Comparison of thermal properties of the fast-growing tree species and energy crop species to be used as a renewable and energy-efficient resource

Abstract

The energy stands of fast-growing tree species and crops are a prospective resource of renewable energy to the future. The paper focuses the assessment and comparison of the thermal properties of selected species of fast-growing trees (Paulownia tomentosa, Salix viminalis clone Tora, Populus × euramericana clone MAX 4) and energy crops (Sida Hermaphrodita, Arundo donax, Miscanthus × giganteus), as well as ash content (mass%). The following fire and thermal and properties were tested: spontaneous ignition temperature, gross caloric value, heating value. Besides those parameters, the elemental composition and ash content of the samples tested were analyzed. The results showed the energy crops to be much more effective for energy production than the energy trees. It is mostly due to higher yields harvested in a relatively short time, increased share of fiber, as well as higher energy efficiency. The highest heating value (energy potential) in case of energy crops showed Miscanthus × giganteus (16.29 ± 0.14 MJ kg−1), which had the lowest ash content (2.67 ± 0.08 mass% on average). The highest heating value in case of fast-growing tree species showed Paulownia (16.40 ± 0.18 MJ kg−1), which also had the lowest ash content (0.75 ± 0.05 mass% on average), while the Populus had the highest one (2.58 ± 0.24 mass% on average).