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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 the 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))

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

Question. Are inventory data available for more than one year?
No - Parties should determine key source categories using the Tier 1 Level assessment and qualitative assessment.
Yes - Question: Are country-specific uncertainty estimates available for each source category estimate?
No - Parties should determine key source categories using the Tier 1 Level assessment, trend assessment and qualitative assessment.
Yes - Determine key source categories using the Tier 2 level and trend assessment, incorporating national uncertainty estimates and evaluating qualitative criteria.

For this inventory submission, the Tier 1 level and trend assessment were applied, including the land use, land-use change and forestry (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 Good Practice Guidance for Land Use, Land-Use Change and Forestry (GPG-LULUCF). The ‘excluding LULUCF’ level and trend assessments are calculated as per equations 7.1 and 7.2 of the 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 the 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 the 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 2008. Key categories are those that comprise 95 per cent of the total
(a) IPCC Tier 1 category level assessment - including LULUCF (net emissions)      
IPCC categories Gas 2008 estimate 
(Gg CO2-e)
Level assessment (%) Cumulative total (%)
Enteric fermentation CH4 22,657.5 21.0 21.0
Conversion to forest land CO2 17,327.7 16.1 37.1
Transport – road transportation CO2 12,670.2 11.8 48.8
Forest land remaining forest land CO2 12,441.1 11.5 60.4
Stationary combustion – gas CO2 8,033.0 7.5 67.8
Agricultural soils –  pasture, range and paddock N2O 7,125.9 6.6 74.5
Stationary combustion – solid CO2 6,148.4 5.7 80.2
Stationary combustion – liquid CO2 3,144.1 2.9 83.1
Conversion to grassland CO2 2,849.6 2.6 85.7
Agricultural soils –  indirect emissions N2O 2,468.8 2.3 88.0
Agricultural soils - direct emissions N2O 1,777.7 1.6 89.7
Metal production - iron and steel production CO2 1,539.2 1.4 91.1
Solid waste disposal on land CH4 1,278.4 1.2 92.3
Transport – civil aviation CO2 942.9 0.9 93.1
Fugitive emissions from oil and gas operations CO2 796.4 0.7 93.9
Consumption of halocarbons and SF6 – refrigeration and air conditioning HFCs & PFCs 727.7 0.7 94.6
Manure management CH4 719.5 0.7 95.2
Grassland remaining grassland CO2 676.1 0.6 95.9
Mineral products - cement production CO2 634.2 0.6 96.4
Metal production -  aluminium production CO2 506.0 0.5 96.9
Fugitive emissions from geothermal operations CO2 445.4 0.4 97.3
Fugitive emissions from oil and gas operations CH4 404.8 0.4 97.7
Fugitive emissions from coal mining and handling CH4 342.6 0.3 98.0
Chemical industry - ammonia production CO2 331.6 0.3 98.3
Transport – navigation (domestic shipping) CO2 295.5 0.3 98.6
Chemical industry - hydrogen production CO2 246.7 0.2 98.8
Wastewater handling CH4 206.3 0.2 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) IPCC Tier 1 category level assessment - including LULUCF (net emissions)      
IPCC categories Gas Base year estimate 
(Gg CO2-e)
Level assessment (%) Cumulative total (%)
Forest land remaining forest land CO2 33,034.1 34.5 34.5
Enteric fermentation CH4 21,837.2 22.8 57.3
Transport – road transportation CO2 7,500.2 7.8 65.1
Stationary combustion – gas CO2 7,306.8 7.6 72.8
Agricultural soils –  pasture, range and paddock N2O 6,858.7 7.2 79.9
Stationary combustion – solid CO2 3,139.7 3.3 83.2
Stationary combustion – liquid CO2 2,501.6 2.6 85.8
Solid waste disposal on land CH4 2,063.2 2.2 88.0
Agricultural soils –  indirect emissions N2O 2,005.1 2.1 90.1
Metal production - iron and steel production CO2 1,310.9 1.4 91.4
Conversion to grassland CO2 1,114.8 1.2 92.6
Transport – civil aviation CO2 771.4 0.8 93.4
Metal production - aluminium production PFCs 629.9 0.7 94.0
Grassland remaining grassland CO2 585.5 0.6 94.7
Manure management CH4 579.1 0.6 95.3
Agricultural soils - direct emissions N2O 515.2 0.5 95.8
Metal production -  aluminium production CO2 449.0 0.5 96.3
Mineral products - cement production CO2 444.7 0.5 96.7
Fugitive emissions from geothermal operations CO2 357.3 0.4 97.1
Chemical industry - ammonia production CO2 278.0 0.3 97.4
Fugitive emissions from coal mining and handling CH4 272.1 0.3 97.7
Fugitive emissions from oil and gas operations CH4 262.5 0.3 98.0
Transport – navigation (domestic shipping) CO2 247.7 0.3 98.2
Fugitive emissions from oil and gas operations CO2 230.1 0.2 98.5
Waste-water handling CH4 207.0 0.2 98.7
Conversion to forest land CO2 166.2 0.2 98.8
Wastewater handling N2O 153.5 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 2008. Key categories are those that comprise 95 per cent of the total.

(a) IPCC Tier 1 category trend assessment - including LULUCF (net emissions)          
IPCC categories Gas Base year estimate 
(Gg CO2-e)
2008 estimate 
(Gg CO2-e)
Trend assessment Contribution to trend (%) Cumulative total (%)
Forest land remaining forest land CO2 33034.12 12441.13 0.204 42.2 42.2
Conversion to forest land CO2 166.24 17327.74 0.141 29.2 71.4
Transport – road transportation CO2 7500.22 12670.17 0.035 7.2 78.6
Stationary combustion – solid CO2 3139.65 6148.38 0.022 4.5 83.0
Enteric fermentation CH4 21837.22 22657.49 0.016 3.3 86.3
Conversion to grassland CO2 1114.80 2849.61 0.013 2.7 89.0
Solid waste disposal on land CH4 2063.21 1278.45 0.009 1.8 90.8
Agricultural soils - direct emissions N2O 515.17 1777.67 0.010 2.0 92.9
Consumption of halocarbons and SF6 - refrigeration and air conditioning HFCs & PFCs 0.00 727.74 0.006 1.2 94.1
Metal production - aluminium production PFCs 629.87 36.47 0.006 1.1 95.2
Agricultural soils –  pasture, range and paddock N2O 6858.75 7125.90 0.005 1.0 96.3
Fugitive emissions from oil and gas operations CO2 230.14 796.37 0.004 0.9 97.2
Stationary combustion – liquid CO2 2501.64 3144.10 0.003 0.6 97.7
Stationary combustion – gas CO2 7306.82 8033.04 0.002 0.3 98.1
Agricultural soils –  indirect emissions N2O 2005.11 2468.78 0.002 0.4 98.4
Mineral products - cement production CO2 444.72 634.24 0.001 0.2 98.6
Fugitive emissions from oil and gas operations CH4 262.46 404.76 0.001 0.2 98.8
Consumption of halocarbons and SF6 - foam blowing HFCs & PFCs 0.00 83.25 0.001 0.1 99.0

 

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