Rice chaff has become the main topic of many research projects and studies, three of which will be presented as the followings.

Rice straw gas stove for drying agricultural products

This is the research topic of a scientific working group including Dr. Chu Van Thien, Dr. Nguyen Minh Thao and BEng. Bui Trung Thanh from the Vietnam Institute of Agricultural Engineering and Post Harvest Technology. The stove’s design is based on a similar stove of the International Rice Research Institute (IRRI). According to Dr. Thien, the principal researcher, when straw is burned at a certain temperature, it releases CH4 and volatile substances, which is also the reason for the name of this stove. 

Straw - a useful by-product for farmers

Presently, the straw gas stove is used in two typical types of drying system in the Mekong Delta, which are the stationary drying machine (with horizontal grates) and the tower drying machine (continuous drying with inversion process).

A straw gas stove has the capacity of 15 tonnes of product and consumes 42kg of straw per batch within five hour of continuous drying. The cost of this stove is at around VND7 million, which is much cheaper than the cost of a diesel stove with the similar capacity.

Currently, there have been six models of this stove designed and improved so that they can be used appropriately in different regions of the Mekong Delta and the Central coast. However, straw gas stove is higher than other kinds of stove, which often causes difficulty in the building and installing process. Scientists are working on research to solve this shortcoming.

Rice straw - an advanced addition agent of construction grout

Recently, the Vietnam Institute for Building Science and Technology under the Ministry of Construction has successfully developed two types of high intensity and non-shrink mortars, which are the flowing grout mortar (GM-F) and pumping grout mortar (GM-P), basing on the use of straw available in water to replace silica fume.

The silica fume in Vietnam is mainly imported from Sweden, Western Australia and Africa, packed with 25 kg per bag and sold at USD0.6 per kg. The activity and dispersity of silica fume can be maintained only when being kept in dry condition. Meanwhile, research results show that after being burned, straw may supply 20 percent of ash in which the main component is active and amorphous silicon. In addition, when using straw as an addition agent, the mortar will have higher intensity than using silica fume because straw is more active and requires less amount of water. Hence, the scientists have made much effort to create GM-F and GM-P to replace silica fume.

Electricity generation from straw

According to Prof. Dr. Pham Van Lang, the principal researcher of this project, the total investment capital of an electricity generation system using straw is USD111,000 which can be recovered within six to eight years. Moreover, this technology can bear great interest because it works on a recirculation production process in which waste in this stage is used as material in another stage.

Moreover, Prof. Lang added, this technology can be used for drying different agricultural products such as rice, soy-bean, and vegetables. This is greatly important to regions which have long rainy season since the system can ensure a large amount of heat for drying products without depending on weather.

He also remarked that although this technology has been tested and it proves many satisfactory results, the investment capital for its implementation on a broad scale is still a big challenge to users. Prof. Lang said that the equipment for generating electricity is the most costly; therefore, if this process is skipped while only focusing on the drying process, the investment cost will reduce considerably. It is estimated that a drying system with the capacity of 10-15 tonnes only costs about VND400 million.

After carrying out a pilot project in the Long An Food Company, three more drying systems have been implemented in Son La province, Dak Lak province and Thanh Hoa city with the purposes of drying wood, drying coffee and using in fertilizer production respectively. 

 By Ngoc Thanh