The particle size distribution is one of the main parameters affecting the quality of a biomass used for energy purposes. Giant reed (Arundo donax L.) is currently harvested using the common self-propelled forage harvesters (SPFH). Often the product presents a distribution skewed towards the finer particles that can negatively influence the qualitative traits of the fuel and the efficiency of power plants. The Agricultural Engineering Research Unit of the Council for Agricultural Research and Economics (CRA-ING), in collaboration with Spapperi Ltd, has designed and developed a prototype for cutting and sectioning the Arundo plants in order to produce a higher proportion of chips longer than the ones obtainable from a forage harvester. A study has been conducted to compare the characteristics of the product obtained from the prototype or from a SPFH commonly used for the harvesting of silage maize and currently employed for the harvest of giant reed. The first results show that the lengthening of the particle size is attainable. In a perspective view, the further improvement of the prototype efficiency will positively affect the feedstock quality, the availability of mechanical solutions, the extension of the harvesting windows, and, finally, the diversification of the final use.