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Biodegradability Claims Explained

Why the claim is almost always incomplete

Biodegradation is a chemical event: microorganisms consume a polymer and convert its carbon into carbon dioxide, water and biomass. That event is real and measurable, but it is entirely conditional. Every material biodegrades eventually; the honest question is how fast, under which conditions, and leaving what behind. A sentence that omits those qualifiers is not a claim, it is a suggestion.

The clearest illustration is time. A polyethylene film mulch may reach 60 percent conversion in laboratory compost after 900 days, which qualifies as biodegradable under a generous protocol and is useless as a product claim. Meanwhile a cellulose-based material reaches the same figure in 60 days. Same word, wildly different meanings, which is exactly why regulators now require the conditions to be stated alongside the adjective.

Waste management guidance published by the EPA frames this well: material recovery only works when the product, the disposal route and the receiving infrastructure all match. A bag certified for industrial composting delivers no environmental benefit whatsoever in a region with no industrial composting collection, which is most of the world. Check what your market actually collects before repeating any claim a laboratory has handed you.

Three words that get used interchangeably and are not

Biodegradable, compostable and bio-based answer three unrelated questions. Biodegradable answers whether microorganisms can metabolise the material and how quickly. Compostable answers whether it does so fast enough and cleanly enough to become usable compost, which is a stricter and more useful claim. Bio-based answers where the carbon came from, and says absolutely nothing about end of life. Keeping those three questions separate resolves most disagreements before they even start.

A polyethylene bottle made from sugarcane ethanol is 100 percent bio-based and behaves exactly like fossil polyethylene at disposal, because it is chemically identical. Conversely, polybutylene adipate terephthalate is entirely fossil-derived and composts readily in industrial conditions. Carbon origin and end-of-life behaviour are orthogonal, and conflating them is the most common source of confusion in this whole category. Both are genuine properties; neither tells you anything useful about the other.

Reading the standards in plain language

The industrial composting family is the one that matters most, and it rests on three tests rather than one. The biodegradation test measures carbon dioxide evolution and requires at least 90 percent conversion within 180 days. The disintegration test requires that after composting, no more than 10 percent of the original dry mass remains on a 2 mm sieve. The ecotoxicity test requires the resulting compost to support plant growth at least 90 percent as well as a control compost.

All three must pass, which is why this family of standards is the only one that carries real weight. A material can pass 90 percent conversion and fail disintegration, giving compost riddled with visible fragments that no facility will accept, or it can pass both and fail ecotoxicity because the additives it carried are harmful to soil organisms. Ask for all three results, because a certificate quoting only one is telling you very little.

The measurement protocols behind those figures are documented by ISO, most usefully in ISO 14855 for controlled composting conditions and in ISO 17556 for soil. Referencing the standard rather than paraphrasing it protects both sides of a commercial conversation, because everyone knows which protocol is being discussed. A shared reference also makes it obvious when somebody has quietly swapped one test for another.

The landfill trap: ASTM D5511 and its misuse

Anaerobic biodegradation testing exists for a legitimate purpose, namely assessing whether material sent to anaerobic digestion will break down in that process. It has been widely borrowed to support landfill claims, because if a material produces biogas under test it is tempting to say it will biodegrade in landfill. In practice modern landfill is dry, compacted and biologically sluggish, and decades-old excavations routinely recover readable newspapers and intact food waste.

The tell is the absence of timeframe. A test that runs 30 days under optimised conditions with an enriched inoculum tells you very little about behaviour in a landfill cell over twenty years. When you see a certificate based on D5511 presented as evidence of end-of-life behaviour, ask what percentage conversion was achieved and over how long, and whether the claim states disposal in anaerobic digestion rather than landfill.

Why TPU dry bags generally do not qualify

A dry bag shell is built for a job that is fundamentally incompatible with rapid biodegradation. It must survive years of salt water, ultraviolet exposure, folding and abrasion while remaining waterproof. Polyether-based TPU is hydrolytically stable by design, precisely so that it does not break down in wet conditions. Polyurethane chemistry can be formulated for biodegradability using ester linkages, but those same linkages hydrolyse, which is why ester-based TPU is associated with shorter service life in wet service.

