A LIFE CYCLE ANALYSIS OF BIOMASS ENERGY SYSTEM TAKING SUSTAINABLE FOREST MANAGEMENT INTO CONSIDERATION

摘要

In this paper, we evaluated life cycle CO_2 (LCCO_2) emissions by comparing biomass power plants with a coal power plant of the CO_2 removal system. For the concrete investigation of the biomass life cycle analysis (LCA), we selected the reforestation sites in Eastern Highland Province and Madang Province in Papua New Guinea (PNG) as model areas. Then, Casuarina oligodon (C. oligodon) and Eucalyptus deglupta (E. deglupta), which are fast growing trees, were adopted as biomass materials. Especially, C. oligodon has the characteristics of nitrogen fixation from air. As the result, nitrogen fixation to soils is expected to mitigate LCCO_2 emissions and direct and indirect energy input in the biomass LCA. The biomass energy system consists of two subsystems, the cultivation process and the energy conversion process. In the cultivation process, we constructed the nutrient circulation model in reforestation area. Nutrients losses by soil erosion are evaluated in this process. In this study, it is assumed that their nutrients are newly supplemented for the purpose of considering the sustainable forest management, and that they are equivalent to chemical fertilizer. In the energy conversion process, we design the Biomass Integrated Gasification Combined Cycle (BIGCC) in PNG In this study, it is assumed that the plant scale is approximately 59 or 110 MW. Especially, using the basic experimental chemical data, we calculate the performance of gasification. Consequently, we estimated that LCCO_2 emissions of BIGCC are 4.4 to 107.2 g-CO_2/kWh (E. deglupta) and 2.1 to 63.5 g-CO_2/kWh (C. oligodon), while that of Coal-IGCC with CO_2 removal equipment is 50.5 g-CO_2/kWh.