Water Capsules that can Reduce Water in Agriculture
Drought is an increasingly threatening problem in agriculture all around the world.
The biggest problem is that most methods of watering crops waste large amounts of water, resulting in inefficient water usage. The conventional method of farming requires phenomenal amounts of water; water is sprayed towards the farm, and large proportions of that water never reach the roots. Thus, not only do we waste thousands of gallons of water from farming each year, but also if a drought strikes, farms and their crops will be devastatingly affected.
Currently, attempts to tackle this problem exist: drip irrigation and mulching are iconic. With drip irrigation and mulching, plants are watered slowly through a pipe near the roots while a substance like plastic vinyl covers the ground. This direct method of watering prevents large evaporation. However, the disadvantage is that the installment is costly and can be harmful to the environment by plastic degradation; one can see a lot of black vinyl littered in the rural areas of Korea. They fail to consider price and pollution of the terrain.
In a project with my friend Jaihyun Kim, we aimed to help resolve that problem. The goal of our project is to create eco-friendly, low-cost methods that can conserve water in agriculture. Our project not only conserves water but is sustainable, eco-friendly, and affordable.
A multi-membrane alginate water-capsule that minimizes water loss.
Our first idea originated from a startup in London that aimed to develop alternatives to plastic bottles by making edible water capsules. They used alginate, a substance extracted from seaweeds, to make the packaging edible and biodegradable; we thought we could apply this in agriculture.
Alginate, the key substance of our invention, is a polysaccharide extracted from brown algae. It is not only biodegradable but also cheap due to the abundance of algae and seaweed wastes; in Goheung, Korea alone, there were 50,000 tons of annual seaweed waste! The price of alginate is about six dollars per kg; since our project requires very small amount of alginate per capsule, it can be mass produced.
Alginate forms a gel, a membrane, when interacted with cations via ionic interactions. Ions that are able to crosslink with alginate are divalent cations such as copper, strontium, calcium, cobalt, and etc. Previous studies have shown that alginate crosslinked membranes show different traits for each type: some ions result in stronger bonds and membranes, while other ions such as magnesium will not even form membranes. Also, the SEM photos of these membranes show that each membrane has different size micropores, which is an important factor that affects the water discharge profile.
Alginate’s ability to form a gel and to absorb and contain water had led its use in various fields such as food preservation and biomedical fields. Alginate’s use in drug delivery system has given us many ideas. Medical researchers has used alginate to create microbeads in size of 100~1000μm in order to convey medicine and microorganisms. There were also other researches that had used additional substances such as chitosan to reduce the permeability of the alginate membrane. These researches provided us factors to control the water discharge rate and the stability of our capsules.
However, these researches were only done on small-size alginate beads. Research on larger scale alginate beads, or capsules, were limited. Also, its applications on agricultural fields were rarely done. Thus, we had to experiment and test various alginate membranes with different composition and find different methods to create large capsules that would be applicable to agricultural fields.
Throughout our 1.5 year of research, we aimed to create and see:
1. The construction of a capsule-in-a-capsule model to control the water discharge rate.
2. The change of the stiffness and water permeability of the capsule by changing the alginate membrane structure by using different crosslinking ions.
3. Increased stability of the capsule for practical applications by adding different encapsulating substances such as chitosan and agarose to the composition.
With endless trial and errors, we were finally able to create a prototype, where we can manipulate the water discharge rate to last a certain amount of period. This feature could be used to customize each capsule to fit different plants and crops.
Hope these research and findings help reduce water use, so that crops can live longer & lives can be saved.
Link to the paper is here:
This research was awarded Regional Finalist for 2018-2019 Google Science Fair.