Triethyl citrate

Biodegradation in soil

Description of key information

In a test according to EPA OPPTS 835.3300 & ASTM D5988 the biodegradation in soil was ≥79 % ThCO2 after 42 d, 60 % within 10-14 days (readily biodegradable);
t50 (0.8 mgC/g soil) = 6.6 d
t50 (3.2 mgC/g soil) = 9.4 d
t50 (12 mgC/g soil) = 43 d
In a further test according to ASTM D 5338 & ASTM D 598 the biodegradation in actively aerated compost was 64.9 % ThCO2 after 45 d (readily biodegradable);
t50 (17.2 mgC/g soil) = 33.4 d

Additional information

In a test on biodegradation in soil according to EPA OPPTS 835.3300 and ASTM D5988 (Farrell, 2000) triethyl citrate (TEC) was found to be readily biodegradable. Decay rates decreased as a function of substrate concentration. Consequently, the time required to achieve 50 % mineralization (t50) or 60 % mineralization (t60) increased as the TEC concentration in the soil increased. Nevertheless, at all substrate concentrations, net mineralization of the TEC was greater than that of the positive control (cellulose). Moreover, biodegradation of the TEC met or exceeded the ‘pass levels’ defined in the ASTM, FDA, and EPA guidelines. That is, conversion of substrate-C into CO₂exceeded 50 % ThCO₂within the 64-day time limit set by the equivalent FDA soil biodegradation test (USFDA, 1987) and 60 % ThCO₂within the time limits set by the equivalent ASTM (≤ 180 days) and USEPA (≤ 64 days) test methods (ASTM, 1999; USEPA, 1998b). These results – plus that fact that at substrate concentrations in the range recommended by the FDA and EPA tests (≤ 5 mg substrate-C g-1 soil), conversion of substrate-C into CO₂exceeded 60 % ThCO₂within a 10–14 day window following the lag period – indicate that TEC can be considered readily biodegradable (US EPA, 1998a).

In another test on ultimate biodegradation in actively aerated compost according to ASTM D 5338 and ASTM D 5988 (Farrell, 2000), mineralization of the test substance reached 64.9 % ThCO₂in 45 days. Both the TEC and cellulose reference achieved total, net mineralization values ≥ 50 % ThCO₂during the 45-day test exposure, cellulose was the only test material to exceed the 60 % ThCO₂pass level defined in the ASTM guideline during the test exposure. Nevertheless, the calculated t₆₀for the TEC was 53 days – well within the time limit defined in ASTM Standard D 6002 (i.e., during a test exposure of up to 180 days).