NSF Convergence Accelerator Track J: Aqua Sacs for Sustainable Agriculture in a Changing Climate

The availability of global water resources is under stress and water scarcity is increasing, particularly in arid and semiarid regions. The situation will only worsen, leading to more severe and frequent droughts followed by flooding, decreasing arable land, and increasing food insecurity. A more efficient irrigation system is needed, especially for water-intensive crops, such as soybeans, wheat, and sugarcane.

Hydrogels added to soil reduce irrigation frequency by absorbing and retaining water and releasing it when the soil dries. They improve the hydro-physical properties of the soil, such as porosity, and they can reduce erosion and runoff and thereby mitigate the effect of flooding. Hydrogels function as small water containers in the ground with osmotic membranes that increase microbial activity, growth, and performance rate.

Currently, most of the hydrogels on the market are synthetic polyacrylates and polyacrylamides, which are petroleum-based materials and not ecologically friendly for large-scale agriculture. Some semisynthetic starch-based polymers are also available. However, a better alternative is possible.

Alginate-based hydrogels have been shown to be efficient in controlling soil moisture for plant growth. In this project, we introduce the ecologically friendly water container Aqua Sac, an alginate-based hydrogel that can be produced in various patterns such as sheets or meshes. Osmotic membranes can be formed by binding calcium at the surface, making them similar in function to synthetic hydrogels.

Moreover, adding alginate hydrogels to soil can stimulate microbial activity, which generates microbial biomass and diversity, and the biodegradation of alginate can contribute to soil health and, in turn, leads to increased crop production. Alginate is extracted from seaweeds, such as kelp, which can be sustainably farmed while providing a suite of environmental benefits.

Seaweeds are a zero-input crop that does not require the use of fertilizers, pesticides, or fresh water. Rather, seaweeds extract excess nutrients from the surrounding waters, including dissolved nitrogen and carbon dioxide, which helps to combat eutrophication. Thus, the development of Aqua Sac will benefit agriculture and soil health on land and the marine environment by helping to increase the demand for aquacultured seaweeds.

This collaborative project aims to understand and develop the industrialization steps required to produce Aqua Sac at a commercial scale. The technique that was developed allows the production of alginate hydrogel in rolls that can be deployed to the field in the form of sheets or meshes of various patterns that can be used as an additive material for applications ranging from soil hydration to food preservation.

The scaling from a laboratory to an industrial scale requires an understanding of seaweed farming, alginate extraction, hydrogel optimization, and field performance. Information obtained from these steps will give us the elements necessary to create a business model and seek industrial partners for the production and distribution of Aqua Sac on an industrial scale.

Specifically, we will seek to: 1) identify seaweed species and growing regions that maximize domestic alginate production and quality; 2) refine methods of alginate extraction and hydrogel production to minimize waste production, 3) optimize the hydrogel membrane for water absorption and retention, and 4) conduct field tests to understand the performance of the hydrogel under actual agricultural conditions. All steps will be developed within a circular economy model to minimize environmental impact. The project will be documented by photo and filmed for public dissemination.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.