United Nations predicts that agricultural productivity needs to be increased by 70% to feed 9 billion population by the mid 21st century. Enriching the soil in arid areas and deserts to a level comparable to a high-quality farming soil is a promising approach. However, the primary challenge is ‘how to preserve water in the sand without the need for irrigation?’. Nanoclay is an emerging material composed of natural minerals and organics. It can absorb, retain, and release water for up to 5 years. A recent study conducted in the desert has proven Nanoclay’s promise in providing sustained irrigation and high crop yield. This proposal will develop a new class of Nanoclay by utilizing soybean starch and natural mineral (montmorillonite) that can provide sustained irrigation for soybean farming.

The primary goal of this proposal is to invent a new class of Nanoclay by utilizing soybean starch and natural mineral and to investigate its ability in absorption, retention, and release of water to the surrounding soil.

This research will result in Nanoclay made of soybean starch and natural mineral that can exhibit a water absorption and retention with a controlled release rate to the surrounding soil. This will be in line with our goal to provide sustained irrigation for soybean farming.

Update:
We have developed and refined a procedure that enables us to efficiently produce a large volume of M-SSM (Montmorillonite-coated Soybean Starch Microbeads). This process involves the blending and optimization of soybean starch and montmorillonite within a co-solvent comprising 90% water and 10% ethanol. The overall solute concentration was maintained at 10 wt.%. In this solution, we added a commercial epoxy-based glue (Norland®) to enhance the adhesion between the soybean starch and montmorillonite. Subsequently, the solution undergoes a 30-minute stirring at room temperature to ensure thorough homogenization.
To fabricate microbeads of M-SSM, we have employed a straightforward yet scalable spraying-based technique by using a readily available commercial sprayer. The droplets generated through this process undergo immediate cross-linking via a brief exposure to ultraviolet irradiation. This cross-linking mechanism enhances the adhesive properties of the epoxy-based glue, facilitating the steadfast attachment of montmorillonite onto the starch solution. Please note that the surface tension of water plays a pivotal role in shaping the starch into distinctive bead structures. Our investigations have pinpointed four key parameters that exert a direct influence on the size of the resultant M-SSM microbeads. These parameters encompass spray pressure, spray distance, temperature, and humidity. Generally, elevated spray pressure coupled with a reduced spray distance leads to the formation of smaller beads. The interplay between temperature and humidity jointly determines the bead size. Typically, a higher temperature and a lower humidity level results in the generation of smaller beads. At present, we are compiling data from our experimental measurements, seeking to establish a clear correlation between the size of the microbeads and these aforementioned parameters.

Challenges: The challenge of augmenting the dissolution of soybean starch within a co-solvent remains a pertinent consideration. Ordinarily, starch exhibits poor solubility in aqueous solutions. Such restricted solubility of starch within a water-ethanol co-solvent can significantly impact the overall yield of M-SSM production per operational unit. While certain commercial solvents, such as ionic liquids, possess the ability to enhance starch solubility in water, their adoption is hampered by either their high cost or their lack of environmental friendliness. At present, our focus persists on utilizing the water-ethanol co-solvent system in our ongoing investigations. While we acknowledge the potential advantages of alternative solvents, we have decided to retain this co-solvent approach for the foreseeable future as we delve deeper into further studies.
Please see the separately attached report.

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The primary objective of this project is to develop a new class of Nanoclay by utilizing soybean starch and natural minerals capable of absorbing, retaining, and releasing water into the surrounding soil. We successfully manufactured the Nanoclay by coating soybean starch beads with montmorillonite. The Nanoclay demonstrated rapid water absorption, absorbing up to five times its weight, and gradual water release into surrounding soil when buried. The water release behavior correlates strongly with soil conditions, particularly humidity. In bench-scale experiments, the Nanoclay released water over four months. We investigated parameters affecting water absorption and release by varying montmorillonite and soybean starch bead compositions, showing that lower montmorillonite composition led to faster absorption and release rates due to increased free surface area. Additionally, adding chemical adhesive to soybean starch bead during mixing with montmorillonite enhanced Nanoclay stability, attributed to chemical compatibility and physical cross-linking.

Future Outlook:
This project demonstrates lab-scale manufacturing of Nanoclay and controlled water absorption and release experiments. To make Nanoclay applicable in the real world, we anticipate the need for refining and optimizing a scalable manufacturing procedure. Furthermore, Nanoclay performance in outdoor settings requires assessment.

The primary audience of this project is the soybean farmers in Kansas. Our technology can significantly increase the ability of soil to absorb, retain, and gradually release water to the soybean plant. Therefore, this project will enable soybean cultivation in the arid and semi-arid areas such as West Kansas (e.g., Wallace, Sherman, Greeley counties). Also, the farmers can benefit from an increase in the yield and a decrease in the irrigation cost.