How to Do a Waste Audit for Carbon Reporting (Scope 3 Category 5)
What Is a Waste Audit?
A waste audit is a systematic review of how much waste your business generates, and what happens to it. For carbon reporting purposes, you need three numbers:
- Annual kg of waste sent to landfill
- Annual kg of waste sent for recycling
- Annual kg of waste sent for incineration (energy from waste)
These three figures map directly to Scope 3 Category 5 emission factors. Most SMEs do not track waste in kg — but your waste contractor does.
Step 1: Call Your Waste Contractor
Your waste contractor sends vehicles to your site and weighs the bins. They are required to report waste tonnage for regulatory purposes. Call your account manager and ask for:
- Annual waste summary report for the reporting year
- Waste transfer notes (these show each collection, weight, and destination)
- Breakdown by waste stream: general waste (landfill), mixed recycling, food waste, incineration
This call takes 10 minutes. The report is usually emailed within a day.
If you use multiple contractors (e.g. separate companies for general waste and dry recyclables), collect data from each.
Step 2: Read the Report Correctly
Waste reports typically show weight in: - Tonnes — divide by 1,000 to get kg if you need kg, or multiply tCO2e factors by 1,000 - Kilograms — use directly with the per-kg factors below
The destination categories you need:
| Waste contractor label | Maps to |
|---|---|
| General waste / municipal waste | Landfill |
| Mixed recycling / dry recyclables | Recycled |
| Food waste to anaerobic digestion | Recycled (use 0.021) |
| Energy from waste / incineration | Incineration |
| Hazardous waste | Report separately (not in DeCarbonOPS) |
Step 3: Apply DEFRA 2023 Emission Factors
| Waste type | DEFRA 2023 factor | Example: 1,000 kg | tCO2e |
|---|---|---|---|
| Landfill (mixed MSW) | 0.459 kgCO2e/kg | 1,000 kg | 0.459 |
| Recycling (mixed) | 0.021 kgCO2e/kg | 1,000 kg | 0.021 |
| Incineration (energy recovery) | 0.021 kgCO2e/kg | 1,000 kg | 0.021 |
Landfill emits 22 times more CO2e per kg than recycling. The accounting reflects decomposing organic material in landfill releasing methane — a potent greenhouse gas.
Worked Example: Office of 30 People, One Year
| Stream | Annual weight | Factor | tCO2e |
|---|---|---|---|
| General waste (landfill) | 2,400 kg | 0.459 | 1.10 |
| Mixed recycling | 1,800 kg | 0.021 | 0.04 |
| Food waste (AD) | 600 kg | 0.021 | 0.01 |
| Total | 4,800 kg | 1.15 tCO2e |
For most office businesses, waste is a small fraction of total emissions. For manufacturers, food processors, and construction companies, it can be 5–15 tCO2e per year.
What to Do If Your Contractor Cannot Provide Kg Data
Some smaller contractors only record bin lifts, not weights. In this case, use estimated average bin weights:
- 1,100-litre general waste bin filled to 80% = approximately 150–220 kg
- 240-litre recycling bin filled to 80% = approximately 25–40 kg
Count your annual bin collections from invoices and multiply. Flag the estimation method in your carbon report.
Reducing Your Waste Emissions
Since landfill carries 22x the emission factor of recycling, the most impactful action is shifting waste from landfill to recycling. Practical steps:
- Install clearly labelled bins for each stream
- Conduct an informal waste-stream analysis (look in the general bin — 60–70% of office landfill waste is typically recyclable)
- Ask your waste contractor if your general waste is sent to a site with energy recovery — if so, you can reclassify from landfill to incineration, which reduces your Category 5 emissions significantly
Entering Data in DeCarbonOPS
In the Waste step, enter the annual kg totals for each stream. The calculator applies DEFRA 2023 factors automatically and includes the result in your Scope 3 total on your Carbon Passport.
Frequently Asked Questions
Why does waste generate carbon emissions?
Waste generates carbon emissions through decomposition. Organic waste in landfill produces methane (CH4) — a potent greenhouse gas with 27× the warming potential of CO2 over 100 years. Incineration releases CO2 and N2O from burning. Recycling has significantly lower emissions because it avoids primary material extraction and processing.
What DEFRA emission factors apply to waste for Scope 3 Category 5?
DEFRA 2023 Scope 3 Category 5 emission factors are: landfill 0.459 kgCO2e/kg, recycling 0.021 kgCO2e/kg, incineration with energy recovery 0.021 kgCO2e/kg, and composting 0.115 kgCO2e/kg. Landfill carries 22× more emissions than recycling per kilogram, demonstrating why diversion to recycling is the priority action.
How do I run a waste audit if I do not have formal waste records?
Start with bin weighing: weigh each waste stream (general waste, recycling, food) once per week for four weeks. Multiply average weekly weight by 52 for an annual estimate. Check your waste contractor invoices — commercial waste collectors often provide annual tonnage certificates. Many councils provide free waste audit templates.
Is waste a significant emission source for office-based SMEs?
For office-based companies, Scope 3 Category 5 (waste) typically represents 1–5% of total emissions — small compared to Scope 2 (electricity) or Scope 3 Category 7 (commuting). However, it is low-effort to reduce (better recycling infrastructure) and looks strong in supplier questionnaires as evidence of operational sustainability management.
What does 'diversion rate' mean in waste reporting?
Diversion rate is the percentage of total waste weight sent to recycling, composting, or energy recovery instead of landfill. A 70% diversion rate means 70% of waste is diverted from landfill. Most CSRD-aligned sustainability reports include diversion rate as a key waste performance indicator. Buyers use it to assess operational sustainability maturity.
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