This study compares thermal degradation and residual-mass behaviour in three cassava cortex–cow bone particulate epoxy formulations using thermogravimetric (TG) and derivative thermogravimetric (DTG) curves. The specimens comprised a hybrid with 20 vol.% each of cow bone and cassava cortex (RDT4PS100), a 40 vol.% cow-bone composite (RBT0PS100) and a 40 vol.% cassava-cortex composite (RFT4PS500). At a programmed heating rate of 10 °C/min, the estimated principal DTG peaks were approximately 400, 415 and 400 °C, respectively; associated peak mass-loss-rate magnitudes were approximately 4.2, 2.5 and 5.0%/min. Residues at the plotted endpoints were approximately 16%, 16–17% and 5%, respectively. The cow-bone-only formulation showed the smallest principal degradation-rate magnitude, whereas the hybrid and cow-bone-only specimens retained substantially more mass than the cassava-cortex-only specimen. The results distinguish peak degradation temperature, degradation-rate intensity and non-volatile residue as separate descriptors. Because particle size and treatment also differed between formulations, the observations support a descriptive formulation-level comparison rather than an isolated hybridisation effect. The findings provide preliminary thermal-characterisation evidence for selecting formulations for further engineering assessment. The comparison uses a fixed total reinforcement fraction of 40 vol.% and separates thermogram-derived evidence from possible compositional explanations. The findings are relevant to screening waste-derived reinforcement systems, but they do not establish fire resistance, mechanical retention during heating or permissible automotive service temperatures. Further matched-control measurements and replicate-level analysis are needed before those engineering properties can be assessed.