Compost Biodegradation Tests

In the first years of the existence of biodegradable plastics, it became clear that the aerobic, aquatic biodegradation tests were not appropriate to evaluate the biodegradation of these polymers in composting. The environmental conditions are of course very different high temperatures up to 60-65 °C in composting as opposed to ambient temperature in water, different moisture content, etc. An important difference is also the activity 

The ISO procedure was adopted in a new edition of the ASTM standard, ASTM D5338-98el [41] and can also be found back in the European norm EN 14046 [43] which is expanding the field of application from plastics to all possible types of packaging materials. In Japan, the ISO 14855 was adopted without changes as JIS K 6953 [44]. 

The absence of an extra carbon source also prevents the phenomenon of a priming effect in a mineral bed test. The addition of a readily degradable and energy-rich test material in a conventional controlled composting test sometimes results in an extra stimulated activity 

The novel method using the vermiculite, mineral inert matrix has been proposed at the ISO TC61/SC 5/WG 22 as an amendment to the ISO 14855 [42]. 

At the end of 2001 the proposal is at the stage of a draft amendment ( DAM 1 ). Some further research and development is still needed but it is expected that the new method will be an official ISO standard within a short term. 

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There have been numerous communications on the subject of biodegradation test methods, including aerobic compost (30), anaerobic bioreactor (31), general methodology and future directions (32—34), and a fine review article (24). ASTM (22) and MITI (35) have also set forth standard testing protocols for plastics, as shown in Table 2, whereas OECD test methods (29) are more suited to water-soluble polymers. 

DIN EN 13432 Packaging - Requirements for packaging recoverable through composting and biodegradation - Test scheme and evaluation criteria for the final acceptance of packaging. 

Carrick DT (1994) Composting of PHBV co-polymers the relationship between laboratory biodegradation testing and practical composting. Symposium on Polymers from Renewable Resources and their degradation. Stockholm November 1994, p 26... 

As a result, specified periods of time, specific disposal pathways, and standard test methodologies were incorporated into definitions. Standardisation organisations such as CEN, ISO, and ASTM were consequently encouraged to rapidly develop standard biodegradation tests so these could be determined. Society further demanded undebatable criteria for the evaluation of the suitability of polymeric materials for disposal in specific waste streams such as composting or anaerobic digestion. Biodegradability is usually just one of the essential criteria, besides ecotoxicity, effects on waste treatment processes, etc. 

As biodegradation test we predominantly used the polyester hydrolysis with lipases. The free acids built during the ester cleavage were monitored via an automatic and improved titration system. Beside the enzyme test we also performed soil burial tests, compost simulations and tests with isolated microorganisms to check whether the results obtained with the lipase can be transferred to natural conditions. 

Activated vermicuhte was found to be a suitable solid matrix for conducting biodegradability testing.Vermicuhte by itself does not affect biological growth but can be activated to perform tasks typicahy associated with mature compost which is a very complex, difficult to standardize biological mixture. 

Requirements for Packaging Recoverable through Composting and Biodegradation— Test Scheme and Evaluation Criteria for the Final Acceptance of Packaging, EN 13432. 

Principles of main standards related to composting and biodegradability testing... 

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