EWC chapter 05: petroleum refining, natural gas and coal pyrolysis waste codes explained

Oil refineries, natural gas plants and coking facilities generate a distinctive set of wastes — heavy sludges, acid tars, spent clays and mercury residues that mostly carry an asterisk. EWC chapter 05 covers all of them, across three tightly defined subcategories. Here is the complete chapter 05 breakdown and the compliance records each waste type requires.

What is EWC chapter 05?

The chapter applies specifically to the industries that convert raw fossil fuels — crude oil refineries, natural gas processing and purification plants, and coking or coal-gasification facilities. Wastes generated by businesses that simply use petroleum products (spent engine oil, hydraulic fluid, fuel contamination) fall under chapter 13 instead.

Chapter 05 contains 24 codes across three subcategories (05 01, 05 06, 05 07). Subcategories 05 02, 05 03, 05 04 and 05 05 do not exist in the List of Waste. Of the 24 codes, 14 carry an asterisk and are hazardous — the majority are absolute hazardous entries with no non-hazardous mirror code.

What is the difference between EWC chapter 05 and chapter 13?

The boundary is the point of production. If your facility converts raw crude oil, natural gas or coal into refined products, the residues and by-products you generate belong in chapter 05. If your facility uses those products in machines or vehicles and produces spent or contaminated oil as a result, use chapter 13 (engine oil is 13 02, hydraulic oil is 13 01).

What are the subcategories in EWC chapter 05?

The complete chapter 05 code set is listed in the table below. Codes marked with an asterisk (*) are hazardous and require a hazardous waste consignment note, a licensed hazardous waste carrier, and disposal or treatment at a permitted hazardous waste facility. Hazardous waste consignment notes must be retained for at least three years.

What are the most important codes in subcategory 05 01?

Ten of the 11 hazardous codes in 05 01 are absolute entries: there is no non-hazardous mirror code. That means the waste is hazardous regardless of composition — you cannot reclassify it on the basis of a waste characterisation test. The only mirror pair in the subcategory is the effluent treatment sludges: 05 01 09* (containing hazardous substances) and 05 01 10 (non-hazardous), where the classification depends on whether the sludge meets the criteria for any hazardous property (HP1–HP15).

• →05 01 03* (tank bottom sludges) — the heavy residue that accumulates at the base of crude oil storage tanks. Always hazardous; no mirror entry.
• →05 01 06* (oily sludges from plant maintenance) — the waste generated when process equipment (heat exchangers, pipework, vessels) is cleaned or serviced. Common across the whole refinery complex; always hazardous.
• →05 01 07* (acid tars) — residues from sulphuric acid-treating processes used in fuel refining. Absolute hazardous.
• →05 01 15* (spent filter clays) — clay-based adsorbents used to decolourise or purify petroleum fractions. Once saturated with hydrocarbons and sulphur compounds, they are absolute hazardous waste.
• →05 01 16 (sulphur from desulphurisation) — the elemental sulphur recovered in a Claus unit during hydrodesulphurisation is non-hazardous and is typically sold as a commodity chemical; only the contaminated residual sulphur stream that cannot be sold falls under this code.

What EWC codes apply to coking plants and coal pyrolysis facilities?

Coal coking (the pyrolytic treatment of coal to produce metallurgical coke) generates substantial tar residues in the by-product recovery plant. Both 05 06 01* (acid tars) and 05 06 03* (other tars) are absolute hazardous entries with no non-hazardous mirror. The 05 06 04 code (wastes from cooling column cleaning) is non-hazardous and covers the solids deposited in the cooling water circuits of the coke oven gas treatment system.

What EWC code applies to mercury waste from natural gas purification?

Natural gas streams can contain trace mercury that must be removed before processing. The spent mercury-removal sorbents and any mercury-laden solid residues from this process are classified as 05 07 01*. Given the extremely strict controls on mercury waste under the UK POPs and mercury regulations, disposal routes are limited — typically specialist retorting, amalgamation or permanent storage at a permitted hazardous waste facility.

The other two codes in 05 07 are non-hazardous: 05 07 02 covers sulphur-containing wastes from gas sweetening (H₂S absorption, amine regeneration by-products) where sulphur cannot be recovered and sold, and 05 07 99 is the catch-all for other gas purification wastes not specified elsewhere.

What compliance records do chapter 05 hazardous wastes require?

Refineries and processing plants must also ensure that each carrier they use holds a valid upper tier waste carrier registration, and that the receiving site's permit authorises acceptance of the specific EWC code being moved. The digital waste tracking duty for receivers has been mandatory since 1 October 2026 in England and Wales (1 January 2027 in Northern Ireland and Scotland) — permitted sites accepting 05 01* or 05 06* or 05 07* wastes must record each arriving load in DEFRA's Digital Waste Tracking service within two working days.

This guide is general information about EWC waste classification, not legal advice. Confirm your specific obligations against the primary sources below and, if in doubt, contact the Environment Agency, SEPA, NRW or NIEA for your nation.