The tremendous increase in the use of post-consumer polyethylene terephthalate (PET) plastic brings with it the challenge of recycling the increase in waste bottles and materials. Breaking down PET scrap to its monomers in an environmentally friendly solvent is a desirable way of processing PET scrap. The analysis of the solubility parameters has inspired the successful use of biomass-derived γ-valerolactone (GVL) for PET dissolution and further accelerated the alkaline hydrolysis of PET waste to its monomers. Hydrogen bonds between PET chains and GVL play an important role in the dissolution. Source differential scanning calorimetry (DSC) has shown that GVL processing of PET involves two steps: swelling and dissolving. The optimal dissolution process by swelling DSC showed that waste PET bottle pieces could swell completely in 1 h at 120 ° C and then dissolve in 2 min at 170 ° C. The maximum solubility of PET in GVL is about 0.25 g · g−1. Here water was used as an anti-solvent to cause PET to reprecipitate from the hot solution. Due to the complete pre-swelling and the very rapid dissolution, the degradation ratio of PET during the dissolution process was only 5.7%. The GVL processing significantly increased the effective surface area of PET, which promoted the subsequent full alkaline hydrolysis of PET in about 8 minutes. This study offers an environmentally friendly, very fast and energy efficient way to recycle PET waste.