The anaerobic digestion of pig carcase with or without sugar beet pulp, as a novel on-farm disposal method

Abstract

Anaerobic digestion was investigated as a potential method for on-farm disposal of fallen stock (pig carcases), degrading the carcase material to produce biogas and digestate. The effects of feedstock (sugar beet pulp or pig carcase material or a 50:50 mix) and organic loading rate (50 g-TS L^-1 or 100 g-TS L^-1), during mesophilic (35 °C) anaerobic digestion were investigated. Anaerobic digestion was achieved for all experimental treatments, however the pig carcase material at the higher organic loading rate produced the second highest methane yield (0.56 Nm³ kg-VS^-1 versus a range of 0.14-0.58 Nm³ kg-VS^-1 for other treatments), with the highest percentage of methane in total biogas (61.6% versus a range of 36.1-55.2% for all other treatments). Satisfactory pathogen reduction is a legislative requirement for disposal of carcase material. Pathogens were quantified throughout the anaerobic digestion process. Enterococcus faecalis concentrations decreased to negligible levels (2.8 log₁₀ CFU g-TS^-1), whilst Clostridium perfringens levels remained unaffected by treatment throughout the digestion process (5.3 ± 0.2 log₁₀ CFU g-TS^-1).

Keywords: Anaerobic digestion; Animal by-product; Carcase disposal; Fallen stock; Pig carcase.