Valorization of Agricultural Waste Biomass into High Performance Superabsorbent Polymers to Improve Water Retention Capacity of Soils

Purpose: The study presents an innovative approach to harness the potential of lignocellulosic waste biomass for the development of superabsorbent polymer (SAP), a soil-moisture enhancing material with proven environmental benefits. It aims to highlight the potential of bio-based SAPs as soil amendments for mitigating water scarcity in agricultural applications. Methods: The present study developed two different SAPs (BM-SAP and BC-SAP) through graft polymerization technique utilizing waste biomass (BM) and biochar (BC) pyrolyzed from the same BM as a precursor, for improving the water retention capacity of soils. Results: The BM-SAP exhibited high water absorption capacity (WAC) of 415 g/g in deionized water and 330 g/g in tap water, whereas BC-SAP showed WAC of 280 g/g and 210 g/g in deionized water and tap water, respectively. Moreover, the performance of BM-SAP was found to be superior in terms of higher swelling rate, better reswelling capacity, and lower salt sensitivity as compared to BC-SAP. The synthesized SAPs were mixed with two different agricultural soils (texture: Sand and Silt) at three concentrations (0.1%, 0.3% and 0.4%), which revealed that addition of 0.4% SAP can enhance the saturated water content (SWC) by 3 times and 1.5 times in sandy soil and silty soil, respectively. Conclusion: The enhanced water retention capacity lead to higher desaturation time in SAP amended soils, which is indicative of longer irrigation time intervals. The transformative process not only presents a sustainable solution for agricultural waste management but also emphasizes the viability of bio-based materials in addressing water scarcity challenges.