This work assesses the potential of stinging nettle (Urd.ca dioica L.) growing on trace element contaminated soils to produoe fibres for rnaterial applications. The nettles studied in this work grew spontaneously and dominated the vegetation cover in poplar short rotation coppices planted for the phytornanagement of lands contaminated by trace elements. Two sites were studied, contaminated by Hg for the first one and a mix of As, Cd, Pb and Zn for the second one. Results show that, for the considered soils, the contaminant contents in nettle bast fibres were at low levels, comparable to those collected at unpolluted control areas. lt rnakes it possible to consider this biornass for material use. The measured rnatter yield was lower than those obtained with traditional fi bre crops cultivated in Europe on agricultural lands. However, the tensile properties of the bast fibres mechanically ex tracted without field retting or prior alkaline treatment were equal to or better than those of industrial hemp and flax, rnaking spontaneous nettles an interesting supplement to traditional European fi bre crops for rnaterial applications.

The effect of three different commercial cellulase treatments applied on softwood bleached kraft pulp before the refining step was studied. Disc refining was applied under similar conditions as usual in paper mills. Two cellulase treatments allowed an energy saving of 20% to reach a given drainage index or breaking length. Water retention value (WRV), which characterizes the water absorption inside the fibre wall, was increased by the cellulase treatment. However, tear index losses were observed upon enzyme treatment. The third cellulase did not have an impact either on any parameters of the refining or on the pulp properties, except WRV. Viscosity measurements showed that the two first cellulases have strong endoglucanase activities but are lacking exoglucanase activities. Probably, endoglucanase activity weakens the fibre structure by generation of weak points or kinks. This hypothesis would explain the important cutting and fibrillation phenomena observed in the case of these two cellulases. It can be concluded that cellulase treatment could save 20% of electrical energy needed for refining, i.e., 50 kWh t-1, if a paper quality with a high tensile resistance but lowered tear strength is acceptable.

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X-ray tomography and densitometry (XRT and XRD) were applied to characterise wood fibre based insulation materials, which were produced by the foam forming technology. XRT is a high resolution approach with long measurement times of around 29 h, while XRD measurement needs only a few minutes. The determination of density distribution of boards in the thickness direction was the focus of this study. Both approaches visualised well the impact of raw materials and manufacturing processes on the structure of the panels. The density profiles were dependent on the pulp applied for panel production, and the processing conditions were also influential. Air flow resistance correlated with the maximum density measured inside the board. Both XRT and XRD revealed similar trends, which are useful for the characterisation of insulation materials.