| Landfill type | Description |
|---|---|
| Municipal (class 1) landfills with gas recovery | Municipal, well-managed landfill where a landfill gas recovery system is installed. Some of the CH₄ produced during the organic decomposition of waste is captured and destroyed. |
| Municipal (class 1) landfills without gas recovery | Municipal, well-managed landfill where all the CH₄ produced during organic decomposition of waste escapes into the atmosphere, apart from that which is oxidised inside the landfill. |
| Non-municipal (class 2-5) landfills | Non-municipal landfills receive construction and demolition, inert and industrial wastes, where CH₄ generated from the decomposition of organic material is released into the atmosphere. |
10 Materials and waste emission factors
10.1 Overview of emission factor changes from 2025 to 2026
| Section | Total EFs | EFs added | EFs removed | EFs changed | Explanation for change |
|---|---|---|---|---|---|
| Waste Disposal | 35 | 0 | 0 | 35 | DDOC values for nonmunicipal waste reflects the correction performed in the 2026 GHG Inventory. Expect Efs to double from previous year. In addition, recovery rate for open landfills with gas collection, and DDOC value for sludge has also been revised. |
For detailed information on the emission factor changes, download the Emission factor changes CSV file from Appendix G.
10.2 Construction materials
In June 2023, the Building Research Association of New Zealand (BRANZ) published its National Embodied Carbon Repository (NECO2) dataset1. These emissions are indirect (Scope 3) if the entity does not own or control the facilities making the materials.
We recommend that users refer directly to the free NECO2 dataset for emission factors for construction materials. The dataset provides embodied greenhouse gas and energy values for building materials including concrete, glass, timber, and metals, as well as products such as bathroom and kitchen fittings.
The NECO2 dataset takes emission factors from Environmental Product Declarations (EPDs) for construction products and is regularly updated. Users could also check the EPD Australasia platform2 for any interim updates to emission factors.
Other useful sources for construction emission factors include the Waka Kotahi New Zealand Transport Agency’s Project Emissions Estimation Tool (PEET),3 which can be used to estimate GHG emissions in the early stages of a land transport infrastructure project.
The Ministry of Business, Innovation and Employment’s Building for Climate Change Programme (BfCC) has been set up to reduce emissions from constructing and operating buildings, and to make sure buildings are prepared for the future effects of climate change.Through the BfCC programme, MBIE is leading the Building and Construction Sector policy for New Zealand’s Emissions Reduction Plan, setting out policies and strategies to meet the Government’s emission budget.
Users should note that in the GHG Protocol, construction materials are classified as Scope 3, Category 1: Purchased goods and services. Buildings are classified as Scope 3, Category 2: Capital goods, which includes the upstream or cradle-to-gate emissions associated with the production of capital goods, such as construction materials. These can form a large proportion of an entity’s GHG inventory.
10.3 Waste disposal
Waste disposal emissions account only for the GHG emitted from end-of-life waste disposal. Currently, this guide covers emissions from waste-to-landfill for municipal and non-municipal landfills, as well as biological treatment (composting and anaerobic digestion).
The units of emissions are kg CO2-e per kg of material. The anaerobic decomposition of organic waste in landfills generates methane. Entities should adjust inventories to account for the landfills that collect and destroy landfill gas. Where methane is collected and destroyed by flaring or combustion to generate energy, the carbon dioxide emitted from the combustion process is regarded as part of the natural carbon cycle. Biogenic carbon dioxide, which is part of the natural carbon cycle, is absorbed by living organic matter and released at the end of its life and is not included in these emission factors since it has no net effect on greenhouse gases.
Emission factors for anaerobic digestion and composting are reported as forms of biological treatment of waste.
The type, age, design, engineering, and management practices of the landfill influences the GHG conversion factor, based on whether there is a methane gas collection system.
Appendix C includes a list of class 1 landfills with gas recovery.
If entities are interested in calculating the emissions from transporting waste materials, they could do so by independently accounting for the distance travelled, using freight emission factors (see Section 8.2).
