rPET Traceability for Knit Bag Programmes: Documents, Percentages and the Audit Trail Behind a Recycled Claim

What Traceability Means on a Knit Bag Order

rPET traceability is the ability to show, document by document, that the recycled polymer claimed on a bag was actually bought, actually entered the yarn, and actually stayed attached to that bag through dyeing, knitting and assembly. It is not a certificate on a wall and it is not a percentage on a hangtag. It is a chain of documents in which every link names the same batch, the same mass and the same percentage, and a programme is traceable only if that chain has no gap.

The distinction that trips buyers up most often is between certifying a site and certifying a shipment. A scope certificate says a facility is audited and allowed to process certified material. A transaction certificate says this particular consignment of this particular mass moved between two certified parties. Only the second document travels with the goods, and only the second one will survive a retailer asking about the specific order in front of them.

For a knit bag programme the chain has four stages: flake or pellet, yarn, knitted panel, finished bag. Each stage has its own document and its own mass figure, and the percentage claimed at the end has to be consistent with the percentage bought at the start. Most traceability failures are not fraud; they are a stage in the middle that kept no record, usually the dyehouse or the assembly floor.

Claimed recycled content

30 percent of yarn mass, stated on every document

Yarn input per tote

about 255 g

Recycled polymer per tote

about 77 g at a 30 percent claim

Chain stages

four: pellet, yarn, panel, finished bag

Documents per shipment

one transaction certificate minimum

Programme data

100 pcs per style and colourway, 7 working days sampling, 30 days bulk

The Five Documents to Collect Before Bulk Starts

• Scope certificate for the yarn route. It names the process category and the certified material the site may handle. Without it no downstream document can be issued at all, so it is the gate on everything else.
• Scope certificate for the dyehouse and the knitting floor. Two more sites, two more certificates. A chain with a certified spinner and an uncertified dyehouse is broken, and the break is invisible unless someone asks.
• Purchase and sales records for the certified input. These carry the mass and the batch number, and they are what the mass balance sheet is later built from. Collect them as they are raised, not at the end.
• A lot numbering rule agreed in writing. Buyer, spinner, dyehouse and knitting floor all use the same lot reference for the same material. An unwritten rule means four different numbering systems and no way to join them.
• The claimed percentage, fixed and stated once. Decide 30 percent or 50 percent before bulk and hold it. A percentage that changes between the yarn document and the bag document is the most common reason a claim is rejected.

Scope Certificate: What It Covers and What It Does Not

A scope certificate is issued to a site after an audit and lists the certified materials that site is permitted to process and the process categories it is permitted to perform. It carries an expiry date and has to be re-issued after the next audit. It is the document to check first on any rPET programme, because every downstream document depends on an unexpired scope certificate at the site that issued it.

What it does not do is prove anything about your order. A site can hold a perfectly valid scope certificate and never process a single kilogram of certified material, because the certificate confirms capability, not throughput. Buyers who check only the scope certificate are checking the wrong document, and it is worth saying plainly: the scope certificate is an entry ticket, not evidence of a shipment.

Three fields on a scope certificate are worth reading rather than filing. The process category must include what the site actually did for you, whether spinning, dyeing, weaving or knitting. The certified material list must include recycled polyester of the type claimed, post-consumer or pre-consumer. And the expiry date must fall after your production window, not merely after your sampling window, because a certificate that expires mid-bulk leaves the second half of the order undocumented.

Transaction Certificate: The Document That Moves With the Goods

A transaction certificate is issued for a specific consignment and states the product, the mass, the recycled percentage, the buyer, the seller and the related batch numbers. It is the only document in the chain that describes your goods rather than a facility's capability, and it is the one a retailer, a customs authority or a claim substantiation file will ask to see. One is required per shipment, not per programme.

Timing is the practical risk. A transaction certificate has to be applied for after the goods move, and the standard sets a deadline measured in months rather than years, so a certificate raised a year after shipment may simply not be issuable. Build the application into the handover checklist at shipment rather than leaving it to the end of the quarter, because by then the batch records are often already archived.

Read three numbers on every transaction certificate and compare them with your own. The mass should reconcile with the yarn input your bag uses: at 255 g per tote, a 12,000 piece order consumes roughly 3,060 kg of yarn, plus waste. The percentage should equal the percentage on your specification. And the batch numbers should appear on the yarn cones or on the packing documents, because a certificate with no matching physical lot marking is a certificate about somebody else's material.

Reading a Recycled Percentage Correctly

A recycled percentage on a bag is a percentage of something, and the something has to be named. In yarn terms it is the proportion of recycled polymer in the yarn by mass; in bag terms it is the proportion of recycled material in the whole article, which is lower, because hardware, linings, labels and thread are usually not certified. A yarn that is 100 percent recycled does not make a bag that is 100 percent recycled.

