Bisphenol A (BPA) is an endocrine disrupting chemical with high detection frequency and content, which seriously harms the ecology and human health. Spirit-based distillers’ grains (DG) are solid residues produced during the brewing process, and their treatment has gotten the concern. It is an attractive effort to combine the comprehensive utilization of DG with the removal of BPA. Herein, O-doped porous biochar (OPB) was fabricated using DG as the precursor and used in an electro-Fenton (EF) system to degrade BPA. OPB exhibited a large surface area (i.e., 1,432 m²/g) and doping of oxygen, which can facilitate dissolved O₂ diffusion and enhance the yield of H₂O₂ (i.e., 3.0-15.5 mmol/L), and 20 mg/L BPA was rapidly removed by the EF system at the optimum condition (i.e., -0.5 V, pH 4, and 0.3 mM Fe²⁺) during 30 min with the apparent kinetic constant of 0.267/min. In addition, OPB demonstrated efficient stability in removing BPA after four cycles in the EF system. According to the results of density functional theory calculation and ultra-performance liquid chromatography–tandem mass spectrometry analysis, the three pathways were inferred to be hydroxylation, ketoneation, oxidation, and benzene ring cleavage, and then further decomposed into CO₂ and H₂O, and the toxicity to the environment gradually decreased with the occurrence of the reaction. This study provides a new idea for resource recovery from waste biomass to solve the problem of water pollution. Copyright © 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.