Landfill is the main technology to dispose solid waste in China, but lack of space for new landfill has become a growing problem especially for large urban areas. One approach to prolong current landfill life span is to excavate the aged MSW and separate the combustibles for thermal treatments, for the combustibles (upper siftings) constituted a major portion(45-62%) of the aged MSW on a volume basis (Wenjing Cui, 2007). Due to the panic of emissions of dioxins, heavy metals, etc, non-incineration methods such as pyrolysis and gasification are paid more and more attentions.