Woodceramics prepared from apple pomace, which were obtained by impregnating it with phenolic resin and sintering the material at different temperatures of 1073 K (sample AWC800) and 1473 K (sample AWC1200), were investigated mainly by X-ray diffraction (XRD) and simultaneous differential scanning calorimetry-thermogravimetry (DSC-TG). The as-prepared samples were amorphous; using XRD, broad peaks with d-spacings of ca. 0.57-0.52 and ca. 0.36-0.38 nm were observed. This result suggested the presence of at least two different phases: the former, which is attributed to a structure derived from aliphatic chains, and the latter, which is attributed to a structure derived from aromatic rings (graphene-like layers). By heating to 1273 K, the aromatic-ring stacking or graphene-like layers developed in three dimensions, whereas the aliphatic chains, which are more prone to oxidization, disappeared when heated in air. Therefore, it was suggested that combustible fragments with aliphatic chains develop via pyrolysis and that these undergo combustion in an oxidizing atmosphere. Furthermore, sample AWC1200 contained additional phases with longer d-spacings, which disappear on heating to 1273 K. Thus, in case of sample AWC1200, the main combustion is preceded by pyrolysis and the combustion of additional matter having a long-range ordering. Woodceramics are structurally different from charcoal or coal, and an ordered structure with a characteristic graphene-like layer is developed through further heat treatment to 1273 K.