Sludge EWC Codes

How to choose the right code

The List of Waste is structured in chapters, and the order of the chapters matters. The general rule is that a waste should be assigned to the chapter that reflects the activity that produced it, rather than the chapter that reflects what the waste is made of. Waste from a wastewater treatment plant therefore normally sits in chapter 19, even though the material is largely water and organic solids. Waste from a septic tank or cesspit is domestic in origin and normally sits in chapter 20.

Within a chapter, the six-digit entries are arranged so that more specific entries take precedence over general ones. If a waste fits a specific entry, that entry is used. A general entry such as 19 08 99 or 20 03 99 is a last resort, not a convenient default. Regulators expect the reasoning to be recorded, and a code chosen simply because it is common is not a classification.

Absolute and mirror entries

An absolute hazardous entry is hazardous where the waste fits that entry, while an absolute non-hazardous entry does not require a hazardous-property assessment to choose between a mirror pair. Mirror entries are paired hazardous and non-hazardous entries for related wastes, and the correct one depends on whether the waste displays a hazardous property. That assessment needs the composition and origin of the waste, not just its name.

This is why a code cannot be assigned from a description alone. Two interceptor sludges with the same appearance can classify differently if one contains solvent residues and the other does not. Sampling and analysis, or a documented assessment against WM3, is what supports the choice.

RPS 231 and sewage sludge

Regulatory position statement RPS 231 applies in England to specified sewage and septic tank sludges under particular exemptions and standard rules permits. It allows specified additional waste codes where its conditions are met, but it is not a substitute for classification and should not be read as a general exemption from testing or assessment. In Wales, Scotland and Northern Ireland, check the relevant regulator’s current guidance before relying on a similar approach.

Sludge codes used most often

The table below covers the entries that come up most often in sludge work. It is a working summary, not the full List of Waste. The full list runs to hundreds of entries and the correct code must be confirmed against WM3 Appendix A for the specific waste.

Two cautions apply to this table. First, 13 05 03* and 16 07 08* are absolute hazardous entries, so if the waste fits the description the hazardous code applies. Second, 19 08 09 only covers edible oils and fats. If mineral oil is present, that entry does not fit and a different code is needed. The code for interceptor sludge is not automatically 13 05 03* in every case, because the chapter and entry must match the source and composition of the waste.

Interceptor and tank cleaning sludge

Interceptor sludge from oil and water separators is listed as 13 05 03*, while oily water from those separators is 13 05 07*. Grease and oil mixtures containing only edible oils and fats may fall under 19 08 09 where that description and source fit. Mixed or unusual inputs need to be assessed against the correct chapter and entry rather than coded from appearance alone.

Tank cleaning sludges are different again. Chapter 16 covers wastes from tank, drum and transport cleaning, and 16 07 08* applies where oil is present. The chapter 16 entry is not a fallback for any tank sludge. It applies where the waste arises from cleaning operations and the description fits.

Where classification ends and documentation begins

A code on a transfer note is a record, not proof that the classification is correct. Waste documentation supports traceability: it shows what was moved, when and by whom. It does not by itself demonstrate legal compliance, and it does not replace the classification assessment. If the code is wrong, the paperwork does not fix it.

Classification also feeds into disposal decisions. A hazardous code changes the receiving site, the consignment note requirements and the treatment options. Dewatering reduces water content and does not by itself make hazardous material non-hazardous. Treatment can affect the waste code or description in some cases, so the output should be checked against the applicable guidance. Waste acceptance criteria for landfill are a separate exercise from waste classification and do not replace it.

Where a waste is hazardous, the duty of care in England and Wales requires the producer to check that the waste is handled by an authorised person and to keep the records. The Environment Agency’s duty of care code of practice sets out those requirements. Similar duties apply in Scotland and Northern Ireland under their own codes.

We can help with sludge classification questions, sampling and the practical side of removal and disposal. Related guidance covers sludge waste classification, sludge sampling and sludge contaminants. If you already know the material and want a starting point, the sludge EWC code checker gives candidate codes, possible contaminants and treatment options for review. For disposal routes, see sludge disposal and hazardous sludge disposal.

Common questions about sludge codes

Most errors come from choosing a code by name rather than by chapter. A waste called “sludge” can sit in chapter 13, 16, 17, 19 or 20 depending on where it came from. The chapter reflects the process, and the entry reflects the specific material. Working through the list in order, and recording the reasoning, is what makes the code defensible.

A second common error is treating a mirror entry as a single code. The hazardous and non-hazardous versions of a mirror entry are different codes, and the choice depends on the waste’s properties. Where the waste contains a substance that could make it hazardous, the assessment needs to consider that substance and its concentration.

Finally, the List of Waste is used across the UK, but regulatory positions, documentation and enforcement arrangements differ across England, Wales, Scotland and Northern Ireland. A code should therefore be supported by the requirements that apply where the waste arises and is handled rather than assumed to be sufficient because it was accepted elsewhere.