Multi-utilization of Chicken Litter as Biomass Source. Part I. Combustion

Chicken litter disposal is a major economic and pollution concern. Poor waste management practices lead to air and water pollution. To produce a useful renewable resource for energy, optimal conditions for combustion were studied. Three samples differing in particle size were obtained from the chicken litter by drying, milling, and sieving, each at a recovery of (A) larger than 150 μm in size, 87.5%; (B) between 150 and 45 μm in size, 6.3%; and (C) below 45 μm in size, 6.3%. Sample A showed the highest calorific value (5 300 BTU lb - 1 = 12 320 kJ kg - 1 ) and lowest ash content (ca. 25%), whereas sample C showed the lowest calorific value (2 900 BTU lb - 1 = 6 740 kJ kg - 1 ) and highest ash content (ca. 54%). Evolved gas analysis (EGA) techniques, including thermogravimetric-mass spectrometry (TG-MS) and TG-Fourier transform infrared (TG-FTIR) were used to identify off-gases. Kinetic analyses using thermogravimetric analysis (TGA) were also performed to find that the combustion process proceeds in four stages (where E represents the activation energy): (I) release of absorbed water and ammonia stemming from ammonium salts (room temp (RT) = 150 °C), E = 61.72 kJ mol - 1; (II) devolatilization (150−350 °C), E = 71.43 kJ mol - 1; (III) char precombustion (350−500 °C), E = 148.5 kJ mol - 1; and (IV) rapid char combustion (500−650 °C), E = 157.6 kJ mol - 1 . In stage III, the combustion is retarded because N concentration is high.