This International Standard specifes a method of evaluating the ultimate anaerobic biodegradability of plastic materials in a controlled anaerobic slurry digestion system with a solids concentration not exceeding 15 %, which is often found for the treatment of sewage sludge, livestock faeces or garbage. The test method is designed to yield a percentage and rate of conversion of the organic carbon in the test materials to carbon dioxide and methane produced as biogas.The method applies to the following materials, provided they have a known carbon content:- natural and/or synthetic polymers, copolymers or mixtures;- plastic materials that contain additives such as plasticizers, colorants, or other compounds;- water-soluble polymers.It does not apply to materials which exhibit inhibitory effects on the test microorganisms at the concentration chosen for the test.NOTE Inhibitory effects can be determined by an inhibition test (e.g. ISO 13641-1 or ISO 13641-2).