Today, renewable energy sources - e.g. forest biomass - are of great importance, not only domestic but also industrial - f.i. wood fired power station - utilization is wide spread as well. However, the comminution of such fibrous texture materials requires relatively high energy and special grinding stress. In the thermal power station of AES Co. Ltd., Berente mainly wood biomass is burned as fuel. The size reduction of biomass is achieved by beater wheel mills, which were designed originally for coal. The aim of the research carried out by the University of Miskolc was to increase the capacity of the fuel supplying system. Systematic industrial and laboratory experimental series were carried out under different conditions and results are presented in this study. During the on-site industrial tests four fuel supplying systems (beater wheel mill, air classifier, heat exchanger, pipes) were equipped with a complete data acquisition system containing different sensors. Three sampling points were built 1) from the feed, 2) from the rejected coarse material after the air classifier and 3) from the final product (isokinetic) from the pneumatic transport pipe. Biomass moisture significantly influenced comminution energy consumption, especially for finer size reduction. (c) 2012 Elsevier B.V. All rights reserved.