Biodegradability testing measures how far micro-organisms break a chemical down, usually in water over a set time. The most common screening tests are the OECD 301 series for ready biodegradability.
It is required by detergent law in the EU and elsewhere, by eco-label schemes, by chemical regulators assessing environmental risk, and by many brand owners in their own specifications.
How the main tests work
OECD 301 covers six methods, labelled 301 A to F. Each exposes the test substance to a mixed population of micro-organisms for 28 days. Depending on the method, the laboratory measures oxygen use, carbon dioxide release or loss of dissolved organic carbon.
A substance is usually called "readily biodegradable" if it reaches 60% of its theoretical oxygen demand or carbon dioxide release, or 70% removal of dissolved organic carbon. For most methods, that level must be reached within a 10-day window that starts when breakdown first reaches 10%. Ask the laboratory to state clearly whether the 10-day window was met.
Substances that fail ready tests may still break down more slowly. Inherent biodegradability tests, the OECD 302 series, and simulation tests are used to show this.
Who asks for it
- EU detergent law requires surfactants in detergents to meet ultimate aerobic biodegradability criteria.
- Eco-label schemes set biodegradability criteria for ingredients in labelled products.
- Chemical regulators, including under EU REACH, use biodegradation data to assess persistence.
- Brand owners and retailers often ask for ready biodegradability data on surfactants, auxiliaries and cleaning ingredients.
The EU detergent rules are changing
As of October 2026, the EU has adopted a new Detergents and Surfactants Regulation, (EU) 2026/405, which will replace Regulation (EC) No 648/2004. Published summaries say it entered into force in March 2026 and mainly applies from September 2029, with transition rules. They also say it keeps the existing surfactant biodegradability rule and adds later requirements for other ingredients.
Responsibility sits with the manufacturer or importer who places the detergent or surfactant on the EU market. Check the text on EUR-Lex and confirm your duties with your regulator or a compliance adviser.
What to ask your supplier
Ask for the full test report, not a one-line claim. Check the method, the laboratory, whether it follows good laboratory practice, and whether the substance tested is the same as the one you are buying. A report on a similar molecule from a literature source is weaker evidence. If no report exists, an accredited laboratory can run the test, which takes at least 28 days plus reporting time. Our guide on reading a lab certificate helps you check the report.
Next step
We collect test reports from shortlisted plants, check that they match the product supplied, and arrange independent testing where needed. Book a free sourcing review.