Increased use of biogas, a mixture of methane and carbon dioxide produced by decomposing organic matter, is expected to fuel the country's drive to advance ecological agriculture and protect its environment, officials and experts agreed at an international meeting that ended over the weekend in Beijing.

In addition to being piped through to kitchen ranges and lamp-stands, biogas is now being used to treat sewage in an increasing number of towns, according to Wang Xiwu, a senior expert on biogas.

Wang told the International Symposium on Biogas Technology and Sustainable Development that more than 7.6 million rural households in China have built family-size compost devices in order to produce the clean energy, which they use mainly for cooking and lighting.

The gas is produced when discarded organic material, such as plant clippings and food scraps, are placed together in a compost bin where they undergo a chemical reaction that produces both methane and carbon dioxide. Households then pump this combination from their backyards directly into their houses.

The increasing use of biogas in China has helped decrease reliance on wood as a fuel source, which has resulted in a reduction of consumption equal to more than 2,000 kilograms of firewood per family per year, according to Omar Salah Ahmed, an official with the Food and Agriculture Organization of the United Nations.

China has been researching and employing biogas for a long time. According to Wang, this experience with the fuel source has enabled the country to develop an alternative to sewage treatment facilities - which are usually expensive - in some of its smaller cities.

These cities have developed a system in which they use a portion of their sewage, which is made up of organic material, to produce of biogas. The energy produced by that biogas is then used to treat some of the remaining sewage using a variety of techniques.

So far, at least 49,300 urban sewage treatment facilities have adopted biogas technology, according to Wang.

Zhang Baowen, vice-minister of agriculture, said the by-products of producing biogas have been widely used as fertilizer for farms and as a food source in fish farming.

Promoting the application of biogas technology is viewed as a key means of improving the fragile ecological system and sustaining the rural economy in China's western regions, he said.

(China Daily 10/31/2000)