Waste to Worth: A Circular Solution through Lignin Engineering

Abstract

Ineffective management of industrial waste poses significant risks to environmental and ecosystem health, highlighting the need for sustainable and scalable solutions. However, current strategies for resource recovery and waste valorization often rely on costly, energy-intensive, and multi-step processes that limit their broader implementation. To address these challenges, we propose a novel and sustainable in-situ one-step strategy for the simultaneous recovery and functionalization of lignin from industrial black liquor, using a sustainable organic acid system assisted by choline chloride, thereby enabling circular remediation. The functionalized lignin adsorbent material (FLAM) exhibited excellent performance and was applied to treat animal feedlot wastewater and recover ammonia. The ammonia-enriched FLAM was subsequently repurposed as a slow-release fertilizer, enhancing plant growth and demonstrating an integrated approach to waste valorization, nutrient recovery, and environmental sustainability. Comprehensive characterization confirmed successful surface modification of FLAM. To investigate the adsorption mechanism, methylene blue (MB) was used as a model compound to simulate the interaction and adsorption behavior of cationic species. The FLAM achieved a high adsorption capacity of 725.98mg/g across a broad pH range, significantly outperforming commercial kraft lignin. Notably, further evaluation under realistic animal feedlot wastewater conditions with ammonia and co-contaminants validated the FLAM's practical applicability. After adsorption, the spent FLAM served effectively as a slow-release fertilizer, closing the loop between lignin valorization, wastewater treatment, and agricultural reuse. This sustainable approach not only adds value to industrial lignin waste but also aligns with circular economy principles by integrating remediation and resource recovery. Overall, the strategy offers a scalable, eco-friendly solution for environmental remediation and sustainable material development, with strong potential for real-world implementation.