The aim of this paper is to present a comparative study in terms of determining general properties of four different agricultural residual substrates before and after the anaerobic fermentation process inside a pilot installation dedicated to this type of applications. The influence of anaerobic digestion can be observed from the modifications it brings to the general properties of the used materials. This work underlines positive and negative influences for pH correction agents relative to material further use in combustion process with impact on the characteristic temperatures on which the materials modify their physical properties. All used materials present a high energetic level making them useful even as residues after anaerobic fermentation.