JKUAT-developed technology converts rice husks into gas and electricity

Rice mills are set to benefit from a new technology that converts waste rice husks into gas and electricity. Currently rice husks provide little economic value and are often heaped and burnt to dispose them. This, researchers say, leads to air pollution, loss of material and wastage of heat energy.

The new technology converts the husks into syngas (synthesis or producer gas) which can then be used for cooking and other applications. When purified, syngas is also used to run electricity-producing gas engines that can generate power for use in the rice mill.

The new technology has been developed by the Jomo Kenyatta University of Agriculture and Technology (JKUAT) through the Japan International Cooperation Agency (JICA)- funded Bright Project aimed at promoting rural electrification and use of renewable energy.

Paul Njogu, the researcher behind the new technology, noted that schools and other institutions that can access rice husks will also benefit from the technology. “We have developed a gasifyer that is sized for secondary schools of about 200 students which they can use for cooking,” said Dr Njogu who is based at JKUAT’s Institute of Energy and Environmental Technology.  

Syngas comprises a mixture of carbon monoxide, carbon dioxide and hydrogen. It is produced by gasification of a carbon containing fuel to a gaseous product that has some heating value. After gasification, the rice husks are converted into carbonated rice husks that can then be used to make energy briquets, water purifiers, and to improve soil porosity and water retention ability.

Syngas has 50 per cent of the energy density of natural gas and is used as a fuel source, often to manufacture steam or electricity. The new technology is wholly developed at JKUAT, including design and fabrication. However, the institution will in future partner with a manufacturer for mass production.

“Once we start getting orders, we will look for a manufacturer to partner with but in the meantime we are doing it ourselves,” said Dr Njogu.

The small gasifyer for schools is currently retailing at Sh225,000 while the large gasifyer for rice mills is selling at Sh550,000. Mass production is expected to bring down the cost of the technology due to economies of scale. 

The larger system for rice mills comes with a gas purification mechanism that removes non combustible gases like carbon dioxide, nitrogen, water vapour and dust particles. The system, however, does not include the generator for power production, which is bought separately.

Future plans include storing the refined gas in cylinders for later use.

Kenya’s annual rice production stands at 45,000 to 50,000 tonnes, 22 per cent of which is rice husks. The husks are low density and cannot be used as animal feeds since they have poor nutrition. 

According to Dr Njogu, the technology does can also be used to convert other forms of biomass waste into syngas.