Skip to main content.

5. Purchasing Natural Gas

See Climate Change (Stationary Energy and Industrial Processes) Regulations 2009: 48–50

5.1   Overview

The formulas for calculating emissions associated with the activity of purchasing natural gas account for greenhouse gas emissions which occur as a result of combustion. Any purchased natural gas which is exported may be explicitly deducted from the calculation.

For each class of pipeline gas purchased from a miner (described in the regulations as classes other than LPG, butane, or propane) there are two reporting options:

  1. standard formula: using direct measurement of the carbon content of the natural gas by gas chromatography (the standard formula used by gas miners), or
  2. field-specific formula: a default emissions factor can be used if the natural gas is purchased from one of the fields listed in Table 10 of Schedule 2.

Any propane, butane and LPG purchased from a gas miner must also be accounted for. Emissions factors are listed in Table 4 of Schedule 2 of the regulations. For LPG mixes other than 60 per cent propane, the regulations provide a calculation method based on the volume fraction of propane in the mix. The calculation is described later in this guide.

An opt-in participant may apply for approval to use a Unique Emissions Factor (UEF) for the CH4 and N2O that arise from natural gas used in particular combustion equipment. Gas used in that equipment must be reported as a separate class.

5.2   Information you are required to collect

The following information must be collected for each class of natural gas purchased from a natural gas miner in the year:

Information to collect How to collect
  • number of tonnes of each class of gas purchased or exported
  • as measured at the point of sale
  • number of terajoules of each class of gas purchased or exported
  • as determined through gas chromatography*
  • can be generated independently by the purchaser or supplied by the gas miner at the time of sale
AND, if option a) above is used:
  • mass fraction of carbon in each class of natural gas
  • as determined through gas chromatography*
  • can be generated independently by the purchaser or supplied by the gas miner at the time of sale
AND, if including a storage adjustment:
  • terajoules injected into the facility
  • between 1 January and 31 December in the year
  • terajoules extracted from the facility
  • between 1 January and 31 December in the year

* The standards and testing methods for gas chromatography are given in Regulation 49

5.3   Example calculation

Smalls Manufacturing Ltd purchases natural gas from two different NZ ETS natural gas mining participants. Smalls Manufacturing has decided that, as it reaches the two petajoule threshold for opt-in participation, it will participate in the NZ ETS.

Smalls purchases 2000 TJ of Kaimiro gas, and 20,000 tonnes of gas from another field for which it is able to account for emissions using the standard formula. None of this supply is exported. It also injects 400 TJ of gas into a storage facility.

Activity Quantity (tonnes/ year) Quantity (TJ/year) Emissions factor tCO2-e/TJ Mass fraction carbon Default
EF		 Emissions
(t CO2-e/TJ)
Term used in regulations C D EF mC EFM +N E
Purchased gas: Kaimiro   2000 55.14     110,280
Purchased gas: other field 20,000 1080   81.5% 0.054 59,783
Storage adjustment N/A 400 53.64 N/A N/A 21,456
Total           148,607

Kaimiro gas (field-specific formula):
E = 55.14 × 2000 = 110,280 tCO2-e

Other field (standard formula):
E = (0.815 × 3.6641 × 20,000) + (1080 × 0.054) = 59,783 tCO2-e

Storage adjustment:
S = (400 – 0) × 53.64 = 21,456 tCO2-e

The total emissions to be reported for the activity of purchasing natural gas are:
TE = 110,280 + 59,783 – 21,456 = 148,607 tCO2-e

 

|