Sustainable degumming of pineapple leaf fiber via bio-oil-assisted retting and biochar-enhanced steam explosion

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The valorization of agri-wastes has recently gained significant attention, particularly in sustainable product development. Natural fibers derived from agricultural residues, such as pineapple, banana, hemp, and bamboo, have attracted increasing interest for textile and fiber-reinforced composite applications. In this study, we focus on developing a cleaner degumming process for pineapple leaf fibers (PALF) by substituting conventional industrial chemicals with by-products derived from agri-residue pyrolysis, thereby improving process efficiency and promoting more sustainable fiber processing. Decorticated PALF were degummed using water retting, optimized for cellulase, xylanase, and pectinase activity by varying process conditions including temperature, initial pH, aeration, and substrate addition. The addition of bio-oil significantly enhanced pectinase activity from 318 U/L to 2630 U/L, reducing retting time from 18 days to 4 days. Under these conditions, pectin content decreased from 5.2 ± 0.035% to 2.3 ± 0.1% and wax content from 8.5 ± 0.08% to 5.4 ± 0.07%. Post-retting, fibers were fractionated using steam explosion following alkali pretreatment with biochar derived from agri-residue pyrolysis. Fiber characterization revealed that steam explosion, in the presence of bio-based alkali, reduced extractives from 5.4 ± 0.07% to 1.16 ± 0.03%, increased α-cellulose content to 73.66 ± 0.53%, and reduced lignin to 4.78 ± 0.13%, with a corresponding high crystallinity of 83.7% — aligning with acceptable limits for textile-grade fibers. These results were comparable to those obtained using conventional NaOH-based treatments. This study demonstrates an approach for PALF processing that reduces chemical dependency while promoting cellulose enrichment and modification of fibers, and the cellulose-rich PALF exhibits properties for applications, including textile and composite uses, although further evaluation of fiber length, fineness, mechanical properties, and processing performance is required to establish suitability for intended uses.