Julian Cribb, Science Alert 18 Mar 10;
“Black carbon”, the soot from billions of domestic fires across the poorer regions of the world, is a powerful, but little-publicized driver of climate change. Scientists now consider it provides around half the global warming potential of CO2.
In a unique marriage of high and low technologies Philippino engineer Alexis Belonio and US physicist Steve Garrett have come up with a way to improve the health of poor people, beat a major global waste problem and develop a fast-track technology to counter global warming.
Belonio is the inventor of the world’s most efficient gas cooker fuelled by waste rice husks, Garrett the genius behind the world’s first truly clean refrigerator, which is cooled using sound waves.
Between them, however, they have hatched an idea that could see the Third World outstrip developed nations in the race to devise rapid solutions to global warming
“Black carbon – which is basically the soot from billions of domestic cooking fires - is about 600 or 700 times more potent than CO2 as a climate warmer: It absorbs more heat because it is black,” Garrett explains. “But it only lasts about 10 days in the atmosphere, so this is a problem you can actually fix quite quickly – as opposed to CO2, which hangs around for centuries.”
If the smoky cooking fires of the developing world could be replaced with low-cost stoves like Belonio’s, which converts rice husks or other biomass to a clean gas, it would start to cut humanity’s carbon emissions within days. Developing countries would become world leaders in combating climate change.
The challenge is to develop a stove cheap and simple enough to go into a billion homes.
Belonio’s stove, now in its third generation, already fulfils most of the criteria. Fuelled by unwanted waste – the 150 million tonnes of husks discarded in rice-growing regions each year – his US$20 cooker turns this free, low-energy fuel into a greenhouse-neutral gas that burns with a clear blue flame. This can save a poor family up to one-tenth of their income every year, as they no longer need to buy gas or kerosene for cooking. Because it burns cleanly, the stove is much healthier to use: the World Health Organization estimates that indoor air pollution caused by smoky fires kills about 1.6 million women and children every year.
Key to the efficiency of the stove is a small electric fan that drives a stream of air through the smouldering rice husks. This produces the gas mixture which the stove then burns, just like a normal gas cooker. The catch is that you need electricity to drive the fan – and half the developing world still lacks this essential energy source.
Enter Steve Garrett of the Pennsylvania State University, who had been working as Scientific Adviser to the U.S. State Department’s South-East Asia bureau. “We were looking for technologies that would assist development, clean up the environment, address global warming and improve health,” he explains. It turned out the Philippino engineer and American physicist had a strong link – both were Laureates of the Rolex Awards for Enterprise. Steve, who became a Laureate in 1993, learned of Belonio’s work when the latter won his award in 2008.
The stroke of genius was the realisation by Garrett that he had a way to turn the heat from Belonio’s stove into sound waves that could in turn be used to produce enough electricity to run the fan. This meant the stove could be used anywhere on Earth where there was a suitable biomass fuel supply – and act as its own electrical power source.
Steven Garrett, 60, specializes in the science of thermo-acoustics. The winner of several major prizes for environmental technology and the holder of over 20 patents for his inventions, he has developed sound-driven refrigerators for the U.S. space program, U.S. Navy and Ben & Jerry’s ice cream, with a view to one day replacing the billions of ‘dirty’ refrigerators and air conditioners worldwide which use either ozone-destroying CFCs or planet-warming HCFCs as coolants . His research group now works on commercial chillers and freezers, including appropriate technology for developing countries. These use electricity to make high-intensity sound waves to compress a clean, inert gas, to initiate the cooling cycle used in refrigeration.
Alexis Belonio, 49, is animated by the ideal of sharing his stove with anyone in the world who wants it. “It is God’s calling,” he says simply. “I have received the knowledge of this stove from God for free, and I must give it for free also.” So far, more than 40 companies, non-governmental organizations, aid agencies and local groups in a dozen countries have adopted his design. With his Rolex Award funding, he has published a technical manual, distributed information via the Internet and run the first of a series of workshops in the Philippines to train the trainers who will distribute his technology far and wide. Belonio himself works with Minang Jordanindo Approtech in Indonesia, who are making 80 stoves a week, and plans to assist similar operations in Vietnam and Cambodia, in addition to his native Philippines. Inquiries are pouring in from countries such as India and China, as well as South-East Asia.
