SCE’s Paper on Vetiver Grass Paddy Storage Receives Award

A paper by Dr. Pichai Nimityongskul of SCE, and his doctoral candidate, Mr. Thammanoon Hengsadeekul of the Structural Engineering Field of Study, has received the Chaipattana Foundation’s Certificate of Excellence at the King of Thailand Vetiver Awards as an outstanding paper demonstrating a high standard of achievement in the category of Vetiver Research (Non-Agricultural Application).

Loading scenario at the pilot vetiver-clay silo, Chitrlada Palace

The paper was entitled “Utilization of Vetiver Grass as Construction Material for Paddy Storage,” and was one of four papers about vetiver grass presented by AIT to the World Vetiver Grass Conference held on October 5-9, 2003, Guangzhou, Guangdong, China. The conference was presided over by HRH Princess Maha Chakri Sirindhorn.
The conference was organized by the Vetiver Network and Continuing Committee of the International Conference on Vetiver (ICV), and was sponsored by the Chinese Academy of Sciences, Guangdong Provincial Government, Chaipattana Foundation of Thailand, and the Vetiver Network. About 300 experts and delegates from 28 countries, including China, Thailand, USA and Australia, attended the conference. Sixty-five full papers and eight abstracts have been selected and published by the China Agriculture Press as the conference proceeding.

Left: Dr. Pichai Nimityongskul presents one of his papers at the Conference.

“This paper is about a patented project initiated by His Majesty King Bhumibol Adulyadej of Thailand to utilize vetiver grass mixed with clay for constructing the paddy storage. His Majesty the King of Thailand has long expressed his ideas about vetiver, the wonder grass with proven potential to prevent erosion and conserve soil moisture, and its many other applications. The project aimed at transforming vetiver from simply being an agricultural material into a low-cost construction product. The objective of this research was to utilize vetiver grass and clay to construct a low-cost paddy storage silo, with the vetiver grass used to reinforce clay slurry or adobe in a vetiver-clay composite. Basically, vetiver grass serves as reinforced fiber and clay as the matrix,” Dr. Pichai told AIT Newsletter.

Dr. Pichai noted that when harvesting time arrives, farmers rush to sell their paddy, thus flooding the market and depressing the price of paddy further. Farmers therefore need a good paddy storage silo to keep the paddy for a longer period of time, when it can be sold at a more favorable price. The storage facility has to be produced at low cost and has to be made from locally available materials. Earlier research found that vetiver grass and clay can be used to construct the silo in Thailand, where a large quantity of vetiver grass is grown.

“We made a pilot project by constructing a cylindrical silo demonstration at the Royal Chitrlada Project. We evaluated changes in the quality of stored paddy in terms of moisture content, bulk density and milling yield collected from various locations in the bin every two weeks for a period of six months. During the storage period, the ambient temperature, relative humidity and temperature at the top, middle and bottom of the bin were recorded,” said Dr. Pichai.

At the Conference’s exhibition booth, from left: Mr. Surak Panichnava, Research Associate under RTG-Joint Research Project; Dr. Pichai; and Mr. Thammanoon.

The research project, which started in 2001, also studied the physical and mechanical properties of the vetiver-clay composite and the properties of vetiver grass and clay. There were also tests of vetiver-clay composite in axial compression, flexural, shearing, tensile, bearing and density, to assure the strength of the pilot silo. An evaluation of the storage performance of the vetiver-clay silo was also conducted.

Mr. Thammanoon (left) and Dr. Pichai show the award certificate beside a silo miniature.	Layers of the silo wall

Mr. Thammanoon explained that the pilot silo has a diameter and height of three meters, and is elevated 1.20 meters above the ground. With a capacity of ten tons, the pilot silo’s main structures consist of a reinforced concrete foundation, a ground wall and slab made from cement block filled with reinforced concrete, the storage wall made from vetiver-clay bundles and coated with a mixture of fresh cow dung, clay and chopped dried vetiver grass, and a bamboo roof thatched with overlapped vetiver grass bundles. To ventilate the ambient temperature inside, the silo is also equipped with a heat ventilation whirl on the roof. A vertical conveyor and a screw conveyor were installed for conveying paddy in and out of the silo.

