Encouraging Invasive Acacia Control Strategies by Repurposing Their Wood Biomass Waste for Pulp and Paper Production

Concerns on the expanding infestation of several Acacia species in the southern Mediterranean European countries have triggered an ever-growing requirement for costly targeted control actions. Valorizing biomass waste produced could help promote and better finance these actions. For that purpose, wood wastes from invasive control actions were tested regarding their pulp and paper potential, aiming to entice cellulose industries to partake in future conservation actions. Wood waste from the five most pervasive Acacia species was studied (Acacia dealbata Link, Acacia longifolia Willd, Acacia mearnsii De Wild, Acacia melanoxylon R.Br, and Acacia saligna Labill) regarding physical and chemical characteristics, and a central composite design was used to optimize alkali charge and reaction temperature on pulping yield and delignification. Bleached kraft pulps were produced with each species’ optimized conditions and for an equitable mixture of all species. Optimized pulp yields (52.6%–53.5%) and pulp polymerization degree (2867–3690) of Acacia species were higher than those of Eucalyptus globulus Labill (used as reference). Optimized bleached pulps were refined and fiber, pulp, and handsheet properties determined. Acacia dealbata and A. longifolia presented high specific wood consumption and lower handsheet strength properties, pointing to overall lower pulping potential, while A. melanoxylon and A. mearnsii characteristics were equal to or higher than those of E. globulus. A. saligna pulp and handsheet characteristics appear more suited for tissue paper. The Acacia mixture achieved acceptable characteristics, enabling the indiscriminate use of Acacia wood regardless of the species. As a shortcoming, the Acacia pulps showed the worst optical characteristics, with brightness dropping substantially with beating (64%–76%) when compared to E. globulus (81%).