New Zealand's Greenhouse Gas Inventory 1990 - 2002

• Executive Summary
• Chapter 1: Introduction
• Chapter 2: Trends in Greenhouse Gas Emissions
• Chapter 3: Energy
• Chapter 4: Industrial Processes
• Chapter 5: Solvent and Other Product Use
• Chapter 6: Agriculture
• Chapter 7: Land-Use Change and Forestry (LUCF)
• Chapter 8: Waste
• Chapter 9: Recalculations and Improvements
• References
• Annex 1: Key Sources
• Annex 2: Detailed discussion of methodology and data for estimating CO2 emissions from fossil fuel combustion
• Annex 3: Detailed methodologies for source or sink categories
• Annex 4: CO2 reference approach and comparison with sectoral approach, and relevant information on the national energy balance
• Annex 5: Assessment of completeness and (potential) sources and sinks of greenhouse gas emissions and removals excluded
• Annex 6: Quality Assurance and Quality Control
• Annex 7: Uncertainty analysis (Table 6.1 of the IPCC good practice guidance)
• Annex 8: Trend tables from the 2002 Common Reporting Format

Chapter 3: Energy

3.1 Sector overview

New Zealand's energy sector produced 32,047.22 Gg CO₂ equivalent in 2002 and represented 42.8% of all greenhouse gas emissions.Emissions from the energy sector are now 35.0% above the 1990 baseline value of 23,746.84 Gg CO₂ equivalent (Figure 3.1.1). The sources contributing most to this increase since 1990 are emissions from road transportation (an increase of 62.5%), public electricity and heat production (an increase of 58.1%) and the manufacture of methanol and urea (an increase of 319.6%). Emissions from the manufacture of solid fuels and other energy industries sub-category have decreased by 80.0% from 1990.

3.2 Fuel combustion (CRF 1.A)

3.2.0.1 Description

The fuel combustion category includes all emissions from fuel combustion activities, specifically energy and transformation industries, manufacturing industries, transport and other sectors namely commercial, residential and agriculture/forestry/fisheries (Figure 3.2.1). These subcategories use common activity data sources and emission factors (refer Annex 2). For this reason information about methodologies, emission factors, uncertainty and quality assurance relevant to several sub-categories are discussed below rather than repeated in individual sub-categories.

3.2.0.2 Methodological issues

Energy sector emissions for New Zealand's inventory are compiled from the MED's energy database along with the relevant emission factors. Generally, greenhouse gas emissions are calculated by multiplying the emission factor of specific fuels by the energy activity data. There are only a few instances where emission factors are unavailable due to confidentiality reasons and instances where natural gas was used as a feedstock.

The fuel combustion category is commonly separated into two groups - stationary combustion and mobile combustion. CO₂ emissions from the stationary combustion of gas, solid and liquid fuels are identified as key source categories for New Zealand in the 2002 inventory. The relevant good practice decision tree (Figure 2.1 in Good Practice - IPCC, 2000) identifies that to meet good practice in methodology, emissions should be estimated using data from sectors correcting for oxidation and stored carbon (the Tier 1 Sectoral Approach). The decision is based on New Zealand having data on fuel combusted by sector but not by plant. The New Zealand methodologies are consistent with the Tier 1 Sectoral Approach. Good practice for methodological choice in the mobile combustion (transport) category is discussed in Section 3.2.3 - Fuel combustion: transport.

Emission factors: New Zealand emission factors are based on the GCV (Gross Calorific Value). This is because energy use in New Zealand is conventionally reported in gross terms with some minor exceptions (refer Annex 2). New Zealand reviewed all emission factors used in the energy sector in 2003 (Hale and Twomey, 2003). The review was commissioned based on recommendations from New Zealand's inventory QA procedures (Clarkson, 2001, 2002). The results of the emission factors review were assessed by an independent review panel of New Zealand energy experts prior to review recommendations being used in the inventory. In accordance with good practice, where there was a significant difference between country-specific and IPCC default emission factors, and a defensible explanation could not be obtained, New Zealand has reverted to the IPCC default emission factors (refer to Annex 2 for detailed information). The 2002 inventory incorporates the emission factors recommended by the review and agreed by the review panel.

