Super absorbent polymers for future agriculture: a circular approach for soil fertilization and irrigation

In recent decades, agricultural productivity has exponentially increased thanks to the widespread adoption of intensive practices promoted by the green revolution. This progress, however, has come at a significant environmental cost. To sustain food production for a rapidly growing global population, fertilizers use has escalated dramatically, surpassing 55 million tons annually [1]. This trend is expected to continue, with projections indicating exponential increases in fertilizers demand, raising serious concerns regarding long-term sustainability, resource depletion, and environment degradation. In this framework, excessive and uncontrolled fertilizers application has led to numerous ecological issues, including soil depletion, water pollution, eutrophication of aquatic ecosystems, and contributions to climate change [2]. At the same time, the growing global water crisis is demonstrating the importance of using water more efficiently in agriculture. To afford these problems, superabsorbent polymers (SAPs), particularly potassium-based polyacrylates (SAP-K), have emerged as promising materials due to their ability to retain significant quantities of water, improve soil moisture [3]. These materials are low-cost, non-toxic, non-polluting, and do not contribute to soil salinization, making them suitable for sustainable agricultural applications [3]. In this work we explore an innovative use of SAPs-K with the dual purpose of: 1) enriching them with nutrients to act as slow-release fertilizers; 2) recovering steam from high-temperature emissions, such as industrial chimneys. To our knowledge, although SAPs-K have been marketed for many years, no studies have yet addressed these combined functionalities. In the present study, commercial SAPs-K were modified with nutrient-rich precursors—such as starch, ethylenediamine, L-asparagine, and hydroxyapatite—to introduce essential elements, like nitrogen, calcium, and phosphorus. The modified materials were tested for their water vapor absorption capacity at 160 °C, and the most promising formulations were further evaluated for nutrient release in soil. The results demonstrated that nutrients enrichment significantly enhanced the water vapor absorption capacity of the polymers (Figure 1a). To validate their potential application in agriculture, nutrients release tests were conducted, showing that the modified materials improved soil water retention up to 40% and enabled the gradual release of nutrients into the soil (Figure 1b). These findings demonstrate the potential of nutrient-enriched SAPs-K as dual-function materials for sustainable agriculture. By combining water vapor recovery with controlled nutrients and water release, the developed systems offer a promising solution to address water scarcity and fertilizer inefficiency. Their low cost, environmental compatibility, and circular approach make them valid candidates for future agricultural innovation. References 1. F. Zapata, Introduction to nitrogen management in agricultural systems, in Guidelines on Nitrogen Management in Agricultural Systems, International Atomic Energy Agency, Training Course Series, No. 29, 2008, Vienna, Austria 2. J. Liu, Y. Su, Q. Li, Q. Yue, B. Gao, Preparation of wheat straw based superabsorbent resins and their applications as adsorbents for ammonium and phosphate removal, Bioresour. Technol. 2013, 143, 32–39. https://doi.org/10.1016/j.biortech.2013.05.100 3. Behera, S., & Mahanwar, P. A. Superabsorbent polymers in agriculture and other applications: a review. Polymer-Plastics Technology and Materials, 2019, 59(4), 341–356. https://doi.org/10.1080/25740881.2019.1647239