In the Republic of Vietnam, the country’s first rice-chaff-burning power station of 10 MW capacity has been in operation since January 2010 at Lap Vo in the province of Dongtap, located about 140 km from and in the southeast of Phnom Penh. The power plant was designed and built in accordance with CDM (Clean Development Mechanism), by RWE Power Co. in Germany. It will provide 72 ~ 80 million kWh of electricity per year. The amount of reduction of CO2 emission is estimated to be 50,000 ton annually, and 350,000 ton in seven 7 years.

Rice chaff has a low calorific value of 3,346 kcal/kg in average. Rice chaff generated in Vietnam in FY2010 was estimated to be 7.52 million ton, and would increase up to 7.90 million ton in FY2020. Currently, a larger rice-chaff-burning power station of 18 MW class is under construction at Kanto City in the Mekong Delta region, which will be completed in this year. Consequently, annual use of rice chaff in this country will become 1.5 million ton that can generate a sum of 1.2 billion kWh of electricity, assuming efficiency of power generation to be 20 %.

In this connection, the following table depicts the present state of chaff-burning power generation in Thailand which is a pioneer in this technology. As noted, the total capacity of chaff-burning-specialized power stations in Thailand has now reached to 88.55 MW.

Fig. A Rice-chaff-loaded truck

In this connection, complete combustion of rice chaff leaves some amount of ash (= rice husk ash) that is composed of 95 % of SiO2, and 1 ~ 2.5 % of K2O, and quite a little portion of impurities. Rice husk ash is a porous material with quite huge surface areas, because when rice chaff is burnt, original cell structure remains in the ash as a 3-D structure of crystallized SiO2. In addition, by controlling combustion conditions, it is possible to control the degree and phase of crystallization of ash. Under low temperature or short time combustion, the ash becomes amorphous silica, whereas under high temperature and long time combustion, the ash changes to cristobalite and later to tridymite. Producing rice husk ash, in this way, as byproduct of high marketability would make the power business much more profitable.

Source:
Vietnam News (14 November 2009)
http://vietnamnews.vnanet.vn/Industries/193994/Viet-Nam-eyes-rice-husks-as-source-of-clean-energy.html
https://rwe.com/web/cms/mediablob/de/359280/data/346364/51634/rwe-power-ag/klimaschutz/cdm-ji/CDM-BIOMASS-POWER-PROJECT-LAP-VO-VIETNAM.pdf