We calculated the waste-to-landfill emission conversion factors based on New Zealand’s Greenhouse Gas Inventory 1990–2024. Table 10.3, Table 10.4 and Table 10.5 show the factors.
| Emissions Source | Unit | kg CO₂–e/unit | CH₄/unit (kg CO₂–e) | Uncertainties |
|---|---|---|---|---|
| Waste to Landfill – With Gas Recovery | ||||
| Known Composition: Waste – Food | kg | 0.971043 | 0.971043 | 40% |
| Known Composition: Waste – Garden | kg | 0.79449 | 0.79449 | 40% |
| Known Composition: Waste – Paper | kg | 1.41243 | 1.41243 | 40% |
| Known Composition: Waste – Wood (combined) | kg | 0.547315 | 0.547315 | 40% |
| Known Composition: Wood (treated) | kg | 0.0882766 | 0.0882766 | 40% |
| Known Composition: Wood (untreated) | kg | 1.23587 | 1.23587 | 40% |
| Known Composition: Waste – Textile | kg | 0.706213 | 0.706213 | 40% |
| Known Composition: Waste – Nappies | kg | 0.353107 | 0.353107 | 40% |
| Known Composition: Waste – Sludge | kg | 0.220692 | 0.220692 | 40% |
| Known Composition: Waste – Other (Inert) | kg | 0 | 0 | 40% |
| Unknown Composition: General waste | kg | 0.333843 | 0.333843 | Not quantified |
| Unknown Composition: Office waste | kg | 0.959037 | 0.959037 | Not quantified |
| Emissions Source | Unit | kg CO₂–e/unit | CH₄/unit (kg CO₂–e) | Uncertainties |
|---|---|---|---|---|
| Waste to Landfill – Without Gas Recovery | ||||
| Known Composition: Waste – Food | kg | 1.848 | 1.848 | 40% |
| Known Composition: Waste – Garden | kg | 1.512 | 1.512 | 40% |
| Known Composition: Waste – Paper | kg | 2.688 | 2.688 | 40% |
| Known Composition: Waste – Wood (combined) | kg | 1.0416 | 1.0416 | 40% |
| Known Composition: Wood (treated) | kg | 0.168 | 0.168 | 40% |
| Known Composition: Wood (untreated) | kg | 2.352 | 2.352 | 40% |
| Known Composition: Waste – Textile | kg | 1.344 | 1.344 | 40% |
| Known Composition: Waste – Nappies | kg | 0.672 | 0.672 | 40% |
| Known Composition: Waste – Sludge | kg | 0.42 | 0.42 | 40% |
| Known Composition: Waste – Other (Inert) | kg | 0 | 0 | 40% |
| Unknown Composition: General waste | kg | 0.635339 | 0.635339 | Not quantified |
| Unknown Composition: Office waste | kg | 1.82515 | 1.82515 | Not quantified |
| Emissions Source | Unit | kg CO₂–e/unit | CH₄/unit (kg CO₂–e) | Uncertainties |
|---|---|---|---|---|
| Non–Municipal Waste | ||||
| Known Composition: Waste – Food | kg | 0.8624 | 0.8624 | IPCC uncertainties |
| Known Composition: Waste – Green Waste | kg | 0.7056 | 0.7056 | IPCC uncertainties |
| Known Composition: Waste – Paper | kg | 1.2544 | 1.2544 | IPCC uncertainties |
| Known Composition: Waste – Wood (timber) | kg | 0.4704 | 0.4704 | IPCC uncertainties |
| Known Composition: Waste – Textiles | kg | 0.6272 | 0.6272 | IPCC uncertainties |
| Known Composition: Waste – Nappies | kg | 0.3136 | 0.3136 | IPCC uncertainties |
| Known Composition: Waste – Sludge | kg | 0.2744 | 0.2744 | IPCC uncertainties |
| Known Composition: Waste – Inert (all other waste) | kg | 0 | 0 | IPCC uncertainties |
| Known Composition: Waste – Average for non–municipal solid waste | kg | 0.307323 | 0.307323 | IPCC uncertainties |
| Emissions Source | Unit | kg CO₂–e/unit | CH₄/unit (kg CO₂–e) | N₂O/unit (kg CO₂–e) | Uncertainties |
|---|---|---|---|---|---|
| Biological Treatment of Waste | |||||
| Composting | kg | 0.1756 | 0.112 | 0.0636 | IPCC uncertainties |
| Anaerobic digestion | kg | 0.0224 | 0.0224 | IPCC uncertainties | |
10.3.1 GHG inventory development
There are two methodologies that entities can follow for calculating waste emissions.
- Where composition of waste is known.
- Where composition of waste is unknown.
The choice of methodology depends on the knowledge of waste composition. It is preferable to know the composition of waste as it allows more accurate calculation of emissions. The example calculations are done using IPCC AR5 GWPs.
Users should collect data on the quantity (kg) and type of waste disposed.
Applying the equation E = Q x F this means:
- E = emissions from the emissions source in kg CO2-e within the reporting period
- Q = quantity of waste disposed (kg)
- F = appropriate emission factors from Table 10.3 to Table 10.5.
10.3.1.1 WASTE DISPOSAL: EXAMPLE CALCULATION
A hotel produces waste in its kitchen, guest rooms and garden. They send it to the regional landfill, which is known to have landfill gas recovery.
