Marine Biodegradation Testing

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. 

The test materials used are all commercially available plastics that are made from corn, namely, polylactic acid (PLA) and polyhydroxyalka-noate (PHA). PLA and PHA materials have passed the ASTM D6400 compostability standard and biodegraded in a simulated industrial compost environment in 180 days. ASTM standards are applicable for plastic molded products and not plastic pellets. The samples for the ASTM D6691 test included the following  

Sustainable Plastics Environmental Assessments of Biobased, Biodegradable, and Recycled Plastics, First Edition. Joseph P. Greene. 

The positive control material is cellulose powder from Avicell and the negative control is LDPE plastic trash bag from Glad. 

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

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. 

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 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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