Recycled Glass Content: How to Read Supplier Claims

A recycled glass content figure means little unless you know what was counted, where, over what period and for which product. Industry bodies define recycled content differently from a plant’s total cullet use, and national or furnace averages do not guarantee anything about the bottle on your purchase order. A claim such as “contains up to 60% recycled glass” can be accurate and still tell you little about your delivery.

This guide breaks a claim into parts a buyer can question: the type of cullet, the plant or furnace behind the number, the reporting period, whether it is an average or a product-specific figure, colour constraints, and who verified it. It also explains how collected glass is turned into furnace-ready cullet, because that step limits what a plant can use. It is an editorial reading of published industry and regulatory sources, not an audit method. For where cullet enters the process, see How Glass Bottles Are Made: From Batch Materials to Inspection.

What counts as recycled content

Cullet is broken glass prepared for remelting. The European container glass federation FEVE separates it into two groups: internal cullet, which is rejects from the glass plant’s own process and circulates without leaving the factory, and external cullet, which comes from outside, either pre-consumer (for example breakages on filling or decoration lines, or flat glass from processing) or post-consumer (for example glass collected in bottle banks).

FEVE’s 2020 paper explains how this maps to ISO 14021, the standard for self-declared environmental claims. Under that definition, recycled content is the proportion by mass of recycled material in a product or package, and only pre-consumer and post-consumer material count. Scrap that is generated within the glass process and can be reclaimed there is excluded. FEVE therefore states that internal cullet cannot be included in a recycled content calculation, while cullet from filling and decoration operations returned to a furnace can be included. In FEVE’s formulation, recycled content equals the external cullet rate plus any other recycled material added to the batch.

British Glass describes the same approach for UK container glass: the agreed method (developed with WRAP in 2008 and aligned with ISO 14021) counts glass packaging waste from recycling collections, waste flat glass from glazing and automotive, and calumite, a by-product of iron production. Process losses such as test runs and rejects are returned to the furnace but are not included in the reported figure unless requested and clearly labeled.

Recycling rate is a different number

A recycling rate measures how much glass put on the market is collected for recycling. FEVE explains the difference: the rate reflects collection, while recycled content reflects what goes into furnaces, and some collected glass is used in non-container products such as insulation. The US EPA, using Glass Packaging Institute (GPI) and state data, reported a glass container recycling rate of 31.3 percent for 2018. That is a collection-side statistic and should not be read as the share of recycled glass in a new bottle.

How collected glass becomes cullet

Recycled glass does not go straight from a collection bin into a furnace. Collected glass is treated to make furnace-ready cullet, and both the collection route and the treatment affect how much good cullet a plant can get for a given colour. That is one reason a recycled content figure varies between plants and over time.

Collection. British Glass contrasts glass banks, which capture glass with lower contamination, with mixed material collections, which are convenient but can have very high process losses: plastics and metals are removed first, and the remaining “MRF glass” contains high levels of non-target material, which raises the cost of cleaning and processing it into furnace-ready cullet. The Glass Packaging Institute (GPI) makes a similar point about single-stream recycling in the United States, where glass is collected with plastic and cardboard.

Treatment. FEVE notes that what arrives at a glass recycling plant includes loose plastic bottles and bags, metal caps, paper and plastic labels, food residues and water, all of which have to be removed. GPI describes cullet as usually colour separated, crushed, screened and vacuumed to remove contaminants such as labels, aluminum caps and non-magnetic metal, followed by a final inspection, often with optical sorting, to remove remaining contaminants such as ceramics or heat-resistant glass. British Glass adds that modern cullet processing equipment can identify and remove most lead glass.

What is hard to remove. British Glass names non-container glass such as ovenware, ceramics and glass-ceramics as particularly difficult to remove from post-consumer glass. Pieces that reach a furnace do not melt and cause inclusions; factory inspection rejects the affected containers, and those rejects are excluded from recycled content when they are remelted. It also says some colour contamination in post-consumer cullet is inevitable despite improved colour sorting, which ties back to the colour limits described below.

Into the furnace. Furnace-ready cullet joins sand, soda ash, limestone and other batch materials, as described in How Glass Bottles Are Made: From Batch Materials to Inspection. Rejects from the plant’s own forming and inspection go back to the furnace as internal cullet, which is not counted as recycled content. FEVE also notes that some collected glass is recycled into other products, such as insulation wool, so collected tonnage is not the same as cullet melted into new bottles.

For a buyer, the practical questions are where a plant’s external cullet comes from, whether cullet of the right colour and quality is available for your bottle, and whether that availability changes during the year. Those questions are included in the supplier list below.

Plant averages versus product-specific claims

Most published figures are averages. FEVE’s paper cites an EU average recycled content of 52 percent from its 2012 life cycle assessment, and says recycled content is product dependent. British Glass states that because cullet availability fluctuates daily, it is not possible to provide individual product recycled glass content, and its national figures are calculated over a calendar year.

