Chemical and physical properties of short rotation tree species

The European Union’s growth strategy (Europe 2020) requires reductions in greenhouse gas (GHG) emissions and increases in both renewable energy sources and energy efficiency. Short rotation forestry (SRF) has achieved greater awareness due to these targets. Short rotations (1–12 years), rapid growth and the ability to coppice are typical for SRF. Salix, Populus, Alnus and Betula have smaller GHG emissions of biomass production than annual agricultural plant species, since management and harvesting are not needed every year. Physicochemical properties of these species must be known when their utilisation is planned and optimised. Seven tree species were studied: three willows (Salix myrsinifolia, Salix schwerinii and Klara), one aspen (Populus tremula), one alder (Alnus glutinosa) and two birches (Betula pendula and Betula pubescens). One stem wood (S) sample and one stem wood and bark (SB) sample of each tree were investigated. Furthermore, seven surface soil samples and four incineration ash samples (two S. myrsinifolia and two S. schwerinii) were also studied. Heating values, densities, ash contents as well as carbon, hydrogen and nitrogen contents of all short rotation biomass samples were usually quite typical for the corresponding tree species. Additional observations included the accumulation of cadmium in willow and aspen samples, small chloride content values, and higher ash- and element contents in SB samples than in the corresponding S samples. Nutrient content of ash was usually higher in the S sample, contradictory to biomass samples, and finally the cadmium content of the ash samples was very high.