3.2.0.3 Uncertainties and time-series consistency

Uncertainty in greenhouse gas emissions from fuel combustion varies depending on the greenhouse gas (Table 3.2.1). The uncertainty of CO₂ emissions is relatively low at ±5% and will be primarily due to uncertainty in activity data rather than emission factors (IPCC, 2000). This is due to the direct relationship between fuels' carbon content and the corresponding CO₂ emissions during combustion. The low level of uncertainty in CO₂ emissions is important as CO₂ emissions comprise 95.5% of emissions in the energy sector. Details of how uncertainty in CO₂ emissions is assessed are provided under each fuel type in Annex 2.

In comparison, emissions of the non-CO₂ gases are much less certain as they vary with the combustion conditions. In addition, many of the non-CO₂ emission factors used by New Zealand are the IPCC default values and the IPCC Guidelines (1996) often do not quantify the uncertainty in the default emission factors. The uncertainties proposed in Table 3.2.1 are thought to be reasonably accurate but lack a rigorous foundation (MED, 2003).

Table 3.2.1 General uncertainty ranges for emission estimates from fuel combustion (MED, 2003)

Gas	Uncertainty
CO2	± 5%
CH4	± 50%
N2O	± 50%
NOx	± 33%
CO	± 50%
NMVOC	± 50%

3.2.1 Fuel combustion - energy industries (CRF 1A1)

3.2.1.1 Description

This category comprises emissions from fuels burnt in stationary combustion including combustion for public electricity and heat production, petroleum refining, and the manufacture of solid fuels and other energy industries.

Emissions in the energy industries category totalled 6,740.94 Gg CO₂ equivalent in 2002 and have increased 11.5% since 1990. The emissions profile in 2002 is dominated by emissions from public electricity and heat production which contribute 81.8 % of the total CO₂ equivalent emissions.

New Zealand's electricity generation is dominated by hydroelectric generation (60-65% of annual electricity needs) with the balance from thermal generation using mostly natural gas (but occasionally some coal). Geothermal power contributes another 6% and there are also contributions from other renewable sources such as wind and co-generation using wood. The emissions from public electricity generation show large year-to-year fluctuations because of the use of thermal stations to supplement electricity generation where the main hydro stations cannot meet the demand for electricity. Generation in a 'normal' hydro year requires lower coal use and a 'dry' hydro year requires higher coal use. This is different from the steady increase in this type of emissions from coal used in electricity generation as found in many other countries.

3.2.1.2 Methodological issues

The owners of the main thermal electricity generating plants in New Zealand are Contact Energy Limited, Genesis Power Limited and Southdown Co-generation Limited. In accordance with IPCC guidelines (IPCC, 1996), where electricity generation is a secondary activity of the co-generation plant, emissions are included in the manufacturing industries category. However, where electricity generation is the primary activity of the co-generation plant the emissions are documented in the energy industries category.

The CO₂ emissions from coal use in electricity generation are derived from coal use figures provided by the sole electricity generator that uses coal.

The data for liquid fuel use are from the 'Delivery of Petroleum fuels by Industry' survey compiled by Statistics New Zealand (Annex 2).

Energy use data for petroleum refining are supplied to the MED by the New Zealand Refining Company Limited. In general, emission factors are used to derive CO₂ emissions using the energy in the fuels consumed. For the refinery, a weighted-average CO₂ emissions factor is estimated based on the fuel used. As there are no data available concerning non- CO₂ emissions from the refinery, the IPCC default (IPCC, 1996) emissions factor for industrial boilers is used.

CO₂ and non-CO₂ emission factors for fossil fuels are discussed in detail in Annex 2. Wood is also used for energy production. For wood consumption, the CO₂ emissions factor is 104.2 kt CO₂ /PJ. This is calculated from the IPCC default emissions factor, assuming the NCV is 5% less than the GCV.

3.2.1.3 Uncertainties and time-series consistency

Uncertainties in emissions estimates are those relevant to the entire fuel combustion sector (refer to Table 3.2.1 and Annex 2).

3.2.1.4 Source-specific QA/QC and verification

The review of energy sector emission factors (Hale and Twomey, 2003) encompassed the emission factors used in the manufacturing industries and construction category. In preparation of the 2002 inventory, the data for electricity production and petroleum refining underwent a Tier 1 QC checklist.

3.2.1.5 Source-specific recalculations

Energy industries data are recalculated for all years to 1990 as a result of the review of energy sector emission factors. Details of the effect of the recalculation on the energy sector are included in Chapter 9.

