A novel route to graphene oxide (GO) is presented where the cellulosic biofilm formed at the air-water interface as a waste product in the kombucha tea beverage fermentation industry is used as the renewable carbon source. A kombucha pellicle was first purified by treatment with 1.0 mol/L aqueous NaOH at 90 °C and bleaching with 1.5% (w/w) aqueous NaOCl at 23 °C and then pyrolyzed at 600-800 °C in air or under an inert atmosphere. The highest GO yield of 22.5% (w/w) was obtained by pyrolysis at 600 °C under Ar. The product was identified as GO using FT-IR, Raman, XPS, XRD, and scanning electron microscopy. The ability to transform to GO by simple pyrolysis may be due to an extraordinarily highly ordered arrangement of glucan chains in kombucha pellicle fibrils. This discovery provides the first sustainable feedstock-based, simple, green route to GO, without the use of concentrated strong acids and oxidizing agents used in current Hummers' method.