Anaerobic treatment of slaughterhouse residues in municipal digesters

Abstract

The tendency to increase the number of units processed per day at slaughter yards (up to 8000 hogs daily), as well as new regulations (recycling and waste laws) in Germany, necessitate extensive utilisation of the residuals coming from slaughter yard operations. Anaerobic digestion appears to be an ideal use for the wet pasty residuals, that have little structure and a water content greater than 70%. The anaerobic digestion of sludges from municipal treatment plants in digesters, has been recognized as the state of the art process for decades. Due to changes in regulations (demands on nitrogen elimination), many digesters still have excess capacities, that allow the co-treatment of additional residuals (cosubstrate). Since little experience has been gained in co-treatment of slaughter waste in municipal digesters, a pilot plant was operated to simulate the process before planning large scale operation. This paper presents the results of the pilot plant, as well as the first months of the co-treatment of stomach contents and slaughter flotation tailings in a municipal digester.