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Chapter 9: Recalculations and improvements

This chapter summarises the recalculations and improvements made to the New Zealand greenhouse gas inventory since the submission of the 2004 NIR (2002 inventory). It summarises material that has already been described in greater detail in Chapters 3-8.

Each year the inventory is updated (existing activity data and/or emission factors may be revised) and extended (the inventory includes a new inventory year). The inventory may also be expanded to include emissions from additional sources if a new source has been identified within the context of the IPCC revised guidelines and Good Practice Guidance, or activity data and emission factors have become available for sources that were previously reported as NE (not estimated) due to a lack of data. The 2003 inventory includes estimates for potential emissions from HFCs, SF6, CO and NOx emissions from aluminium production back to 1990 which were all recorded as NE in the 2002 inventory.

Updating the New Zealand inventory involves revision of last year's activity data for the agriculture sector and LULUCF category forest land. This is because New Zealand uses three-year averages of activity data in these sectors. The updating process replaces the provisional numbers used in last year's average with actual numbers. For example, the 2003 inventory uses an average of the 2002, 2003 and 2004 year numbers. The 2002 and 2003 years are actual data, but only provisional data is available for the 2004 year. In the 2004 inventory, the provisional 2004 figures will be replaced by actual figures and the 2003 inventory will be recalculated.

The use of revised methodologies and activity data in any sector will result in recalculation of the whole time-series from 1990 to the current inventory. This means estimates of emissions of a given year can differ from emissions reported in the previous inventory.

9.1 Explanations and justifications for recalculations

9.1.1 Energy sector

Emission factors

  • Separate emission factors are used for the first time in the 2003 inventory for the three key ranks of coal (bituminous, sub-bituminous and lignite). Previously, the emissions factor for sub-bituminous coal was used for all coal use.
  • In accordance with the recommendations in Hale and Twomey (2003), the CH4 emission factors for gasoline and diesel used in road transport, rail transport and mobile agriculture should have been changed from New Zealand specific factors to IPCC default emission factors. The NOX emission factors for the same fuels and sectors should also have been updated. In each case, the New Zealand specific emission factors were used for all years in the 2002 inventory. This has been fixed by using the recommended emission factors in this inventory.

Activity data revisions

  • During 2004, a review of the data provided by the oil companies to Statistics New Zealand via the Deliveries of Petroleum Fuels by Industry (DPFI) survey uncovered substantial misreporting of certain liquid fuels. This lead to some revisions of liquid fuel consumption data, especially for 2002. The result is that energy sector emissions from liquid fuels are lower for the 2002 year than reported in last year's inventory. The emissions estimate for the transport sector has also been decreased given that the bulk of liquid fuels are used in this sector.
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  • Fugitive emissions from coal mining have been recalculated due to the revision of data on tonnes of coal mined from surface and underground mines. New Zealand has switched to a new data series (that is considered to be of higher quality) based on energy resource levy payment.
  • From 1999, LPG consumption in the transport sector has been revised downward and emissions in the 'manufacturing industries and construction' category have been revised upwards.

Methodology revisions

  • A Tier 2 approach has been developed in line with good practice to be used in parallel with emissions from road transport (estimated using the Tier 1 approach). The Tier 2 methodology provides an important quality check for the Tier 1 top-down approach for calculating CO2 emissions. A reliable and accurate bottom-up CO2 emissions estimate increases confidence in the underlying activity data used for the inventory and these attributes in turn are important for the bottom up calculation of CH4 and N2O emissions from road transport.

Reallocations

  • In previous inventories, estimates of sectoral coal consumption shares were based on surveys undertaken by Coal Research Limited (CRL) in 1990 and 1995 with the exceptions of the electricity generation, steel production and residential categories. Sectoral coal shares in other years were based on interpolated values (between 1990 and 1995) and extrapolated values (after 1995). However, total coal consumption across all categories (excluding electricity generation) was based on Statistics New Zealand's Annual Coal Sales Survey. In order to avoid basing emissions estimates on extrapolated data and to be consistent with national energy statistics, estimates of sectoral coal use are now based exclusively on the Coal Sales Survey. This change has resulted in a reallocation of emissions from the 'manufacturing industries and construction' category to the 'commercial/institutional' category. There have also been some reallocations of emissions to and from the agriculture/forestry/fishing subcategories depending on the year.
  • Emissions from gas used in the iron and steel industry are provided separately for the first time - previously they were included in the 'manufacturing industries and construction (other)' category.
  • Emissions from urea production are no longer included under 'chemicals' in the energy sector and are included under 'industry chemicals' in the industrial processes sector. The rationale behind this re-allocation of urea production is one step further on from ammonia production (ammonia is used in the production of urea) and most of the emissions are emitted in the stage where ammonia is being produced. In New Zealand, all ammonia produced is used in the production of urea.
  • Fugitive emissions previously assigned to the 'natural gas\transmission' category have been reallocated to the 'natural gas\distribution' category as almost all of the emissions from gas transportation are actually from the distribution network rather than from the transmission network. Emissions from transmission and distribution are combined for confidentiality reasons.
  • Fugitive emissions previously assigned to the 'venting and flaring\flaring\combined' category have been reallocated to the 'venting and flaring\flaring\gas' category as virtually all of the flaring is of gas. There was only an insignificant amount of condensate flaring in 1991.

