ASTM D5511 vs ASTM D5526: reading a biodegradability claim
Two suppliers can both hold a valid test report and quote figures that cannot be compared. The method and duration matter more than the percentage.
Two suppliers can both hold a valid biodegradability test report and quote figures that cannot be compared. The reason is almost always that they used different methods, or the same method over different durations. If you are evaluating biodegradable gloves in a tender, the method and the duration matter more than the percentage.
Both methods are anaerobic, and neither is composting
A point worth clearing up first, because it appears in a lot of published material including an earlier version of this article: D5511 and D5526 are anaerobic tests. Neither measures compostability.
Composting is an aerobic process, and compostability is assessed under different standards – ASTM D6400 or EN 13432. A glove tested to D5511 or D5526 has been assessed for behaviour in an oxygen-poor environment such as a landfill. Describing that as compostable is wrong, and in a tender response it is the kind of wrong that a technically literate evaluator will notice.
Both methods measure biodegradation by capturing evolved gas – carbon dioxide and methane – and expressing the carbon converted as a percentage of the carbon originally present in the sample.
ASTM D5511
Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-Digestion Conditions.
Conditions are deliberately favourable: high solids content, around 52 °C, an actively inoculated anaerobic digester. It is designed to establish whether a material is inherently biodegradable under anaerobic conditions, and to do so within a practical timeframe – typically measured across weeks to a few hundred days.
What it is good for: comparing materials against each other, and demonstrating that a formulation is biodegradable in principle.
What it is not: a prediction of behaviour in a specific landfill. A real landfill is cooler, drier, less uniformly inoculated and less well mixed than a D5511 digester. Results will be faster than field reality.
Our Prosenso™ biodegradable nitrile glove is tested to this method: 43.0 % biodegradation at 513 days.
ASTM D5526
Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions.
D5526 is designed to simulate a landfill rather than a digester. Moisture content is lower, the inoculum is landfill-derived, and the test runs longer. It is the more conservative and more realistic of the two, and it is correspondingly slower and more expensive to run.
What it is good for: the closest available approximation of landfill behaviour.
The consequence for buyers: a D5526 result will normally be a lower percentage than a D5511 result on the same material over the same period. A supplier quoting D5526 is not offering a weaker product; they may be offering a more honest number.
Why the percentage alone tells you nothing
Three rules make claims comparable:
1. Same method. A D5511 figure and a D5526 figure are not comparable numbers. 2. Same duration. Biodegradation curves are not linear. A percentage without a day count is not a result. 3. Report, not brochure. Ask for the laboratory report. A number in marketing material with no report behind it should be treated as unverified.
What we would put in a tender
Two lines, which any supplier with real testing can satisfy and no supplier without it can:
Biodegradability demonstrated by laboratory test report to ASTM D5511 or ASTM D5526, stating the test method, the percentage biodegraded, and the test duration in days.
Where results from different methods are submitted, bidders shall state the method for each. Results obtained under different methods will not be compared directly.
That second sentence is the one that protects the evaluation. Without it, the bidder with the least conservative method wins on a number that means less.
Where end-of-life sits in the whole picture
Biodegradability addresses one stage of a product's life. It says nothing about the carbon emitted in producing the glove, which is usually the larger share of its footprint. For that, the relevant instrument is a life cycle assessment – see how to read an LCA study.
The two are complementary and a serious sustainability specification asks for both. A glove with excellent landfill behaviour and a poor manufacturing footprint is not obviously better than the reverse; the point of asking for both is to be able to tell.
Note also that for clinically contaminated waste, incineration is the required disposal route and biodegradability is not the operative property. Split the requirement by waste stream. See biodegradable nitrile gloves for how the formulation works.
Frequently asked questions
Which method should we require? Either, provided the bidder states which. Requiring D5526 specifically will reduce the field, because fewer manufacturers have run it. Requiring "D5511 or D5526, method stated" gets you comparable evidence without excluding suppliers unnecessarily.
Is a higher percentage always better? Within one method and duration, yes. Across methods, no – see the comparability rules above.
Does 43 % at 513 days mean the glove half-disappears in 18 months? It means 43 % of the carbon in the sample was converted to gas within 513 days under D5511 conditions. Under real landfill conditions it will be slower. Against 100–200 years for conventional nitrile it is still a material difference, and that relative comparison is the defensible claim.
Are these standards current? Both are maintained by ASTM and periodically reapproved. Cite the edition designation your supplier's report states, and check currency the same way you would for any standard – see our note on edition provenance.
Key takeaways
Seventeen years sourcing and supplying medical gloves and PPE to governments, UN agencies, NGOs and healthcare systems. Writes on glove standards, quality management and responsible sourcing for institutional buyers, working from the source standards rather than secondary summaries.
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