Fig. 2-48 Production of bio ethanol from waste wood materials

* The technology for producing ethanol used in this plant was provided by Marubeni Corporation and Tsukishima Kikai Co., Ltd. Source: Bio Ethanol Japan

### 4. Technologies for Metal Circulations

Every economic and social activity has a material basis. Metals ? in the form of home appliances, automobiles, and buildings ? are especially important to supporting life in modern society. This section discusses a sound material-cycle society from the perspective of metals, explaining the cyclic use of major metals such as iron, copper and aluminum, as well as and rare metals, and the technologies that enable cyclical use.

## (1) Iron, copper and aluminum

By-products and waste should be recycled and reused or properly disposed whenever recycling and reuse is difficult. The highest priority, however, is to avoid discharging waste. The material industry in Japan is working to reuse and recycle by-products and waste produced in manufacturing processes within a plant as a way to minimize the waste discharged by the production system. The industry also smelts and refines scrap metal collected in town for use in production.

Iron is the most common metal to man. The quantity of crude steel produced in Japan is about 110 million tons annually. The steel industry recycles internally produced scrap and scrap collected in town as a production resource. Every year about 48 million tons of scrap iron is used in electric furnace processes where the scrap is melted by electricity for use in steel production or by blast furnaces where scrap iron is used in the converter step of steel manufacturing in which iron ore and coal are used as materials.

To produce one ton of pig iron, about 1.5 tons of iron ore, about 0.8 tons of coal, and about 0.2 tons limestone are consumed in the production process. Components other than the iron in iron ore melted in a blast furnace to produce pig iron are separated and recovered in the form of blast-furnace slag, including limestone and the ash component of coke, as auxiliary materials. Blast-furnace slag is produced at a ratio of about 290 kg to one ton of pig iron. In the production process with a converter and an electric furnace, about 110 kg of steel-production slag is produced for every ton of pig iron. In the overall steel industry, about 47 million tons of steel-production slag is produced annually, of which 99% is used as materials for cement or road subbase course materials. (Fig. 2-49)

Copper is used as a material for power lines, and copper and copper alloy products such as plates, pipes, and rods, due to its excellent workability and conductivity. In Japan about 1.38 million tons of copper refined by means of electrolysis (copper ingots) was produced in 2004. Copper and copper alloy scrapped after use in products is returned to smelters and copper/copper alloy factories according to the type, quality, and form of the scrap and melted and reused. (Fig. 2-50)

Aluminum is used in transportation equipment, building structures, and food containers due to its lightness and high strength. Because the process of producing aluminum from ore (bauxite) requires an enormous quantity of electricity in the bauxite smelting phase, little aluminum is produced by that process in Japan. Instead, new aluminum ingots imported from overseas and recycled aluminum ingots produced from domestic aluminum scrap are used as aluminum materials. In 2004, about 2.5 million tons of new ingots and about 1.96 million tons of recycled ingots were used. As a result, recycled ingots account for about 40% of total demand. (Fig. 2-51)