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Climate New Zealand's Greenhouse Gas Inventory 1990 - 2007 Online version
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:
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NCV = 0.95 × GCV for coal and liquid fuels
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NCV = 0.90 × 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 Gross CO2 emission factors used in the energy sector in 2007 (before oxidation)
| Emission factor (t CO2/TJ) |
Emission factor (t C/TJ) |
Source | |
|---|---|---|---|
| Gas | |||
| Maui | 52.2 | 14.2 | 1 |
| Kapuni Treated | 53.2 | 14.5 | 1 |
| Kapuni LTS | 84.1 | 22.9 | 2 |
| Weighted average for distributed gas | 53.8 | 14.7 | |
| Methanol – mixed feed (1990–1994) | 62.4 | 17.0 | 3 |
| Methanol – LTS (1990–1994) | 84.0 | 22.9 | 3 |
| Kaimiro | 65.2 | 17.8 | 2 |
| Ngatoro | 53.1 | 14.5 | 3 |
| Rimu | 53.7 | 14.6 | 3 |
| Waihapa/Ngaere + Tariki/Ahuroa (1990)* | 56.2 | 15.3 | 3 |
| Waihapa/Ngaere + Tariki/Ahuroa (2002) | 54.2 | 14.8 | 3 |
| McKee | 54.3 | 14.8 | 3 |
| Mangahewa | 52.3 | 14.3 | 3 |
| Turangi | 55.6 | 15.2 | 3 |
| Pohokura | 55.1 | 15.0 | 3 |
| Liquid fuels | |||
| Regular petrol | 66.4 | 18.1 | 4 |
| Petrol – premium | 66.8 | 18.2 | 4 |
| Diesel (50 ppm) | 69.4 | 18.9 | 4 |
| Aviation fuels | 68.4 | 18.7 | 4 |
| Av gas | 65.9 | 18.0 | 4 |
| Fugitive – flared | 65.1 | 17.8 | 4 |
| LPG | 60.4 | 16.5 | 4 |
| Heavy fuel oil | 73.6 | 20.0 | 4 |
| Light fuel oil | 72.9 | 19.6 | 4 |
| Bitumen (asphalt) | 76.9 | 20.8 | 4 |
| Biomass | |||
| Biogas | 101.0 | 27.5 | 5 |
| Wood (industrial) | 104.2 | 28.4 | 5 |
| Wood (residential) | 104.2 | 28.4 | 5 |
| Coal | |||
| All sectors (sub bit) | 91.2 | 24.9 | 2 |
| All sectors (bit) | 88.8 | 24.2 | 2 |
| All sectors (lignite) | 95.2 | 26.0 | 2 |
* For the years 1991–2001, the emissions’ factors for these gas streams are interpolated between the 1990 and 2002 values.
1. Derived by the transmission operator (Vector Ltd) through averaging daily gas composition data
2. New Zealand Energy Information Handbook (Baines, 1993)
3. Specific gas field operator
4. New Zealand Refinery Company
5. IPCC guidelines (1996).
Table A2.2 Methane emission factors used in the energy sector (before oxidation)
| 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 | 0.19 | IPCC Tier 2 (Table 1–49) diesel engines (agriculture) |
| Mobile sources | ||
| LPG | 28.5 | IPCC Tier 2 (Table 1–44) passenger cars (uncontrolled) |
| Petrol | 18.525 | IPCC Tier 2 (Table 1–27) passenger cars (uncontrolled – mid-point of average g/MJ) |
| Diesel | 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 Nitrous oxide emission factors used in the energy sector (before oxidation)
| 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 | 0.38 | 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 has a ±5 per cent uncertainty associated with the sectoral energy allocation. However, certainty is likely to be greater for the annual totals (Ministry of Economic Development, 2006).
As the survey is run as a census there is no sampling error. The main sources of non-sample error are:
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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
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processing error: 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 (19937). The New Zealand Refining Company estimates a ±5 per cent uncertainty in emission factors (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, has 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 greater uncertainty 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 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 due to 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 ±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 emissions’ factors are ±2 per cent of the revised 1996 IPCC default values (IPCC, 1996).
A2.3 Emissions from gaseous fuels
A2.3.1 Activity data
Vector Limited, a gas transmission and distribution company, 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. Consequently, uncertainty is assumed to have an upper limit of ±2 per cent (Ministry of Economic Development, 2006).
A2.3.2 Emission factors
As discussed in section 3.2.1.5, New Zealand now uses all of the gas production data reported in the New Zealand Energy Data File (Ministry of Economic Development, 2008b) 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 each gas stream are shown in Table A2.1. The CO2 emission factors for distributed gas are shown in Table A2.4.
Table A2.4 Variation in CO2 emission factors for distributed natural gas (before oxidation)
| Year | National Average (kt CO2 / PJ) |
|---|---|
| 1990 | 53.2 |
| 1991 | 52.7 |
| 1992 | 52.7 |
| 1993 | 52.5 |
| 1994 | 52.3 |
| 1995 | 52.1 |
| 1996 | 52.3 |
| 1997 | 52.3 |
| 1998 | 52.2 |
| 1999 | 51.9 |
| 2000 | 52.0 |
| 2001 | 52.0 |
| 2002 | 52.4 |
| 2003 | 52.3 |
| 2004 | 52.4 |
| 2005 | 52.3 |
| 2006 | 52.7 |
| 2007 | 53.3 |
A2.4 Energy balance for year ended December 2007
Table A2.5 New Zealand energy balance for year ended December 2007 (Ministry of Economic Development, 2008b)
7 The LPG CO2 emissions factor was confirmed by checks of 2002 gas data.
