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Water Producing Tree Guard: From Demonstrator to Large Scale Production

Periodic Reporting for period 1 - TreeSponsh (Water Producing Tree Guard: From Demonstrator to Large Scale Production)

Reporting period: 2020-12-01 to 2022-01-31

Water is the source of life. Without water, everything stops.
Man-induced increase of carbon levels result in global warming, droughts, and desertification. According to the United Nations and the Intergovernmental Panel on Climate Change (IPCC), planting trees is one of the most effective ways to reduce carbon levels.

Besides carbon sequestration, planting trees increases biodiversity, stops desertification and restores livelihood for drought-stricken communities. For that reason, the number of reforestation projects is increasing rapidly. Reforestation projects could be implemented on 2 billion hectare of degraded land world-wide. However, water shortage prevents trees surviving the first harsh summers: young trees only have a survival rate of 10-30% in these areas.

Alternative water sources like water wells and reservoirs are drying up. Other water provision solutions like desalination are capital intensive, requiring massive piping networks and consume massive amounts of energy. To reforest those 2 billion hectares, it is crucial to develop new solutions that provide off-grid and affordable water in dry remote regions to help seedlings survive.

This project supports Sponsh’s mission to regreen the planet with water from air. By looking at how plants and animals in dry coastal areas collect water from air, Sponsh develops technology to collect and release water from the air using a temperature-sensitive nanomaterial. During the night, when it is cold and humidity is higher, the material absorbs large amounts of water from air. During the day, as temperatures rise, the water is expelled from the material and guided to the roots of the trees. This water helps the seedlings survive the first harsh summers and grow into strong large trees that can sustain themselves. This in turn helps turning degraded land back into fertile forests and stopping desertification.

Within this mission, this project specifically looks at the following objectives:
1. Synthesise hydrogels capable of collecting water from the atmosphere at lower temperatures and high RH. In the same instance the hydrogel should release water as vapour at high temperatures and low RH.
2. Develop a device to enhance the water vapour absorption/desorption cycles and maximise liquid water collection.
3. Optimise both hydrogels and water collection device concept in terms of water absorption and release at RH<95%, durability in real-life conditions and scalability. Using performance feedback from laboratory and open field testing for their continuous improvement.
4. Based on experimental results, update requirements for the water collection device and screening of suitable supports with end-user and performance feedback;
5. To define a measurement protocol to determine the efficiency of the water collection device efficiency.
6. To define a list of technical challenges that need to be solved for commercialisation and possible solution directions.
The Innovation Associate project is part of Sponsh’s R&D programme. The project is divided into three main phases:
1. Hydrogel Elaboration and Synthesis Optimisation
2. Hydrogel Absorption and Desorption efficiency
3. Prototype design and development

1. Hydrogel elaboration and synthesis optimisation
In this phase of the project, a thorough academic research was performed to define a strategic path for the hydrogel chemical formulation and synthesis. Several hydrogels capable of absorbing water at high levels of humidity were developed. Based on the water absorption and desorption efficiency, 3 groups of hydrogels were selected as subjects of interest. These hydrogels were optimised by the alteration of their component’s chemical stoichiometry and processing routes.

2. Hydrogel absorption and desorption efficiency
The hydrogels were tested for their capacity to absorb and desorb water in both laboratory-controlled environments and exposed to the open air where the environment conditions can’t be controlled. The conditions created in the laboratory always aimed to mimic the environment characteristics in which the product would be utilised.
The experiments carried out in the laboratory revealed that the hydrogels absorbed up to ~120 % of their own mass in water at relative humidity levels between 85 and 90 %.
Open field testing was carried out utilising the sun as the source of energy for the desorption process and the night dew as the controlling agent for the absorption process. The specimens were exposed to the open field in day and night cycles for pre-swollen and dry specimens. The open field results were proven to be inferior to those in controlled laboratory environments where hydrogels did not absorb more than 40% of their own mass in water.
The team learned that the desorption efficiency was directly connected to the heat distribution in the interface hydrogel/container. The container was defined as the surface holding the hydrogel during experiments.

3. Prototype design and development
The hydrogel technology was applied to a functional design, that allowed the collection of water from the air followed by water release and collection. Several designs were created, and their respective prototypes were built to test their efficiency. The prototype testing was focused on both laboratory and field conditions. Most prototypes did not yield the required results, but did yield valuable information. The main issue was that the desorption and condensation required different parameters. A prototype utilising Sponsh’ technology and separating these processes, was capable of releasing over 6 mL of water per desorption cycle.
To date, the prototypes did not yield sufficient performance to justify scaling up. The adsorption of the developed hydrogels is lower than anticipated, especially in real-life conditions. Nonetheless the team acquired essential know-how for further development. Building on that know-how, Sponsh will continue researching and developing better performing hydrogels and devices.

By the end of the project, Sponsh produced a prototype that collects over 6 mL of liquid water in a full cycle (absorption/desorption) per 17.9 g of hydrogel. This prototype was named “convection chamber” and it utilises the natural convection between cold and hot air to promote water desorption in the desorption chamber and condensation on the wall of the condensation chamber. The absorption and desorption processes did not occur in a continuous cycle and manual intervention was required for the prototype functioning. With further research, the results described in this project would be improved causing a major positive impact on reforestation efforts. Upgrading the device to meet a daily 50-100 mL water production will be required for application of seedling irrigation. This will support and impulse the reforestation of lands that struggle with water scarcity. On a large scale, the survival of such young trees will be crucial to increase CO2 capturing in our atmosphere. In addition, green areas can be brought back to desert places that are usually considered unsustainable for life to grow.
Sponsh tree guard