The procedure of silo construction starts with the foundation set up on the sufficient bearing load level. This is followed by construction of the lower wall with cement blocks filled with reinforced concrete. An exit door for removing the paddy is also made. Next is construction of the storage wall. “For constructing the wall, vetiver grass and clay must be prepared. From our study, only fresh vetiver grass should be used and this must be dried for four to five days to reduce the water content to less than 10 percent and to prevent insects and fungi fertilization. The clay used for the fabrication of the vetiver-clay bundles must be cohesive and must have high plasticity. It should be fine, smooth and uniform, and free from impurities such as broken tiles, roots, twigs, or other organic matter. The clay should be sun-dried for at least four to five days to reduce its water content to less than five percent. Then, the sun-dried clay would be soaked in water at the ratio 2:1 (clay:water) for twenty-four hours and mixed manually until a uniform slurry is formed,” Mr. Thammanoon explained how the silo wall was constructed.

In the study, each vetiver-clay bundle should have an average diameter of five cm. and 100 cm. in length, composing of 130-140 pieces of vetiver grass and clay slurry. To make the silo wall, layers have to be added one at a time. One layer comprises four vetiver-clay bundles horizontally and eight vetiver-clay bundles vertically, and measures about 35-40 cm. in height. The number of layers depends on the height of the wall. The next layer can be done made completely drying the previous layer for a few days.
When the silo wall is completely dried, it has to be coated with cow dung mixed with clay, rice husk and water, which is used as a natural coating material. To protect the vetiver-clay bundle from the rain, the coating should be 1.0-1.5 cm. thick, and should be sun-dried for a few days.

Next the roof structure is constructed using bamboo as the major material. A heat ventilation whirl installed at the center of the top. Vetiver-clay bundles were then laid on the lower layer of the roof structure as a ceiling, while the upper layer of the roof is composed of small pieces of bamboo covered by bundles of dried vetiver grass as a shield from sunlight and rain.

Once the silo was completed, the researchers concentrated on testing paddy quality. The test results revealed that with this pilot silo, the temperature and relative humidity inside the loading silo was consistent, whereas outside the silo there was a difference of seven degrees Celsius and 30 percent relative humidity. The experiment showed that the quality of paddy stored in a vetiver-clay silo was unchanged. It also indicated that the moisture content of paddy stored in the top and bottom layers of the silo was slightly lower than that stored in the middle layer.

Dr. Pichai and Mr. Thammanoon, with the research project, “Development of Prefabricated Vetiver-Clay Composite for Housing Applications”

This silo can store paddy for six months at normal moisture content (below 14%). It should be able to store paddy at higher moisture content. Therefore, a further study on how long the paddy can be stored or whether to use a blower to lessen humidity, is planned. “We might also propose to any research or government agencies for funding to construct the prototype for each region in Thailand, and train local people to build it as well as doing joint research with them,” Mr. Thammanoon told us.

The research also showed that, apart from the benefit of land rehabilitation and water conservation, vetiver grass could be used as fiber reinforcement in the clay matrix to make the composite suitable for the construction of a silo. Moreover, with abundant vetiver grass and clay available in Thailand, the construction cost of the silo is low and requires local labor skills. Therefore, developing countries now facing problems at the commercial level should be able to overcome the problem of paddy storage, thus improving the economy and living standards.

Dr. Pichai and Mr. Thammanoon are also working on a research project, “Development of Prefabricated Vetiver-Clay Composite for Housing Applications” for constructing a low-cost house for farmers or poor people. A delegation from UNHCR recently showed interest in vetiver grass projects, especially in the utilization of vetiver grass as construction materials for constructing camps for refugees. “They are interested in prefabricated systems so that the knock-down materials can be produced first and can later be constructed as houses within a one week,” Dr. Pichai concluded.