Pinoy invents eco-friendly stove powered by rice hulls

MANILA, Philippines – A Filipino inventor believed that there is more to ipa or rice husks other than being a mere good fertilizer additive.

Engineer Alexis T. Belonio, a native of Nueva Ecija, started to work with rice husks in 2003. At the time, fuel and energy prices all over the globe started to shoot up, impairing oil importers like the Philippines.

Belonio recounted that, aside from the energy crisis then, the use of wood for fuel in the country’s rural areas also became alarming as it caused forest denudation.

The rising amount of greenhouse gases present in the atmosphere also became one of his concerns. It made him think of producing low-cost fuel that could help even the poor families in the rural areas.

Belonio said that because liquefied petroleum gas (LPG) is costly, domestic cooking is affected, so he thought of designing a stove that uses biomass but works like an LPG cooker.

He said, “Hindi ko naman kinokontra ang LPG. Pwede nating gamitin iyan sa transport sector, sa industries… Pero ‘yung biomass natin, gamitin natin sa rural areas kasi marami sila.” (Not that I am not in favor of using LPG. It can still be useful for the transport sector and for industry purposes but we can use biomass in rural areas, where they are abundant.)

The abundant solution

Rice husk, the shell from which palay is removed when milled, is one of the largest agricultural waste produced in the country.

Yearly, the Philippines generates about two million tons of rice hulls. If converted to rice, it could feed the entire country daily for almost two months. 

Rice husks are mostly used as fertilizer additives, landfilling or paving materials, and for making stockbreeding rugs. They do not decompose unless burned because of their high silica content. Silica is a common raw material for semiconductor components.

But, it can also be used as biomass fuel, like in Belonio’s stove. Basically, the stove works like a normal cooking range but it is powered by burning rice hulls. It is comprised of a burner, a gasifier reactor, a char chamber, a fan and a control switch.

The idea is to limit the amount of air when burning the hulls. This process allows the cooker to produce a luminous blue flame, similar to LPG-powered stoves.

Currently, a single-burner stove costs around P2,000 to 3,000 per unit, depending on the design.

The stove is not only environment-friendly, it is also cost-efficient, said Belonio.

A kilo of rice husks lasts for an hour. It costs around P2/kg – in some areas it can even be acquired for free – plus the electric consumption of the fan which may be around P1/hour.

This means cooking using the rice husk stove costs only P3 per hour, while using an LPG cooker could amount to P17 per hour.

Technology for all

This stove has already won various local and international prizes, the latest of which is the National Winner for the Philippines of the Energy Globe Award 2014, an annual prize given by the Energy Globe Foundation, through the Austrian embassy.

Rice husk stove technology had been introduced in 1986 under the Department of Agriculture – International Rice Research Institute (DA-IRRI) Program for Small Farm Equipment to replace the use of wood and charcoal for domestic cookers.  

After being given a study grant in Thailand in 2003, Belonio started to develop his own rice husk gasifier. His first prototype came out in 2004 and he has been producing various models for local and international use since.

“Older rice husk stove technology burns rice hulls with sufficient amount of air. The newer version is oxygen-starved so that while burning, the gas will come out in the form of a blue flame. The older version produces more smoke,” said Belonio in a mix of English and Filipino.

Less smoke means reduced carbon dioxide emissions, he added.

However, Belonio wanted to keep his innovation as open-source, which is currently under the Center for Rice Husk Energy Technology (CRHET), College of Engineering of the Central Luzon State University in Nueva Ecija.

Belonio said, “When you keep it open-sourced, you will trigger the others to innovate. You cannot solve the problems of the world alone.”

Belonio believes that knowledge multiplies when it is shared. His stove is now being marketed in other countries like Sri Lanka, Vietnam, India and Cambodia.

He is working for the Philippine Rice Research Institute (PhilRice) as a senior research fellow. He is currently studying bioethanol and its capacity to be a source for electric power generation. – Rappler.com