Wood chip screenings as a source of energy, kraft pulp and functional chemicals: a Nordic perspective

A virtual pulp mill producing bleached softwood kraft pulp was examined in this study and the amount of wood chip screenings was estimated based on real pulp mill operating in the Nordic countries. Wood chip screenings are defined as undersize fraction that forms during wood chipping and it is screened out from the accept chip fraction. The generation of heat and steam and the amount of bleached kraft pulp able to be produced from wood chip screenings were calculated. Chemical composition of wood samples from softwood kraft pulp mill was determined. The production of ethanol fuel and functional chemicals from the analysed wood materials was examined, based on existing and potential technologies. In addition, basic financial calculations were done and the different processes were evaluated. We found that heat and steam generation is rather profitable but not as profitable as producing bleached kraft pulp. Ethanol fuel production is not profitable because of expensive pulpwood and sawmill chips and low ethanol price. We suggest that valuable wood residues should be utilised for production of high-added valued functional chemicals in Europe and especially in Nordic countries where wood is expensive. The production of functional chemicals can be almost 100 times more profitable than heat generation.