This test method covers determination of the degree and rate of aerobic biodegradation of synthetic plastic materials (including formulation additives that may be biodegradable) in contact with soil, or a mixture of soil and mature compost, under laboratory conditions. This test method is designed to rate the biodegradability of plastic materials relative to a standard in an aerobic environment. This test method is designed to be applicable to all plastic materials that are not inhibitory to the bacteria and fungi present in soil and compost. The values stated in SI units are to be regarded as the standard. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. A specific hazard statement is given in Section 8. This ASTM test method is equivalent to ISO 17556:2003.