When material removed during silo cleaning cannot return to production, the site must determine whether it remains usable product, has another legitimate use or has become waste. If it is waste, its composition and classification determine how it can be stored, transferred and sent for recovery or disposal.
Removing material from a vessel does not automatically establish its legal status. Equally, describing unwanted residue as a by-product does not make it suitable for unrestricted reuse.
Is the removed material still a product?
The starting point is why the material was removed and what is intended to happen to it.
Consider a silo containing commercially usable powder that must be emptied for planned maintenance. Material recovered in suitable condition may potentially remain product if it can legitimately continue in its intended use.
Now consider old deposits mixed with other substances, deteriorated material or residue from a previous production campaign. If the holder discards it, intends to discard it or is required to discard it, waste legislation becomes relevant.
In England and Wales, the waste duty of care code of practice explains the legal concept of discarding and the responsibilities that apply to waste holders.
The decision must reflect the facts of the material’s intended destination. Possible recovery value does not, by itself, prevent a substance from being waste.
Why the identity of the residue matters
Two silos can contain similar-looking deposits requiring entirely different waste management arrangements. Appearance alone cannot establish chemical composition or hazardous properties.
For example, a fine white powder could originate from several industrial processes. Its colour and texture do not establish its identity, purity or suitability for a particular waste route.
Relevant information may include:
- Original substance: The stored product’s identity, specification and available composition information.
- Process history: Previous contents, known contamination and changes in production use.
- Condition: Whether the material contains moisture, degraded product, mixed substances or cleaning residues.
- Hazardous properties: Whether identified constituents or the material’s characteristics affect its classification.
- Origin: The activity that generated the residue, which can affect the appropriate classification code.
The Environment Agency’s waste classification guidance collection provides access to the technical framework used to identify waste and distinguish hazardous from non-hazardous classifications.
Where available information is insufficient, further assessment may be needed before an appropriate destination can be selected. A waste code should not be chosen simply because it appears to describe the physical form of the residue.
Removal and classification are separate decisions
The equipment or technique used to remove a deposit does not determine its waste status. Vacuum recovery, mechanical removal or another suitable cleaning method can each produce material requiring classification.
Likewise, collecting a residue in a sealed container does not make it non-hazardous. Containment addresses part of the handling requirement, while classification determines what the waste is and which controls apply.
This distinction is particularly important during chemical silo cleaning, where the history of the stored substance can materially affect the handling and destination of recovered deposits.
What must be established before collection?
For a site in England, waste classification should be completed before the material is collected for recovery or disposal. The waste duty of care also requires appropriate arrangements for transferring waste to authorised parties.
Before collection, the site and those arranging removal need to establish:
- The material’s waste status and appropriate classification, including whether hazardous properties are present.
- A sufficiently accurate description of its composition, quantity and physical condition.
- Suitable storage and containment pending collection.
- Whether the proposed carrier and receiving facility hold the relevant authorisations.
- Which transfer or consignment documentation is required.
Hazardous waste can involve additional documentation and movement requirements. Responsibilities do not necessarily end when the collection vehicle leaves the site.
Agree the destination before removing the deposits
Planning the material’s destination before cleaning reduces the risk of accumulating containers of unidentified residue with no agreed collection route.
The site manager should establish who holds the product and process information, who is responsible for classification and which authorised route will receive the material.
The cleaning contractor’s removal scope and the waste management arrangements should be clearly distinguished. A completed cleaning operation does not itself prove that the recovered material has been correctly classified or lawfully transferred.
For residues that cannot return to production, an identifiable material, an appropriate classification and a suitable receiving route are the basis of an organised collection.
