Ultimate biodegradability

The methacrylates ate slightly to essentially nontoxic to fish and other aquatic species. Hydrolysis data suggest rapid breakdown at alkaline conditions, and studies show that MMA is ultimately biodegradable ia sewage sludge samples. Based on this information, the methacrylates ate not considered to be a significant environmental hazard. 

In a continuous model river test system it can be shown that after passage through a sewage treatment plant ester sulfonates have no significant influence on the qualitative and quantitative composition of the biocenosis of a receiving water [113]. All the investigations into the environmental fate of a-sulfo fatty acid esters demonstrate that aquatic toxicity is alleviated by their fast ultimate biodegradability, which allows them to be classified as environmentally compatible. 

Ultimate biodegradability (OECD 301) <60% within 28 days >60% within 28 days >50% within 10 days window... 

Staples CA, Naylor CG, Williams JB, Gledhill WE (2001) Ultimate biodegradation of alkylphenol ethoxylates surfactants and their biodegradation intermediates. Environ Toxicol Chem 20 2450-2455... 

Support for this hypothesis on iso-LAS is given through the findings of Nielsen et al. [100] in a degradation study carried out with radiolabelled substrate, in which it was reported that most of the iso-LAS isomers underwent ultimate biodegradation (79-90%), although some of their carbon (10-20%) was released as water-soluble intermediates. Furthermore, Kolbener et al. [90] could identify structures... 

Aerobic degradation of diethyl phthalate by acclimated soil and activated sewage sludge microbes was studied using an acclimated shake flask CO2 evolution test. After 28 d, loss of diethyl phthalate (primary degradation) was >99%, with a lag phase of 2.3 d, and ultimate biodegradation (CO2 evolution) was 95%. The half-life was 2.21 d (Sugatt et al., 1984). 

The ultimate biodegradability of a substrate, such as is depicted in Figure 4, may, in addition to oxygen uptake, be measured by disappearance of organic carbon, CO2 evolution and the formation of water. A radiotracer approach provides a more accurate determination and is the only feasible way of measuring the formation of water in the aqueous medium required for all metabolic processes. 

Ultimate Biodegradation of the Four Types of Nonionic Ethoxvlates... 

Figure 7. Ultimate biodegradation of nonionic surfactants by CO2 evolution.

Table II lists the radioactivity balance for the 28-day slipstream study (33) in which doublelabeled C12.15LPAE-9 was also a substrate. The considerably greater amount of effluent 3H2O found at the completion of the study for C12.15LPAE-9 (91.6%) compared to that found for NPE-9 (28.3%) indicates the ultimate biodegradation of the...

To prove the ultimate biodegradability of a biodegradable polymer and that there is no adverse effect on the user or the environment, as well as to successfully market a plastic material as biodegradable, there are international standards in place according to which these materials can be certified. Both Ecoflex and Ecovio are certified worldwide as compostable and are approved for contact with food. 

CO2, a blank compost inoculum without an additional carbon source (polymer sample) is simultaneously tested under the same conditions. The CO2 content of the exhaust air of both vessels is compared. After subtracting the CO2 evolution of the blank inoculum, the CO2 evolution related to the test polymer is monitored and plotted as a biodegradation curve (see Fig. 1). Finally, the activity of the compost inoculum in the controlled composting test is validated using a cellulose reference instead of the polymer. In Fig. 1, the biodegradation curve of Ecoflex is depicted. After 80 days, 90% of the theoretical CO2 evolution is reached. Thus, Ecoflex is ultimately biodegradable according to the ISO standard for compostable polymers (ISO 17088), which requires 90% of the theoretical CO2 evolution within 180 days. 

Apart from the pure process-driven requirements of the disintegration within a defined time span and the proof of ultimate biodegradability, it is necessary to make sure that there is no negative impact of degradation products or intermediates of the degradation process on the environment. Adequate information has to be provided for a comprehensive assessment of environmental and toxicological safety. 

Plant cell walls are complex, heterogeneous structures composed mainly of polymers, such as cellulose, hemicelluloses, and lignins. In spite of several decades of research, cell wall assembly and the biosynthesis and ultimate biodegradative pathways of individual polymers are still far from being fully understood. One simple example will suffice Even today, no enzyme capable of catalyzing cellulose formation in vitro has been obtained. 

Ultimate biodegradation without formation of stable metabolites was confirmed in a modified coupled units test... 

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