Save Money, Water, the Environment - Benefits of Natural Polymers

Published: 16 August 2013

Radiation processing is used to break chemical bonds and create new ones. Radiation makes it possible to redesign a particular material so that it can serve a very specific purpose. The polymer cassava starch from this edible root-cassava-is one such material that is redesigned using radiation. Cassava starch is the base material used to make super water absorbents (SWA), which can take up an incredible amount of moisture and release it slowly over time. SWA (at left) looks like large sugar crystals and are even harmless if eaten, although it is doubtful that anyone would want to test that theory for taste reasons alone. When SWA crystals encounter and suck up moisture... ...they become translucent and squishy. Super water absorbents processed by radiation are particularly useful for agriculture in dry areas where there is little rain, or where there are frequent periods of drought. When a field is irrigated, anywhere from 50% to 65% of the moisture leaves the soil through evaporation or as runoff, and is therefore unavailable to the plants. Placed in the soil near plants' roots, 1kg of SWA crystals can absorb and hold 200 litres of water from rainfall and irrigation. It's also being used to reduce the amount of time and water given to rooftop gardens like this one, owned by supermarket chain owner Nguyen Van Dong. 1kg of SWA is sold for US$ 2.50 in Vietnam. After 9 months SWA crystals disintegrate, leaving no residue and no harmful after-effect on the surrounding environment. In Vietnam, super water absorbents produced by the Vietnam Atomic Energy Institute, are used on rubber plantations (like this one in the mountains of Phuong Lam, Dong Nai province), in home gardens, and is also exported to Australia, where it is used in large-scale farming. Farmers who plant high-value cash crops use 30kg-60kg of SWA per hectare. SWA crystals are also used to absorb and slowly release liquid fertilizer, making it available to plants over time.  According to Dr. Doan Binh, Quality Control Officer at Vietnam's Research and Development Center for Radiation Technology, large amounts of liquid fertilizer applied to plants can run off into waterways, or move away from plant roots by other natural processes. Using super water absorbents keep the fertilizer close to the roots for as long as they need it. This reduces waste, reduces pollution of waterways, and saves farmers money. <strong>How It's Made:</strong> Cassava (tapioca) starch is mixed with potassium hydroxide and then irradiated. Joining polymer chains together is called crosslinking. This is what radiation does to the cassava starch. Unlike chemical crosslinking, the process of radiation crosslinking requires no chemical additives, doesn't require extreme heat and can be done at room temperature, and creates no residues that need to be removed, usually using large quantities of water.<br /><br /> (Photo: Irradiation facility at the Vietnam Atomic Energy Commission, Ho Chi Minh City) The irradiated cassava starch/potassium hydroxide mixture comes out as a gelatinous mass... ...which is then extruded (broken into smaller gelatinous masses)... ...oven dried at high temperature. It comes out looking like this. It's then ground until it reaches the right consistency... ...that is, looking like sugar crystals. The super water absorbents are subsequently packaged for export or sold to local distributors like Ho Chi Minh City Agricultural Service and Technology, which sells in small quantities (like the packages at left), as well as to large farmers. There are many other natural polymers being modified with radiation to create useful, specialised, environmentally friendly and non-toxic products. They are extracted from things like seaweed, shrimp shells, palm oil and sago starch. Products being made from natural polymers are used in medicine, agriculture, environment protection, cosmetics, and a variety of industrial applications. The IAEA has been promoting the radiation processing of natural polymers in its Member States for over 30 years. <br /><br />© IAEA