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Annex 2: Methodology and data collection for estimating emissions from fossil fuel combustion

New Zealand emission factors are based on GCV (gross calorific value). Energy activity data and emission factors in New Zealand are conventionally reported in gross terms, with some minor exceptions. The convention adopted by New Zealand to convert GCV to NCV (net calorific value) follows the Organisation for Economic Co-operation and Development (OECD) and International Energy Agency (IEA) assumptions:

  • NCV = 0.95 x GCV for coal and liquid fuels

  • NCV = 0.90 x GCV for gas.

Emission factors for gas, coal, biomass and liquid fuels used in New Zealand are shown in Tables A2.1–A2.3.

Table A2.1 CO2 emission factors used in the energy sector

  Emission factor
(t CO2/TJ)
Emission factor
(t C/TJ)

Gas

   

Maui

52.0 (2006)

14.2 (2006)

Treated

53.5 (2006)

14.6 (2006)

Kapuni LTS

84.1

22.9

Weighted average of Maui and Kapuni treated

52.3 (2006)

14.3 (2006)

Methanol – mixed feed (1990–1994)

62.4

17.0

Methanol – LTS (1990–1994)

84.0

22.9

Kaimiro

65.2

17.8

Ngatoro

53.1

14.5

Rimu

53.7

14.6

Waihapa/Ngaere + Tariki/Ahuroa (1990)*

56.2

15.3

Waihapa/Ngaere + Tariki/Ahuroa (2002)

54.2

14.8

McKee

54.3

14.8

Mangahewa

52.3

14.3

Turangi

55.6

15.2

Pohokura

55.1

15.0

Liquid fuels

   

Regular petrol (all petrol 1990–1995)

66.2

18.1

Petrol – premium (1996 and onwards)

67.0

18.3

Diesel

69.5

19.0

Aviation fuels

68.1

18.6

Av gas

65.0

17.7

Other

72.9

19.9

Fugitive – flared

65.1

17.8

LPG

60.4

16.5

Heavy fuel oil

73.5

20.0

Light fuel oil

72.0

19.6

Averaged fuel oil

73.0

19.9

Bitumen (asphalt)

76.1

20.8

Biomass

   

Biogas

101.0

27.5

Wood (industrial)

104.2

28.4

Wood (residential)

104.2

28.4

Coal

   

All sectors (sub bit)

91.2

24.9

All sectors (bit)

88.8

24.2

All sectors (lignite)

95.2

26.0

* For the years 1991–2001, the emissions factors for these gas streams are interpolated between the 1990 and 2002 values.

Table A2.2 CH4 emission factors used in the energy sector

  Emission factor
t CH4/PJ
Source

Natural gas

   

Electricity – boilers

2.745

IPCC Tier 2 (Table 1–15) average for natural gas boilers and large gas-fired turbines >3 MW

Commercial

1.08

IPCC Tier 2 (Table 1–19) natural gas boilers

Residential

0.9

IPCC Tier 2 (Table 1–18) gas heaters

Domestic transport (CNG)

567

IPCC Tier 2 (Table 1–43) passenger cars (uncontrolled)

Other stationary (mainly industrial)

1.26

IPCC Tier 2 (Table 1–16) small natural gas boilers

Liquid fuels

   

Stationary sources

   

Electricity – residual oil

0.855

IPCC Tier 2 (Table 1–15) residual oil boilers – normal firing

Electricity – distillate oil

0.855

IPCC Tier 2 (Table 1–15) distillate oil boilers – normal firing

Industrial (including refining) – residual oil

2.85

IPCC Tier 2 (Table 1–16) residual oil boilers

Industrial – distillate oil

0.19

IPCC Tier 2 (Table 1–16) distillate oil boilers

Industrial – LPG

1.045

IPCC Tier 2 (Table 1–18) propane/butane furnaces

Commercial – residual oil

1.33

IPCC Tier 2 (Table 1–19) residual oil boilers

Commercial – distillate oil

0.665

IPCC Tier 2 (Table 1–19) distillate oil boilers

Commercial – LPG

1.045

IPCC Tier 2 (Table 1–18) propane/butane furnaces

Residential – distillate oil

0.665

IPCC Tier 2 (Table 1–18) distillate oil furnaces

Residential – LPG

1.045

IPCC Tier 2 (Table 1–18) propane/butane furnaces

Agriculture – stationary

3.8

IPCC Tier 2 (Table 1–49) diesel engines (agriculture)

Mobile sources

   

LPG

28.5

IPCC Tier 2 (Table 1–44) passenger cars (uncontrolled)

Petrol – 1990 onwards

18.525

IPCC Tier 2 (Table 1–27) passenger cars (uncontrolled – mid-point of average g/MJ)

