4. Refrigerant and other gases

4.1 Overview of changes since previous update

This guide includes the 100-year global warming potentials (GWPs) of gases reported under the Paris Agreement and the Montreal Protocol.

As with the previous edition, we use the GWPs published in the IPCC’s Fifth Assessment Report (AR5) in this update. This is a change from 2022, which used the IPCC’s Fourth Assessment Report (AR4) values where available. Almost all changes in GWP are less than 20 per cent, although there are some significant changes in some gases. The largest reduction was in methyl bromide (decreasing by 60 per cent) and the largest increase was seen in HFE-356pcc3 (increasing by 275 per cent). Only six refrigerants remained unchanged.

4.2 Refrigerant use

GHG emissions from hydrofluorocarbons (HFCs) are associated with unintentional leaks and spills from refrigeration units, HVAC systems, air conditioners and heat pumps. Quantities of HFCs in a GHG inventory may be small, but HFCs have very high GWPs so emissions from this source may be material. Also, emissions associated with this sector have grown significantly as they replace ozone depleting chemicals such as CFCs and HCFCs.

The list of refrigerant gases is continuously evolving with technology and scientific knowledge. We note that if a known gas is not listed in this guide, it does not imply there is no impact.

Emissions from HFCs are determined by estimating refrigerant equipment leakage and multiplying the leaked amount by the GWP of that refrigerant. There are three methods depending on the data available, see section 4.3.1 to section 4.3.3.

If you consider it likely that emissions from refrigerant equipment and leakage are a significant proportion of your total emissions (eg, greater than 5 per cent), include them in your GHG inventory. You may need to carry out a preliminary screening test to determine if this is a material source.

If the reporting entity owns or controls the refrigeration units, emissions from refrigeration are direct (Scope 1). If the entity leases the unit, associated emissions should be reported under indirect (Scope 3) emissions.

4.3 Global warming potentials (GWPs) of refrigerants and other GHGs

Table 7 details the GWPs of the refrigerants included in this section. The GWP is effectively the emission factor for each unit of refrigerant gas lost to the atmosphere. The guide uses the 100 year GWPs from the IPCC’s AR5 to ensure consistency with New Zealand’s Greenhouse Gas Inventory 1990–2022.

Some refrigerants are a mixture (or blend) of gases. If you know the blend composition, you can calculate the GWP based on the percentage mass of each gas. Alternatively, for the AR5 GWP of various refrigerant mixtures, see table B2 in Appendix B: Alternative methods of calculating emissions from refrigerants.

These emission factors refer to direct emissions, not the indirect emissions associated with the production and supply of these refrigerants.

Table 7: Global warming potentials (GWPs) of refrigerants

4.3.1 GHG inventory development

There are three approaches to estimate HFC leakage from refrigeration equipment, depending on the data available. The ideal method is the top-up method, Method A. Method B is the next best option. Method C is the least preferred because it has the most assumptions.

It is stressed that for all methods, users must individually identify the type of refrigerant because the GWPs vary widely.

Entities should indicate the method(s) used in their inventories to reflect the levels of accuracy and uncertainty.

4.3.2 Method A: Top-up

The best method to determine if emissions have occurred is through confirming if any top-ups were necessary during the measurement period. A piece of equipment is ‘charged’ with refrigerant gas, and any leaked gas must be replaced. Assuming that the system was at capacity before the leakage occurred and is full again after a top-up, the amount of top-up gas is equal to the gas leaked or lost to the atmosphere. The equipment maintenance service provider can typically provide information about the actual amount of refrigerant used to replace what has leaked.

Gas used (kg) × GWP = Emissions (kg CO₂-e)

Where:

• E = emissions from equipment in kg CO₂-e

• GWP = the 100-year global warming potential of the refrigerant used in equipment (table 7).

4.3.3 Methods B and C: Screening

If top-up amounts are not available, we recommend using one of the following two methods for estimating leakage, depending on the equipment and available information. Appendix B: Alternative methods of calculating emissions from refrigerants details both methods.

Method B is based on default leakage rates and known refrigerant type and volume. Use Method B when the type and amount of refrigerant held in a piece of equipment are known.

Method C is the same as Method B except that it allows default refrigerant quantities to be used as well as default leakage rates. Use Method C to estimate both volume of refrigerant and leakage rate when the amount of refrigerant held in a piece of equipment is not known.

Methods B and C are based on the screening approach outlined in the GHG Protocol HFC tool(WRI/WBCSD, 2005).

For most equipment, Method B is acceptable, especially for factory and office situations where refrigeration and air-conditioning equipment is incidental rather than central to operations. In some cases, Method C is only suitable for a screening estimate. Screening is a way of determining if the equipment should be included or excluded based on materiality of emissions from refrigerants. Entities should then try to source data based on the top-up-method.

We provide refrigerant emissions calculation examples below.

Company A performs a stocktake of refrigeration-related equipment and identifies the following units:

• one large commercial-sized chiller unit

• one commercial-sized office air conditioning unit.

Using the top-up approach, the calculation is as follows:

REFRIGERANT USE METHOD A: EXAMPLE CALCULATION

If information was not available from the technician, Company A could use the following approach:

REFRIGERANT USE METHOD B: EXAMPLE CALCULATION

Note: Numbers may not add due to rounding.

The difference between Method A and Method B suggests that the leakage of refrigerant exceeds the default leakage rate, so improved maintenance of the refrigeration systems could help reduce leakage.

4.4 Medical gases use

This section covers emissions from medical gases. Anaesthetic medical gases can be a significant source of direct (Scope 1) emissions in hospitals. The most accurate way to calculate emissions from medical gases is based on consumption data.

4.4.1 Global warming potentials of medical gases

Table 8 details the GWPs of the medical gases included in this section. The GWP is effectively the emission factor for each unit of medical gas lost to the atmosphere. The guide uses IPCC AR5 GWPs.

Some medical gases consist of a mixture (or blend) of gases. If you know the blend composition, you can calculate the GWP based on the percentage of each gas.

Table 8: GWPs of medical gases

4.4.2 GHG inventory development

To calculate medical gas emissions, collect consumption data for each medical gas used by the entity, and multiply this by the GWP for each gas.

Gas used (kg) × GWP = Emissions (kg CO₂-e)

Medical gases are supplied in bottles or cylinders. If only the volume of the gas is known, an additional calculation to calculate the mass of the gas is required to estimate emissions. This should be done by multiplying the volume (L) of gas by its density (g/mL or kg/L).

MEDICAL GAS USE: EXAMPLE CALCULATION

4.4.3 Assumptions

This approach assumes that all anaesthetic gases used are eventually emitted, including the gases inhaled by patients.