If the waste comprises 150 kg food waste, 50 kg general waste from guest rooms and 60 kg of garden waste, the hotel calculates emissions as follows:
| Emission Source | Gas | Calculation | Emissions (kg CO₂-e) |
|---|---|---|---|
| Food Waste | Total CO₂-e emissions | 150 x 0.971043 kg CO₂-e per kg | 146 kg CO₂-e |
| General Waste | Total CO₂-e emissions | 50 x 0.333843 kg CO₂-e per kg | 16.7 kg CO₂-e |
| Garden Waste | Total CO₂-e emissions | 60 x 0.79449 kg CO₂-e per kg | 47.7 kg CO₂-e |
The hotel’s total emissions from waste disposal are:
146 kg CO₂-e + 16.7 kg CO₂-e + 47.7 kg CO₂-e = 210 kg CO₂-e
Note: Numbers may not add due to rounding
10.3.2 Emission factor derivation methodologies
We broke down data derived from the National Inventory Report into the categories in Table 10.7 alongside their proportion of the waste to landfills.
| Component | Estimated composition of waste to municipal landfills | Estimated composition of waste to non-municipal landfills |
|---|---|---|
| Food | 9.0120 % | 0.0000 % |
| Green Waste | 5.7424 % | 3.0000 % |
| Paper | 5.8899 % | 5.4671 % |
| Wood (timber) | 12.6231 % | 32.7028 % |
| Textiles | 5.0214 % | 9.9298 % |
| Nappies | 2.4711 % | 0.0500 % |
| Sludge | 1.9224 % | 0.4757 % |
| Inert (all other waste) | 57.3176 % | 48.3746 % |
Note: Landfill waste composition (municipal and non-municipal) was revised in 2024 using updated levy data and survey results prepared for the 2025 GHG inventory submission. These composition has remained the same for the 2026 inventory. Totals may not sum to 100% due to rounding. Columns may not total to 100% due to rounding.
Substances such as plastics, metals and glass are inert because their decomposition in landfills does not directly produce GHG emissions. Only waste that contains degradable organic carbon produces methane as it breaks down.
We provide no methodology for nitrous oxide emissions from waste disposal because the IPCC4 has found them to be insignificant.
10.3.3 When composition of waste is known
If the composition of waste is known, use the specific emission factors for each waste stream based on kilograms of waste produced.
We generated emission factors for each waste category, following a simplification of the IPCC First Order Decay model. In the implemented workflow, we first derive decomposable degradable organic carbon (DDOC), then convert that DDOC into potential methane, and finally adjust for oxidation and gas recovery to estimate net methane emitted.
\[ \mathrm{DDOC} = \mathrm{DOC} \times \mathrm{DOC_f} \]
For aggregate waste categories such as general waste, office waste, or average non-municipal waste, we first estimate a DDOC value from the underlying waste composition and then use that DDOC in the same methane calculation.
\[ \begin{aligned} \mathrm{CH4_{potential}} &= \mathrm{DDOC} \times F \times \mathrm{MCF} \times \text{conversion} \end{aligned} \]
\[ \begin{aligned} \mathrm{CH4_{net}} &= \mathrm{CH4_{potential}} \times (1 - \text{oxidation}) \times (1 - \text{recovery}) \end{aligned} \]
\[ \begin{aligned} \text{emission factor} (\text{kg}\,\mathrm{CO_2e}\,\text{kg}^{-1}) &= \mathrm{CH4_{net}} \times \mathrm{GWP} \end{aligned} \]
Where:
- DOC = fraction of waste mass that is degradable organic carbon
- DOCf = fraction of DOC assumed to decompose in landfill
- DDOC = methane-generating share of the waste after applying the degradable-carbon and decomposition assumptions
- F = fraction of CH4 in the gas that is generated inside the landfill
- MCF = methane correction factor (the extent that the landfill is anaerobic)
- conversion = conversion of carbon to methane (molecular weight ratio CH4/C)
- CH4potential = methane generated before oxidation and recovery are applied
- CH4net = methane emitted after oxidation and recovery are applied
- recovery = fraction of methane recovered where landfill gas systems are in place, otherwise use 0
- oxidation = oxidation factor of methane that degrades before being emitted
- GWP = global warming potential of methane.
For landfill disposal factors in this guide, the resulting emission factor is a methane-only CO2-e factor. Biogenic CO2 is not included, and we do not provide landfill N2O factors.
