Standards organizations biodegradable polymers

No standards are available to deal with the changes in the qnality of soil and aquatic ecosystems caused by biodegradation of polymers. Again, the intentions of the standards for organic recovery shonld be extrapolated to those environments too. Since the chemical compositions of different soils as well as of aqnatic ecosystems and their sediments could be very different from each other, the definition of acceptable changes will cause many more problems than for compost. For those ecosystems the application of biotests will be the most important impact control for biodegradable polymers. 

Several standard test protocols for measurement of polymer biodegradation are presently available. Organizations which have published such tests include the American Society for Testing and Materials (ASTM), Ministry of International Trade and Industry (MITI) (Japan) [40] and the Organization for Economic Cooperation and Development (OECD) [41]. They are, however, for the most part deficient to the extent that they have no control over the nature of microbial inoculum used, or the possible preadaptation of the mixed populations to specific substrates, and over the adequate control of particle size of the substrate. The relevance of these factors to laboratory assessment of the biodegradabUity of synthetic polymers has been recently discussed [1]. Most of these test methods have been derived from tests first used with detergents [42], and are not always well-suited for solid polymer substrates. 

The evaluation scheme can also be applied to substances other than monomers, such as additives used to enhance polymer properties and processability. Standards on organic recycling allow a maximum 1 % by weight of a nonbiodegradable substance, or a substance whose biodegradability has not yet been determined, on the condition that the overall sum of such substances is <5%. 

For good reasons, no standards are available which define the acceptance levels for changes of soil quality or for influences on aquatic ecosystems caused by the biodegradation of polymers. The parameters of stable, balanced arid soil may differ more from those of a typical wetland than the influence of polymer degradation may ever exert. Measurement of chemical parameters may never be sufficient. The application of biotests with representative organisms will, most probably, be the most appropriate impact control. Monitoring of microbial populations using molecular... 

The necessity of ecotoxicological investigations is clearly stated in standards dealing with the organic recovery of biodegradable materials. This is not only because of the possible formation of unknown metabolites, but also because of the behaviour of additives in polymers (e.g., conventional softeners) which are already known to be problematic. 

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