Composting (Biological Treatment)
Reviewed by Afonso Firmo, Co-Founder & Director · Updated 7 July 2026
Composting carries a factor of 0.046 t CO₂-e per tonne of waste treated under NGA Factors 2025. See worked examples, FAQs and a calculator for reports.
Emission Factor Value
0.046 t CO₂-e/tonne
Try it with your own numbers
Estimated emissions
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Emissions from waste you compost yourself are reported under Scope 1. Calculated as tonnes of organic waste composted × 0.046 t CO₂-e per tonne (NGA Factors 2025).
Official Source & Citation
This emission factor is sourced from the Australian National Greenhouse Accounts Factors 2025 , Table 19 — Biological treatment of waste, published by the Department of Climate Change, Energy, the Environment and Water (DCCEEW).
Citation: DCCEEW (2025). Australian National Greenhouse Accounts Factors 2025. Commonwealth of Australia. Available at: https://www.dcceew.gov.au/climate-change/publications/national-greenhouse-accounts-factors-2025
Notes
Scope 1 factor for organisations operating composting facilities or on-site composting, from the NGA Factors 2025 biological treatment of waste tables. Emissions are the methane and nitrous oxide released during aerobic decomposition. 1 tonne of organic waste composted = 0.046 t CO₂-e — around 98% below the 2.1 t CO₂-e landfill factor for food waste. If a third party composts your waste, the operator reports these emissions under its Scope 1.
Calculation Example
If your facility composted 5,000 tonnes of organic waste during the year:
| Working | Result |
|---|---|
| 5,000 t × 0.046 t CO₂-e/t | 230 t CO₂-e (Scope 1) |
Composting is the quiet achiever of waste management: it turns the most emission-intense waste streams into some of the least. Where a tonne of food waste in landfill generates 2.1 tonnes of CO₂-e, the same tonne through a composting process generates just 0.046 tonnes — reported under Scope 1 by whoever operates the process.
For councils, commercial composters and organisations running on-site systems, this factor is how the residual emissions of composting enter the inventory. For waste generators, it is the number that makes the business case for diversion almost write itself.
Quick Verdict
Composting has an emission factor of 0.046 t CO₂-e per tonne of organic waste treated under the Australian National Greenhouse Accounts Factors 2025. The emissions are the methane and nitrous oxide released during decomposition and are reported under Scope 1 by the organisation operating the composting process — a council facility, a commercial composter or a business composting on site. The factor applies to the 2025–26 Australian reporting year. It is roughly 98% below the 2.1 t CO₂-e per tonne landfill factor for food waste, which is why diverting organics is one of the highest-impact waste actions available. A Scope 1 and 2 calculator can apply the factor directly from weighbridge or contractor records.
How to Calculate Composting Emissions
Emissions (t CO₂-e) = Organic waste composted (tonnes) × 0.046
Worked Example 1: On-site composting
An office campus composts 12 tonnes of food and garden organics on site during the year.
12 t × 0.046 = 0.552 t CO₂-e (Scope 1)
Worked Example 2: Commercial composter
A commercial composting business processes 750 tonnes of organic feedstock in the reporting year.
750 t × 0.046 = 34.5 t CO₂-e (Scope 1)
Worked Example 3: Council facility
A council organics facility composts 5,000 tonnes of kerbside FOGO collections.
5,000 t × 0.046 = 230 t CO₂-e (Scope 1)
Composting vs Other Waste Pathways
| Waste pathway | Factor (t CO₂-e/t) | Scope (who reports) |
|---|---|---|
| Food waste to landfill | 2.1 | Scope 3 (generator) |
| Garden and green waste to landfill | 1.6 | Scope 3 (generator) |
| Municipal solid waste to landfill | 1.6 | Scope 3 (generator) |
| Composting | 0.046 | Scope 1 (operator) |
| Anaerobic digestion | 0.028 | Scope 1 (operator) |
All factors from NGA Factors 2025. Composting a tonne of food waste instead of landfilling it avoids around 2.05 t of CO₂-equivalent emissions.
NGER and AASB S2 Reporting
Composting emissions are Scope 1 for the operator, so large facilities count them toward NGER thresholds alongside any fuel use. Under AASB S2 climate disclosures, operators include the factor in Scope 1, while waste generators can show diversion to composting as a concrete Scope 3 reduction. Keep weighbridge records as the audit trail and apply the NGA Factors 2025 value consistently across periods.
Related Emission Factors
Frequently Asked Questions
Disclaimer
This page is provided for general information, not professional or compliance advice. The factor shown is reproduced from the official publication cited above, and while we work to keep it current, government factors change — the publication is always the authoritative source.
- Before using this value in any formal reporting — including under the National Greenhouse and Energy Reporting Act 2007 — confirm it against the current official publication and the methods specified by the Clean Energy Regulator.
- NetNada is independent of the Australian Government, DCCEEW, and the Clean Energy Regulator. Government data is Crown copyright, Commonwealth of Australia.