Experiments with two short rotation woody energy crops, common osier (Salix viminalis L.) and black poplar (Populus nigra L.) were carried out in Western Lithuania (55°43′ N, 21°27′ E) on a naturally acid moraine loamy Retisol. According to the results averaged over the two successive growing rotations (2008–2012 and 2013–2016), the dry matter (DM) yield of common osier amounted to 74.76 t ha−1 and 71.63 t ha−1, respectively and that of black poplar totalled 42.28 and 54.24 t ha−1. Nitrogen fertilization significantly increased the number of stems and DM yield for both crops, while stem height was increased only for osier. High-quality chaff of common osier and black poplar was produced using a screw chopper. Our study evidenced that common osier and black poplar biomass feedstock meets the requirements for high quality solid biofuel. When chopped by a screw chopper, wet chaff (40–55% moisture content) may be burned in high and medium power boilers equipped with combustion devices suitable for the incineration of wet chopped woody plants.