The present study shows the treatment of slaughterhouse wastes of Badajoz municipal in Spain by an anaerobic codigestion process. The experimental device used was a completely mixed type (6-1 capacity) continuous bio-digester with recirculation of the methane produced in the anaerobic digestion. Under mesophilic conditions (37 degrees C), the biological anaerobic degradation, biogas production, and inhibition processes were analyzed for six flow rates; 200, 275, 350, 400, 537, and 672 ml/day. It was found that the environmental optimum flow rate is 350 ml/day for energy production. (C) 2011 Elsevier B.V. All rights reserved.