Anaerobic co-digestion of grease trap and sewage sludge from a wastewater treatment plant is evaluated.Enzyme-lipase application, both addition and dosage, are evaluated by fitting the methane productionof biochemical potential tests with the first order model. The enzyme addition effect, at 2, 5 and 10% ofgrease trap (%GT VSFED−1) and the enzymes doses, between 0.25 and 1.67% (v/v), without and with greasetrap presence were studied. Grease trap addition showed a negative effect on the waste biodegradability,which was completely overcome by the addition of lipase. Enzyme addition improved notably themethane production for all grease trap fractions studied. In regards to the dosage, the best result wasachieved between 0.33 and 0.83% (v/v) of enzyme. The co-digestion of sewage sludge and grease trapmay be a feasible process by using lipases due to the saving in operational costs and the increase in thebiogas production