LIFE CYCLE IMPACT ASSESSMENT OF POWER GENERATION AND COMBINED HEAT AND POWER GENERATION BY WOODY BIOMASS

摘要

Since a feed-in-tariff (FIT) was introduced in Japan, the power generation which used woodyrnbiomass is attracting more attention. Profitability of the plant above a certain scale would be able to be secured byrnFIT. On the other hand, it is also necessary for the plant to implement life cycle assessment (LCA). First of all, werndeveloped the simulator which enabled to estimate the overall efficiency of the plant by entering the supply amountrnof wood and extraction condition of steam and so on. Environmental performance of power generation, andrncombined heat and power generation by woody biomass were evaluated based on LCA. The following 3 scenariosrnwere schemed on the condition that the woody biomass of 200,000 m~3 (log equivalent)/year was available. Thernfollowing three scenarios for woody biomass systems were considered for LCA: scenario B1: 200,000 m~3 of woodyrnbiomass is consumed by one power plant that produces power only; scenario B2: 200,000 m~3 of woody biomass isrndivided evenly and consumed by each of two power plants that produce power only; scenario B3: the 200,000 m~3 ofrnwoody biomass is divided evenly and consumed by each of two CHP plants that produce heat and power. Thernexternal costs associated with woody biomass systems are at least 24%, at most 69% lower than thosernassociated with fossil fuel systems, and woody biomass systems are more eco-friendly than fossil fuelrnsystems. The reduction in external costs is greater for CHP systems that produce both heat and power thanrnsystems that product power only. Recycling ash and combustion residue and preventing these materialsrnfrom being landfilled are important means for efficiently lowering the external costs associated withrnwoody biomass systems.