Fibre morphological characteristics, chemical composition and fuel properties of paulownia COTEVISA-2 wood

The aim of this study was to determine the elemental composition and the fibre morphological characteristics, chemical and fuel properties of wood from paulownia COTEVISA-2 clone growing on a plantation near Granada, Spain. The research was carried out on five boards representing five 5-year-old trees, taken from a height of approximately 2–3 m. Morphologically, COTEVISA-2 wood has fibres with mean length 0.923 mm, diameter 0.029 mm, lumen width 0.026 mm, and cell wall thickness 0.0015 mm. The slenderness ratio ranged between 19.27 and 64.31, the Runkel ratio between 0.060 and 0.4259, the rigidity index between 2.83 and 19.94, Mühsteph’s index between 0.1099 and 0.5082, and the flexibility coefficient between 0.701 and 0.943. Significant differences between trees were found for the values of morphological characteristics of fibres and the derived indices, apart from the solids index. Mean values of chemical properties obtained from two parallel determinations for each sample showed that the wood contains on average 48.15% cellulose, 27.48% lignin, 7.38% pentosans and substances soluble in cold water (2.38%), hot water (3.87%), ethanol (5.51%) and 1% NaOH (19.64%). The elemental composition of paulownia COTEVISA-2 wood is as follows: C – 49.06%, H – 6.19%, N – 0.43%, S – 0.021%, Cl – 0.05%. The wood contained 0.4% ash. The heat of combustion of paulownia COTEVISA-2 wood is 18.58 MJ/kg, and the calorific value is 17.18 MJ/kg. The results suggest that paulownia COTEVISA-2 is a promising wood for energy and paper production.