Other (errors)

  • In previous inventories there was some double-counting of emissions in the 'public electricity and heat production' and 'manufacturing industries and construction (other)' categories. The emissions were subtracted from the 'electricity and heat production' category as it was decided to re-classify the co-generation plants.
  • There have also been several other minor re-calculations. These are documented in the common reporting format tables.

9.1.2 Industrial processes sector

Mineral products - cement production

The calculation of CO2 emissions from cement production uses Tier 1 methodology (1990-1996) and Tier 2 methodology (1997-2003). In previous inventories, a Tier 1 methodology was used for all years.

Chemical industry - urea

As mentioned in the previous section, emissions from urea production have been re-allocated from the energy sector to the industrial processes sector. Further, CO2 emissions from urea production have been revised upwards since the 2002 inventory as the carbon sequested in the urea is no longer taken into account. This carbon is now assumed to be released when the urea is applied to the land.

Chemical industry - methanol production

Activity data for methanol production back to 1990 became available so CH4 emissions for the entire time-series were able to be calculated (the 2002 inventory was only able to use activity data back to 1997).

Metal production - iron and steel

Emissions from iron and steel production have been revised downward due to methodological changes and corrections in the data supplied by one of the steel plants. Firstly, New Zealand is now accounting for the amount of carbon sequested in the steel produced by New Zealand's biggest steel maker, which produces steel from ironsand. Secondly, there have been revisions to the CO2 emissions from New Zealand's other plant which produces steel from mainly scrap metal using an electric arc furnace. Estimates have been based on a mass balance approach. However, due to errors in the assumed carbon contents of the scrap metal input and the steel produced, the levels of emissions for the 2002 inventory were grossly over-estimated. For all years from 2000, emissions have been re-calculated based on corrected carbon content values of scrap and steel. Due to lack of data for the years prior to 2000, it is assumed (based on the average implied emissions factor since 2000) that 1 t of steel produced is associated with 0.1 t of CO2. Emissions of CO2 from iron and steel production now range from 11 kt to 21 kt compared with 24 kt to 70 kt previously.

Consumption of halocarbons and SF6

There were inconsistencies in the methods used to estimate SF6 emissions for the years 1998 and 1999 compared with the rest of the time-series in the 2002 inventory which resulted in the emissions approximately doubling for those years. This has been corrected by interpolating values for those years using the average SF6 values for the periods 1994-97 and 2000-03.

9.1.3. Solvents and other products

No recalculations made for this sector.

9.1.4 Agriculture sector

Animal statistics: for every year of inventory there is a recalculation for the previous year, as the provisional animal population is updated with the actual population.

Sheep numbers used for the calculations between 1993 and 1996 were corrected. In these years a category 'other' appeared on the Statistics New Zealand data. Expert opinion is that these animals were probably new born lambs that were on the farm when the census is completed. In the 2003 inventory, these animals were treated as lambs and added to the lamb total for the purposes of estimating CH4 and N2O emissions.

Enteric fermentation: the Tier 2 model used to estimate emissions from enteric fermentation was modified to update several factors and correct small errors in algorithms (refer to section 6.2.5).

Manure management: there were substantial recalculations for this source in the 2003 inventory. The main change was the redistribution of waste between AWMS for dairy cows, from 11% of dairy excreta in anaerobic lagoons and 89% on pasture in previous inventories, to 5% in lagoons and 95% on pasture in the 2003 inventory (see section 6.3.5).

The CH4 emissions factor for goats was changed from 0.12 kg CH4/head/yr (the IPCC value for a cool climate) to 0.18 kg CH4/head/yr (the IPCC value for a temperate climate) to make the allocation of goats consistent with other livestock using IPCC default values.

