Wood ash as a resource for the production of innovative composite materials

For process heat and district-heating purposes, 2.8 million of m3 of wood is annually burned in Switzerland 9.This process generates 24'000 tons of wood ash/year, which require an environmentally compatible way of disposal. Currently, most of the wood ash generated in Switzerland is landfilled, while the rest is recovered as soil supplement and miscellaneous applications. However, at the same time as the cost of landfilling is increasing, national environmental regulations strongly limit the recovering of wood ash as fertilizer. These environmental concerns and economic realities provide an incentive to develop new solid waste management technology. Most attractive are those that have the potential to produce saleable products. Owing to its pozzolanic behavior, wood ash may be assimilated to fly ash, which is extensively used in the concrete industry. Thus, part of the wood ash generated in Switzerland, may be also suitable for other applications such as filler in paints and composite materials. Aim of this investigation was to investigate the potentials of wood ash as a resource for the production of an innovative natural fibres reinforced bio-based composite. As results of the study the optimal composition (wood ash/natural fibres) for the targeted product was defined and the characteristics of the composite were measured. On the mechanical point of view, the composites showed a consistent internal bond (I.B.) and substantial water resistance. Additional tests showed that wood ash can have a strong influence on both curing kinetics of the binders and final properties of the boards.