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Chapter 10: Recalculations and improvements

This chapter summarises the recalculations and improvements made to the New Zealand greenhouse gas inventory following submission of the 1990-2005 inventory. The chapter summarises material that has already been described in Chapters 3–8.

Each year the inventory is updated (existing activity data and/or emissions factors may be improved) 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 revised 1996 IPCC guidelines (IPCC, 1996) and good practice guidance (IPCC, 2000 and 2003). Recalculations may also occur if 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 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 in a given year may differ from emissions reported in the previous inventory.

10.1 Explanations and justifications for recalculations

10.1.1 Energy sector

In previous inventory submissions, constant calorific values were used to convert tonnes (t) of fuel to peta joules (PJ) of fuel. For the 2008 inventory submission year-specific calorific values have been introduced for all fuel types to improve the accuracy of the activity data between 1990 and 2006. Recalculations for the entire energy sector have resulted in a decrease of 78.4 Gg CO2-e in 1990 and an increase of 100.3 Gg CO2-e in 2005.

10.1.2 Industrial processes sector

Mineral products

Activity data and the CO2 emissions attributed to cement production have been updated and recalculated for the years 1995–1998. The revision has been due to the inclusion of data from a small cement company operating in New Zealand who produced clinker from 1995–1998. This data had not been included in previous submissions.

Emissions arising from limestone, coke and electrodes used in the iron and steel making process have been reported separately from the rest of the process CO2 emissions for the first time in the 2008 inventory submission. Data provided by the iron and steel companies cannot be broken down any further (ie, limestone emissions on their own). Emissions from limestone/coke/ electrode use make up 1 to 2 per cent of total process iron and steel emissions. This has resulted in recalculations for the 1990–2005 time series for the mineral products (limestone and dolomite use) category.

Recalculations for the “mineral products” category resulted in an increase of 17.1 Gg CO2-e in 1990 and 44.0 Gg CO2-e in 2005.

Chemical industry

There was a minor recalculation for ammonia production for 2003 due to rounding. No other recalculations took place in the “chemical” industry category in the 2008 inventory submission.

Metal production

New Zealand has been able to separate emissions arising from limestone, coke and electrodes used in the iron and steel making process from the rest of the process CO2 emissions for the first time in the 2008 inventory submission. This has resulted in recalculations for the 1990–2005 time series for the metal production (iron and steel production) category.

Activity data and resulting CO2 and PFC emissions from aluminium production was updated for the 1990–2006 time series. Rio Tinto Aluminium provided a new time series of data to reflect CO2 and PFC emissions calculated using the methodologies outlined in the Aluminium Sector Addendum to the WBCSD/WRI Greenhouse Gas Protocol. The addendum was released in October 2006 by the IPCC and International Aluminium Institute (IAI).

Recalculations have resulted in a decrease of 31.8 Gg CO2-e in 1990 and a decrease of 29.3 Gg CO2-e in 2005.

Consumption of halocarbons, PFCs and SF6

As a result of a thorough survey of the HFC and PFC importers and distributors in 2007 (CRL Energy Limited, 2007) estimates of gas stocks and emissions over the time series have been revised. The main changes have occurred within the stationary refrigeration and mobile air conditioning sub-sectors. Further explanations can be found in section 4.7.5. The recalculations have resulted in an increase of 0.4 Gg CO2-e in 1992 (the first year HFCs were used in New Zealand) and a decrease of 79.4 Gg CO2-e in 2005.

10.1.3 Solvents and other products

The 2007 industrial processes survey (CRL Energy Limited, 2007) revealed some inconsistencies in the activity data for N2O use in New Zealand for the period 2002–2005. The activity data for the period was updated by linear interpolation. The recalculations have resulted in a decrease of 4.0 Gg CO2-e in 2005.

