Environmental degradation and biofouling of 'green' plastics including short and medium chain length polyhydroxyalkanoate
Catherine A. Woolnough, Lachlan H. Yee, Tim Charlton, John R. Foster
Biopolymers derived from natural resources are potential alternatives to recalcitrant synthetic plastics; however, studies investigating the degradability of these biopolymers in natural environments are relatively few. This study compares the environmental degradation of polymers described as green plastics in garden soil in terms of weight loss, topographical changes and biofilm attachment. Poly (3-hydroxybutyrate) (PHB) and poly [(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] (P (HB-co-8HV)), (copolymer containing 8 mol% HV) films degraded rapidly, losing 50% of their initial weight in 50 days. In contrast, after burial for 380 days, the medium chain length polyhydroxyoctanoate (PHO) lost 60% of its weight, poly (D,L-lactide) (PDLL) 18% and poly[(D,L-lactide)-co-glycolide] (PDLLG) 35%. Polystyrene (PS) and ethyl cellulose (EC) showed no significant degradation. Both weight loss and biofouling occurred in the following sequence: P (HB-co-8HV) = PHB > PHO > PDLLG > PDLL > PS = EC. The surface rugosity and surface areas of PHB and P (HB-co-8HV) increased three- and twofold, respectively, during degradation, indicating surface erosion. The surface rugosity of PHO increased twofold and the surface area increased by 25%. This in situ study demonstrates a quantifiable relationship between biofilm attachment, surface rugosity and polymer degradation. PHB and P(HB-co-8HV) showed greater biofouling and increased surface rugosity, and degraded significantly faster than the other polymers studied.
Keywords:biopolymers in natural environments are relatively few,polyhydroxyoctanoate,biofilm attachment, surface rugosity and polymer degradation.