3.2.1.6 Source-specific planned improvements

Consideration will be given to separating sectoral coal consumption into three key ranks of coal (bituminous, sub-bituminous and lignite) and using a specific emissions factor for each rank of coal.

3.2.2 Fuel combustion: manufacturing industries and construction (CRF 1A2)

3.2.2.1 Description

This category comprises emissions from fuels burnt in manufacturing industries and construction including iron and steel, other non-ferrous metals, chemicals, pulp, paper and print, food processing, beverages and tobacco, and other uses.

Emissions in the manufacturing industries and construction category totalled 6,440.02 Gg CO₂ equivalent in 2002. The level of emissions in 2002 is 34.9% over the 1990 baseline. The largest single source in 2002 is emissions from natural gas consumption in the manufacture of the chemicals methanol and urea. This sub-category comprised 34.2% of emissions from manufacturing industries and construction and has increased from 525.42 Gg CO₂ equivalent in 1990 to 2204.42 Gg CO₂ equivalent in 2002 - an increase of 319.6%.

3.2.2.2 Methodological issues

The energy data for methanol and urea production are supplied directly to the MED by industry. CO₂ emissions are calculated by comparing the amount of carbon in the gas purchased by the plants and the amount stored in products (refer Box 4.2 in the 'Industrial Processes' chapter). The energy data has been aggregated to protect commercially sensitive information. The data for other industry uses of gas is from the energy supply and demand balance tables in the Energy Data File (MED, 2003).

CO₂ emissions from liquid fuels and coal are more straightforward to calculate than natural gas because it is assumed that all carbon in these fuels is oxidised to CO₂ during combustion. Liquid fuel data are extracted from the Deliveries of Petroleum Fuels by Industry survey conducted by Statistics New Zealand. Coal consumption data are determined from the New Zealand Coal Sales Survey conducted by Statistics New Zealand combined with a sectoral allocation supplied by Coal Research Limited. These sources of activity data are further described in Annex 2. A considerable amount of coal is used in the production of steel, however virtually all of the coal is used in a direct reduction process to remove oxygen from iron sand and not as a fuel. Emissions are therefore included in the industrial process sector.

In the CRF tables, no disaggregated activity data according to fuel types and corresponding CO₂ emissions have been provided for any sub-category except for chemicals. The reason for this is that detailed energy use statistics by industries (according to complete ANZSIC codes similar to the ISIC codes) are collected and reported in New Zealand for electricity consumption only. For the other energy/fuel types such as gas, liquid fuel and coal, data are collected and reported at a much higher level. This is a reflection of the historical needs and practices of energy statistics collection in New Zealand. Gas use statistics by industries according to ANZSIC codes have been collected since 2001 and will be incorporated when they have been adequately verified. The sub-category chemicals has an entry because it relates to gas used by Methanex in particular.

3.2.2.3 Uncertainties and time-series consistency

Uncertainties in emission estimates are those relevant to the entire energy sector (refer Table 3.2.1 and Annex 2).

3.2.2.4 Source-specific QA/QC and verification

The review of energy sector emission factors (Hale and Twomey, 2003) encompassed the emission factors used in the manufacturing industries and construction category. In preparation of the 2002 inventory, the data for CO₂ emissions from stationary combustion - manufacturing industries and construction underwent a Tier 1 QC checklist.

3.2.2.5 Source-specific recalculations

Manufacturing industries and construction data are recalculated for all years to 1990 as a result of the review of energy sector emission factors. Details of the effect of the recalculation on the energy sector are included in Chapter 9.

3.2.2.6 Source-specific planned improvements, if applicable

Consideration will be given to validating the sectoral allocation of coal consumption according to national circumstances and priorities for inventory development.

3.2.3 Fuel combustion: transport (CRF 1A3)

3.2.3.1 Description

This category comprises emissions from fuels burnt in transportation including civil aviation, road transport, rail transport and national navigation. Emissions from international marine and aviation bunkers are reported but not included in the total emissions.

Emissions from the transport category totalled 14,208.22 Gg CO₂ equivalent in 2002 and have increased 60.7% from the 8,840.5 Gg CO₂ equivalent emitted in 1990. The emissions profile in 2002 is dominated by emissions from road transportation which accounted for 88.6% of total transport emissions. CO₂ emissions from mobile combustion (road vehicles) was identified as a key source category in the level and trend analysis where it was the 2nd largest source and made the largest contribution to the trend (Tables 1.5.2 and 1.5.3).