10.1.4 Agriculture sector

For the 2008 inventory submission all agricultural activity data is reported using single year values rather than 3-year averaged values. This change was introduced in the agriculture and LULUCF sectors to allow more time for inventory quality checking prior to submission. The recalculations have resulted in an increase of 1.8 Gg CO2-e in 1990 and an increase of 133.9 Gg CO2-e in 2005.

10.1.5 LULUCF

For the 2008 inventory submission all LULUCF activity data is also reported using single year values rather than 3-year averaged values. Other recalculations made in the LULUCF sector were mainly to the forest land category. The recalculations were made to reflect:

  • The new age class distribution and hence the new carbon yield table.

  • Updated harvesting and new planting data.

  • Use of single year values instead of three-year averages.

  • New assumptions for clearance of grassland with aboveground woody biomass and biomass burning.

There were also minor recalculations made in the grasslands category due to revised activity data.

The recalculations have increased removals by 1,527.1 Gg CO2-e in 1990 and decreased removals by 818.9 Gg CO2-e in 2005.

10.1.6 Waste

Solid Waste

Municipal solid waste composition values for the years from 2003 to 2005 were updated to reflect the revision of sampling errors outlined in the Waste Composition and Construction Data Report (Waste Not Consulting, 2006).

The waste generation rate per capita decreased for 2005 due to extrapolating from recent national data that was published in the 2006/07 National Landfill Census (Ministry for the Environment, 2007).

The waste generation rate per capita increased for 1996, 2000 and 2004 due to changes in the formula used to adjust for calendar leap years. A similar adjustment decreased the DOC modelled as in landfills prior to 1990, thereby decreasing 1990 gross emissions onwards.

Recalculations resulted in a decrease of 1.4 Gg CO2-e in 1990 and an increase of 60.1 Gg CO2-e in 2005.

Waste Water

The inventory of emissions from domestic and commercial waste water treatment has been updated following the development of a national treatment facility database in 2006. New total organic product data for 2006 was used to recalculate CH4 emissions from 2002 to 2005.

Improvements to the accuracy of calculations for emissions of CH4 from industrial waste water treatment resulted in recalculations for emissions estimates for all years from 1990.

The recalculations resulted in a decrease of 0.2 Gg CO2-e in 1990 and a decrease of 10.7 Gg CO2-e in 2005.

Incinerated Waste

New Zealand has included emissions from incinerated waste for the first time in the 2008 inventory submission. The inclusion of emissions from incinerated waste has increased total emissions in 1990 by 14.5 Gg CO2-e and 6.0 Gg CO2-e in 2006.

10.2 Implications for emission levels

The overall effect of all recalculations in the 2008 inventory submission is shown in Figure 10.3.1. There is a 0.1 per cent (47.7 Gg CO2-e) increase in emissions for the base year, 1990 and a 0.3 per cent (194.6 Gg CO2-e) increase in emissions for the 2005 year.

10.3 Implications for emission trends

In New Zealand’s 2007 inventory submission (1990-2005), emissions were 24.7 per cent above the level reported in 1990. As a result of the recalculations in the 2008 inventory submission, total emissions for 2005 were 24.9 per cent above 1990. Changes in trends for individual sectors (excluding solvents) are discussed in the following sections. Solvents are not included because emissions are insignificant throughout the time-series.

Figure 10.3.1 Effect of recalculation on total greenhouse gas emissions

Year

2005 inventory (submitted in 2007)
(Gg CO2-equivalent)

2006 inventory (submitted in 2008)
(Gg CO2-equivalent)

1990

61,996.0

61,947.9

1991

62,295.4

62,433.1

1992

64,145.0

63,591.0

1993

63,774.4

62,984.6

1994

64,256.1

64,179.8

1995

64,681.4

64,461.1

1996

66,411.0

66,016.0

1997

68,585.4

68,789.0

1998

67,614.6

66,915.9

1999

69,260.7

68,782.3

2000

70,421.3

70,711.7

2001

73,168.3

73,082.3

2002

73,716.4

73,435.2

2003

75,700.2

75,983.8

2004

75,171.0

74,941.5

2005

77,159.1

77,353.7

Energy sector

The recalculations made within the energy sector (Figure 10.3.2) are explained in section 10.1.1. Emissions in 1990 have decreased 78.4 Gg CO2-e and increased by 100.3 Gg CO2-e in 2005 (Figure 10.3.2). The recalculations have resulted in a reduction in total emissions in 1990 of 0.1 per cent and an increase of 0.2 per cent in 2005.

