The shape of the biodegradation curve for low and high density polyethenes in prolonged series of experiments

Previous work on the 14 CO 2 liberation (measured by liquid scintillation) after biodegradative attempts was extended from two to four years in the case of LDPE ([ 14 C]-labelled material mixed in the bulk) and was compared with results on HDPE (homogenously labelled by mixing in [ 14 C]monomer). The trends for LDPE degradation with or without u.v.-sensitizer and its dependence on the surface/volume ratio were found to be similar to HDPE in spite of the fact that LDPE is more inert. The degradation curves were characterized by a straight line progression in the first 100 days of observation before declining parabolically. This is probably due to a rapid exhaust and enzymatic cleavage of the extractible short chain materials from the bulk. The trend was occasionally reversed to a progressive increase of 14 CO 2 liberation in some of the long term runs. Elucidation of this anomaly is being attempted.