A simple and green procedure for bulk polymerization of ε-caprolactone (CL) has been developed using yttrium triflate (trifluoromethanesulfonate) as a catalyst under air in a simple glass vial. The efficiencies of various initiators such as diol or triol with acid or base were discussed. Little water was found to be necessary in this polymerization system. The biodegradation of direct molded poly(ε-caprolactone) (PCL) film during polymerization in aqueous solution with commercial compost was also studied by measuring the biochemical oxygen demand (BOD).