The thermal degradation of eggshell has two main steps: a first mass loss step below 300 °C attributed to moisture elimination concomitant with organic membrane degradation; and a second step related to calcite decomposition below 700 °C . The eggshells are mainly composed by CaCO3, as attested by XRD pattern (Fig. ), which is also confirmed by the small difference from experimental residue (56%) and the theoretical (59%):