Rice waste may build new Asian homes
	Waste not: Ash from burning rice hulls can be substituted for cement
By Julian Lee A common South East Asian waste product may soon be used to provide cheap housing in the region, thanks to the work of an ANU engineering student. The hulls of rice, left over after the edible seed is removed, are usually burnt creating up to 100 million tonnes of ash a year. Now, the rice hull ash has been shown to be a suitable cement substitute to make building materials. Honours engineering student Jane Lynch at ANU's Department of Forestry has been experimenting with the mix of rice hull ash, cement and wood as part of a project to manufacture low cost housing materials for the National Shelter Program in the Philippines where housing is in chronic short supply. The project is funded by the Australian Centre for International Agricultural Research. "Up to 20 per cent rice hull ash improved the water resistance of the material, and all the boards I made met the British standard for strength," Ms Lynch said. "The reason why we wanted to try rice hull ash was because 50 per cent of the board is cement and rice hulls are a really big waste product," she said, "The way they dispose of them is to just burn them. They are already there, and it's causing a lot of pollution. Lots of silica goes up into the air and contributes to eye and lung diseases." Composite boards are commonly used in building houses. However they are difficult to use in tropical countries such as the Philippines because the wood fibres absorb water. This causes the wood to swell, weakening the boards. Using rice hull ash avoids this problem because the ash mixed with cement is very porous. The water enters the ash and not the wood, stopping the wood from swelling. Ms Lynch said another advantage of using rice hull ash was that normal production of cement was polluting and expensive. "If you can substitute even a little bit with ash, it will reduce environmental and financial costs," she said. Ms Lynch is travelling to the Philippines to talk with others in the program. "I will make boards with them, tell them what I've found out and hear about what they've found out. I'm also going to see some of the factories," she said. She also has plans for future projects. "I'd really like to keep working on developing low cost materials that can be manufactured in an environmentally friendly way at the community level," she said.