Figure 10.3.2 Effect of recalculation on the energy sector

Year

2005 inventory (submitted in 2007)
Gg CO2-equivalent)

2006 inventory (submitted in 2008)
(Gg CO2-equivalent)

1990

23,655.1

23,499.1

1991

23,932.2

23,775.2

1992

25,694.5

25,502.5

1993

24,965.3

24,805.5

1994

25,213.3

25,064.6

1995

25,118.1

24,998.5

1996

26,169.5

26,044.9

1997

28,501.8

28,399.5

1998

27,098.2

27,012.3

1999

28,446.2

28,251.1

2000

28,946.2

28,934.8

2001

30,891.9

30,806.5

2002

30,887.1

30,887.9

2003

32,306.1

32,491.8

2004

31,647.9

31,704.9

2005

33,481.7

33,582.0

Industrial processes

The recalculations made within the industrial processes sector (Figure 10.3.3) are explained in section 10.1.2. Emissions in 1990 have increased 111.4 Gg CO2-e and decreased 91.0 Gg CO2-e in 2005. The recalculations have resulted in an increase in total emissions in 1990 of 0.2 per cent and a decrease of 0.1 per cent in 2005.

Figure 10.3.3 Effect of recalculation on the industrial processes sector

Year

2005 inventory (submitted in 2007)
(Gg CO2-equivalent)

2006 inventory (submitted in 2008)
(Gg CO2-equivalent)

1990

3,214.6

3,402.7

1991

3,490.5

3,553.9

1992

3,579.8

3,622.1

1993

3,620.1

3,297.6

1994

3,246.5

3,242.7

1995

3,390.5

3,386.7

1996

3,576.5

3,554.0

1997

3,297.9

3,298.8

1998

3,600.0

3,512.8

1999

3,655.2

3,666.1

2000

3,588.3

3,643.3

2001

3,862.6

3,767.5

2002

4,065.4

3,975.5

2003

4,354.7

4,280.1

2004

4,202.5

4,042.4

2005

4,385.1

4,245.7

Agriculture

Calculating emissions using single year activity data instead of 3-year averages for the agriculture sector resulted in the recalculation of the whole time series (Figure 10.3.4).

Emissions in 1990 have increased 1.8 Gg CO2-e and 133.9 Gg CO2-e in 2005. The recalculations have not resulted in a change in total emissions in 1990 but have increased total emissions by 0.2 per cent in 2005.

Figure 10.3.4 Effect of recalculation on the agriculture sector

Year

2005 inventory (submitted in 2007)
(Gg CO2-equivalent)

2006 inventory (submitted in 2008)
(Gg CO2-equivalent)

1990

32,498.9

32,498.9

1991

32,222.4

32,529.2

1992

32,245.0

31,931.0

1993

32,517.4

32,331.1

1994

33,129.9

33,346.3

1995

33,707.1

33,745.3

1996

34,172.0

34,074.5

1997

34,296.6

34,760.0

1998

34,521.3

34,116.0

1999

34,912.8

34,714.3

2000

35,652.4

35,959.1

2001

36,237.1

36,380.4

2002

36,650.6

36,477.8

2003

36,968.0

37,136.2

2004

37,349.6

37,186.1

2005

37,445.3

37,579.1

LULUCF

Calculating emissions using single year activity data instead of 3-year averages for the LULUCF sector resulted in the recalculation of the whole time series (Figure 10.3.5). There were significant recalculations made to the forest land category as explained in section 10.1.5. The forest land category recalculations have resulted in an increase in net removals from 1990 to 1998. In 1990 removals increased by 1,416.2 Gg CO2-e. From 1999 until 2005 recalculated net removals decreased. In 2005, net removals are 818.9 Gg CO2-e lower than they were in the 2007 inventory submission. The recalculations for the LULUCF sector have resulted in a decrease in total emissions of 3.7 per cent in 1990 and an increase in total emissions of 1.5 per cent in 2005.

