This study aims to derive a qualitative model for energy requirements of the wood chipping process. A relationship is shown between energy requirements and properties of biomass, which is a quite variable material.The relationship between comminution machinery and energy which is necessary for the process is highlighted. The derivation of the model is focused on chipping, but it is generally possible to make it available for both different types of biomass (f. ex. agricultural residues)and different types of comminution machinery (f. ex. hammermills) by using different material properties adjusted to the machinery mechanics. The properties which are used in the derivation are meant to be easy to measure. Furthermore, the model is meant to be used as a base for a quantitative model that, thanks to measurements taken from real comminution machinery and thanks to using wood with known properties, could answer two important questions:- Would hypothetical changes in the desired size of output material increase the total system efficiency, taking into consideration the lowest efficiency of the combustion process (e.g., higher amounts of unburned fuel)?- Considering the energy used for the process, how can comminution as an operation in the biofuel supply chain be optimised?Answers for the above questions could highlight new possibilities in terms of further energy savings and a maximising of the energy efficiency of the bioenergy sector. Furthermore, the results could motivate optimized choices of comminution machinery for the biofuel supply chain as well as for other applications.Another important feature of this study is its unique holistic point of view that takes into consideration aspects from the fields of mechanics, material sciences and natural sciences to deliver the full picture to the reader.