Emission factors for solid waste were developed using information presented in the waste chapter of New Zealand’s Greenhouse Gas Inventory.
| Waste category | DDOC | F | MCF | Conversion | Ox | R |
|---|---|---|---|---|---|---|
| Food | 0.11 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Garden | 0.09 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Paper | 0.16 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Wood (combined) | 0.062 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Wood (treated) | 0.01 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Wood (untreated) | 0.14 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Textile | 0.08 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Nappies | 0.04 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Sludge | 0.025 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
| Other (Inert) | 0 | 0.5 | 1 | 1.333333 | 0.1 | 0.474544 |
Note: R only applies for landfills with gas recovery.
| Waste category | DDOC | F | MCF | Conversion | Ox | R |
|---|---|---|---|---|---|---|
| Food | 0.11 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
| Green Waste | 0.09 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
| Paper | 0.16 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
| Wood (timber) | 0.06 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
| Textiles | 0.08 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
| Nappies | 0.04 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
| Sludge | 0.035 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
| Inert (all other waste) | 0 | 0.5 | 0.42 | 1.333333 | 0 | 0 |
10.3.4 When composition of waste is unknown
If the composition is unknown, select a general waste or an office waste default emission factor.
We based the default emission factor for general waste on national average composition data from New Zealand’s Greenhouse Gas Inventory 1990–2024 (see Table 10.7).
The following is the composition used to calculate office waste data.
Table 82: Composition of typical office waste
| Waste component | Percentage |
|---|---|
| Food | 20.8% |
| Paper | 53.6% |
| Inert | 25.6% |
10.3.5 Determining with or without landfill gas recovery
If you do not know whether the waste goes to a landfill with or without gas recovery, either find out whether the receiving landfill has gas recovery, or choose one of the conservative assumptions. Nationwide, 94 per cent of waste disposed to municipal (class 1) landfills in 2024 went to a landfill with gas recovery.
We recommend checking Appendix C to identify if your region has a landfill with gas capture. If it does, use the value with gas recovery. To be more certain, consider contacting the local council or disposal operator and ask them what landfill the waste is disposed to and if it has gas recovery. If it is not possible to identify the landfill, choose one of the following conservative assumptions:
For a conservatively high estimate of emissions from waste disposed to a municipal (class 1) landfill, assume it is disposed to a landfill without gas recovery.
For a conservatively low estimate of emissions avoided by diverting waste away from a municipal (class 1) landfill, assume it is from a landfill with gas capture.
10.3.6 Composting and anaerobic digestion
We calculated emission factors for composting and anaerobic digestion using IPCC default emission factors as shown in Table 10.11.
| Calculation component | Composting CH4 | Composting N2O | Anaerobic digestion CH4 | Anaerobic digestion N2O |
|---|---|---|---|---|
| EF (kg gas/kg waste) | 0.004 | 0.00024 | 0.0008 | Assumed negligible |
| GWP (IPCC AR5) | 28 | 265 | 28 | 265.0 |
| EF (CO₂-e) (kg CO₂-e/kg waste) | 0.112 | 0.0636 | 0.0224 | 0 |
From this table the combined emission factors are calculated as follows:
| Treatment method | Emission factor (kg CO₂-e / kg waste) |
|---|---|
| Composting | 0.1756 |
| Anaerobic digestion | 0.0224 |
10.3.7 Assumptions, limitations and uncertainties
The uncertainties for emission factors used in methane emissions from managed municipal landfills is ±40 per cent. This is consistent with the estimates in the IPCC Guidelines. New Zealand’s Greenhouse Gas Inventory 1990–2024 states that “the emission factor uncertainty is set at this level, while better-quality parameters are used in this category, most of the parameters are based on international data and are not site specific”.
If an entity has an advanced diversion system (to recycling and composting) then using the ‘average waste’ category in the methodology will overestimate emissions. If an entity has no diversion system, then it could underestimate emissions.
The default emission factor for average waste is based on national average composition data from New Zealand’s Greenhouse Gas Inventory 1990–2024. Only waste to municipal and non-municipal landfills is considered.
The nitrous oxide emissions associated with anaerobic digestion are assumed to be negligible.
The guide does not cover methodologies to determine emissions from solid waste incineration, as we assume emissions are negligible at the individual entity level.
National Embodied Carbon Repository: https://www.neco2.co.nz/.↩︎
Environmental Product Declaration: epd-australasia.com/.↩︎
Waka Kotahi New Zealand Transport Agency: www.nzta.govt.nz/roads-and-rail/highways-information-portal/technical-disciplines/environment-and-sustainability-in-our-operations/environmental-technical-areas/climate-change/climate-change-mitigation/project-emissions-estimation-tool-peet.↩︎
www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/5_Volume5/V5_3_Ch3_SWDS.pdf.↩︎