This paper presents a new energy recuperation concept through the use of gas separation．In a conventional way, steelworks by-product gases that have been generated from coke oven, blast furnace, and converter have been used directly for fuel. Blast furnace gas that has generated over 50% amount of by-product gases, which is loaded with CO₂ and N₂ gases. So, we propose that CO₂ and N₂ gases should be separated from blast furnace gas. This heat value will increase the original heat value of blast furnace gas．This blast furnace gas will increase the efficiency of the newest Gas Turbine Combined Cycle(GTCC) power plants by +5% and reduce the CO₂ emission by ▲25% at a conventional steelworks with 10 million ton-steel/year yield.

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A matrix method has been applied to investigate environmental burdens on a complex production system with some feedback flows. Process activities in the system should be consistently calculated by simultaneous equations of an inverse matrix. However, there are two theoretical problems to be solved for using a matrix method. Firstly, the matrix between processes and materials in a production system should be a regular matrix. Secondly, environmental burdens of a system are analyzed only for processes but not for materials by the conventional matrix method. The study aims to develop a new method which can solve the problems. We propose a new method to analyze process activities of a production system with feedback material flows. In the method the number of processes and materials in a production system is changed to construct a regular matrix. An analytical method is also developed to estimate environmental burdens of material products in the system. The two proposed methods are applied to a case study which estimates process activities and CO₂ emissions. The results indicate that environmental burdens of the complex system are consistently investigated by the new method. In addition, the results of process activities are compared with the conventional method to confirm the validity of our method.

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Plug-in hybrid electric vehicles (PHEVs) will be widely implemented as general passenger cars, and they will be effective and practical to reduce CO₂ emission. However, a ratio between electric and gasoline drive of PHEV affects the fuel cost and CO₂ emission. In this study, we estimated the probability distribution of daily mileage using a questionnaire, and we calculated the reduction rate of CO₂ emission from PHEV.
We did the questionnaire survey concerning the average daily mileage on each day of the week and the number of days of long distance drive. From the questionnaire results, we calculated the ratio of electric drive and the effect of CO₂ reduction by introducing PHEVs.
The result shows PHEVs can reduce about half of CO₂ emission even when their electric drive range is only 20 km. We also studied major factors affect the electric drive rate, such as yearly mileage, major drive object and size of cars.

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Interventions to promote energy conservation among households have been employed with varying degrees of success. Especially, energy audits had been considered to be an effective intervention. The purpose of this paper is to investigate the effect of home energy audits and examine underlying psychological determinants of energy use and energy savings. Measurement survey was carried out at 48 households in Kashiwano-ha Campus City, who were recruited to participate in this experiment. Energy audits were sent to them providing their current consumption and giving a range of energy-saving options based on their situation. As a result, it was found that energy audit may cause attitude change, but may not cause behavior change. And the contents must be edited to suit the value sense and characteristics of different consumers to promote behavior change. Also, lower consumers of electricity, who had received home energy audit, tend to have more positive effect on electricity conservation. This paper shows the short-term effects of energy audits from psychological aspect and electricity consumption aspect.

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