The purpose of this study was to evaluate biomethane production in anaerobic digestion of swine slaughterhouse waste (SSW) and the effect of lipase pretreatment on biomethane yield. Lipase extracted from porcine pancreas was employed to hydrolyze SSW at 37 degrees C for 24 h. Three different lipase concentrations of 0.04, 0.2, and 0.4% (w/v) were adopted. Anaerobic digestion was carried out in batch style for 50 days. The results showed that the highest experimental biomethane yield (EMY) of 851.6 mL/g of VSadded was achieved when the lipase concentration of 0.2% (w/v) was used, which was significantly higher (18.4%; alpha < 0.05) than that of the untreated group. Furthermore, the highest biodegradability (B-d) of 72.7% was also achieved at 0.2% (w/v) lipase-pretreated group. Results proved that the conversion of SSW to biomethane was improved through pretreatment of lipase hydrolysis and offered a promising method for disposal of SSW.