Methods for separating the lignocellulosic fibers from the açaí pulping waste: quality for kraft pulping

ABSTRACT Background: Converting açaí waste fibers into kraft pulp and paper demands high amounts of preserved fibers. Manual removal preserves the fibers, but mechanical methods are faster. Therefore, this work aimed to compare three methods to extract açaí fibers from the seed’s surface concerning efficiency and fiber quality for cellulose pulping. Results: Açaí waste fibers have ≈ 34 % of cellulose and ≈ 61% of non-cellulose structural components (based on extractive free mass) and ≈ 6% of non-structural extractives and ashes (based on total mass). They occur united into bundles that dissociate into short (388 µm) fiber cells. Their pulp-paper quality indexes were aspect ratio (31.8-41.2), wall fraction (52.8 %), flexibility coefficient (47.2 %), boiler index (0.6), Runkel index (1.2), and Mulsteph index (0.8). The manual removal preserved the fibers but had the lowest efficiency (0.1 g/min). The food processor provided intermediate preservation of the fibers and efficiency (0.5 g/min). Despite the highest efficiency (3.9 g/min) of the hammer mill method, the friction with the hammers damaged the fibers and increased the levels of extractives from 4 to 8% and hemicelluloses from 34 to 40%. Conclusion: Açaí waste fiber bundles are dissociable into short fibers and have a favorable chemistry for kraft pulping and developing cellulose products. The fiber morphology is not ideal, but not limiting, demanding adjustments in the future kraft pulping parameters. The extraction of the fiber by the food processor is recommended, which is manageable to the local communities to support an integrated bioeconomy of the açaí waste.