Diesel – 1990 onwards

3.8

IPCC Tier 2 (Table 1–32) passenger cars (uncontrolled – g/MJ)

Navigation (fuel oil and diesel)

6.65

IPCC Tier 2 (Table 1–48) ocean-going ships

Aviation fuel/kerosene

1.9

IPCC Tier 2 (Table 1–48) jet and turboprop aircraft

Coal

   

Combustion 

   

Electricity generation

0.665

IPCC Tier 2 (Table 1–15) pulverised bituminous combustion – dry bottom, wall fired

Cement

0.95

IPCC Tier 2 (Table 1–17) cement, lime coal kilns

Lime

0.95

IPCC Tier 2 (Table 1–17) cement, lime coal kilns

Industry

0.665

IPCC Tier 2 (Table 1–16) dry bottom, wall fired coal boilers

Commercial

9.5

IPCC Tier 2 (Table 1–19) coal boilers

Residential

285

IPCC Tier 1 (Table 1–7) coal – residential

Biomass 

   

Wood stoker boilers

14.25

IPCC Tier 2 (Table 1–16) wood stoker boilers

Wood – fireplaces

285

IPCC Tier 1 (Table 1–7) wood – residential

Biogas

1.08

IPCC Tier 2 (Table 1–19) gas boilers

Table A2.3 N2O emission factors used in the energy sector

  Emission factor
t N2O/PJ
Source

Natural gas

   

Electricity generation

0.09

IPCC Tier 1 (Table 1–8) natural gas – all uses

Commercial

2.07

IPCC Tier 2 (Table 1–19) natural gas boilers

Residential

0.09

IPCC Tier 1 (Table 1–8) natural gas – all uses

Domestic transport (CNG)

0.09

IPCC Tier 1 (Table 1–8) natural gas – all uses

Other stationary (mainly industrial)

0.09

IPCC Tier 1 (Table 1–8) natural gas – all uses

Liquid fuels

   

Stationary Sources

   

Electricity – residual oil

0.285

IPCC Tier 2 (Table 1–15) residual oil boilers – normal firing

Electricity – distillate oil

0.38

IPCC Tier 2 (Table 1–15) distillate oil boilers – normal firing

Industrial (including refining) – residual oil

0.285

IPCC Tier 2 (Table 1–16) residual oil boilers

Industrial – distillate oil

0.38

IPCC Tier 2 (Table 1–16) distillate oil boilers

Commercial – residual oil

0.285

IPCC Tier 2 (Table 1–19) residual oil boilers

Commercial – distillate oil

0.38

IPCC Tier 2 (Table 1–19) distillate oil boilers

Residential (all oil)

0.19

IPCC Tier 2 (Table 1–18) furnaces

LPG (all uses)

0.57

IPCC Tier 1 (Table 1–8) oil – all sources except aviation

Agriculture – stationary

28.5

IPCC Tier 2 (Table 1–49) diesel engines – agriculture

Mobile sources

   

LPG

0.57

IPCC Tier 1 (Table 1–8) oil – all sources except aviation

Petrol

1.425

IPCC Tier 2 (Table 2.7 in GPG (IPCC, 2000))

US gasoline vehicles (uncontrolled)

Diesel

3.705

IPCC Tier 2 (Table 2.7 in GPG (IPCC, 2000)) all US diesel vehicles

Fuel oil (ships)

1.9

IPCC Tier 2 (Table 1–48) ocean going ships

Aviation fuel/kerosene

1.9

IPCC Tier 1 (Table 1–8) oil – aviation

Coal

   

Electricity generation

1.52

IPCC Tier 2 (Table 1–15) pulverised bituminous combustion – dry bottom, wall fired

Cement

1.33

IPCC Tier 1 (Table 1–8) coal – all uses

Lime

1.33

IPCC Tier 1 (Table 1–8) coal – all uses

Industry

1.52

IPCC Tier 2 (Table 1–16) dry bottom, wall fired coal boilers

Commercial

1.33

IPCC Tier 1 (Table 1–8) coal – all uses

Residential

1.33

IPCC Tier 1 (Table 1–8) coal – all uses

Biomass 

   

Wood (all uses)

3.8

IPCC Tier 1 (Table 1–8) wood/wood waste – all uses

Biogas

2.07

IPCC Tier 2 (Table 1–19) natural gas boilers

A2.1 Emissions from liquid fuels

A2.1.1 Activity data and uncertainties

The Delivery of Petroleum Fuels by Industry Survey conducted by Statistics New Zealand is assumed to have a five per cent uncertainty associated with the sectoral energy allocation although the annual totals are likely to be more certain (Ministry of Economic Development, 2006).