Figure 10.3.5 Effect of recalculation on LULUCF net removals

Year

2005 inventory (submitted in 2007)
(Gg CO2 equivalent)

2006 inventory (submitted in 2008)
(Gg CO2 equivalent)

1990

18,977.9

20,507.7

1991

17,550.4

18,648.5

1992

15,794.6

16,646.9

1993

14,619.4

16,957.1

1994

14,227.2

16,479.6

1995

15,084.3

15,924.9

1996

15,396.9

16,647.5

1997

17,059.5

17,719.5

1998

19,308.8

19,675.9

1999

19,924.5

19,557.8

2000

20,215.7

19,974.3

2001

20,513.4

20,092.1

2002

21,243.9

20,673.3

2003

22,742.2

20,619.6

2004

24,482.6

24,230.3

2005

24,500.8

23,681.9

Waste

The recalculations made within the waste sector (Figure 10.3.6) are explained in section 10.1.2. Emissions in 1990 have increased 12.9 Gg CO2-e and 9.0 Gg CO2-e in 2005. The recalculations have resulted in an increase in total emissions in 1990 of 0.02 per cent and an increase of 0.07 per cent in 2005.

Figure 10.3.6 Effect of recalculation on the waste sector

Year 2005 inventory (submitted in 2007) (Gg CO2-equivalent) 2006 inventory (submitted in 2008)
(Gg CO2-equivalent)
1990 2,482.8 2,505.7
1991 2,512.4 2,532.0
1992 2,475.2 2,492.4
1993 2,492.2 2,506.7
1994 2,470.1 2,481.9
1995 2,274.1 2,285.7
1996 2,282.3 2,296.7
1997 2,263.8 2,284.6
1998 2,201.2 2,228.4
1999 2,068.1 2,104.0
2000 2,080.8 2,127.3
2001 2,025.5 2,080.5
2002 1,966.3 2,037.8
2003 1,929.1 2,023.4
2004 1,840.0 1,959.8
2005 1,847.1 1,902.5

10.4 Recalculations in response to the review process and planned improvements

10.4.1 Response to the review process

The UNFCCC secretariat facilitated an in-country review of New Zealand’s national system and Kyoto Protocol base year inventory as part of the Kyoto Protocol initial review process. This review took place in Wellington from 19–24 February 2007.

The final review report was published on the Climate Change Convention website in August 2007 (UNFCCC, 2007). The review report recommends New Zealand intensify the time and resources directed at implementing the QA/QC plan with the aim of reducing the number of minor errors and inconsistencies. New Zealand has responded to the recommendation by changing the inventory compilation schedule to allow more time for quality checking. For the 2008 inventory submission all sector level data was entered into the CRF Reporter by January 2008. The earlier deadline allowed two months for more quality checking at the sector level (between data spreadsheets and the CRF tables) and checking consistency between the CRF tables and the NIR. A consequence of the earlier deadline is activity data has changed from 3 year averages to single year values for the agriculture and LULUCF sectors.

KPMG were contracted for 3 months to complete quality checks on key category data and to develop data quality objectives to further advance the implementation of New Zealand’s QA/QC plan. KPMG checked the calculations and assumptions used in the key spreadsheets and models were consistently applied, that the data from the spreadsheets and models were accurately transferred to the CRF Reporter and data from the CRF tables was accurately represented in the draft NIR. Automatic checks using an excel tool highlighted any unique formulae and hard coded data. KPMG did not identify any significant errors within the source data spreadsheets or between the spreadsheets and the CRF Reporter and the NIR.

