Abstract Electrochemical upcycling of waste polyethylene terephthalate (PET) into biodegradable polyglycolic acid (PGA) is a promising solution to relieve plastic pollution. However, both the low current density and tedious separation process for target glycolic acid (GA) products in a flow electrolysis have hindered industrial-scale applications. Here, we show an interfacial acid-base microenvironment regulation strategy for the efficient oxidation of PET-derived ethylene glycol (EG) into GA using Pd-CoCr2O4 catalysts. Specifically, only a cell voltage of 1.25 V is needed to deliver a current density of ca. 290 mA cm–2. Moreover, a green separation method is developed to obtain high-purity GA (99%). 20 kg of waste PET is employed for the pilot plant test (stack electrolyzer: 324 cm2 × 5), which exhibits 93.0% GA selectivity at 280 mA cm–2 (current: 90.72 A) with a yield rate of 0.32 kg h–1. After polymerization, PGA yield can reach up to 87%, demonstrating the potential of this technique for large-scale PGA production from waste PET.