ASTM D6139-17

5.1 Results from this CO₂ evolution test method suggest, 5.2 Because of the stringency of this test method, a low yield of CO₂ does not necessarily mean that the test material is not biodegradable under environmental conditions, but indicates that further testing needs to be carried out in order to establish biodegradability.

5.3 Information on the toxicity of the test material to the inoculum may be useful in the interpretation of low biodegradation results.

5.4 Activated sewage-sludge from a sewage treatment plant that principally treats domestic waste may be used as an aerobic inoculum. An inoculum derived from soil or natural surface waters, or any combination of the three sources, may also be used in this test method.

5.5 A reference or control material known to biodegrade under the conditions of this test method is necessary in order to verify the activity of the inoculum. The test method must be regarded as invalid and should be repeated using a fresh inoculum if the reference does not demonstrate biodegradation to the extent of >60 % of the theoretical CO₂ within 28 days.

5.6 The water solubility or dispersibility of the lubricant or components may influence the results obtained and hence the procedure may be limited to comparing lubricants or components with similar solubilities.

5.7 The ratio of carbon incorporated into cellular material to carbon metabolized to CO₂ will vary depending on the organic substrate, on the particular microorganisms carrying out the conversion, and on the environmental conditions under which the conversion takes place. In principle, this variability complicates the interpretation of the results from this test method.

5.8 The behavior of complex mixtures may not always be consistent with the individual properties of the components. The biodegradability of the components may be suggestive of whether a mixture containing these components (that is, a fully formulated lubricant) is biodegradable but such information should be used judiciously.

1.1 This test method covers the determination of the degree of aerobic aquatic biodegradation of fully formulated lubricants or their components on exposure to an inoculum under controlled laboratory conditions. This test method is an ultimate biodegradation test that measures carbon dioxide (CO_{1.2 This test method is intended to specifically address the difficulties associated with testing water insoluble materials and complex mixtures such as are found in many lubricants.}

1.3 This test method is designed to be applicable to all non-volatile lubricants or lubricant components that are not toxic and not inhibitory at the test concentration to the organisms present in the inoculum.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all 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 to determine the applicability of regulatory limitations prior to use. Specific hazards are discussed in Section 10.