3.2.3.2 Methodological issues

Emissions from transportation are compiled from the MED's energy database. It is good practice to use a Tier 1 approach for calculating CO₂ emissions as this provides the most reliable estimate, however it is also good practice to use a Tier 2, bottom-up, approach to confirm the Tier 1 estimate (IPCC, 2000). The current New Zealand methodology is a Tier 1 approach, estimating emissions using country-specific emission factors.

Activity data on the consumption of fuel by the transport sector are extracted from the Deliveries of Petroleum Fuels by Industry survey conducted by Statistics New Zealand. LPG and CNG consumption figures are reported in the Energy Data file (MED, 2003). The CO₂ emission factors used in previous inventories were sourced from the New Zealand Energy Information Handbook (Baines, 1993). These are replaced with the emission factors for individual liquid fuels derived from NZRC data on carbon content and calorific values (Annex 2) as a result of the 2003 review of energy sector emission factors.

Road transport

Accurately calculating non-CO₂ emissions from road transport requires a Tier 2 or higher methodology as it is dependent on the knowledge of the distribution of emission controls in the fleet. However, the Tier 1 approach used by New Zealand is consistent with good practice for the choice of methodology, as non-CO₂ emissions from road transport are not key source categories for New Zealand and information on fuel consumption by vehicle type are under development.

Navigation

Good practice in methodology choice for navigation in New Zealand is to use a Tier 1 approach with country specific carbon contents for estimating CO₂ emissions and IPCC default emission factors for CH₄ and N₂O (IPCC 2000). The current New Zealand methodology meets good practice. Prior to the 2002 inventory, New Zealand specific emission factors are used for CH₄ and N₂O emissions from fuel oil in domestic transport. The 2003 review of emission factors recommended reverting to the IPCC default factors (Hale and Twomey, 2003).

Aviation

The New Zealand methodology for estimating emissions from domestic aviation is a Tier 1 approach that does not use landing and take off (LTO) cycles. There is no gain in inventory quality by moving from a Tier 1 to a Tier 2 approach using LTOs (IPCC, 2000).

3.2.3.3 Uncertainties and time-series consistency

Uncertainties in emission estimates are those relevant to the entire fuel combustion sector (refer Table 3.2.1 and Annex 2).

3.2.3.4 Source-specific QA/QC and verification

The review of energy sector emission factors (Hale and Twomey, 2003) encompassed the emission factors used in the transport sector.

CO₂ emissions from road transport and aviation are identified as key source categories for New Zealand in the 2001 inventory. In preparation of the 2002 inventory, the data for these emissions underwent a Tier 1 QC checklist.

3.2.3.5 Source-specific recalculations

Emissions are recalculated for all years to 1990 as a result of the energy sector emissions factor review. Details of the recalculation on the energy sector are included in Chapter 9.

3.2.3.6 Source-specific planned improvements, if applicable

New Zealand will investigate implementing a Tier 2 method to estimate CO₂ emissions from road transportation to support the figures produced from the Tier 1 methodology.

3.2.4 Fuel combustion: other sectors (CRF 1A4)

3.2.4.1 Description

This sector comprises emissions from fuels burnt in the commercial/institutional category, the residential category and the agriculture, forestry and fisheries sub-category.

Emissions from 'Fuel combustion: other sectors' totalled 3,290.58 Gg CO₂ equivalent in 2002 and are 11.8% over the 1990 baseline value of 2,944.25 Gg CO₂ equivalent. The emissions profile in 2002 is divided between the commercial and institutional category (39.3%), and the agriculture, forestry and fisheries sub-category (41.6%). The residential category comprises the remaining 19.1% of emissions.

3.2.4.2 Methodological issues

The energy activity data are obtained from the same sources as other energy categories (Annex 2). However, in partitioning energy use between categories, the emissions from the agriculture, forestry and fisheries sub-category are likely to be underestimated (MED, 2003). This is because there are no separate estimates of fuel use by this group, apart from liquid fuels used in agriculture. However, these emissions have been included in other sectors such as industry and transport and are therefore included in New Zealand's total emissions.

The solid fuel used in this sector is predominantly sub-bituminous coal, hence the emissions factor for sub-bituminous coal is used for all solid fuel emissions calculations (MED, 2003).

3.2.4.3 Uncertainties and time-series consistency

Uncertainties in emission estimates are those relevant to the entire energy sector (refer Table 3.2.1 and Annex 2).

