Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2009
Publication Date: 5/16/2009
Citation: Ro, K.S., Cantrell, K.B., Hunt, P.G., Ducey, T.F., Vanotti, M.B., Szogi, A.A. 2009. Thermochemical conversion of livestock wastes: Carbonization of swine solids. Bioresource Technology. 100:5466-5471.
Interpretive Summary: Animal manure is an abundant resource that can be used to generate alternative energy products. Animal manure from swine can be converted using slow heating into charcoal or bio-char. However, one must understand how swine manure breaks down in terms of rate and temperature range. In this paper, we monitored weight changes of three different types of swine manure (house flushed, separated solids, and lagoon sludge) as a slow increase in temperature was applied to the samples. Using this information and available mathematical models, we determined the energy required to begin the first stage in the break down of manures. Compared to the lagoon sludge, the flushed and separated solids required less energy to begin bio-char formation. Bio-char formation from swine manure was more complex than that from woody biomass.
Technical Abstract: Animal manure represents a significant portion of the total sustainable U.S. renewable energy sources that can serve as a bioenergy feedstock in thermochemical conversion processes. The process of slow pyrolysis or carbonization promotes the conversion of animal manure like swine manure into charcoal. The kinetics of the thermal decomposition play an important role in design and operation of animal manure carbonation. 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 first order cellulose decomposition, 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 identical values of E and A, confirming the validity of these methods.