Thermochemical conversion of livestock wastes: Carbonization of swine solids

Slow pyrolysis or carbonization promotes the conversion of animal manures such as swine manure into charcoal. In this paper, the carbonizing kinetics of swine solids taken from different treatment stages were investigated with a thermogravimetric analyzer. Compared to their biologically stabilized counterpart (lagoon sludge) with an activation energy of 160 kJ mol−1, the activation energies for fresh swine solid samples such as homogenized flushed manure and dewatered solids were much lower between 92 and 95 kJ mol−1. Compared to the kinetics of first order decomposition of cellulose, the pyrolytic decomposition of the swine manures were more complex with the reaction orders varying at 3.7 and 5.0. The two different mathematical methods employed in this paper yielded the similar values of activation energy (E) and pre-exponential factor (A), confirming the validity of these methods. The results of this study provide useful information for development of farm-scale swine solid carbonization process.