Since wet-biomass such as sewage sludge contains much water, it is necessaiy to be dried before its utilization for fuels. Therefore, we have developed a carbonization process combined with diying step by fennentation. The sewage sludge of ca.80 wt% moisture was dried to ca 30 wt% moisture by fermentation based on the composting technology. The dried sludge of 0.1 t/h was carbonized at 430℃ by using a rotaly kiln which was externally heated by burning the volatile matter evaporated from the sludge. In this process, the wet-biomass can be dried and carbonized without fuels except for the start-up of the plant.