In low carbon society, it was thought that substitutes of biomass would be changed from fossil resource to clean one by future technologies. Life cycle analysis was conducted to evaluate greenhouse gas (GHG) reduction effect by waste wood utilization in current and future society Five technologies, that is, incineration, heat utilization, pyrolytic gasification and power generation by gas engine (GE), pyrolytic gasification and Fischer Tropsch (FT) synthesis, Ethanol fermentation technology were compared. In actual technological level, it was appeared that heat utilization by wood pellet and GE power generation were favorable. In low carbon society about 2030, diffusions of low CO2 emission power supply, heat pump and battery electric vehicle were expected. In addition, biomass conversion technologies such as FT synthesis and ethanol fermentation would be also elevated future. As a result of analysis with these considerations, greenhouse gas reduction effects by all biomass utilization technologies were reduced to 8-42% (36-82 kg-0O2/t-wet) and it was because of degradation of substitution effect. It was appeared that GE power generation might be the most favorable utilization scenario in low carbon society.