Converting açaí waste fibers into paper-grade cellulose by soda pulping: Temperature and time effects on efficiency, cost, and sustainability

Açaí waste fibers are widely available in the Amazon and are promising for producing cellulose-based, eco-friendly products if proper pulping is achieved. This study aimed to investigate how soda pulping temperature (140°C and 160°C) and time (60 min and 90 min) combinations affect the efficiency, cost, and sustainability for converting açaí waste fibers into paper-grade cellulose. The investigated outcomes were yields, delignification, fiber individualization, cellulose integrity, handsheet properties, unitary costs, and environmental hotspots by a qualitative gate-to-gate life cycle assessment (LCA). Increasing pulping time and temperature remarkably dropped the yield from 40% (140°C/60min) to 16% (160°C/90 min). Higher levels of screening rejects (>2%), poor delignification, and defibrillation indicated improper pulping at 140°C, especially for 60 min. In contrast, 160°C pulping decreased insoluble lignin contents from 23.0% to 8.9% (60 min) and 5.9% (90 min) and effectively individualized the fibers from the natural bundles. Despite the decrease in the crystalline index from 32.8% (raw fibers) to 24.1%, the most drastic pulping (160°C/90 min) provided the most mechanically resistant, color-homogeneous, and brighter handsheets. Nevertheless, pulping at 160°C for 60 min was selected as the standard combination for future studies based on intermediate pulping effectiveness, yield (21%), and unitary cost per handsheet (US$12.37). The LCA indicated that valorizing açaí waste supports circular bioeconomy strategies, but environmental performance depends on the management of the NaOH, energy, and water consumption, besides the recovery of the effluent and innovative solutions for its application.