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2.6 Biorefinery based on side-streams from agriculture

The environmental aspects connected to waste handling and valorization, future fiber shortages and increasing pulp prices, require a circular and resource-efficient cellulose economy in Sweden.  Widely discussed possibilities are the recycling of cellulose fibres available in form of textiles, printing paper and cardboard including streams from biorefineries based on wood or annual plants. In this work we focus on the cellulose residues  from agricultural waste and their potential for a biorefinery approach. The agricultural waste can be considered low value lignocellulosic feedstocks. Including them in a biorefinery process would open a possibility for increasing their value by production of high value products such as dissolving pulp supplemented by lignin based products. The Swedish agricultural production was mapped for potential resources within its side streams. Both the primary agricultural residuals produced directly at the fields and secondary - side streams after processing, were considered. Four streams were selected: wheat straw, oat husks, potato pulp and sugar beet pulp. The investigations included pre-treatment, chemical delignification and bleaching as well as pulp analysis. The delignification of the raw materials was relatively easy compared to the delignification of wood while the removal of hemicelluloses and ash appeared problematic. The properties of the pulp could be to some extent regulated by the process parameters. For a holistic approach of a biorefinery, two scenarios of black liquor utilization are considered: production of bio-based chemicals through photochemical reactions using light from LEDs or its utilization for CO2 uptake.