The arithmetic on a knit bag is unusually favourable, because a knitted bag has few components. A tote at 255 g of certified yarn with about 25 g of non-certified thread, label and hardware sits near 91 percent recycled content as an article. Add a polyester lining and a zip and the figure falls. State which basis you are using, yarn or article, because the two numbers can differ by 20 points on the same bag and both can be correct.

There is also a threshold question. The Global Recycled Standard sets a minimum recycled content for certification and a higher threshold before its logo may be used on a product, so a claim at 20 percent and a claim at 50 percent are treated differently in what may be published. Confirm the threshold that applies to the label artwork before the artwork is printed, not after, because reprinting a hangtag run is a real cost with a real lead time.

Mass Balance: How the Arithmetic Has to Close

Mass balance is the rule that makes a chain credible: certified input into a site must equal certified output plus documented loss, and the loss has to be measured rather than assumed. If a spinner bought 10,000 kg of certified flake and sold 9,600 kg of certified yarn, the 400 kg of difference has to appear as recorded waste, not as an unexplained gap. An auditor will follow that gap, and an unexplained one invalidates the chain behind it.

On a knit bag programme the loss figures are knowable and worth stating in advance. Knitting waste on a shaped panel runs about 2 to 4 percent of yarn input; yarn breaks and cone remnants add around 1 percent; dyeing loses a little mass in scouring. A realistic total loss from yarn to finished bag is about 6 to 8 percent, and a mass balance sheet showing 25 percent loss is a sheet that needs explaining.

The practical step is to ask for the mass balance sheet covering your production period, not a generic one. It should show your batch number, your input mass and your output mass, and it should be dated inside your production window. A sheet from a different period, or one with no batch reference, tells you nothing about your order however tidy its arithmetic looks.

Lot Numbers, Dye Lots and Keeping the Chain Unbroken

The chain breaks most often at the dyehouse, because dyeing is where a certified yarn lot gets split, blended and renumbered. A dyehouse receiving two certified lots may combine them into one bath for shade consistency, which is technically acceptable if recorded, but it usually is not recorded, and afterwards no one can say which bag came from which lot. Require in writing that certified lots are kept separate through dyeing.

The same applies at knitting. If certified and non-certified yarn run on adjacent machines with no physical separation, the risk is not deliberate substitution but simple mix-up: a cone picked up from the wrong rack. Physical separation of certified yarn in a marked area, and a knitting plan that names the lot per machine, solves this at almost no cost and is the most effective control in the whole chain.

Sampling deserves a note, because sample rounds rarely carry certificates and buyers rarely notice. If a sample bag is made from certified yarn and no transaction certificate is raised for it, that is normally fine, since sampling is not a commercial shipment. But if the approved sample is later used as the reference for bulk and the bulk yarn is a different lot, the reference no longer matches the goods, and a shade or handle dispute follows.

Where Traceability Breaks in Real Programmes

A Traceability Checklist by Programme Stage

1. At quotation: fix the claimed percentage and the basis, yarn or article, and write both into the specification.
2. At yarn booking: obtain the spinner's scope certificate and confirm the process category and the expiry date.
3. At sampling: confirm the dyehouse and the knitting floor hold their own scope certificates before the first lot moves.
4. Before bulk: agree the lot numbering rule in writing across all four stages of the chain.
5. During bulk: require certified yarn to be physically separated in a marked area on the production floor.
6. At each shipment: apply for the transaction certificate at handover, and compare mass, percentage and batch numbers against your own records.
7. At inspection: add a documentation check to the AQL 2.5 inspection under ISO 2859-1 so the paperwork is treated as part of the delivery.
8. After delivery: file the certificates with the batch numbers so a claim made two seasons later can still be evidenced.

What Traceability Does Not Do

Traceability proves the recycled content of material, and nothing else. It does not prove that the bag was made under acceptable labour conditions, which is what a social audit such as a BSCI audit for bag programmes covers, and it does not prove that the material is free of restricted substances, which is what restricted substance testing covers. Buyers frequently treat one certificate as covering all three, and it does not.

It also does not settle the carbon question. A recycled yarn has a lower fibre factor than virgin, which is the subject of the carbon footprint of a knitted bag, but the certificate itself contains no emissions data. Where a buyer wants both a recycled claim and a footprint figure, they are two workstreams with two sets of evidence, and they should be planned as such from the start.

Asking for the Evidence Without Slowing the Order

The reason traceability is skipped is that it looks like added lead time, and on a programme running 7 working days sampling and 30 days bulk there is no spare time. The way to avoid that is to request the documents in the order the programme needs them rather than all at once: scope certificates at quotation, lot rule before bulk, transaction certificates at each shipment. Nothing in that sequence adds a day.

The one request that does add time is a mid-programme change of claimed percentage, because it forces the yarn to be re-booked and the chain restarted. Decide the percentage once, at quotation, and treat it as a locked specification line alongside yarn, gauge and fabric mass. Programmes that treat it as a marketing detail to settle later are the ones that end up with documents that disagree.

Frequently Asked Questions

People Also Ask