Oxidative pyrolysis of biomass waste: Efficient production of humic substances with enhanced agricultural potential and environmental benefits

Abstract

This study reports an innovative oxidative pyrolysis-based technology for the high-value conversion of biomass waste, achieving efficient co-production of humic acid (24.2 wt%), fulvic acid (7.9 wt%), and humin (15.0 wt%) under optimized reaction conditions (400 °C, <5 min). This breakthrough addresses long-standing challenges in humic acid production, particularly in terms of efficiency and energy consumption. Multi-scale characterization techniques, including FTIR and TG, revealed unique structural features of the products: compared to standard humic acid, the humic acid and humin derived from oxidative pyrolysis exhibit a higher proportion of lightweight components (e.g., carboxylic acids, polysaccharides, and phenols), lower aromaticity, and reduced molecular weight. These characteristics, characterized by low polymerization and high bioactivity, significantly enhance their potential for agricultural applications. A life cycle assessment (LCA) further quantified the environmental benefits of this technology, demonstrating a reduction of 12,700 tons of CO₂-equivalent emissions per 10,000 tons of humic acid produced, alongside a waste resource utilization rate of approximately 75 %. The work establishes a rapid waste-to-product conversion route, elucidates transformation mechanisms, and provides a sustainable biomass utilization model, advancing green agriculture.