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A Guide to WM3: How to Classify Your Waste in 7 Simple Steps

Sep 6, 2023 | Waste Management

Around 70% of construction waste is soil & stones, and while over 70% of that waste is recycled, soil & stones still accounted for 38% of all the waste that was sent to landfill in Scotland (SEPA, 2018 pre COVID & cyber-attack). This is a staggering amount of material that needs to be processed correctly. It is important to classify this waste, as it helps us to understand exactly what is in our waste, allowing us to recycle our materials more efficiently, while ensuring that hazardous wastes are dealt with appropriately. SEPA’s WM3 waste classification guidance is the key document for classifying waste in our industry, aiming to help anyone who produces, transports or manages waste.


Waste Classification for the Construction Industry

A WM3 waste classification assessment is more than a lab test – it requires a degree of interpretation and knowledge of the waste that you are dealing with.

Any construction sites or facilities that produce industrial or commercial waste should comply with the WM3 standards.


Waste classification and assessment procedure


1. Check if the waste needs to be classified.

Nearly all household, commercial and industrial wastes do need to be classified. There are some waste that are excluded from classification:

waste exclusions

2. Identify the code or codes that may apply to the waste. 

You need to identify how the waste is classified in the List of Waste (known otherwise as the European Waste Catalogue). The following codes are those most used in the construction industry: 

EWC code

A full list of wastes, and their classification code (see step 7) can be found here (page A7-A39). 

3. Identify the assessment needed to select the correct code. 

You now need to work out if an assessment is needed and how it affects the classification of the waste. The assessment needed depends on the type of code identified. These are divided into four types of entry: 

If your waste is AN or AH, you can now skip to step 7 to establish the waste classification code.


4. Determine the chemical composition of the waste. 

If the waste is a manufactured product whose composition has not changed, you can get this information from the manufacturer’s safety data sheet. You can also get this information by sampling and analysing the waste to determine its composition (see page D1 for full rundown of waste sampling).

In the case of soils, this information will not be available and therefore chemical analysis should be undertaken at a UKAS accredited lab. The suite of tests should be based on the materials history – don’t just ask for a WM3 – the contaminants tested for should be specific to the waste. The minimum you would expect for made ground soils from a Brownfield site would be heavy metals, speciated polyaromatic hydrocarbons, pH and asbestos. However, depending on the site history, a wider suite may be needed.

5. Identify if the substances in the waste are ‘hazardous substances’ or ‘Persistent Organic Pollutants’ (POPs). 

Once you know the chemical composition, you need to identify whether any substances in your waste are hazardous or POPs.

The government’s technical guidance on waste classification and WM3 explains in further detail how to identify if a substance is a ‘hazardous substance’, as well as the hazard statement codes assigned to it (See page B1 onwards).

6. Assess the hazardous properties of the waste (if hazardous properties are present). 

In this step, you need to consider all hazardous properties. These properties are numbered HP1-HP15 and can be found here.

Where chemical testing has been undertaken this step will involve the assessment and interpretation of lab data. The chemical testing results from the lab will tell you the concentration of contaminants within your waste, however you will then need someone to assess these results in accordance with WM3 guidance.

The government guidance provides detailed instructions on how to assess each hazardous property (see page C1 onwards). 

7. Assign the classification code and describe the classification code. 

At this step, the types of entry identified in steps 2 and 3 are important. 

If the waste displays a hazardous property or contains POPs above the specified concentration limit, a MH code should be assigned.  

If a waste is AN, in almost all cases, it is non-hazardous, not needing any further assessment (will generally be an inert, clean pile of concrete/bricks).  

If the waste does not display hazardous properties, nor contain POPs, then ‘mirror non-hazardous’ code can be assigned.  

If the waste is AH (e.g., bituminous mixtures containing coal tar), then the following applies: 

  • Use of classification code provided. 
  • Note that waste is hazardous. 
  • Composition and hazardous properties identified should be used to complete the consignment note. 

SEPA provides a list of examples to show how waste classification and assessment is applied to various materials. (Page 21-29). 


Waste Acceptance Criteria (WAC) 

WAC only pertains to landfill and would be easier to understand if it was simply named ‘Landfill Acceptance Criteria’ or ‘LAC’. With waste soil, you should first use a WM3 assessment to classify it as either non-hazardous or hazardous. If there is no viable reuse, recycle or recovery outlet for the waste and landfill is the only option, then you will also require a WAC analysis.  

A WAC analysis applies to soil that will be sent to landfill and should not be used for waste classification when sent to recycling or recovery operations. The analysis allows us to understand the leaching ability of contaminants in the soil to see how contaminants are going to act when they go to landfill. It will not be able to indicate if your waste is hazardous or non-hazardous. 


To conclude, the classification of your waste must be worked out before the waste is moved, disposed of, or recycled. If your waste is hazardous (determined by a WM3) or cannot be recycled for other reasons, it is likely that you will need a WAC assessment before the landfill site accepts it. 

Waste classification has always been a complicated topic in the construction industry, with so many different conditions on how to classify waste it’s no wonder it’s one of the most common questions for customers using recycling facilities like our own to repurpose their waste.  

The team at Brewster Brothers are always happy to help guide customers to the right resources and demystify waste classification so that you can be sure your waste is going to the right place.  Albion environmental, experts in waste, can offer more technical guidance and training should you wish to learn more about waste classification.