BIODEGRADABILITY OF SOME FOOD-PACKAGING MATERIALS IN SOIL

The imminent shift of urban solid waste disposal from landfilling to recycling-composting programs directs attention to the biodegradability of certain food packaging items that are not suitable for recycling. Novel plastic wrap formulations claiming to be more degradable than their predecessors are now being marketed. Because biodegradability claims often appear in poorly documented promotional literature only, a comparative biodegradability survey of some novel highly plasticized polyvinyl chloride (PVC), traditional polyethylene (PE) and polypropylene (PP) wraps as well as coated or impregnated paper products was made. All materials were exposed in soil under conditions generally favorable for biodegradation. The measurement of CO2 evolution in Biometer flasks, decline in tensile strengths, in combination with newly developed residual weight determinations, and other residue analysis techniques were utilized in assessing biodegradation. During 3 months of exposure, traditional PE and PP films did not undergo measurable deterioration, but a group of newly formulated and heavily plasticized PVC films underwent extensive biodeterioration and up to 27.3% of their carbon was converted to CO2. However, gas chromatography, residual weight determination, chloride release and viscosity measurements indicated that only the plasticizer but not the PVC resin was mineralized. The wax-impregnated paper products were rapidly and completely mineralized. The PE-coating did not prevent the rapid mineralization of the cardboard, even when the material was left unshredded.