The introduction of new species in forest management must be undertaken with a degree of care, to help prevent the spread of invasive species. However, new species with higher profitability are needed to increase forest products value and the resilience of rural populations. Paulownia tomentosa has an extremely fast growth. The objective and novelty of this work was to study the potential use of young Paulownia trees grown in Portugal by using heat treatment to improve its properties, thereby allowing higher value applications of the wood. The average chemical composition of untreated and heat-treated wood was determined. The extractive content was determined by successive Soxhlet extraction with dichloromethane (DCM), ethanol and water as solvents. The composition of lipophilic extracts was performed by injection in GC-MS with mass detection. Insoluble and soluble lignin, holocellulose and α-cellulose were also determined. Physical (density and water absorption and dimensional stability) and mechanical properties (bending strength and bending stiffness) and termite resistance was also determined. Results showed that extractive content increased in all solvents, lignin and α-cellulose also increased and hemicelluloses decreased. Compounds derived from the thermal degradation of lignin were found in heat-treated wood extractions. Dimensional stability improved but there was a decrease in mechanical properties. Resistance against termites was better for untreated wood than for heat-treated wood, possibly due to the thermal degradation of some toxic extractives.

Chemical composition influences the calorific power of wood, mainly due to the calorific power of structural compounds and extractives. Heat treatment changes the chemical composition of treated wood. This work studies the relationship between chemical composition and calorific power improvement by heat treatment. Samples were heat-treated by the ThermoWood process ^® for 1 h and 2 h. High heating value (HHV) and chemical composition; lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol, and water were determined. The HHV of untreated wood ranged between 18.54–19.92 MJ/kg and increased with heat treatment for all the tested species. A positive linear correlation was found between HHV and Klason lignin (R² = 0.60). A negative trend was observed for holocellulose, cellulose, and hemicelluloses content against HHV, but with low determination coefficients for linear regression. The best adjust for polysaccharides was found for hemicelluloses content. A positive correlation could be found for dichloromethane extractives (R² = 0.04). The same was obtained in relation to ethanol extractives with R² = 0.20. For water and total extractives, no clear positive or negative trends could be achieved. The results showed that the HHV of wood increased with heat treatment and that this increase was mainly due to the increase in lignin content.

Cork Liquefaction for Polyurethane Foam Production

The treatment of agricultural and forest residues (AFRs) has become an important issue nowadays, both to avoid improper management and for their enhancement. In the study area of Viseu (Portugal), the AFRs are taken to a Residual Biomass Collection Centre. These are valorised in a Biomass Power Plant to produce electricity. Two further processes could be implemented to valorise this biomass: mulching and composting. This study aims to understand the best strategy to enhance this type of biomass residual considering their environmental performance. The Life Cycle Assessment (LCA) was applied considering a cradle-to-grave approach. Different processes of all the technologies were analysed, and the data collected enabled a comparison of 11 environmental impact categories. The results show that composting is the best alternative, except for global warming and ozone layer depletion, and energy valorisation has the greatest impact on five of the considered categories. In the three processes, impacts are mainly associated with the production and shredding phases of the residual biomass, rather than the transportation stages, due to the short distances covered. In all cases, the value of the final product generates market consequences in terms of electricity and fertiliser production. In line with the aim of the study, its outcomes may provide scientific support to local decision makers in defining best practices in the management of the AFRs.