KMPG developed a risk register to highlight potential risks in the inventory data compilation process. The Ministry for the Environment intends to use the risk register on a regular basis to prioritise further improvements to the New Zealand inventory.

10.4.2 Planned improvements

Priorities for inventory development are guided by the analysis of key categories (level and trend), uncertainty surrounding existing emission and removal estimates and recommendations received from previous international reviews of New Zealand’s inventory. The inventory improvement plan and the quality control and quality assurance plan are updated annually to reflect current and future inventory development. As discussed in 10.4.1 the development of a risk register will also help New Zealand prioritise improvements to the inventory.

Planned improvements to methodologies and emission factors are discussed under each sector as appropriate.

10.5 Summary of recent improvements to the inventory

New Zealand’s QA/QC and improvement plans ensure continuous improvement of the inventory. Tables 10.5.1 to 10.5.3 show the improvements made to the inventory from the 2001 to 2008 inventory submissions.

Table 10.5.1 Improvements made to New Zealand’s 2001 to 2004 inventory submissions

Area of improvement

Inventory submission year
2001 2002 2003 2004

National System

     

Complete CRF tables

Explanatory text increased

Sector Energy       Explanatory text increased
Industrial Processes HFCs, PFCs and SF6 upgraded to Tier 2 method Lime & Dolomite included   Upgraded Tier 3 methodology for SF6 electrical equipment CH4 from methanol production reported back to 1997 Explanatory text increased
Solvents       Anaesthesia use of N2O included
Agriculture     CH4 ruminant emissions upgraded to Tier 2 N2O EF & excretion rates revised    

LULUCF

         
Waste   Solid Waste upgraded to Tier 2      

QA/QC

     

Plan developed

Trial of Tier 1 quality check sheets

Table 10.5.2 Improvements made to New Zealand’s 2005 to 2007 inventory submissions

Area of improvement

Inventory submission year
2005 2006 2007

National system

Explanatory text increased

UNFCCC CRF reporter tool applied

 

 

Sector

Energy Coal emission factors revised Explanatory text increased Vehicle fleet model used to verify CO2 emissions Included national energy balance  
Industrial Processes CH4 from methanol production reported for entire time series Explanatory text increased Improving halocarbon data collection, especially HFC from air conditioning units Included soda ash CO2 emissions  
Solvents        
Agriculture Included horse excreta N2O emissions Explanatory text increased Reallocated dairy excreta between lagoons & pasture CH4 manure management upgraded to Tier 2 N2O emission factor (EF1) changed to be country specific Calculation spreadsheets improved by reducing the number of externally linked sheets.
LULUCF Added emissions & removals for all categories where AD available    
Waste        

QA/QC

Extension of Tier 1 QC checks to incl. number of non-key sources

Extension of Tier 1 QC checks to include a number of non-key source

 

Table 10.5.3 Improvements made to New Zealand’s inventory submission for 2008

Area of improvement Improvements made
National system Explanatory text increased

Sector

Energy Updated constant calorific values to year-specific values for all fuel types
Industrial Processes Cement activity data updated Separated limestone, coke & electrode emissions from iron & steel Updated activity data for aluminium time series Updated activity data on HFC and PFC consumption
Solvents 2002 - 2005 time series updated based upon updated activity data
Agriculture All data recalculated to single year values
LULUCF

All data recalculated to single year values.

Forestland removals updated based upon updated carbon yields; harvesting & new planting data; new assumptions for the clearance of grassland with aboveground woody biomass and biomass burning.

Waste Solid waste emissions updated 2003 - 2005 to correct sampling errors Domestic & commercial wastewater emissions were updated 2002-2005 based on new organic product data Industrial waste water time series updated Incinerated waste data included
QA/QC

Inventory compilation deadline moved to allow more time for CRF and NIR quality checking.

KPMG quality checked key category data for consistency between data spreadsheets, the CRF Reporter and the NIR.

Risk register established.