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Chapter 10: Recalculations and improvements
This chapter summarises the recalculations and improvements made to the New Zealand GHG inventory since the submission of the 2003 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 emissions 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.
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 2004 inventory uses an average of the 2003, 2004 and 2005 years numbers. The 2003 and 2004 years are actual data, but only provisional data is available for the 2005 year. In the 2005 inventory, the provisional 2005 figures will be replaced by actual figures and the 1990-2004 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.
10.1 Explanations and justifications for recalculations
10.1.1 Energy sector
No major recalculations have occurred between the 2003 and 2004 inventories. The Ministry of Economic Development advises the small differences that have occurred in the various categories are due to some minor rounding errors and updates to data in their energy greenhouse gas emissions report (MED, 2005).
10.1.2 Industrial processes sector
Mineral products
The inclusion of CO2 from soda ash has been included for the first time in the 2004 inventory. Estimates have been included for all years from 1990 and this category has been recalculated for the entire time-series.
Chemical industry
Methane emissions from urea production have been removed from the industrial processes sector as industry experts consider all methane emissions from this process to be attributed to fuel combustion (CRL Energy Ltd, 2006). This has resulted in a slight reduction (1.5 Gg CO2 equivalent) in methane emissions for the "chemical industry" category.
The 2004 inventory has reallocated CO2 emissions from urea production from a previous country-specific "urea" category to the "ammonia" source category as recommended by the international review team in the 2005 review report (UNFCCC, 2006).
Consumption of halocarbons and SF6
The 2005 survey for industrial processes was redesigned to capture more importers of HFCs and PFCs and to better identify the refrigerants associated with imported and exported factory charged refrigeration and air conditioning units. This has resulted in increased HFC and PFC emissions compared with the 2003 inventory.
10.1.3 Solvents and other products
No recalculations were made for this sector.
10.1.4 Agriculture sector
Animal statistics
Every year of inventory there is a recalculation for the previous year as the provisional animal population is updated with the actual population.
Manure management
The methodology for this source was upgraded to a Tier 2 approach. Emissions were recalculated for the entire time-series (further details can be found in section 6.3.5).
Agricultural soils
The EF1 emission factor has been upgraded to a country-specific emission factor of 1 percent. This has resulted in a reduction in N2O emissions from agricultural soils for the entire time-series (a 3.4 percent reduction for this category when compared to the 2003 inventory).
10.1.5 LULUCF
The carbon yield tables have been updated to better reflect the diversity represented in the National Exotic Forest Description (NEFD) data. Regimes were modelled based on averages from permanent soil plot data, rather than as notional NEFD regimes. This had the effect of smoothing fluctuations during the period of silvicultural activity and also a minor effect on predicted root/shoot biomass ratios. In addition, dead fine roots were removed from the yield table to avoid double counting with soil carbon estimates. Further explanation on these recalculations can be found in section 7.2.5.
10.1.6 Waste
Methane emissions from solid waste disposal have been recalculated for the entire time-series. This was due to a survey completed in 2005 which showed methane recovery rates were not as high as initially calculated in the early to mid 1990s.
10.2 Implications for emission levels
The overall effect of all recalculations is shown in Figure 9.3.1. There is a 0.2 percent increase in emissions for the 2003 year and a 0.02 percent reduction in emissions for the base year, 1990.
10.3 Implications for emission trends
In New Zealand's 2003 inventory, emissions were 22.5 percent over the level reported in 1990. In the 2004 inventory, New Zealand's total emissions for 2004 are 21.2 percent over the level in 1990. As a result of the recalculations, total emissions for 2003 increased and emissions for 2003 were recalculated as being 22.7 percent 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.
Energy sector
The Ministry of Economic Development advises the small differences that have occurred in the various categories are due to some minor rounding errors and updates to data in their energy greenhouse gas emissions report (MED, 2005).
