In the present study, low frequency ultrasound was used as pre-treatment step to improve the anaerobic biodegradability of meat processing effluent. The effect of ultrasound system on anaerobic degradability was evaluated in terms of biochemical methane potential (BMP) by applying different specific energy inputs, (SE). The degree of organic matter solubilization at low frequency ultrasound was assessed by determining variation in dissolved organic carbon/total volatile solids (DOC/VS) ratio. Specific energy input was varied between 0 and 750 MJ/kg total solid (TS) while keeping ultrasonic frequency constant at low level of 20 kHz. The results indicated that effective anaerobic biodegradability can be obtained even at very low frequency ultrasound in meat processing effluent. The DOC/VS ratio increased from 0.4 to 0.73 by increasing SE up to 120 MJ/kg TS and no further improvement in the ratio was observed for higher SE inputs. Similarly, the maximum cumulative methane volume was obtained at 120 MJ/kg TS as 376 mL The volume for non-pretreated effluent was only 304 mL which indicates that ultrasound application as pre-treatment could provide 24% improvement in the methane production. Ultrasonic pre-treatment enhanced the anaerobic biodegradability in terms of solid's solubilization and methane production for meat processing effluent. (C) 2010 Elsevier B.V. All rights reserved.