New Product Applications Using Hybrid Aspen Bark as Raw Material

The extracts and chemical composition of hybrid poplar bark allow it to be used in many applications in the chemical industry. In the doctoral dissertation of Pasi Kurcalo, researcher at the Institute of Natural Resources Finland (LOK) and doctoral student at the Sustainable Chemistry Unit of the University of Oulu, the chemical composition of hybrid poplar bark biomass was studied, activated carbon was produced from bark extract, and a pesticide chemical was produced From hemicellulose bark. All chemical products were separated from the biomass following sequential treatment principles.

The hybrid aspen tree, a species that originated from the crossing of European and American poplars, was introduced to Finland in the 1950s. Its rapid growth made it an attractive raw material for the timber industry. However, hybrid aspen did not reach the same value as other dominant tree species on the market, as the market changed dramatically before hybrid aspen plantations were ready for harvest.

“Currently, hybrid poplar is seen as an opportunity to increase diversity in conifer-dominated forests. Applied chemistry can explore new uses and value-adding for the trees,” says Pasi Corcalo.

Enhancing the utilization of the bark by successive processing

The extractives and chemical composition of hybrid poplar bark make it suitable for various applications in the chemical industry. The goal of his doctoral research was to produce different parts of the same bark biomass for further processing, using the principle of cascading processing.

First, rigid carbon foam has been produced from hybrid poplar bark extracts, which can replace fossil-based foaming chemicals in insulation or padding applications that require heat tolerance. Solid foam also works well as a starting material for activated carbon.

After separating the extracts from the bark, the remains of the extract were used by heat treatment, that is, roasting under oxygen-free conditions. The method produced a distillate that was found to be an effective chemical in controlling some weeds and fungal diseases of vegetable crops. The study found that a hot water extract of the bark, which was used to separate the raw materials for foam, improved the performance of the chemical from the extraction residue against weeds.

Finally, after the production of chemicals, biomass remains from the hot bark, which can also be used as raw materials for biochar or in energy production.

Corcalo concludes, “Using successive bark processing, many possibilities for use and added value can be realized from a single source of raw materials. This, in turn, can spark new interest in the possibilities of using hybrid poplar and detached biomass.”

In cascade processing, the various valuable components and bioproducts are separated from the raw materials, that is, the main or side stream of biomass, by sequentially connected technological unit operations. All biomass is used completely in products, nutrients and energy with the highest possible added value, while avoiding the creation of new unused by-products.