Wastewater treatment emission factor by year
| Year | Scope 3 (kg CO2e per cubic metre) | Change |
|---|---|---|
| 2026 | 0.17088 | 0.0% |
| 2025 | 0.17088 | -8.0% |
| 2024 | 0.18574 | -7.7% |
| 2023 | 0.20132 | -26.0% |
| 2022 | 0.27200 | 0.0% |
| 2021 | 0.27200 | -61.6% |
| 2020 | 0.70800 | 0.0% |
| 2019 | 0.70800 | – |
Total kg CO2e for the seven greenhouse gases, from the official DESNZ files for each year. 2026 factor ID: 18_405_4006_1_1. Where a factor jumps sharply between two years, it is usually because DESNZ changed its method or data source, not because the activity itself changed.
Worked example
Take an office sending 950 cubic metres of wastewater to sewer a year. 950 cubic metres × 0.17088 kg CO2e = 0.16 tonnes CO2e, reported as Scope 3, category 5 (waste generated in operations).
How to report it
Wastewater treatment is Scope 3 category 5, waste generated in operations. If your bill doesn't show it separately, water companies usually assume about 95% of the water supplied goes back to sewer.
Where the data comes from
You'll usually find it in your water bills, which show wastewater or sewerage volumes, in cubic metres. Keep the source documents: anyone checking your Carbon Reduction Plan or SECR report may ask how each figure was worked out.
Read more about how the factors change each year in our guide to the 2026 conversion factors, or see how we apply them in our methodology.
Related emission factors
- Water supply: 0.19130 kg CO2e per cubic metre
- Commercial waste to landfill: 520.58 kg CO2e per tonne
- Mixed paper and card recycling: 4.6536 kg CO2e per tonne
- All UK emission factors