Agricultural soils: emissions from the agricultural soils category were recalculated due to a number of changes (further details can be found in section 6.5.5):

  • reallocation of dairy excreta between lagoons and pasture
  • changes in the Nex values
  • correction of sheep numbers from 1993 to 1996
  • recalculation of fertiliser sales figures from updated information
  • correction of an error in inputs from crop residue
  • N2O from horse excreta included for 2003 and back-calculated for all years.

Nitrogenous fertiliser usage: the nitrogenous fertiliser statistics for 2002 were revised due to a re-examination of sales figures. This affected the 2001 and 2002 inventory. No other years were affected.

9.1.5 LULUCF

In previous inventories, New Zealand has only included information on net changes in the living biomass from the LULUCF category 'forest land remaining forest land (planted forest)' and emissions and removals from the planting of forest on grassland. In the 2003 inventory, New Zealand has improved the completeness of the LULUCF sector reporting by including a Tier 1 estimate for all LULUCF land-use categories from 1997 to 2003. This has reduced the estimates of LULUCF for the years 1997-2002. As a result of using the LULUCF categories, land previously reported by New Zealand as non-forest scrubland is classified as grassland as per GPG-LULUCF definitions.

Removals in planted forest for all years (1990-2002) are also recalculated as a result of backcasting and recalculation of the planted estate from the current forest model. New proportions of area by NEFD regime are used to weight the carbon yield for planted forests.

9.1.6 Waste

There have been changes to the methodology for the solid waste disposal category. The publishing of the 2002 Landfill Review and Audit and the 2003 SWAP baseline results allowed the total solid waste sent to landfill to be recalculated and re-analysis of the composition of the waste stream from 1995-2003 (see section 8.2.5 for further details).

9.2 Implications for emission levels

The overall effect of all recalculations is shown in Figure 9.3.1. There is a 2.3% reduction in emissions for the 2002 year primarily because of the correction of liquid fuel data in the energy sector.

9.3 Implications for emission trends

In New Zealand's 2002 inventory, emissions were 21.6% over the level reported in 1990. In the 2003 inventory, New Zealand's total emissions for 2003 are 22.5% over the level in 1990. As a result of the recalculations, total emissions for 2002 decreased and emissions for 2002 were recalculated as being 19.0% over 1990 (Figure 9.3.1). Changes in trends for individual sectors are discussed in the following sections. Solvents are not included because of the very low level of emissions throughout the time-series.

Figure 9.3.1 The effect of recalculation on total emissions

Year Inventory submitted in 2004 (Gg CO2 equivalent) Inventory submitted in 2005 (Gg CO2 equivalent)
1990 61,639.97 61,525.43
1991 62,210.35 62,033.02
1992 63,710.13 63,552.73
1993 63,710.92 63,457.24
1994 64,076.91 63,768.75
1995 64,783.47 64,277.82
1996 66,205.66 65,665.38
1997 67,977.83 67,876.39
1998 67,126.57 66,732.62
1999 69,111.24 68,535.28
2000 70,419.32 69,695.65
2001 73,681.07 72,623.27
2002 74,976.34 73,233.20
2003   75,345.29

Energy sector

Several recalculations affecting most categories in the energy sector (as explained in section 9.1.1) have occurred in this inventory. Figure 9.3.2 shows that apart from the correction of fuel data in 2002, the overall effect of the recalculations was small.

Figure 9.3.2 The effect of recalculation on the energy sector

Year Inventory submitted in 2004 (Gg CO2 equivalent) Inventory submitted in 2005 (Gg CO2 equivalent)
1990 23,746.84 23,594.11
1991 24,077.09 23,873.37
1992 25,747.77 25,632.75
1993 25,016.36 24,897.86
1994 25,220.78 25,134.51
1995 25,259.53 25,072.53
1996 26,362.69 26,118.62
1997 28,375.86 28,511.48
1998 27,037.86 27,045.43
1999 28,690.26 28,379.88
2000 29,196.46 28,905.79
2001 31,280.43 30,828.75
2002 32,047.22 30,864.67
2003   32,320.92

Industrial processes

There were a number of recalculations within the industrial processes sector in this inventory (explained in section 9.1.2) with the biggest effect being the inclusion for the first time of ammonia/urea emissions (Figure 9.3.3).

Figure 9.3.3 The effect of recalculation on the industrial processes sector

Year Inventory submitted in 2004 (Gg CO2 equivalent) Inventory submitted in 2005 (Gg CO2 equivalent)
1990 2,934.09 3,211.70
1991 3,196.29 3,487.37
1992 3,320.98 3,576.65
1993 3,341.76 3,617.58
1994 2,918.95 3,209.68
1995 3,019.24 3,325.21
1996 3,186.37 3,486.07
1997 2,980.85 3,268.11
1998 3,203.01 3,479.85
1999 3,252.55 3,560.62
2000 3,203.31 3,511.70
2001 3,351.91 3,673.27
2002 3,535.12 3,824.38
2003   4,014.19

Agriculture

There are a number of recalculations within the agriculture sector in this inventory (explained in section 9.1.4). The combined effect of these emissions has had only a small effect on the total emissions from the agriculture sector.

