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))

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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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