3.2.4.4 Source-specific QA/QC and verification

In preparation of the 2002 inventory, the data for the "other sectors" category underwent a Tier 1 QC checklist.

3.2.4.5 Source-specific recalculations

Data are recalculated for all years to 1990 as a result of the energy sector emissions factor review. Details of the effect of the recalculation are included in Chapter 9.

3.3 Fugitive emissions from fuels (CRF 1B)

3.3.1 Fugitive emissions from fuels: solid fuels (CRF 1B1)

3.3.1.1 Description

Fugitive emissions arise from the production, processing, transmission, storage and use of fuels, and from non-productive combustion. New Zealand's fugitive emissions from solid fuels are a product of coal mining operations.

CH₄ is created during coal formation. The amount of CH₄ released during coal mining is dependant on the coal rank and the depth of the coal seam. Surface mines are assumed to emit relatively little CH₄ compared to underground mines. In New Zealand, 87% (2002) of the CH₄ from coal mining comes from underground mining however most of the coal mined in New Zealand is taken from surface mines (80% in 2002). There is no flaring of CH₄ at coal mines and CH₄ is rarely captured for industrial uses. CH₄ is also emitted during post mining activities such as coal processing, transportation and utilisation.

Fugitive emissions from solid fuels produced 354.08 Gg CO₂ equivalent in 2002. This is an increase of 68.6% from the 210.02 Gg CO₂ equivalent reported in 1990. Fugitive emissions from solid fuels (CH₄) are identified as a key source category in the 2002 trend assessment (Table 1.5.3).

3.3.1.2 Methodological issues

Good practice in methodology choice for estimating fugitive emissions from coal mining is to focus on the sub-source category that dominates the emissions. New Zealand therefore focuses on estimating emissions from underground mining. The methodology consistent with good practice is to estimate emissions using direct measurements (Tier 3) supplemented with country-specific emission factors where there is no measurement (Tier 2). The current New Zealand methodology is a Tier 1 approach using the top end of the IPCC default range in emission factors (Table 3.3.1). The emission factors used for surface mining, handling of surface-mined coal and handling of underground-mined coal are the middle values from the IPCC default range (Table 3.3.1). The values for bituminous and sub-bituminous coal are combined into a single value (13.74 tCH₄/kt coal) for use on underground mining based on the relative production of bituminous and sub-bituminous coal. In 2002, the coal production by weight was 320 kt bituminous coal and 585 kt sub-bituminous coal.

Table 3.3.1 Methane release factors for New Zealand coal

Activity	New release factors (tCH4/kt coal)	Previous release factors (tCH4/kt coal)	Source of new emission factors
Surface mining	0.77	0.77	Mid-point IPCC default range (0.2-1.34 t/kt coal)
Underground: bituminous mining	16.75	35.2	Top end of IPCC default range (6.7-16.75 t/kt coal)
Underground: sub-bituminous mining	12.1	12.1	Beamish and Vance, 1992
Surface post mining	0.067	0.067	Mid-point IPCC default range (0.0-0.134 t/kt coal)
Underground post mining	1.6	1.6	Mid-point IPCC default range (0.6-2.7 t/kt coal)

Note: there is no release factor for lignite from underground mining as all lignite is taken from surface mining.

3.3.1.3 Uncertainties and time-series consistency

Uncertainties in emissions are those relevant to the entire energy sector (refer Table 3.2.1 and Annex 2).

3.3.1.4 Source-specific QA/QC and verification

The review of energy sector emission factors (Hale and Twomey, 2003) encompassed the emission factors used in this sector. In preparation of the 2002 inventory, the data for fugitive CH₄ emissions from solid fuels underwent a Tier 1 QC checklist.

3.3.1.5 Source-specific recalculations

Data are recalculated for all years from 1990 as a result of the energy sector emissions factor review. In previous submissions, the emission factors for underground coal mining were based on the New Zealand specific values established by Beamish and Vance (1992). The 2003 review of emission factors (Hale and Twomey, 2003) noted that the New Zealand factor (35.2 t CH₄/kt coal) was more than twice the top end of the IPCC Tier 1 range and was based on a small sample of mines. In response, New Zealand has adopted the top end of the IPCC range of emission factors for the 2002 inventory (16.75 t CH₄/kt coal) and will review when more country-specific information is available. Details of the effect of the recalculation are shown in Chapter 9.

