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2. Emission factors and methods – context

The emission factors reported in this guide are intended to be default factors (ie, to be used in the absence of better information). They are designed to be consistent with the reporting requirements of ISO 14064-1 and The GHG Protocol. The emission factors are also designed to be aligned with the emission factors used for the Ministry’s national greenhouse gas inventory reporting.

The purpose of providing these emission factors is to:

  • collate an official set of annually updated emission factors for voluntary corporate reporting
  • present emission factors in an easy to use form which will facilitate reporting by organisations
  • provide guidance on a consistent approach to choosing emission factors for financial-year and calendar-year reporting.

As explained previously, these emission factors are largely derived from technical information published by New Zealand government agencies. 4The key source of information is the Ministry of Economic Development.  Each section gives the particular source for each emission factor and how the factors are derived.

This guidance covers the six direct Kyoto gases (CO2, CH4, N2O, HFCs, PFCs and SF6) covered by ISO 14064-1 and The GHG Protocol. This is also consistent with the reporting requirements for New Zealand’s Greenhouse Gas Inventory 1990–2007.

Greenhouse gases (GHGs) vary in their radiative activity and atmospheric residence time. This means that different GHGs have different global warming potentials (GWPs). To enable a meaningful comparison between gases, GHG emissions are commonly expressed as carbon dioxide equivalent or CO2-e. The emission factors in this guide therefore convert activity data into the equivalent estimate of CO2-e per unit of activity data (eg, kg CO2-e/litre of petrol).

Under the reporting requirements of ISO 14064-1 and The GHG Protocol, GHG emissions should be reported in tonnes CO2-e. This guidance presents emission factors in kg CO2-e per unit. Division by 1000 converts kg to tonnes (see example calculations on the following pages).

In line with the reporting requirements of ISO 14064-1, the emission factors allow calculation of CO2, CH4 and N2O separately, as well as the total CO2-equivalent for Scope 1 emission sources (discussed in Section 2.2).

CO2 emission factors are based on the carbon and energy content of a fuel. CO2 emissions therefore remain constant regardless of the way in which a fuel is combusted. However, CH4 and N2O (ie, non-CO2) emissions depend on the manner in which the fuel is being combusted. The emission factors for CH4 and N2O therefore vary depending on the combustion process.5 Separate CO2-e emission factors for commercial and industrial users are presented in Table 1 on page 7. The relevant Ministry of Economic Development publication describes assumptions made.

As well as providing common emission factors, the Ministry considers it useful to illustrate how these emission factors have been derived. Appendix 1 discusses and provides an example of how the emission factors have been calculated.

2.1   Timing of emission factors and annual reporting

Organisations can choose to report on a calendar or financial year basis.

Calendar year: If you are reporting on a calendar year basis, then the latest published emissions factors should be used and the inventory may have to be recalculated when the most appropriate emissions factors are published at a later date. Many emission factors will rely on a review of historical data, such as the proportion of renewable generation feeding into the electricity grid. The previous calendar year’s emission factors will therefore be provided in this guide each year, following the release of the Energy Greenhouse Gas Emissions, New Zealand Energy Data File and New Zealand’s Greenhouse Gas Inventory publications.

Financial year: If you are reporting on a financial year basis then you could either:

  • choose to pro rata the emission factors according to the specific financial year used by your organisation, or
  • use the emissions factors for the 2008/2009 inventory with an explanation that these are the latest available published emissions factors.

2.2   The concept of “scope”

The GHG Protocol categorises emission sources into Scope 1, Scope 2 and Scope 3 activities as follows:

  • Scope 1: Direct GHG emissions occurring from sources that are owned or controlled by the company (ie, sources within the organisational boundary). For example, emissions from combustion of fuel in owned or controlled vehicles. The GHG Protocol and ISO 14064-1 require Scope 1 emissions to be reported.
  • Scope 2: Indirect GHG emissions occurring from the generation of purchased electricity consumed by the company. The GHG Protocol and ISO 14064-1 require Scope 2 emissions to be reported.
  • Scope 3: Other indirect GHG emissions occurring as a consequence of the activities of the company, but generated from sources not owned or controlled by the company (eg, emissions from air travel). Under the reporting framework of The GHG Protocol and ISO 14064-1, Scope 3 is an optional reporting category that allows for the treatment of all other indirect emissions. The GHG Protocol states that Scope 3 emissions should be reported if they are 1) significant in the context of the whole inventory, 2) material to stakeholders, and 3) easy to reduce.

Section 3 of this guide presents emission factors according to each category of activity.

4. For instance, the energy emission factors are largely sourced from the Energy Greenhouse Gas Emissions (2009) publication, produced by the Ministry of Economic Development. References for specific emission factors are included on the following pages.

5. For example, the CH4 and N2O emission factors for diesel used for industrial heating are different to the CH4 and N2O emission factors for diesel used in vehicles.