Marine biodegradation tests

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. 

the first standards were developed for simple and pure chemical substances, and published as OECD 308. For bioplastics, the first norm was published by ASTM in 1993 ASTM D5437-93 - Standard practice for weathering of plastics under marine floating exposure. 

A standard for measurement of true biodegradation was published afterwards ASTM D6691-09 - Standard test method for determining aerobic biodegradation of plastic materials in the marine environment by a defined microbial consortium or natural seawater inoculum. 

OECD 306 [69] on biodegradability in seawater describes two test methods. The first one, the shake flask method, is based on the determination of loss of DOC and can therefore be rarely used for biodegradable plastics. The second one, the closed bottle test, is based on oxygen consumption and uses very low concentrations of test item (2 mg/1). Therefore, again, it is not really suited for biodegradable plastics. 

Another test has been developed by the ASTM committee D20.96, ASTM D5437-93 [70]. 

Another ASTM method, ASTM D6691-01 [71] is determining the aerobic biodegradation of plastic materials in the marine environment by a defined microbial consortium. The latest development at ASTM is the inclusion of a marine variant in a new revision of the Sturm test, ASTM D5209 [10]. Yet, this project is still in development. As it looks now, it would be the first norm that determines the biodegradation of plastics under marine conditions by measuring directly the mineralisation and not a secondary parameter. 

Within the CEN organisation, the TC/249/WG/9 on characterisation of degradability of plastics has included biodegradation of plastics under marine conditions as one of the working items. However, progress is very slow. 

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

An attempt has been made to isolate P(3HB)-degrading microorganisms from the marine environment (sea water), where we carried out the biodegradation tests of polyesters. The sea water sample was filtered through a 0.45 pm Millipore filter, and the filter-adhered microorganisms... 

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... 

Satisfactory rate of biodegradation of the plastic material that is under aerobic marine water test of 30°C in 6 months, that is, more than 30% of the carbon in the original plastic sample is converted into CO2 as measured by measuring the amount of release CO2. 

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... 

The blend compositions are currently being exposed to accelerated landfill, simulated marine, and aerobic composting environments to measure the degradability of these blends in more realistic biodegradation tests. 

The environmental behaviour of LAS, as one of the most widely-used xenobiotic organic compounds, has aroused considerable interest and study. As a result, it has been determined that, under certain conditions, LAS compounds are completely biodegradable however, in the marine environment their degradation is known to be slower. The presence of metabolites of the anionic LAS surfactants, the long and short chain SPC derivatives, in the aqueous environment is well known, and as such these degradation intermediates needed to be monitored (and tested for their toxic effects). 

Several specific studies have been made on the LAS transport processes in a variety of different estuarine and marine environmental compartments (e.g. LAS removal by biodegradation and/or adsorption), including the flux of LAS from freshwater to a coastal environment [3,6, 29,40]. However, a complete study of LAS behaviour requires knowledge of their primary biodegradation intermediates, SPC, that have been detected in different laboratory tests [15,36,37], Their existence in fresh-water [2,13] and marine water [5] has been demonstrated recently. 

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