There is also a construction obstacle. A laminate is a composite of a woven face fabric and a film. Even if a bio-based or compostable film layer were used, the polyester or nylon face would remain, and certification systems require the finished article to pass rather than one constituent layer. Some certification schemes permit a small minority of non-compostable components, but the shell represents well over half the mass of a typical bag.

Then there is the additive package. Welded construction, print inks, hardware and thread all enter the calculation. A nickel-plated buckle or a pigment with heavy-metal content will fail the ecotoxicity test on its own, regardless of how well the polymer performs. This is why chemical screening should precede any end-of-life claim rather than follow it, a topic covered in our chemical migration testing article.

Bio-based content, measured honestly

Bio-based content is the claim most dry bag brands can legitimately make, and it is measured using radiocarbon analysis. Contemporary biomass contains a known level of carbon-14, whereas fossil carbon has decayed to effectively none, so measuring the ratio of carbon-14 to total carbon gives the share of modern carbon directly. The method is standardised and results are reported as a percentage of total carbon, not as a percentage of mass.

That distinction matters. A TPU film can be 45 percent bio-based by carbon content because the polyol side of the molecule comes from plant oils, while the isocyanate side remains fossil-derived. Reporting that honestly means stating the measurement basis, typically as bio-based carbon content measured to a named method. Reporting it as a mass percentage inflates the figure, sometimes substantially, because carbon is a minority of total mass in most polymers.

Partial bio-based content is still a meaningful step. Replacing even half the fossil feedstock reduces cradle-to-gate emissions, though the exact saving depends entirely on the feedstock, land use and processing. That nuance is why we pair every bio-based claim with a note about what it does and does not cover, and why our recycled TPU overview treats recycled content separately from bio-based content.

Oxo-degradable: the claim to avoid entirely

Oxo-degradable materials contain additives that accelerate oxidative fragmentation, so a discarded bag breaks into visible pieces faster than ordinary plastic. The fragments persist as microplastic, because oxidation alone does not deliver complete biodegradation within any reasonable timeframe. The visible result is a bag that disappears from the beach while leaving exactly the problem that campaigns against single-use plastic were trying to solve.

Regulators have responded. The European single-use plastics directive restricts oxo-degradable plastic, and advertising standards bodies in several markets treat unqualified degradable claims as misleading. Any programme that wants to keep its packaging and product claims defensible should simply never use this term, and should check that no additive package has been introduced into its materials that would create the behaviour.

How to verify a certificate

Start with a single request: ask for the standard number and its revision year, not merely the test outcome. That request resolves most cases, and everything below is a refinement of it. Certificates issued by recognised bodies always carry the scheme owner’s name, a licence or registration number, a defined scope listing which products are covered, and an expiry date. Scope is the one most often stretched: a certificate covering a tray and lid does not extend to a welded bag simply because both were purchased from the same film converter.

Verify against the registry rather than the document. Every credible scheme maintains a public list of licensees and certified products, cross-checked in about two minutes. Look for the licence number rather than the brand name, because several company names can share a certificate and several certificates can share a confusingly similar logo. Logos are cheap to print; registry entries decidedly are not.

Four greenwashing patterns specific to this category

The first is the unqualified adjective: a product described simply as biodegradable with no numbers anywhere on the page or hangtag. The second is the certificate applied out of scope, typically a raw-material test presented as product certification. The third is the disposal route that does not exist, most often a claim requiring industrial composting in a market where no such collection exists for soft goods.

The fourth is the most subtle and the most common in our category: implying that durability and biodegradability are both present. A waterproof bag cannot be both long-lived in wet service and rapidly metabolised, because both outcomes follow from the same hydrolytic stability. Any product page that leans on both halves of that contradiction is telling you something about its marketing rather than about the material.