3.3.1.6 Source-specific planned improvements, if applicable

Research is currently underway to determine an updated New Zealand specific emissions factor determined by direct measurement at underground coal mines.

3.3.2 Fugitive emissions from fuels: oil and natural gas (CRF 1B2)

3.3.2.1 Description

Fugitive emissions from oil and gas comprised 1013.38Gg CO₂ equivalent in 2002. This is an increase from 930.30 Gg CO₂ equivalent in 1990 - an increase of 8.9%.

The main source of emissions from the production and processing of natural gas is the Kapuni gas treatment plant. The plant removes CO₂ from a portion of the Kapuni gas before it enters the distribution network. CO₂ is also produced when natural gas is flared at the wellheads of other fields. The combustion efficiency of flaring is 95-99% (MED, 2003), leaving some fugitive emissions due to the incomplete combustion. Fugitive emissions also occur in transmission and distribution of the natural gas.

This sector also includes emissions from geothermal operations. Some of the energy from geothermal fields is transformed into electricity, thus emissions from these sources are reported as fugitive emissions in the energy sector. This is because they are not the result of fuel combustion, unlike the emissions reported under 'Energy Industries'. Sites with naturally occurring emissions where there is no use of geothermal steam for energy production are excluded from the inventory.

3.3.2.2 Methodological issues

Venting and flaring from oil and gas production

The CO₂ released through flaring is either supplied directly by field operators or calculated from the supplied energy data using the emission factors from Baines (1993). The Natural Gas Corporation (NGC) supplies estimates of CO₂ released during processing. These values are aggregated to derive annual emissions.

Gas transmission and distribution

Gas leakage occurs almost exclusively from low-pressure 'distribution' pipelines rather than from high-pressure 'transmission' pipelines. Approximate estimates of annual leakage from transmission pipelines provided by the NGC are about 10 tonnes of CO₂ and 100 tonnes of CH₄ (MED, 2003).Therefore, the gas quantity shown in the worksheets excludes the gas used in electricity generation and by others that take their gas directly from the transmission network. The NGC estimates that around 3.5% of the gas entering the distribution system is unaccounted for and that around half of this (1.75%) is actually lost through leakage, whilst the other half is unaccounted for due to metering errors and theft. The split between fugitive CO₂ and CH₄ emissions is based on gas consumption data. The emissions data are used to calculate fugitive emission factors for the two gases.

Oil transport, refining and storage

Fugitive emissions from oil transport, refining and storage are calculated from an IPCC Tier 1 approach of activity data and emission factors. For oil transport, the fuel quantity is the total New Zealand production of crude oil reported in the Energy Data File (MED, 2003), and the CH₄ emissions factor is the midpoint of the IPCC default value range (0.745 t CH₄ / PJ). Oil refining and storage uses the same CH₄ emissions factor but the fuel quantity is the oil intake at New Zealand's single oil refinery.

Geothermal operations

The geothermal field operators measure the emissions of CO₂ and CH₄ at their plants and supply the figures to the MED. No fuel is burnt in the geothermal operations as the process harnesses the energy in tapped geothermal fluid. High pressure steam (26 bar) is used to power the main electricity-producing back pressure turbines. In some plants, the low pressure exhaust steam is then used to drive secondary (binary) turbines. CO₂ and CH₄ dissolved in the geothermal fluid are released along with steam.

3.3.2.3 Uncertainties and time-series consistency

The time-series of data from the various geothermal fields varies in completeness. Some fields were not commissioned until after 1990 and hence do not have records back to 1990.

3.3.2.4 Source-specific QA/QC and verification

No specific QA/QC activities are performed for this category.

3.3.2.5 Source-specific recalculations

Emissions from the Wairakei and Ohaaki geothermal fields have been revised from 1996 onwards, however industry was not able to provide emission estimates for the years 1990-1995 on the same basis. Emissions for these years are set at the 1995 level.

3.4 Other information

3.4.1 Comparison of sectoral approach with reference approach

The calculation for the reference approach identifies the apparent consumption of fuels in New Zealand from production, import and export data. This information is used as a check for combustion related emissions. The check is performed for all years from 1990 - 2002. The majority of the CO₂ emission factors for the reference approach are New Zealand specific (Annex 2: Table A2.1). Natural gas emission factors are estimated from the sectoral approach analysis whereby the aggregated CO₂ emissions, including carbon later stored, are divided by aggregate energy use.

