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Set-Up
The Ready Biodegradability  Test uses microorganisms obtained from a wastewater treatment plant. These organisms are put into glass jars with the test compound for 28 days, and carbon dioxide gas is measured in the air above the test solution. If the compound biodegrades, CO2 will be detected. The more carbon dioxide produced, the greater the biodegradation of the test compound. This simple test has been highly automated and is usually conducted on an instrument called a respirometer, which automatically measures the carbon dioxide produced by the bacteria.
In this test, the concentration of the tested chemical is very high and the number of bacteria very small compared to what can be found in a wastewater treatment plant (only a few drops coming from a wastewater treatment plant are added to litres of water). If, under such difficult conditions, the ingredient degrades, it is expected that it will degrade very well in the natural environment.
International Compliance
This test is used in most of the worldwide regulatory requirements to ensure that new chemicals put on the market are biodegradable (or safe when a full risk assessment is conducted). In the EU for example, the requirement is that more than 60% of CO2 must be produced in a time period of 10 days (after the degradation has reached at least 10%). All the surfactants we use in our detergents meet this criteria. (See ingredient safety information on this site.)
Acclimatation and Lag Phase
This test uses a dilute microbial innocula which has never seen the test compound before. This means that if the chemical is new (newly created by chemists), the bacteria will need first to synthesise the necessary enzymes before degradation can start. This is called the acclimatation phase and can be observed in the graph at the left. The tested chemical was introduced in a flask where the bacteria have never seen the chemical before (blue line) and in a flask where bacteria were first exposed to the chemical in a separate chamber (red line).
The lag phase between Days 0 and 5 for the blue line indicates that the non-acclimated bacteria needed up to 5 days to produce this new enzyme, allowing the bacteria to start using the carbon in the molecule as a food source.
When a Ready Test is conducted, there is always a control flask that contains a rapidly biodegradable substance (glucose, for example) to ensure that the bacteria taken in the wastewater treatment plant are still alive. The biodegradation profile of this substance is shown by the black line.
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