Marine Biodegradability

No norms exist with specifications for anaerobic digestion from other standards organisations. Nevertheless, several producers of biodegradable polymers felt this was a requirement and it can be expected that in the next few years (2014-2015) serious efforts will be undertaken to develop more detailed and valuable standards on specifications for anaerobic digestion. 

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Spence, K.E. A.L. Allen S. Wang J.L. Jane. Soil and Marine. Biodegradation of Protein-Starch Plastics. In R. M. Ottenbrite, S. J. Huang and K. Park., editors Hydrogels and biodegradable polymers for bioapplications. ACS symposium series 627 American Chemical Society Washington DC, 1996 pp. 149-158 (Chapter 12). 

Compostable plastics are those that pass the ASTM D6400 biodegradation requirements of greater than 90% carbon conversion to CO2 after 180 days while exposed primarily to hot composting conditions of 58°C and 50% moisture. Marine biodegradable plastics are those that pass the ASTM D7081 of greater than 30% carbon conversion to CO2 after 180 days while exposed to cool marine water of 30° C for 180 days. This is explained in more detail in Chapter 8. 

Solid waste disposal environments for plastic materials can include industrial compost, home compost, anaerobic digestion, landfill, litter, and ocean water. Only two disposal environments have both biodegradation standards for test methods and biodegradation performance standards, for example, industrial compost and marine biodegradation environments. Test method standards are available for anaerobic digestion, home compost, and landfill environments. The second necessary performance specification standard for biodegradation performance is not available for anaerobic digestion, home compost, or landfill... 

Marine biodegradation standards require that the plastic samples should also pass the ASTM D-6400 standard for biodegradation under industrial aerobic compost conditions. The ASTM D-6400 standard requires plastic samples to convert 90% of the carbon in the plastic sample to CO2 after 180 days while at 58°C. 

FIGURE 8.2 Experimental setup for laboratory environment of marine biodegradation test. 

Q.8.8 ASTM D6691 is the test method for marine biodegradation and requires that the samples pieces and marine water be held at 30°C for 180 days. T or F ... 

Marine biodegradation is measured according to ASTM D6691 test methods with measurement of CO2 evolution from the plastic samples. As per ASTM standards of using actual marine water rather than synthesized one, ocean water was retrieved from beaches in Half Moon Bay, California, with a surface temperature of approximately 20°C. Water was maintained at room temperature until testing began. The marine water was not characterized for sea microorganisms. 

Marine Biodegradation Results for PHA, PLA, and Control Test Samples after 180 Days... 

Another category is marine biodegradation tests. Some promising applications of bioplastics are related to the marine environment (e.g., fishing lines, fishing nets, disposables on ships and so on). In particular, the US Navy has been spearheading the developments for many years. 

Figure 2, Marine biodegradation behavior of 2 and generations of pure Boltorn hyperbranched aliphatic esters.

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