Belonio is now working on his Phase 3 model stove. In this model, a container of rice husks is loaded into the stove and burned until used up, then exchanged for another, like swapping the bottles on a gas barbecue. The aim, he explains, is to make the rice cooker available in towns and villages where rice is not produced locally. This will create jobs for workers in rice areas who will gather the unwanted rice husks and pack them into fuel containers. It will also greatly increase the places the stove can be used – and provide a new, low-cost cooking fuel for urban families. The ash from the burned husks can be mixed into the soil, where its ability to hold moisture results in crop yields 10 to 20 per cent higher.
But what could spread the stove worldwide would be the addition of its own power source. Garrett points out: “Take a look on the internet at the dark areas of the planet at night. These are the places where there is no electricity, where people burn biomass to cook or warm their homes. That is where most of the black carbon comes from. In Asia, unlike the developed world, one half of the global warming potential is due to black carbon and other products of incomplete combustion such as methane, carbon monoxide and ozone precursors.
“It is also a big deal using a simple stove to put electricity into people’s lives in areas that may never be on the grid. They can also use it to charge a battery to light their home, or to power a cell phone.”
Working from the meticulous detail that Belonio has publicized, Garrett says it is possible to convert heat to sound, and sound to electricity, in essence reversing the process used in his acoustically-powered fridge. “All you need is 2-3 watts to run the stove’s fan and a few watts more to run other devices. We would like to use the stove’s heat to generate sound waves and use that sound in a linear alternator - a sort of highly efficient microphone - to make electricity.”
There are other ways to turn stove heat into electricity, he adds – using thermoelectric methods or co-generation of steam to run a micro-turbine. They all need to be explored.
Belonio is apprehensive about the possible cost of the upgraded stove. He has struggled for years to design the cheapest, most practical stove possible, which can be made in an ordinary village workshop from scrap metal and is affordable to the poorest of the poor. He has got the price down to $20-$25 a unit, and is worried about the added cost that a high-tech power source might involve. “I’m dealing with the household sector,” he says. “They want to save their money.”
Garrett adds that it is possible to produce electricity thermoacoustically with inexpensive components. If it can be shown to work successfully and also fixes the black carbon issue, governments and aid agencies will be very interested in providing funding to make the stove affordable for worldwide distribution, possibly offsetting part of the additional cost with carbon credits. He is offering the state-of-the art instrumentation of his lab at Penn State to assist Belonio in designing the most efficient and cost-effective small-scale electrical generator possible that will work with his stove.
The teeming mind of Alexis Belonio never rests. He is well advanced in the design of a super-burner that produces a far hotter flame by injecting steam. This could be used to provide boilers and dryers for small industry, fire kilns and bakery ovens or generate electricity from waste on a scale ranging from a single household to one megawatt.
Garrett adds: “The world needs technologies that will help economic development, improve people’s health, clean up the environment, and address global warming. This partnership looks to us like a win-win-win-win situation. That’s the upside.
“The big challenge is, you need to do it a billion times,” he admits. “We have to get this technology out to 3 billion people who are burning biomass, more than half of whom have no access to electricity. The challenges of low-cost manufacturing, distribution, adoption, and marketing seem more daunting to me than the technological challenges.” He is already drawing up a technology roadmap to persuade governments to get behind the plan to put to put clean, self-powered, fuel-efficient stoves in hundreds of millions of homes.
The two Laureates met to discuss their new concept at a conference in Bangkok in mid-November 2009, where tests on seven low-polluting stoves found that Belonio’s stove had the lowest black carbon emissions of all.
If it works as well as they hope, the combination of Belonio’s simple but elegantly efficient stove and Garrett’s brilliant thermoacoustic technology could begin to help cool the planet by removing a major warming agent – black carbon – within a decade.
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