Industrial processes
The largest recalculation for industrial processes was from the updated data on HFC and PFC use from the 2005 industrial processes survey (CRL Energy Ltd, 2006a). This resulted in an increase in emissions for the "consumption of halocarbons and SF6" category of 324.67 Gg CO2 equivalent in 2003. This increased total greenhouse gas emissions by 0.4 percent for 2003. This data represents an upper limit for HFC/PFC emissions from commercial refrigeration and air conditioning but is the most accurate and complete data currently available.
Agriculture
There are two prominent recalculations in the agriculture sector for the 2004 inventory. The first is the upgrade of manure management methodology from a Tier 1 to a Tier 2 approach. This resulted in an increase in emissions for the "manure management" category of 182.24 Gg CO2 equivalent in 2003. This increased greenhouse gas emissions by 0.2 percent for 2003. The second recalculation resulted from a change in the EF1 emission factor. This reduced emissions in the "agricultural soils" category by 439.23 Gg CO2 equivalent in 2003. This reduced total greenhouse gas emissions by 0.6 percent for 2003.
LULUCF
Recalculations within the LULUCF sector are explained in section 9.1.5. Differences between the carbon yield tables are not constant across age classes, so there is an interaction with forest areas (which are also not constant across age classes) which explains the differences in net removals in the LULUCF sector between the 2003 and 2004 inventories (Figure 9.3.5).
Waste
Methane emissions for 1990-2003 from solid waste were recalculated as a result of methane recovery data being updated due to commissioned work undertaken in 2005. This resulted in a slower recovery of methane than previously estimated as shown in Figure 9.2.6. The recalculation resulted in an increase of 174.64 Gg CO2 equivalent in 2003. This increased total greenhouse gas emissions by 0.2 percent for 2003.
10.4 Recalculations in response to the review process and planned improvements
10.4.1 Response to the review process
The UNFCCC secretariat facilitated a centralised review of New Zealand's 2003 inventory submission (UNFCCC, 2006).
A number of recommendations have not yet been addressed due to the very short amount of time between the review report being published (end of March 2006) and the submission of this inventory (15 April 2006). During 2006 the recommendations of the review team will be incorporated into New Zealand's improvement plan and addressed as time and resources allow.
10.4.2 Planned improvements
Improvements to methodology/emission factors are discussed under each sector as appropriate.
For this inventory submission (2006) the emphasis has been on ensuring completeness and transparency across all source categories in line with good practice. Priorities for inventory development are guided by analysis of key sources (level and trend) and uncertainty surrounding existing emissions estimates and recommendations received from previous international reviews of New Zealand's inventory. The inventory improvement plan and the quality control and assurance plan are updated regularly to reflect current and future development. New Zealand will endeavour to undertake Tier 2 quality checks of key categories as resources permit.
The Ministry for the Environment will work towards the development of an inventory database system during 2006 to improve the inventory generation process.
10.5 Summary of recent improvements to the inventory
10.5.1 Improvements to the 2004 inventory
The focus of the 2004 inventory was on completeness, ensuring all estimates were calculated in accordance with good practice and increased transparency. The inclusion of data using a Tier 1 analysis for all LULUCF categories from 1990 is a significant improvement from the 2003 inventory (where data from 1997 was provided).
The other major improvements to the 2004 inventory include:
- Upgrading the methodology for CH4 from manure management to a Tier 2 approach.
- Including estimates of CO2 emissions from soda ash use.
- Including a national energy balance for 2004.
- Changing the EF1 emission factor for nitrous oxide emissions from direct nitrogen application to a country-specific emission factor of 1 percent.
- Improving the coverage of data collection for halocarbons, especially HFCs from air conditioning units.
- Implementing a number of recommendations from the quality management review (see Annex 6). This has led to a more structured QA/QC plan and programme.
10.5.2 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 was available.
- Using the UNFCCC CRF reporter tool to improve the quality of data entered into the CRF.
10.5.3 Improvements in the 2002 inventory
In the 2004 submission for the 2002 inventory, the focus was 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 sector.
10.5.4 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 ongoing 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.
10.5.5 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.
