CO2 Evolution Test (Sturm Test)

OECD 301 B, Regulation (EC) No 440/2008, C.4-C, DIN EN ISO 9439, ISO 14852 as well as ASTM D5864-11


The „CO2 Evolution Test“ is a method to determine the “ready” ultimate biodegradability of non-volatile chemicals in aqueous media.


The amount of CO2 produced by the biodegradation of substances is determined. The test item as sole source of carbon is incubated together with activated sludge of a municipal sewage treatment plant (30 mg/L) and a mineral media for 28 days. The test vessels are aerated with CO2-free air. The resulting CO2 is absorbed in NaOH in successively connected absorption bottles as NaHCO3/Na2CO3. The amount of CO2 bound in NaOH is determined as DIC (dissolved inorganic carbon) and is a direct measure for the mineralised carbon of the test substance, after subtraction of the blank values.


A degradation extent of > 60% ThOD within 28 days and within a "10-days window" after the end of the lag-phase is defined as criterion for classifying a particular test substance as "readily” biodegradable.

Test substance properties

The CO2 evolution test is applicable for soluble and insoluble substances as well as nitrogen-containing materials without disturbances caused by oxygen-consuming nitrification processes.