What a genuinely biodegradable bag would feel like

Take the thought experiment seriously for a moment. If a dry bag met the industrial composting criteria, it would begin losing tensile strength the first time it stayed damp and warm for several days. Leave it packed wet after a rainy weekend and by the following month it would have measurably weakened. A season of normal use would produce a bag with noticeably reduced tear strength, and storage errors would be irreversible rather than recoverable.

This is not hypothetical naysaying; ester-based polyurethanes genuinely do behave this way, which is why they appear in some short-life marine and agricultural products and not in paddling equipment. The performance envelope that makes a dry bag useful is the same envelope that excludes compostability, and anyone selling you both is selling you a contradiction. The honest position is to choose durability first and then design honestly for what happens afterwards.

The practical conclusion for buyers is that service life is the primary environmental lever for waterproof equipment. Our recyclability discussion works through what happens at genuine end of life, and the numbers there are far more relevant to your footprint than any adjective on a hangtag. Doubling the working life of a bag halves its footprint per season, which no certificate can match.

Recyclability versus biodegradability for waterproof products

Where biodegradability is chemically unrealistic for a welded composite, recyclability is a design problem rather than a contradiction. A mono-material shell built entirely from one polymer family can be reground and re-extruded, whereas a polyester face laminated to TPU has to be separated or downcycled. Designers influence this directly by specifying compatible face and film at the outset. That decision is locked in long before anybody starts writing claims about end of life.

Mechanical recycling tolerates contamination poorly, which is where hardware matters. Removing buckles in under two minutes with common tools is a genuine design feature, not a nicety. Conversely riveted or over-moulded metal hardware can make an otherwise recyclable shell unrecyclable in practice, because nobody will spend ten minutes dismantling a bag to recover two hundred grams of polymer. Design for a two-minute strip-down and recovery becomes realistic rather than theoretical.

Chemical recycling routes exist for some polyurethane streams, though availability remains regional and volumes small. The honest near-term position for most water sports equipment is therefore this: maximise service life, enable repair, keep the material stream simple, and be transparent about what happens at the end. Our eco-focused range page sets out how those priorities translate into a construction brief.

Writing a claim that survives review

A defensible claim has three parts: the measured fact, the condition under which it is true, and the route by which the user acts on it. Written well, it reads like this: 45 percent bio-based carbon content measured to ASTM D6866, with industrial composting certification to EN 13432 for the valve component only, recyclable through our take-back scheme at end of service. Longer than an adjective, immeasurably more defensible.

Avoid the two constructions that most often draw regulator attention. First, do not combine an environmental claim with an implication of universality: recyclable everywhere, compostable anywhere, or safe for every disposal route. Second, do not suggest third-party endorsement unless a named scheme has certified that specific article, and remember that internal testing does not become certification because it was performed in a good laboratory.

Keep the evidence file alongside the claim. Every figure quoted on a page should trace back to a report with a date, a laboratory and a sample description retained for at least the life of the product plus two years. When a retailer or regulator asks, having that file ready in minutes is worth far more than any argument about interpretation.

How we handle the claim internally

Our team has produced waterproof bags since 2014 in an SGS-verified 4,950 m2 facility, and the standing rule is simple: we do not use the word biodegradable on a product page. We publish bio-based carbon percentages where a named test method supports them, we state recycled content separately, and we describe end-of-life honestly, including the parts of the construction that are not recoverable today.

That approach has commercial value beyond compliance. Overstating end-of-life behaviour creates a liability that surfaces years later, usually during a retailer audit or a competitor complaint, and unwinding it costs far more than the original claim ever earned. Programs starting at 500 pieces with sampling in 6 to 10 working days give ample time to run proper testing rather than extrapolating from a film data sheet.

If you are assembling requirements for the first time, the production programme sets out how evidence, artwork and claims review fit into the sampling timeline. Pair that with the buyer checklist in our sustainable purchasing guide, and see our PVC-free alternatives page for the material substitutions that most often accompany these claims. Taken together, all three give you a defensible position rather than a slogan.