This comes from an old story but it is more relevant today than ever! The photo is a typical rotary furnace sold today so you can get an idea of how it works.
“Frank Angelo of Jonesboro, Arkansas was about to be fined $10,000 a day for burning 200 tons of bark, chips, sawdust, and shavings a week … leftovers from the chicken coops that he manufactures. So, Angelo invented a 70-ton rotary furnace from an abandoned railroad car, an afterburner, and recycled conveyor belts and pipes. The furnace is now generating up to 20 million Btu’s an hour … enough energy to power 750 Jonesboro homes. A by-product of Frank’s invention—activated carbon—is sold as a filter to remove cancer—causing agents from air and water.”- Source

Great new service from Google –