Energy crops and thermal conversion of the obtained biomass is a feasible route for the production of energy. In this work, dehydrated composted sewage sludge (BIOSOLIDS) and sludge from dairy waste-water treatment (MUD) were used as organic amendments on four different poplar clones (UNAL, 1-214, AF-2 and AF-8) and. These amendments were yearly applied throughout a four years' study aiming to find out the effects on both agronomic (diameter, height and biomass volume of the trees) and thermal (fuel and thermogravimetric analysis) properties of the poplars. The application of MUD improved the agronomic characteristics of the poplars, especially those of UNAL and AF-2. Thermal results were not as conclusive, but pointed to an improvement of the thermal behavior of UNAL under BIOSOLIDS treatment and of AF-2 and AF-8 under MUD fertilization. On the whole, the most favorable case was that of the AF-2 under fertilization with MUD. (C) 2016 Elsevier Ltd. All rights reserved.