paper containers, plastic bottles (including styrene foam trays for foods and food bags), and “packagings”, which include package paper and wrapping, that households dispose of are to be made once again into commercial goods. Such containers and packagings account for about 60% by bulk and about 20% by weight of total household garbage. Of those containers and packagings, this section addresses waste plastic and PET bottles and discusses technologies for recycling them. Although there are many kinds of waste plastics, only PET bottles and foam styrene food trays are collected as separate categories.

The technologies for recycling waste plastics are categorized into material recycling that uses the materials in their original plastic form and chemical recycling that chemically treats the material for use as a chemical material.

In material recycling, collected waste plastics are made into materials for plastics in the form of flakes, fluffs, and pellets through the processes such as removal of foreign matter, sorting, and cleaning. They may then be mixed with new materials for necessary component adjustment to make them into materials such as pellets. (Fig. 2-25)

On the other hand, waste containers and packagings and waste PET bottles are recycled into textile products such as working clothes and carpet, sheet products, such as egg packs, and containers for cup noodles, hangers, and planters. A technology to make PET bottles from waste PET bottles has also been put into practical use, with about 12,000 tons of PET bottles manufactured in this way in 2005. (Fig. 2-26)

For PET bottles, a technology to separate the body from the cap and the ring (i.e., the thing left on the main body when the cap is screwed off) has also been put into practical use. This technology involves flattening a PET bottle with gears and cutting it in a longitudinal direction so that it is easy to separate the body from the cap and ring manually. (Fig. 2-27)

Chemical recycling has been implemented particularly in the fields of steel manufacturing and chemicals. In steel manufacturing, coke is used to reduce iron ore to iron in a blast furnace, and waste plastics can be substituted for coke after they are processed into grains. This is because carbon and hydrogen contained in plastics can function as a reducer. Plastics blown into a blast furnace decompose into hydrogen and carbon monoxide at high temperatures of about $ 2000^{\circ} $ C and react with iron oxide as the main component of iron ore to reduce it to pig iron. The residual hydrogen and carbon monoxide after the reduction reaction are recovered as blast furnace gases and used as a fuel for power generation. (Fig. 2-28)

For a coke furnace, there is also technology to thermally decompose waste plastics and reuse them as resources. This technology involves heating waste plastics in a closed chamber, called a carbonizing chamber, in a coke furnace without oxygen at about $ 1,200^{\circ} $ C, thus generating hydrocarbon oils (light oils and tar) and coke furnace gases (hydrogen, methane, etc.) from the hot gases.

Fig. 2-27 PET-bottle bulk reducer

Source: Meiwa Kousakusyo Corporation

Fig. 2-28 Waste plastics recycling by a blast furnace