The thermodynamic parameters of the conversion of two companion pair materials, i.e., rice straw vs dairy manure, and rice bran vs chicken manure, to biochars were characterized by thermogravimetric analysis. The overall changes of activation energy (E-a) were well described by the Flynn-Wall method. The E-a values increased steeply from about 120 to 180 kJ/mol at the mass conversion (alpha) at 0.2-0.4, followed by a relatively steady change at 0.4 < alpha < 0.65, thereafter showed a quick increase at alpha > 0.65. The higher contents of minerals in manures resulted in the larger E-a. The individual conversion of hemicellulose, cellulose and lignin in the feedstocks was identified and their thermodynamic parameters (Delta H degrees, Delta G degrees and Delta S degrees) were calculated. The yields of biochars calculated from TG curve were compared with the determined yields of biochars using muffle pyrolysis. Along with Fourier transform infrared spectra data, the distinct decompositions of biomasses and manures were evaluated. (c) 2013 Elsevier Ltd. All rights reserved.