Test Methods for Testing Biodegradability of Lubricants - Complete or Not Complete?
For testing biodegradability there are many different test methods but there are only two different main principles: primary degradation or mineralization. The mineralization methods are often called “complete degradation” because the molecules of the sample could be broken down to the final product carbon dioxide, which is an indicator for how much of the test substance is already degraded. But this doesn’t mean that all molecules of the sample are broken down to carbon dioxide, because a biodegradation rate of 60% is enough to be considered as biodegradable. In case of a sample which contains only one kind of molecules (pure substance), this interpretation may be right. But in case of a mixture an interpretation of a positive test result (>60%) is impossible, as there could be components, which are not at all biodegradable. In this case the term “complete degradation” is a misleading description. Methods for primary degradation are easier and much more precise.