Energy Recovery Efficiency of Poultry Slaughterhouse Sludge Cake by Hydrothermal Carbonization

Hydrothermal carbonization (HTC) is a promising technology used for bioenergy conversion from bio-wastes such as sewage sludge, livestock manure, and food waste. To determine the optimum HTC reaction temperature in maximizing the gross energy recovery efficiency of poultry slaughterhouse sludge cake, a pilot-scale HTC reactor was designed and operated under reaction temperatures of 170, 180, 190, 200 and 22 degrees C. During the HTC reaction, the gross energy recovery efficiency was determined based on the calorific value of the HTC-biochar and ultimate methane potential of the HTC-hydrolysate. The poultry slaughterhouse sludge cake was assessed as a useful source for the bioenergy conversion with a high calorific value of approximately 27.7 MJ/kg. The calorific values of the HTC-biochar increased from 29.6 MJ/kg to 31.3 MJ/kg in accordance with the change in the reaction temperature from 170 degrees C to 220 degrees C. The ultimate methane potential of the HTC-hydrolysate was 0.222, 0.242, 0.237, 0.228 and 0.197 Nm(3)/kg-CODadded for the reaction temperatures of 170, 180, 190, 200 and 220 degrees C, respectively. The potential energy of feedstock was 4.541 MJ/kg. The total gross energy recovery (GERtotal) was 4318 MJ/kg, of which the maximum value in the HTC reaction temperature was attained at 180 degrees C. Thus, the optimum temperature of the HTC reaction was 180 degrees C with a maximum GERtotal efficiency of 95.1%.