Recently, the conversion of livestock manure to solid fuel via torrefaction has brought more attention to moving forward to a carbon neutral society. A proper design of livestock manure to solid fuel is key for sustainable waste management. In this study, cow manure, as a representative of livestock manure, was examined for solid fuel production, focusing on enhancing the heating value. The torrefaction process was adopted as a main solid fuel generation process and compared to simple drying. The heating value of the torrefied cow manure was increased as the torrefaction temperature increased from 200 °C to 300 °C. The heating value was nearly saturated at around 30 min when the torrefaction temperature was increased from 20 min to 40 min. The heating value was further increased when the cow manure was mixed with sawdust or rice straw. The sawdust, which originally possessed a higher heating value, showed its potential as a candidate for additives to the torrefaction of cow manure. Compared to simple drying, torrefaction showed a higher heating value and energy density, successfully converting to stable carbon material.