handling CH4 450.20 0.4 97.0
Emissions from ammonia/urea production CO2 381.63 0.4 97.3
Mobile combustion – marine CO2 324.89 0.3 97.6
Fugitive emissions from geothermal operations CO2 305.68 0.3 97.9
Fugitive emissions from oil and gas operations CH4 302.17 0.3 98.2
Emissions from hydrogen production CO2 227.76 0.2 98.4
Emissions from wastewater handling CH4 209.88 0.2 98.6
Emissions from wastewater handling N2O 167.40 0.2 98.8
Mobile combustion – rail CO2 155.16 0.1 98.9
Mobile combustion – road vehicles N2O 136.78 0.1 99.0

 

Table A1.2 Results of the key category level analysis for 99 per cent of the total emissions and removals for New Zealand in 1990. Key categories are those that comprise 95 per cent of the total.

(a)Tier 1 Category Level Assessment – including LULUCF
IPCC Categories Gas Base year estimate Gg Level assessment Cumulative total
Emissions from enteric fermentation in domestic livestock CH4 21810.44 25.6 25.6
Forestland remaining forest land CO2 21397.92 25.1 50.6
Emissions from stationary combustion – gas CO2 7691.14 9.0 59.7
Mobile combustion – road vehicles CO2 7534.97 8.8 68.5
Emissions from agricultural soils – animal production N2O 6850.46 8.0 76.5
Emissions from stationary combustion – solid CO2 3148.78 3.7 80.2
Indirect emissions from nitrogen used in agriculture N2O 2702.16 3.2 83.4
Emissions from stationary combustion – liquid CO2 2546.55 3.0 86.4
Emissions from solid waste disposal sites CH4 2121.53 2.5 88.9
Emissions from the iron and steel industry CO2 1312.27 1.5 90.4
Mobile combustion – aviation CO2 772.83 0.9 91.3
Conversion to grassland CO2 704.22 0.8 92.1
PFCs from aluminium production PFC 641.68 0.8 92.9
Emissions from manure management CH4 578.59 0.7 93.6
Cropland remaining cropland CO2 538.67 0.6 94.2
Direct emissions from agricultural soils N2O 487.19 0.6 94.8
Emissions from aluminium production CO2 443.27 0.5 95.3
Emissions from cement production CO2 441.67 0.5 95.8
Other (including liming) CO2 373.83 0.4 96.2
Fugitive emissions from geothermal operations CO2 357.34 0.4 96.7
Emissions from ammonia/urea production CO2 274.53 0.3 97.0
Fugitive emissions from coal mining and handling CH4 272.13 0.3 97.3
Fugitive emissions from oil and gas operations CO2 263.48 0.3 97.6
Fugitive emissions from oil and gas operations CH4 258.74 0.3 97.9
Mobile combustion – marine CO2 247.82 0.3 98.2
Emissions from wastewater handling CH4 222.73 0.3 98.5
Emissions from hydrogen production CO2 152.29 0.2 98.6
Emissions from wastewater handling N2O 146.92 0.2 98.8
Conversion to forest land CO2 141.28 0.2 99.0

 

Table A1.3 Results of the key category trend analysis for 99 per cent of the total emissions and removals for New Zealand in 2006. Key categories are those that comprise 95 per cent of the total.

(a) Tier 1 Category Trend Assessment – including LULUCF  
IPCC Categories Gas Base year estimate Gg 2006 estimate Gg Trend assessment Contribution to trend Cumulative total
Emissions from enteric fermentation in domestic livestock CH4 21810.44 24110.67 0.034 16.0 16.0
Mobile combustion – road vehicles CO2 7534.97 12606.68 0.032 15.2 31.2
Emissions from Stationary combustion – solid CO2 3148.78 6754.95 0.029 13.5 44.7
Conversion to forest land CO2 141.28 2127.72 0.020 9.4 54.2
Emissions from stationary combustion - gas CO2 7691.14 7938.09 0.018 8.4 62.6
Emissions from solid waste disposal sites CH4 2121.53 1475.39 0.012 5.8 68.3
Direct emissions from agricultural soils N2O 487.19 1736.81 0.011 5.4 73.8
Forest land remaining forest land CO2 21397.92 25859.65 0.011 5.0 78.8
Direct emissions from agricultural soils – animal production N2O 6850.46 7609.13 0.010 4.9 83.7
PFCs from aluminium production PFC 641.68 82.49 0.007 3.5 87.2
Emissions from substitutes for Ozone depleting substances HFCs & PFCs 0.00 601.35 0.006 2.9 90.1
Fugitive emission from oil and gas operations CO2 263.48 657.47 0.003 1.6 91.7
Conversion to grassland CO2 704.22 661.04 0.002 1.1 92.7
Other (including liming) CO2 373.83 676.11 0.002 1.0 93.7
Emissions from stationary combustion – liquid CO2 2546.55 3008.08 0.002 0.9 94.7
Fugitive emissions from geothermal operations CO2 357.34 305.68 0.001 0.7 95.4
Mobile combustion – aviation CO2 772.83 1114.18 0.001 0.7 96.1
Fugitive emissions from coal mining and handling CH4 272.13 450.20 0.001 0.5 96.6
Conversion to cropland CO2 37.35 123.31 0.001 0.4 96.9
Emissions from wastewater handling CH4 222.73 209.88 0.001 0.3 97.3
Mobile combustion – rail CO2 78.01 155.16 0.001 0.3 97.6
Mobile combustion – road vehicles N2O 64.04 136.78 0.001 0.3 97.8
Emissions from ammonia/urea production CO2 274.53 381.63 0.000 0.2 98.0
Emissions from hydrogen production CO2 152.29 227.76 0.000 0.2 98.2
Mobile combustion – road vehicles CH4 69.00 52.19 0.000 0.2 98.4
Emissions from iron and steel industry CO2 1312.27 1622.36 0.000 0.1 98.5
Non-CO2 emissions from stationary combustion N2O 75.67 120.94 0.000 0.1 98.6
Conversion to settlement CO2 97.16 97.16 0.000 0.1 98.7
Emissions from limestone & dolomite use CO2 17.13 44.70 0.000 0.1 98.8
Fugitive emissions from oil and gas operations CH4 258.74 302.17 0.000 0.1 99.0