Substitution rate assumptions in a circular economy statement

A circular economy statement reuse rate is only as good as the evidence behind it, and most statements submitted at planning quote a figure that nobody has tested against a specification. The question a reviewer asks is simple: which materials, in what quantity, are being substituted by reused or recycled material rather than bought new, and what secures that at construction stage. A statement that answers with percentages and no mechanism is a commitment to nothing.

In London the requirement comes from the London Plan 2021, where Policy SI 7 sets targets for reuse, recycling and recovery of demolition, construction and excavation waste, and requires referable applications to submit a statement. Outside London the policy basis varies, so check the adopted plan.

What the statement has to quantify

Four quantities carry the weight, and they are different things that get conflated.

The proportion of the existing building retained, measured by mass or by element, which is the largest single lever available and the only one that reduces new material demand rather than changing where it comes from.

The proportion of new material demand met by reused components or by recycled content, expressed by material stream rather than as one headline figure. Aggregates, steel, concrete, plasterboard and insulation behave differently and should be reported separately.

The proportion of arising waste reused, recycled or recovered, against the targets in the applicable policy. In London, Policy SI 7 sets targets of at least 95 per cent for demolition waste, at least 95 per cent for construction waste and at least 95 per cent for excavation waste.

And the proportion of the proposed building designed for future disassembly, which is a qualitative commitment that a quantity should still be attached to.

Reuse on site against reuse off site

These are counted differently and the difference matters for how much credit a scheme can claim.

Material reused on site, such as crushed concrete used as sub-base, retained structural frame, or reclaimed brick re-laid in new walls, reduces new material purchased. That shows up as reduced product stage carbon in the carbon assessment and as a reuse rate in the circular economy statement, with the processing and handling energy still counted.

Material sent off site for reuse in another project is diversion from landfill. It is a legitimate and valuable outcome, and it counts against the waste targets, but it does not reduce your scheme's material demand and it should not be presented as though it does.

The cleanest way to present this is a table with two columns, one for on-site reuse and one for off-site, totalled separately. Reviewers who see a single combined figure assume the on-site number is being flattered, and they are usually right.

Recycled content and how it is evidenced

Recycled content claims for steel need particular care, because the recycled content of a section depends on the production route rather than on the supplier's general position. Quote the route and the declaration rather than an industry average.

Where reclaimed structural steel is proposed, say how it will be tested and who will accept it. That is the question an engineer will ask first, and a statement that commits to reusing steel without addressing certification will be read as aspirational.

Design for disassembly commitments

Design for disassembly is where statements become vague, because the measures are design properties rather than numbers. Four commitments can be made specific enough to condition.

1. Mechanical rather than chemical fixing for stated elements, with the elements named.
2. Bolted rather than welded structural connections above a stated size, with exceptions listed.
3. Avoidance of composite build-ups that cannot be separated, with the build-ups identified on a drawing.
4. A material passport or asset register delivered at practical completion, with a stated scope.

The fourth is the one that survives into occupation and the one authorities increasingly ask for. Define what it will cover, in what format, and who holds it, because a commitment to produce a passport with no scope produces a spreadsheet of product names.

Partitions, raised floors, ceilings and services are the elements where disassembly actually pays, because they change on a shorter cycle than the structure. A statement that concentrates on demountable structural connections and says nothing about fit-out has the emphasis the wrong way round.

Diversion from landfill targets

Diversion is the easiest target to hit and the easiest to over-claim. Recovery includes energy from waste, which counts towards a combined reuse, recycling and recovery target but sits far down the waste hierarchy, so a statement reporting 97 per cent diversion with most of it going to energy recovery is meeting a number rather than a purpose.

Report the split. Reuse, recycling and recovery as separate figures, by stream, with landfill as the residue. Then state which contractor arrangements deliver it: the waste carriers, the receiving facilities and the reporting frequency.

Excavation waste is the stream that moves the totals most on a scheme with a basement, and it is also the one most often omitted from the baseline. Where the volume is large, a soil reuse strategy on site is worth more than any other single measure.

Evidence at planning against evidence at completion

At planning you are committing to specification clauses and processes, not reporting outcomes. Say so plainly. Give the commitments, the mechanism for each, and the reporting arrangement at completion.

Three documents do the work together. A Pre-redevelopment Audit records what exists, its condition and what can be reused, which is the baseline every reuse percentage is calculated from. The Circular Economy Statement sets the targets and the mechanisms. A Site Waste Management Plan carries the operational detail through construction.

Where the audit has not been done, the reuse figures in the statement are estimates and should be labelled as such. An unlabelled estimate that turns out wrong at completion is the thing that makes a condition impossible to discharge.

Conditions that secure the commitments

The usual wording requires a post-completion circular economy report comparing actual performance against the approved statement, submitted within a stated period after practical completion. Some authorities add a requirement for an updated statement before works start, reflecting the contractor's actual arrangements.

Two practical points. Ask for the reporting period to be long enough to assemble the records, because waste data arrives after the contractor has left. And make sure the condition refers to the approved statement by date and revision, so that a later amendment does not leave you measured against a superseded set of targets.

Councils usually expect a suitably qualified author for this work, and professional review before submission is strongly advised. An AI-assisted draft can structure the statement and list what each stream needs, and it should leave the quantities marked as unconfirmed rather than filled with plausible percentages. Reports should be reviewed before submission, and PlanScope does not guarantee planning approval.

To see which supporting documents a scheme is likely to need alongside the waste and circularity work, enter your postcode on PlanScope.