CO2 emission from biomass power generation system with sustain-able afforestation was evaluated by LCA (Life Cycle Assessment) methodology. Cal-culation was conducted for typical case (15km×15km). CO2 emission from sustainable afforestation system was calculated to be 2.1×107 kg-CO2/y. That from construction of biomass power plants was calculated to be 5.0×105 kg-CO2/y. CO2 emission from power plant construction was negligibly small. Net CO2 reduction effect of replacing coal by biomass was calculated to be 2.4×108 kg-CO2/y. It was suggested that the biomass power generation system possibly educes large quantity of CO2 emission by the replacement. CO2 emission from afforestation was about 8% of the CO2 reduction effect. Finally, the energy payback time of the biomass power generation system with sustain-able afforestation was calculated to be about 0.2 year.
For the purpose of revealing the progress of coal liquefaction at the reaction fields, we gave attention to coal particles and coal-derived materials that are hydrogenated and/or carbonized in the liquefaction reactors, and tried evaluation using microscopic technique. On the basis of microscopic textures and optical properties, carbonaceous subst-ances in withdrawing from reactor bottom could be classified into five categories that in-clude vitroplast, mesophase/anisotropic semicoke, non-plastic and partially plastic coal particle, pyrolytic carbon like material and vitrinite remnant, and we clarified its micros-copic compositions. Furthermore, the effects of operating conditions on the properties of carbonaceous substances from the principally reflectance of non-plastic coal particle were researched. Consequently, when the severity of operating conditions was raised, the properties of carbonaceous substances indicated that carbonization was superior to hydrogenation under the atmosphere of initial liquefaction stage. As the reaction proceeds, hydrogena-tion became to predominate over carbonization. At high concentration coal/solvent slurry, we confirmed that hydrogen availability tended to reduce for coal particles. However, we could clear this problem by improve-ment in hydrogen donor ability of recycle solvent.
The recycling of waste plastics in the blast furnace has been in-vestigated with the test furnace and the commercial blast furnace. From the results of these experiments, it was found that the combustion and gasification behavior of waste plastics injected into the raceway of the blast furnace was much different from those of pulverized coal. Pulverized coal injected into raceway was consumed in the combustion zone of the raceway and converted into CO2 and H2O rapidly. On the other hand, waste plastics was mainly converted into CO and H2 by gasification with CO2 generated in the combustion zone of the raceway. Combustion and gasification efficiency of waste plas-tics was much higher than that of pulverized coal in spite of large particle. Waste plas-tics like -10mm particle can be effectively gasified due to the circulation effect of coarse particle in the raceway. Recycling effciency of waste plastics in the blast furnce was estimated to be 76%. It is considered that waste plastics injection into the blast furnace is a favorable way to realize material recycling of waste plastics and to solve environ-mental issue.