What changed in the 2026 emission catalogue, and how to respond
The Ministry for the Environment's 2026 emission catalogue draws on New Zealand's Greenhouse Gas Inventory 1990-2024, and several of its changes carry direct consequences for how you build an inventory and how a verifier should scrutinise one. This is a practitioner's read of what changed, what it means for your inventory, and how to act on it.
Orange marks changes to act on; grey marks no real change.
One clarification first, since it is easy to misattribute: the move to the IPCC's AR5 global warming potentials was already in place in the 2025 catalogue. The 2026 catalogue continues on that basis, so although it restates those AR5 values there is no GWP change to act on in this update.
Waste factors: the most material change
The single most operationally significant change sits in waste disposal. Non-municipal (Class 2-5) landfill emission factors have approximately doubled, following a correction to DDOC (decomposable degradable organic carbon) values that flows from the 2026 GHG Inventory correction. For any entity with industrial or commercial waste streams going to non-municipal landfill, this is not a marginal adjustment.
For any entity with industrial or commercial waste streams to non-municipal landfill, this is not a marginal adjustment. A figure that looks stable year-on-year may simply be masking the change, and a municipal factor applied where a non-municipal one belongs will now understate emissions significantly.
Non-municipal (Class 2-5) landfill factors: 2025 vs 2026
Electricity: expanded time series and updated quarters
The purchased electricity section now includes annual rows for 2010 and 2011, and the quarterly factors have been updated. Of the 32 electricity emission factors, 21 have changed. The choice between an annual average factor and a time-specific quarterly factor now matters more, and entities should be consistent about which they apply and why. Transmission and distribution (T and D) loss factors cascade from the electricity updates, so a change to a grid factor flows through to its associated loss factor. Check both.
Travel: changes across nearly every sub-category
Almost every travel sub-category moved. Domestic air factors are now sourced directly from Air New Zealand for medium and large aircraft. International air factors have been updated via DESNZ 2025, including revised radiative forcing (RF) multipliers; the catalogue continues to flag the genuine scientific uncertainty around RF, so treat any RF-inclusive figure with that caveat in view. Accommodation factors have been refreshed using Cornell HSBI 2025, with 14 factors added and 2 removed.
Light passenger vehicle factors have been corrected for vehicle fleet year grouping. This is a classification fix with retroactive implications for anyone who applied the prior grouping.
Refrigerants: CO2 fields now populated
Refrigerant and medical gas factors that previously carried null CO2 fields now show a value, populated by duplicating the CO2e figure, because these emissions are already expressed in CO2e terms. Nothing has changed in substance. The practical point is for automated tools and audit checklists: a null-CO2 check that previously flagged these refrigerant rows will now behave differently. Anyone maintaining factor-validation logic should expect the change rather than treat it as a data error.
Taken together, the update is broad: the chart below shows where the revisions concentrate across the categories above.
Emission factors revised in the 2026 catalogue, by category
Assurance and verification
On assurance, the catalogue (Section 2.4) endorses ISAE 3410 and ISO 14064-3:2019 as applicable standards. The licensing regime for assurance providers in New Zealand is still evolving, with MfE consultation ongoing, so the provider landscape may yet change. Two obligations are firm: CNGP participants must use an independent approved verifier, and entities reporting under the Financial Markets Conduct Act must obtain third-party assurance over their climate-related disclosures.
What this means for your inventory
The catalogue is a companion to the GHG Protocol Corporate Standard and ISO 14064-1:2018, not a standalone standard, and its factors are national averages rather than entity-specific values. Acting on the 2026 changes is largely disciplined housekeeping: refresh the factors you rely on, re-estimate where one has moved materially, and keep a clear record of which year's catalogue produced each figure so that next year's comparison can separate a real emissions change from a factor update.
Waste and electricity are the priorities for most entities. Waste-heavy operations should re-estimate non-municipal landfill emissions rather than carry last year's numbers forward, since those factors have roughly doubled. Anyone relying on time-specific electricity factors should refresh both the grid values and the transmission and distribution losses that follow from them, and travel data spanning several years needs its light passenger vehicle fleet-year bands revisited before the calculation is re-run.
What to do now
- Update your emission factor files to the 2026 catalogue across all affected categories, prioritising waste and electricity.
- Re-estimate non-municipal landfill emissions wherever the doubled factors apply.
- Record which year's catalogue you used for this inventory.
- Assess whether the non-municipal waste factor change triggers a base year recalculation under ISO 14064-1:2018 or your applicable standard.
- If you assure inventories: scrutinise waste classification and factor selection, and confirm the catalogue year used is stated in the disclosure.
How Opportune can help
We help corporates, councils and public sector organisations keep their greenhouse gas inventories accurate and defensible as the underlying factors change. For the 2026 update that means re-estimating the waste and electricity emissions that have moved most, refreshing factor files across every affected category, and documenting the catalogue year and methodology so prior-year comparisons hold up under scrutiny.
We also provide independent assurance and verification against the standards the catalogue points to, ISAE 3410 and ISO 14064-3:2019. If you report under the Financial Markets Conduct Act or participate in the Carbon Neutral Government Programme, independent assurance is a requirement rather than an option, and we can help you meet it or prepare for it.
To work through what the 2026 changes mean for your inventory, or to arrange assurance against them, get in touch with Opportune.
