Some Daxu stoves also come with a back boiler, bringing running hot water and central heating to rural families, for the first time.
Although many parts of rural China have access to mains electricity, most families still cook and heat their homes using stoves that burn coal or wood. This has led to severe deforestation and contributed significantly to greenhouse gas emissions. Coal use in particular leads to dangerous levels of indoor air pollution, and also contributes to the poor outdoor air quality in much of China.
Crop waste, which is widely available in many parts of rural China, could provide an alternative source of fuel for cooking. However most current stove designs do not burn this waste effectively.
In 2000 Mr Pan Shijiao together with others began researching and developing a stove design that could effectively burn crop waste in addition to burning wood much more efficiently. Satisfied that they had come up with an innovative new design that could do the job, in April 2005 Shijiao set up the Beijing Shenzhou Daxu Bio-energy Technology Company Ltd (Daxu) to commercialise the new improved stove.
The Daxu stove is specifically designed to use either loose or compressed crop waste as well as wood. The stove is over 40% efficient and produces hardly any smoke. This is achieved by burning the fuel using a controlled supply of air that produces gas which then rises to meet 'secondary' air causing the fuel to burn more thoroughly. This ensures that the fuel burns more efficiently and that heat is transferred to the pots more quickly which allows a meal to be cooked in 15 -20 minutes with minimal smoke pollution.
The Daxu stove has radically improved the lives of farming families in the regions where it has been sold. Its two hotplates allow a stir-fry dish and steamed rice to be cooked at the same time, it reduces the cost of cooking and heating by 50% whether it is using crop waste or wood and it significantly reduces levels of indoor air pollution and smoke. Some of the Daxu stoves also come with a back boiler, bringing running hot water and central heating to rural families for the first time.
As one stove user, Zhang Qinhua put it: "it's much cleaner - my kitchen isn't dirty and smoky like it used to be and we can wash properly now we have hot water - there wasn't much point in washing before anyway because it was so dirty with all the coal dust."
Another stove user, Zhao Yucheng, marvels at the benefits: "It is so much quicker; with coal, it used to take half an hour just to get a good flame. With this stove, we can start cooking almost as soon as it is lit. I don't spend a penny on fuel now - we get all the briquettes we need for free.. so we must save about 1,000 yuan from summer cooking alone."
Such is the efficiency of the Daxu stove that it is estimated that using one instead of coal prevents the production of over 8 tonnes/year CO2.
The Daxu stove model has proved so efficient that it was singled out for achieving the highest efficiency of any entrant in a stove competition organised by the China Association for Rural Energy Industries and the Shell Foundation.
To date, 25,000 Daxu stoves have been sold with 10,000 having been sold in the first three months of 2007. These sales are due in part to subsidies provided by the Yangqing County authorities in a drive to combat deforestation and indoor air pollution in a region with an abundant source of crop waste.
There is enormous potential for introducing such technology throughout China, since over 20 million wood and coal stoves are sold each year. Daxu is negotiating agreements with other local authorities and promoting its stoves through agricultural shows and village exhibitions to encourage the wide-spread use of this highly efficient stove model.