Because the survey is run as a census there is no sampling error. The main sources of non-sample error are:

  • Respondent error: Statistics New Zealand makes every effort to confirm values supplied by respondents, and given assurances of accuracy. Statistics New Zealand is bound to accept them. If a discrepancy is discovered at a later date, revised values are supplied at the earliest possible opportunity.

  • Processing error: there is always the possibility of error, however, Statistics New Zealand has thorough checking procedures to ensure that the risk of processing errors is minimised.

A2.1.2 Emission factors and uncertainties

Carbon dioxide emission factors are described in Table A2.1. The CO2 emission factors for oil products are from the New Zealand Refining Company, import data from industry and from Baines (19935). The New Zealand Refining Company estimates the uncertainty in emission factors to be within five per cent (Ministry of Economic Development, 2006).

A2.2 Emissions from solid fuels

A2.2.1 Activity data and uncertainties

The New Zealand Coal Sales Survey conducted by Statistics New Zealand is an ongoing quarterly survey. The survey began in 1981. The survey is a full coverage of the sector and therefore there are no sampling errors. Non-sampling errors in the survey data may result from errors in the sample frame (eg, units with the wrong New Zealand Standard Industrial Classification), respondent error (eg, wrong values supplied) and errors made during processing survey results or non-response imputation. Statistics New Zealand adopts procedures to detect and minimise these potential errors.

The process of dividing coal use between different sectors will introduce uncertainty larger than the uncertainty in total coal sales. Uncertainty is also introduced from the assumption that coal used by sector is an average of the different ranks. These assumptions are thought to introduce an uncertainty of ± 5 per cent (Ministry of Economic Development, 2006).

The sectoral partitioning used for coal was examined in 2003 by officials from the Ministry for the Environment. There was concern in extrapolating sectoral allocations from 1995 to 2002 given some probable changes in sectoral coal usage. However, New Zealand coal industry experts did not consider a survey could be justified because of the difficulty and expense in collating and verifying data from a number of sectors. In addition, the major categories of coal exports, coal used by the residential sector and coal used for steel production and electricity generation are all known accurately and are not affected by the sectoral partitioning.

A2.2.2 Emission factors and uncertainties

The CO2 emission factors for coal are shown in Table A2.1. The non-CO2 emission factors are shown in Tables A2.2 and A2.3. The estimated uncertainty in coal emission factors is taken as ± 3 per cent (Ministry of Economic Development, 2006). An uncertainty of ± 2 per cent is used for the sub-bituminous coal used in public electricity generation. All New Zealand values are within 2 per cent of the revised 1996 IPCC default values (IPCC, 1996).

A2.3 Emissions from gaseous fuels

A2.3.1 Activity data and uncertainties

Vector Limited has contracts with large gas users that allow metering errors of ± 2 per cent. Whenever the error between the meter-reading and actual gas supplied exceeds 2 per cent, adjustments are made to the reported quantities of gas supplied. The uncertainty is therefore assumed to have an upper limit of ± 2 per cent (Ministry of Economic Development, 2006).

A2.3.2 Emission factors and uncertainties

As discussed in section 3.2.1.5, New Zealand now uses the Maui and Kapuni gas production data reported in the New Zealand Energy Data File (Ministry of Economic Development, 2007b) to support the calculation of a weighted average annual CO2 emission factor for natural gas. This average emission factor is applied to a number of categories in the energy sector, such as the “manufacturing industries and construction category”.

The emission factors for the various gas fields in New Zealand are shown in Table A2.1. The emission factors are calculated by averaging daily gas composition data supplied by industry. Taking annual bounds, it is estimated that the uncertainty in the natural gas emission factors is ± 1.7 per cent (Ministry of Economic Development, 2006).

Table A2.4 Variation in CO2 emission factors for natural gas

Year Maui
(kt CO2 / PJ)
Treated
(kt CO2 / PJ)
Average
(kt CO2 / PJ)

1990

53.2

52.4

53.1

1991

52.9

52.8

52.9

1992

52.9

52.8

52.8

1993

52.6

52.5

52.6

1994

52.4

52.2

52.4

1995

52.1

52.9

52.2

1996

52.2

52.9

52.3

1997

52.3

52.4

52.3

1998

52.1

52.2

52.1

1999

51.8

52.4

51.9

2000

52.1

52.1

52.1

2001

51.9

52.6

52.0

2002

52.3

52.5

52.3

2003

52.0

52.6

52.1

2004

51.9

53.7

52.2

2005

52.0

52.6

52.1

2006

52.0

53.5

52.3

A2.4 Energy balance for year ended December 2006

Table A2.5 New Zealand energy balance for year ended December 2006 (Ministry of Economic Development, 2007b [PDF, 13 KB]

 

5  The LPG CO2 emissions factor was confirmed by checks of 2002 gas data.