Comparison of the reference approach and sectoral approach total in 2002 shows that the sectoral total of CO₂ emissions is 2.94 % less than the reference total (Table 3.4.1). This is mainly related to the differences in the energy consumption data where there is a -1.75 % difference in liquid fuel consumption and a 4.03 % difference in solid fuel consumption.

In the New Zealand energy sector inventory, the activity data for the reference approach are obtained from 'calculated' energy use figures. These are derived as a residual figure from an energy balance equation comprising production, imports, exports, stock change and international transport on the supply side from which energy use for transformation activities is subtracted. The activity data used for the sectoral approach are referred to as 'observed' energy use figures. These are based on surveys and questionnaires administered by Statistics New Zealand on behalf of the MED or by the MED itself. The differences between 'calculated' and the 'observed' figures are reported as statistical differences in the energy balance tables contained in the Energy Data File (MED, 2003).

The time-series comparison with the IEA data (IEA Statistics, 2003) shows that the differences between the sectoral and reference approach reported in CRF 2002 are less than those reported by the IEA. There are clear differences in the early part of the time-series and there is a clear trend narrowing the difference between the two sources that indicates stronger correlation in the reporting process developed over the annual inventory preparation process.

Table 3.4.1 Difference between the reference and sectoral approach for New Zealand's inventory and the IEA reference and sectoral comparison

View difference between the reference and sectoral approach for New Zealand's inventory and the IEA reference and sectoral comparison (large table)

3.4.2 International bunker fuels

The data on fuel use by international transportation come from the Energy Data File (MED, 2003). This sources information from oil company returns provided to the MED. Data on fuel use by domestic transport are sourced from the Deliveries of Petroleum Fuels by Industry survey undertaken by Statistics New Zealand.

3.4.3 Feedstocks and non-energy use of fuels

The fuels supplied to industrial companies are used both as fuel and as feedstock. The emissions are calculated using the total fuel supplied to each company (this includes fuel used as feedstock) and estimating the difference between the carbon content of the fuels used and the carbon sequestered in the final output (this is based on the industry production and the chemical composition of the products). This difference is assumed to be the amount of carbon emitted as CO₂. Examples of the calculations for methanol and ammonia/urea are shown in Boxes 4.2 and 4.3 of the industrial processes sector. A considerable amount of coal is used in the production of steel, however virtually all of the coal is used in a direct reduction process to remove oxygen from ironsand and not as a fuel.

3.4.4 CO2 capture from flue gases and subsequent CO2 storage

There is no CO₂ capture from flue gases and subsequent CO₂ storage occurring in New Zealand at present.

3.4.5 Country specific issues

Energy sector reporting shows very few areas of divergence from the IPCC methodology. The differences are listed below:

• A detailed subdivision of the manufacturing and construction source category as requested by the IPCC reporting tables is currently not available due to historical needs and practices of energy statistics collection in New Zealand.
• Some gas usage data from large industrial consumers in New Zealand and some emission factors for gas have been withheld for confidentiality reasons.
• Some of the coal production in the reference approach activity data are used in steel production. The CO₂ emissions from this coal are accounted for under the 'industrial processes' sector and have been netted out of the energy reference approach using the Estimating thecarbon stored in products Table (refer calculation Worksheet 1.1).
• The activity data shown in the CO₂ worksheets (Worksheet 1.2) under the sectoral approach exclude energy sources containing carbon that is later stored in manufactured products (rather than emitted during combustion) , specifically methanol and urea. This means that there is no subsequent downward adjustment required in carbon emissions and is necessary to preserve the confidentiality of the gas-use data mentioned above.
• An additional worksheet is included to cover fugitive emissions of CO₂ and CH₄ from geothermal fields where electricity or heat generation plants are in operation.

3.4.6 Ozone precursors and SO2 from oil refining

New Zealand's only oil refinery does not have a catalytic cracker. The emission factors used are the IPCC default values. The amounts of sulphur recovered at the refinery are provided by the New Zealand Refining Company. All storage tanks at the refinery are equipped with floating roofs and all but two have primary seals installed.

Worksheets accompanying the energy sector

The worksheets for the energy sector document the underpinning data (energy consumption data, emission factors and emissions data) used to collate the energy sector emissions.

Download energy sector worksheets (PDF 173 KB)

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