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Carbons formed from biomass have many potential applications including as absorbents for environmental contaminants, catalysts, and constituents of various medicines. Bamboo and Japanese cedar leaves were used as the starting materials for carbonization at temperatures up to 200° C using dry steam below the saturated vapor pressure which has the ability to dehydrate hydrocarbons. These carbonization processes were studied using a continuous pipe line autoclave under non‐equilibrium conditions. The effect of various reaction conditions on carbonization were examined by thermal analysis, extraction components, and surface observation. The bamboo carbonization product exhibited the ability to highly adsorb chlorinated organic compounds such as chloroform in aqueous solution compared with a commercial activated carbon.

As one of main biomass wastes in Japan, Sugi (Japanese cedar) leaves were chipped and treated for preparation of charcoal at mild temperature (250 – 450 °C) using superheated steam with controllable pressure. After the treatment, the solid residual charcoal was examined by FT‐IR and CHN elemental analysis. The results suggest that degree of carbonization was significantly affected by treating temperature, time and partial pressure of steam. A temperature above 400 °C and a partial pressure of steam above 4 MPa are necessary for accelerating and completing the carbonization within 2 hours. Adsorption experimental results of charcoal show that the residual charcoal has an excellent absorbability for ammonia gas and heavy metal ion Pb2+. Therefore it is expectable to develop mild superheated steam as reaction medium for preparing valuable charcoal products from biomass wastes with lower energy cost.