A supplier may offer a product-level number or an “up to” range. Ask whether it is a plant or furnace average, a product-family range, or a value for the production run you will receive. A ceiling without a period or verification document is not a delivery commitment.

Reporting period

A figure without a period is incomplete. Calendar-year averages smooth out seasonal and supply variation, while a single production campaign may differ from them. Ask for the period, the plant or furnace, and the colour. If you need a stable number for a sustainability report, ask whether the supplier can commit to an annual average for your product and plant rather than a one-off figure.

Colour and quality constraints

Colour limits how much cullet can be used. British Glass explains that clear glass requires colour contamination in cullet to be kept very low, that there is greater tolerance for green glass, and that amber needs fine control of composition because its colour comes from trace iron oxide and can be affected by organic contamination. It adds that “super-flint” premium glass may sometimes need virgin raw materials only. British Glass also notes that non-container glass, ceramics and pyro-ceramics in cullet can cause inclusions, so cullet quality matters as well as quantity.

GPI says container glass can typically contain up to 70 percent recycled glass, and adds that higher percentages are limited to special batch runs with extremely high-quality cullet to meet colour-consistency goals. For a buyer, a high recycled-content request may conflict with a tight colour or clarity specification. British Glass suggests brand owners explore whether colour and clarity requirements can be adjusted and avoid stipulating minimum recycled content so manufacturers can maximise it when good cullet is available. Whether to specify a minimum is a commercial decision, but you should know the trade-off. The published energy step, the flint and amber windows, and the stone-fault count are calculated in recycled glass bottles: cullet percentage and quality.

Verification and claim wording

Ask for the basis of any claim and who checked it. The US Federal Trade Commission’s Green Guides (16 CFR 260.13) state that it is deceptive to claim recycled content unless the material has been diverted from the waste stream during manufacturing (pre-consumer) or after consumer use (post-consumer), and that if pre-consumer material is claimed the marketer should have substantiation that it would otherwise have entered the waste stream. For partly recycled products, the Guides say the claim should be clearly and prominently qualified about the percentage by weight, and that any pre-consumer or post-consumer breakdown needs substantiation. One of the Guides’ examples says reuse of spills and scraps within the original process is not a valid recycled-content claim, which parallels the internal-cullet exclusion above. These are US marketing rules; check which rules apply to your market.

Evidence to request:

• The calculation method (ISO 14021-aligned, FEVE or national method) and whether internal cullet is excluded.
• The plant or furnace, colour, period and whether the figure is post-consumer only or total.
• Whether a third party verified the figure and under what scheme, and a copy of the statement.
• Whether the claim applies to your specific bottle or to a plant average.

Copy a claim evidence card

Copy this blank card into your specification notes. Enter “unknown” for missing evidence; do not enter zero. It records a supplier declaration, not a site audit or certification.

Product / article / color: ______
Product-specific or average: ______
Plant / furnace: ______
Reporting period / lot: ______
Internal cullet included?: ______
External pre-consumer (%): ______
External post-consumer (%): ______
Total recycled content (% mass): ______
Calculation method: ______
Verifier / scheme: ______
Statement reference: ______
Source URL or file: ______
Document version / access date: ______
Unknowns / owner / next review: ______
Claim wording / evidence: ______

Ask how external cullet availability changes with color and period, and whether any agreed minimum is reported before or after production.

Add any agreed recycled-content requirement and its basis to your bottle specification; Glass Bottle Specifications: A Checklist for Supplier Enquiries shows where such items fit. For the carbon side of lighter and recycled-content bottles, see Lightweight Wine Bottles: What Buyers Should Verify.

Evidence and limitations

This guide explains how to interpret claims; it does not give typical recycled-content values, which depend on the plant, colour, local cullet supply and period. Definitions differ between the ISO 14021-aligned approach used by FEVE and British Glass and other schemes or regional rules, so confirm the method a supplier used. The FTC reference is US marketing guidance, not a glass standard.

• FEVE paper on how to calculate the Recycled Content and the Post-Consumer Recycled Content (PCR) of glass containers, FEVE: internal versus external cullet, ISO 14021 definition, recycling rate versus recycled content, and what must be removed at the recycling plant. Accessed October 8, 2026.
• Recycled content in glass packaging, British Glass: UK calculation method, calendar-year reporting, colour and cullet-quality limits, collection routes and contaminants that are hard to remove. 2019 document, accessed October 8, 2026 via browser PDF retrieval.
• Facts About Glass Recycling, Glass Packaging Institute: typical recycled content, the note on higher percentages, and single-stream collection issues. Accessed October 8, 2026.
• What Is Glass, Glass Packaging Institute: how cullet is colour separated, crushed, screened and optically sorted to remove contaminants. Accessed October 8, 2026.
• Glass: Material-Specific Data, US EPA: 2018 glass container recycling rate. Accessed October 8, 2026.
• 16 CFR 260.13 Recycled content claims, US Federal Trade Commission Green Guides via eCFR: substantiation and qualification of recycled-content claims. Accessed October 8, 2026.