Figure 9.3.4 The effect of recalculation on the agriculture sector

 

Year Inventory submitted in 2004 (Gg CO2 equivalent) Inventory submitted in 2005 (Gg CO2 equivalent)
1990 31,911.15 32,193.76
1991 31,852.83 32,119.70
1992 31,881.31 32,140.22
1993 32,552.45 32,739.36
1994 33,203.29 33,316.76
1995 33,760.83 33,770.26
1996 33,922.78 33,993.67
1997 34,048.48 34,223.33
1998 34,330.23 34,341.70
1999 34,631.90 34,757.85
2000 35,550.95 35,509.21
2001 36,553.55 36,349.64
2002 36,856.64 36,762.40
2003   37,203.24

LULUCF

The recalculations within the LULUCF sector (explained in section 9.1.5) in this inventory has resulted in a small decrease in net removals (Figure 9.3.5). The decrease is more pronounced for the years 1997-2003 because the emissions from all LULUCF categories are included, whereas the information was not available for 1990-1996.

Figure 9.3.5 The effect of recalculation on LULUCF net removals

 

Year Inventory submitted in 2004 (Gg CO2 equivalent) Inventory submitted in 2005 (Gg CO2 equivalent)
1990 21,665.87 21,366.19
1991 20,339.59 20,096.63
1992 17,882.65 17,659.17
1993 15,548.31 15,236.12
1994 14,585.20 14,154.42
1995 15,053.53 14,645.86
1996 15,324.37 14,917.93
1997 16,994.29 16,451.70
1998 20,058.26 19,298.36
1999 21,863.67 21,106.78
2000 23,541.39 22,818.93
2001 23,875.33 23,186.69
2002 24,076.44 23,326.73
2003   22,861.60

Waste

The emissions for 1990-2002 from solid waste disposal sites based on changed total solid waste are recalculated back to 1995 and recalculations as a result of the reclassification of the waste stream were performed back to 1990. These resulted in a lower Lo(x) value compared with previous inventories and a 15% reduction in the 1990 baseline as shown in Figure 9.3.6.

Figure 9.3.6 The effect of recalculations on the waste sector

 

Year Inventory submitted in 2004 (Gg CO2 equivalent) Inventory submitted in 2005 (Gg CO2 equivalent)
1990 2,908.46 2,480.06
1991 2,951.30 2,505.89
1992 2,614.83 2,155.56
1993 2,625.96 2,153.04
1994 2,542.59 2,057.07
1995 2,557.03 2,058.70
1996 2,528.26 2,014.18
1997 2,352.49 1,819.72
1998 2,366.72 1,812.95
1999 2,363.36 1,784.60
2000 2,319.89 1,717.40
2001 2,348.82 1,719.87
2002 2,394.18 1,729.32
2003   1,754.48

9.4 Recalculations in response to the review process and planned improvements

9.4.1 Response to the review process

The UNFCCC secretariat conducted a centralised review of New Zealand's inventory (UNFCCC, 2005). Table 9.2 provides an overview of the actions taken to improve the NIR and inventory in response to the comments made by the expert review team (ERT).

A few tasks have not been finished in time to be incorporated into this inventory submission but are included in the New Zealand improvement plan to be actioned during 2005 (with the aim of being included in the next submission in 2006).

Table 9.4 Details of improvements to the NIR and inventory in response to the UNFCCC 2004 review

ERT comment Action taken

Improve transparency of methodological descriptions of country-specific methods & EFs (esp. agricultural sector).

There are continuous improvements in transparency. The NIR has increased in size by 18% since last year's inventory.

Include complete set of EFs used in energy sector.

Included in Annex 2 of the NIR.

Include national energy balance in future NIRs to improve transparency.

Recommendation noted with a view to incorporating this in a future submission.

Indicate whether information on international bunker fuels obtained from MED and Statistics NZ is in accordance with IPCC GPG.

More information will be included in the next submission.

Variability in CO2 IEFs for gaseous fuels.

Additional information has been added to the NIR.

Implement Tier 2 methodology to estimate CO2 emissions from road transportation.

A Tier 2 model was implemented and some results included in the 2005 NIR.

Review method of estimating CO2 emissions from cement production.

Additional explanation was added to the NIR.

