CHARACTERIZING AND SEPARATING THE LIGNOCELLULOSIC FIBERS FROM THE AÇAÍ PULPING WASTE: TOWARDS KRAFT PULPING

Abstract

Background: Over 80% of the açaí fruit is a valuable lignocellulosic waste. Kraft pulping is an alternative for future industrialization to convert açaí waste fibers into paper, but it demands high amounts of undamaged fibers.  Therefore, this work aimed to characterize the açaí waste fiber, and to test three fiber extraction methods from the seed’s surface, one manual and two mechanical, focusing on the papermaking industry.

Results: Açaí waste fibers have ≈ 50 % of cellulose with lower contents of extractives (≈ 4.7 %) and non-cellulosic structural components (≈  43.3 %). Microscopic açaí fibers are bundles that dissociate into short fiber cells (388 µm). Their pulp-paper quality biometry 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 Mulstep index (0.8). The manual removal preserved the fibers but had the lowest efficiency (0.1 g/min). The food processor balanced intermediate preservation of the fibers and efficiency (0.5 g/min). Despite the highest efficiency (3.4 g/min), the hammer mill method damaged the fiber morphology and increased the levels of extractives (> 3%) and hemicelluloses (> 10%).  

Conclusion: Açaí waste macroscopic fibers are dissociable into short fibers and have a favorable chemistry for kraft pulping and developing cellulose products. The fiber biometry 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 transferrable to the local communities, assuring an integrated bioeconomy of the açaí waste.