Scope 3 waste emissions are reported under Category 5, “Waste generated in operations”, and the GHG Protocol says you can calculate them using either supplier-specific, waste-type-specific, or average-data methods. The most practical approach for most organisations is to collect waste quantities by material and treatment route, then multiply those activity data by suitable emission factors.
What Scope 3 waste covers
Category 5 includes emissions from third-party treatment and disposal of waste generated in your owned or controlled operations during the reporting year, including solid waste and wastewater. It can cover landfill, incineration, recycling, composting, waste-to-energy, and wastewater treatment, while waste handled in facilities owned or controlled by your organisation sits in Scope 1 or 2 instead. The GHG Protocol also notes that some companies may optionally include emissions from transporting waste in third-party vehicles.
What waste data to collect
The key is to collect enough detail to match each waste stream to the right emission factor. The GHG Protocol recommends distinguishing both waste type and waste treatment method, because emissions vary depending on the material and how it is handled.
Typical data sources include:
- Cleaner or facilities contractor records, such as waste transfer notes, monthly reports, or bin collection summaries.
- Landlord or building manager data, especially in leased offices where waste is often contracted centrally.
- Waste contractor invoices and weighbridge dockets.
- Internal facilities, procurement, or ESG systems.
For each waste stream, aim to capture:
- Waste type, such as mixed municipal waste, paper/cardboard, food waste, plastics, metals, glass, hazardous waste, or wastewater.
- Quantity, usually in tonnes, kilograms, or cubic metres for wastewater.
- Treatment type, such as landfill, recycling, composting, incineration, waste-to-energy, or wastewater treatment.
Calculation methods
The GHG Protocol gives three calculation routes. The supplier-specific method uses waste treatment companies’ allocated Scope 1 and Scope 2 emissions, so you do not need to apply your own emission factors. The waste-type-specific method is usually the most useful when you know the material split and treatment route, because it uses emission factors for each waste type and treatment combination. The average-data method is simpler and uses the total mass of waste multiplied by average treatment factors, but it is less accurate.
A practical formula for the waste-type-specific approach is:
For example, if you have 10 tonnes of food waste sent to composting and an emission factor of 0.05 tCO2e per tonne, emissions are 0.5 tCO2e. If the same 10 tonnes were landfilled with a factor of 0.4 tCO2e per tonne, emissions would be 4 tCO2e. The treatment choice clearly matters.
Using emission factors to calculate waste emissions
The GHG Protocol says emission factors for waste should be waste-type-specific and treatment-specific, and should cover end-of-life processes only. For wastewater, it points users to the 2006 IPCC Guidelines, which provide methods and default factors for biological treatment and sludge handling.
Publicly available factor sources you can use include:
- GHG Protocol Technical Guidance for Category 5, which includes calculation structure and examples.
- UK Government greenhouse gas conversion factors, which include waste-related factors for company reporting.
- US EPA WARM model documentation and emission factors for waste materials and pathways.
- IPCC 2006 Waste Guidelines for wastewater and biological waste treatment.
- DEFRA/BEIS factors via the GHG Protocol third-party databases page.
When using factors, make sure the factor matches:
- The geography or reporting boundary.
- The waste type.
- The treatment route.
- The unit of activity data, such as tonnes, kilograms, cubic metres, or spend-based data.
A simple worked example
Suppose an office generates:
- 8 tonnes of mixed residual waste to landfill.
- 2 tonnes of cardboard to recycling.
- 1 tonne of food waste to composting.
If the relevant emission factors are 0.25 tCO2e per tonne for landfill, 0.02 tCO2e per tonne for cardboard recycling, and 0.05 tCO2e per tonne for composting, then the calculation is:
- Landfill: 8 × 0.25 = 2.0 tCO2e.
- Recycling: 2 × 0.02 = 0.04 tCO2e.
- Composting: 1 × 0.05 = 0.05 tCO2e.
Total Scope 3 waste emissions = 2.09 tCO2e. The exact numbers will depend on the factors you select, but the structure of the calculation is the same.
Reporting tips
If your office is in a leased building, waste data often comes from the landlord or managing agent rather than from direct contracts, so it is useful to agree a reporting template early. The GHG Protocol also expects companies to disclose the type and source of data and emission factors used, along with how much of the total was based on primary data. Where data is incomplete, start with the average-data method, then improve to waste-type-specific or supplier-specific data as your waste reporting matures.
Sources
- GHG Protocol, Category 5: Waste Generated in Operations — link
- GHG Protocol, Scope 3 Calculation Guidance — link
- GHG Protocol, Scope 3 Frequently Asked Questions — link
- UK Government, Government conversion factors for company reporting — link
- US EPA, WARM documentation — link
- IPCC, 2006 Guidelines, Volume 5: Waste — link