From food waste to water: A new research shows how new biomass hydrogels could help turning discarded food and agricultural waste into a source of atmospheric water for irrigation and sustainable farming

What if food scraps, discarded branches and seashells could be transformed into materials capable of producing water from the air?

Researchers at the University of Texas at Austin have developed a new class of biomass-based hydrogels that can capture atmospheric moisture and release it as clean water using relatively mild heat. The research, published in the peer-reviewed journal Advanced Materials, could offer a more sustainable approach to atmospheric water harvesting.

The study, titled Molecularly Functionalized Biomass Hydrogels for Sustainable Atmospheric Water Harvesting, was authored by Weixin Guan, Yaxuan Zhao, Chuxin Lei, Yuyang Wang, Kai Wu and Guihua Yu.


Rather than developing one specialised synthetic material, the researchers created a molecular engineering strategy that can convert naturally abundant polysaccharides, including cellulose, starch and chitosan, into water-absorbing hydrogels.

In outdoor testing, the cellulose-based material produced up to 14.19 kilograms of water per kilogram of sorbent per day under the tested conditions.

The researchers say the approach could eventually support portable water harvesters and decentralised systems in areas where conventional water infrastructure is difficult to build.

How the biomass hydrogel captures water from the air

Atmospheric water harvesting works by extracting water vapour that is naturally present in the air. However, doing so efficiently becomes more difficult as humidity levels fall.

An effective sorbent must therefore be able to capture water molecules even under relatively dry conditions and then release that moisture without requiring excessive energy.

The Texas researchers addressed both requirements through molecular engineering.

According to the study, the team first grafted thermoresponsive groups onto the natural polysaccharide backbone through alkylation. It then incorporated zwitterionic groups to improve the material’s ability to absorb water.

This molecular structure allows the hydrogel to attract and retain moisture from the atmosphere and subsequently release the captured water when heated.

In laboratory experiments, the cellulose hydrogel captured between 0.86 and 1.32 grams of water per gram of material at relative humidities ranging from 15% to 30%.

The material was able to release 95% of the captured water at 60°C.

The relatively low temperature required for water release is important because regeneration is one of the key energy challenges in atmospheric water harvesting. Capturing moisture is only the first step; the water must then be extracted from the sorbent before it can be collected and the material reused.

Outdoor testing produced up to 14.19 kg of water

The researchers subsequently tested the cellulose-based hydrogel outdoors.

Under the conditions tested, the material produced up to 14.19 kilograms of water per kilogram of sorbent per day using electrical heating.

The University of Texas at Austin said conventional sorbents commonly produce around 1–5 litres of water per kilogram per day, although output varies depending on factors such as humidity, temperature and operating conditions.

The reported performance therefore suggests that the biomass-based material could have significant potential for atmospheric water harvesting.

However, the results from laboratory and controlled outdoor testing do not by themselves establish that the technology is ready for commercial-scale deployment.

Real-world systems would need to account for fluctuations in humidity and temperature, energy requirements, water collection efficiency, material durability and the cost of producing the sorbent at scale.

Why biomass could make water harvesting more sustainable

One of the key aspects of the research is the choice of starting materials.

Cellulose, starch and chitosan are naturally abundant polysaccharides that can be obtained from a range of biological sources. The broader approach described by the University of Texas could therefore include materials such as food waste, branches, seashells and other biomass-derived resources.

The idea is not that untreated waste can simply be placed inside a device and immediately produce drinking water. The biomass must first provide a suitable polysaccharide structure or be processed into an appropriate material. Molecular functionalisation then gives the resulting hydrogel the properties required to capture and release atmospheric moisture.

The researchers’ innovation lies in developing a strategy that can be applied across different biomass feedstocks rather than designing an entirely new sorbent for every source material.

This could reduce dependence on specialised synthetic materials and create opportunities to use inexpensive, renewable biomass as a starting point for water-harvesting technologies.

Could the technology help areas without conventional water infrastructure?

Atmospheric water harvesting has a key advantage: it does not require a nearby river, lake or groundwater source.

As long as there is sufficient moisture in the atmosphere, the technology can potentially generate water at the point of use. This makes it particularly relevant for remote communities, decentralised water systems and emergency situations.

The UT Austin researchers are now looking at scaling up production and developing practical systems, including portable water harvesters, self-sustaining irrigation systems and emergency drinking-water devices.

The technology could also have applications where conventional water infrastructure is damaged or unavailable, including disaster-affected areas.

From waste biomass to off-grid water systems

The work builds on a broader research programme at UT Austin focused on using hydrogels to address water scarcity.

Earlier research by Guihua Yu’s group explored molecularly engineered hydrogels capable of extracting atmospheric moisture using solar energy, while other work has investigated hydrogel-based water filtration.

The new research combines two challenges — waste utilisation and water scarcity — through materials science.

Instead of treating biomass waste and water harvesting as separate problems, the researchers have developed a way to transform naturally abundant biological materials into sorbents that capture atmospheric moisture and release it using relatively mild heat.

Guihua Yu, the study’s corresponding author and a professor of materials science and mechanical engineering at UT Austin, described the research as a strategy for transforming diverse natural materials into high-efficiency sorbents. Lead researcher Weixin Guan also highlighted the potential of using abundant natural resources to produce water from atmospheric moisture.

The findings do not suggest that atmospheric water harvesting can replace conventional water infrastructure overnight. The bigger takeaway is that a wide range of biomass materials can potentially be molecularly engineered into efficient water-harvesting hydrogels.

If the researchers can scale production and develop energy-efficient devices around the material, future off-grid water systems could potentially turn what was once considered waste — from food scraps and plant material to other biomass — into a useful resource for extracting water from the air.