More information on iron and steel methodology for CO2 emissions.

Additional explanation was included in the NIR.

Estimate and report potential emissions for halocarbons & SF6.

Potential emissions included in the CRF.

Report ammonia production under industrial processes rather than energy sector.

Ammonia/urea production included in the industrial processes sector in NIR.

Soda ash production/use should be estimated and reported.

New Zealand will endeavour to get an estimate during 2005 to be included in the 2006 submission.

Various comments on explanations of country specific EFs and methodologies in the agricultural sector.

Additional explanations have been included in the NIR.

Use default values to give estimate for C fluxes in subcategories previously reported as NE.

A Tier 1 value was calculated for all LULUCF categories (where GPG provided a Tier 1 method) for the years 1997-2003. A lack of any data prevented completing the time-series 1990-1996.

Various comments on the waste sector to improve completeness and update MSW generation waste data.

Total SWD values were updated and a recalculation of the time-series was included in the 2005 NIR. Investigations to get estimates on sub-categories not currently reported are being undertaken and results reported in future submissions.

9.4.3 Planned improvements

Improvements to methodology/emission factors are discussed under each sector and/or category as appropriate. New Zealand will undertake additional Tier 2 checks of key categories as resources permit.

New Zealand is aware of the requirement under Article 5.1 of the Kyoto Protocol to have in place a national system for its greenhouse gas inventory. Although New Zealand is yet to formally describe the national system, many of the arrangements detailed in the guidelines for national systems are described in this NIR e.g. designation of the national identity and assignment of responsibilities for inventory preparation, and the development of remaining requirements in progress.

The MfE anticipates adding additional human resources to ensure sufficient capacity for timely performance for estimating anthropogenic greenhouse gas emissions by sources and removals by sinks (FCCC/CP/2001/13/Add.3). The MfE will also investigate application or development of an inventory information system to improve inventory generation processes.

9.5 Summary of recent improvements to the inventory

9.5.1 Improvements in the 2003 inventory

The overall focus of the 2003 inventory was an improvement in the accuracy of the inventory. This is shown in the number of recalculations that were applied across all sectors. The major improvements to the 2003 inventory include:

  • Separating sectoral coal consumption into three key ranks of coal and using specific emission factors for each.
  • Reporting emissions from a Tier 2 approach for mobile combustion from road transport. This was developed from a vehicle fleet model at the Ministry of Transport.
  • Continuing development of the QA/QC system and extension of Tier 1 QC checks to include a selection of non key sources and a Tier 2 QC check on the solid waste disposal key source category (refer to Annex 6).
  • Reporting CH4 emissions from methanol production for the entire time-series due to activity data becoming available prior to 1997.
  • Increasing explanatory text in the NIR to help understanding of the methodologies and address questions raised by UNFCCC expert review teams, especially in the energy, industrial processes and agricultural sectors.
  • Revising the allocation of dairy excreta between lagoons and pasture.
  • Including N2O emissions from horse excreta.
  • Adding emissions and removals for all LULUCF categories where activity data were available.
  • Using the UNFCCC CRF Reporter tool to improve the quality of data entered into the CRF.

9.5.2 Improvements in the 2002 inventory

In the 2004 submission for the 2002 inventory, the focus was to provide a complete series of common reporting format tables for the period 1990-2002. Other improvements included:

  • The development of a preliminary QA/QC plan and the trial of Tier 1 QC checksheets.
  • The trial of a Tier 3 questionnaire to calculate emissions of SF6 from electrical equipment.
  • Reporting N2O use in anaesthesia for the solvent sector.
  • Reporting CH4 from methanol production back to 1997.
  • Increasing explanatory text in the NIR to help understanding of the methodologies and address questions raised by the UNFCCC expert review teams, especially in the energy and industrial processes sectors.

9.5.3 Improvements in the 2001 inventory

In the 2003 submission, the methodology used to estimate CH4 emissions from ruminants was upgraded from Tier 1 to a Tier 2 approach consistent with good practice.

As part of the on-going improvement to estimates of N2O from agricultural sources, a complete recalculation of the time-series was carried out using revised emission factors from IPCC (2000), some revised country specific emission factors and new annual nitrogen excretion rates for the most significant animal classes.

9.5.4 Improvements in the 2000 inventory and prior inventories

In the 2002 submission for the year 2000,emissions from solid waste disposal were upgraded to Tier 2 and emissions from small sources previously unreported (lime and dolomite) were included.

In the 2001 submission for the year 1999, estimates of emissions of the fluorinated gases (HFCs, PFCs and SF6) gases were upgraded to IPCC (2000) Tier 2 methodology.