Hazardous waste: segregation and mixing

Explains what is prohibited, how to describe and classify it and the duty to separate mixed waste.

Mixing of hazardous waste is prohibited

You must segregate waste, or items of waste, of different types.

You must not mix:

  • a hazardous waste with non-hazardous waste
  • a hazardous waste with a non-waste
  • different types (categories) of hazardous waste with each other
  • waste oils with different characteristics

If you do wish to mix hazardous waste, it must be specifically authorised by your environmental permit and be the best available technique.

Categories of waste

Categories are defined by differences between wastes, rather than on their List of Waste codes. For example, wastes would be in a different category where their mixing could result in:

  • a chemical reaction between one or more components of each. For example, an acid and an alkali would react, so would be considered to be in different categories even if they have the same List of Waste code, such as 16 05 06*
  • the identity of one of the wastes being removed, or reduced. For example, where the waste classification and description of the mixed waste does not clearly identify its presence, or its presence was not obvious to carriers or consignees conducting visual duty of care checks
  • a reduction in hazardous properties of one of the wastes as a result of dilution
  • a recovery or recycling option no longer being available for one of the wastes
  • any adverse affect on the disposal or recovery options available for one of the wastes. For example you cannot mix a waste that can either be treated or incinerated with one that can only be incinerated

Waste oils and vehicle fluids such as:

  • mineral oils, cooking oils, halogenated oils, brake fluids, antifreeze, washer fluids and oily waters are different categories and must not be mixed by producers or carriers collecting them
  • oil and water mixes, with different concentrations of similar oils, can be mixed – the resultant mix is classified as a hazardous waste
  • mineral oils of similar composition from different sources can be mixed – if they have different classifications, each would need to be classified separately

The different categories of healthcare waste that must be segregated to meet the legal requirements are set out in the safe management of healthcare waste.

Classifying and describing a mixed waste

In most cases if you place 3 wastes in a container you get a container with 3 wastes in it. Each of the 3 wastes must be described and classified.

You can find further advice in Appendix A of the technical guidance on waste.

Co-collected waste

Discrete items or units of waste may be co-collected in a vehicle or container, this will not be classed as mixing as long as:

  • they are not physically mixed together and no cross contamination can occur during storage and transport
  • each waste in the container is separately classified, described, and quantified, that is number of units, bags, drums and so on, on the accompanying waste documentation
  • any container used for co-collection does not result in one or more of the wastes being hidden from the subsequent holders

Duty to separate mixed waste

Producers must have reliable segregation procedures in place to stop mixed waste being produced.

If for any reason, a batch of mixed waste is produced the waste producer has an additional duty to separate it. This also applies to anyone that later receives the waste. For example, where an item of hazardous waste is placed in the wrong container at a civic amenity site the site operator has a duty to separate this item.

You must separate a batch of unlawfully mixed waste where it is both:

  • technically feasible to do so
  • required to address health issues or to reduce any substantial environment risks

Each waste in the mixed waste must be described and classified separately.

Producing a mixed waste by an industrial process

Where a production process naturally results in a mixed waste it is not classed as mixing but you must still classify and describe each waste in the mix.

A process that produces separate wastes that are subsequently mixed, for example where 2 wastes are placed in the same container, is classed as mixing.

Mixed municipal waste

The prohibition on mixing does not apply to domestic householders. They can put any items of domestic waste (other than asbestos) in their mixed municipal waste as long as they meet the waste segregation instructions from their local authority.

Other businesses, including tradesmen visiting domestic premises, are prohibited from putting any items of hazardous waste into the mixed municipal waste stream. They must follow the waste duty of care to manage their waste correctly.

Published 4 April 2014
Last updated 1 October 2020 + show all updates
  1. Updated the sections on 'Mixing of hazardous waste is prohibited' and 'Duty to separate mixed waste' in line with The Waste (Circular Economy) (Amendment) Regulations 2020.

  2. First published.