This paper aims to derive qualitative model for energy requirements for wood chipping process. There is relationship shown between energy requirements and properties of biomass, which is quite variable material. Relationship between comminution machinery and energy necessary for the process is highlighted. Derivation of the model is focused on chipping but in general it’s possible, to make it available both for different types of biomass (f. ex. agricultural residues) or for different type of comminution machinery (f. ex. hammermills) just by using different material properties adjusted to machinery mechanics. Properties used in derivation are mend to be easy to measure. Model is mend to be used as a base for quantitative model that, thanks to measurements performed on real comminution machinery and using wood with known properties, could give answers for two important questions: Would hypothetical changes in desired size of output material increase total system efficiency, taking into consideration lowest efficiency of combustion process (i. ex. higher amounts of unburned fuel)? How to optimise comminution as an operation in biofuel supply chain, with respect to energy used for the process?