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OECD 302C inherent biodegradation test is the second tier of test in OECD standard methods aiming at screening inherently biodegradable materials. 
Measurement is based on nonspecific parameter BOD, and the prolonged exposure of the test substance to microorganisms and a low ratio of test substance to biomass are allowed. 

As the second tier of tests in OECD standard methods for biodegradability evaluation, OECD 302A-D are designed to determine whether a material is inherently biodegradable.
Prolonged exposure of the test substance to microorganisms and a low ratio of test substance to biomass are allowed, which offers a better chance to obtain a positive result compared to tests for ready biodegradation.

Biodegradation percentages above 20% may be regarded as evidence of inherent, primary biodegradation, whereas biodegradation percentages above 70% may be regarded as evidence of inherent, ultimate biodegradation. This indicates that the material is not likely to persist indefinitely in the environment.

If a sample does not pass the 70% threshold, it may lead to a preliminary conclusion of environmental persistency. The higher tier of tests OECD 303 may be performed to evaluate the degradation under environmentally realistic conditions, or an evaluation of the environmental effects of the degradation products may be performed.

Learn More at Aropha Resource Center
OECD 302 test overview

OECD 302C Modified MITI Test (II)

Similar to OECD 301D, the OECD 302C Modified MITI Test (II) measures the DO consumption during biodegradation and the degradation percentage is calculated as the ratio of DO consumption to the theoretical oxygen demand (ThOD). This process also involves the calculation of BOD (biochemical oxygen demand).

Compared to other methods in the OECD 302 series, OECD 302C has the top levels of simplicity and applicability.

The formula of the test substance and its purity may be known to calculate the ThOD. If the ThOD cannot be obtained, the chemical oxygen demand (COD) may be experimentally determined and used as a less satisfactory alternative. At Aropha, we provide free COD analysis if this method is to be used.

This method is capable of testing samples that are highly soluble, poorly soluble, volatile, and/or adsorbing. While testing poorly soluble compounds, however, the shaking or stirring of the solutions during incubation might be helpful to improve the dissolution/dispersion.

OECD 302C closed bottle test setup

Requirement and Applicability

Different testing methods are applicable for materials with different properties. Below is a summary of the applicability of OECD 302C. You can find the applicability for many other methods on Aropha Resource Center

Test Analytical method Sample info required Poorly soluble Volatile Adsorbing
302C (Modified MITI Test (II))
Respirometry: dissolved oxygen
ThOD or COD +/- + +

*"Sample info required" is the information needed to calculate the biodegradation percentages. This must be available for a selected method.
*"COD" analysis is available and free at Aropha.

Aropha Resource Center

To learn more about different types of biodegradation tests, their applicability, biodegradation mechanisms, and many other information such as case studies, publications, and blogs, please check our Aropha Resource Center

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