Mechanical Thermal Expression (MTE) is a dewatering technology ideally suited for the dewatering of internally porous biomaterials. In the MTE process, the combined application of temperature and compressive force enhances the collapse of the porous structure, resulting in effective water removal. In this paper, a comparison of the dewatering of titania, which is an ideal incompressible material, and lignite, which is a plant-based biomaterial, is presented. The comparison is based on the parameters critical to dewatering, namely the material compressibility and the permeability. With the aid of mercury porosimetry results, a detailed discussion of the pore destruction resulting from MTE processing is presented. It is illustrated that there is a well defined relationship between the pore size distribution after MTE dewatering and the MTE temperature and pressure. The discussion is extended to an investigation of the effects of MTE processing conditions on the effective and non-effective porosity. The effective porosity is defined as the interconnected porosity which contributes to flow through the compressed matrix while the non-effective porosity is the remaining porosity which does not contribute to flow. It is illustrated that there is a linear relationship in both the effective and non-effective porosity with the total porosity. The linear relationship is independent of the processing conditions. It is also shown that MTE processing collapses the effective and non-effective pores at roughly the same rate.