Pig Manure as an Energy Source Final Processing Facilities Are Full Farewell to Dioxins

Farewell to Dioxins

Japan produces over 50 million tons of general waste material per year. Although some of it is processed directly, 80% is incinerated to reduce the volume. One reason for this is Japan’s small land mass. There are hopes that a new type of facility called a “gasification melt system” will solve the problem of dioxins produced by conventional incineration facilities. The gasification melt system melts and breaks down waste materials at very high temperatures to minimize the amount of dioxins generated. Taking the shaft type gasification melt system developed by Sumitomo Metals as an example, waste products are incinerated at a very high temperature of 1200°C, thus breaking down almost 100% of the dioxin precursors (that form dioxins). Dioxins would be formed if the temperature of the gas generated by incineration were lowered gradually, but the system uses specialized equipment to cool the gas temperature instantly to 170°C to prevent dioxins from being resynthesized. This is the cutting-edge feature of the Sumitomo Metals system, which studies have found to produce a mere 1-2% of the volume of dioxins compared with other gasification furnace systems. High quality slag collected from the shaft type gasification melt system can be used as base coarse material for roads or raw material for cement.

The shaft type gasification melt system represents the most advanced technology of its kind. Founded on technology developed in steel manufacturing, it incorporates pre-drying, oxygen utilization, high temperature meltdown, and fast cooling of generated gases. It is a safe gasification melt system that does not require additional fuel such as coke.

Garbage Converted to Gas or Electricity

The gasification melt system extracts energy from waste materials during the treatment process—another aspect in which Sumitomo Metals’ system excels. Many gasification melt systems collects energy extracted from waste materials as steam, but Sumitomo Metals’ system collects it in the form of gas. “The difference is significant,” explains Hisao Gotou, general manager of Sumitomo Metals Environmental Plant Engineering Division. “The clean gas with high calorific value that is generated from the process can be used either as fuel, or converted to electric power in a boiler or gas engine. It is also technically possible to collect hydrogen from the gas or to use it in a fuel cell. Thus, by extracting energy in the form of gas rather than steam, we can use it for a broader range of applications. The system can also be added onto conventional manufacturing facilities. By linking it with a manufacturing facility, we can process the waste materials economically and use the energy that is generated to power production equipment. The technology is versatile, being a good match with existing gas-powered manufacturing facilities, and so looks promising not only for users in Japan, but also for marketing overseas. The Sumitomo Metals system also collects safe, high-quality slag (solid glass waste material) low in dioxins and heavy metals. The slag is the same quality as blast furnace slag and can be used as a base coarse material for road construction and as a raw material for cement. Sumitomo Metals began gasification melt system research in 1995, when its Corporate Research & Development Laboratories embarked on basic research in this area. It was a relatively late start, but the company did not rush into importing technology from overseas, preferring instead to develop its own. A pilot plant with a 2-ton processing capacity was completed at the R&D Laboratories in 1996, and a pilot facility with a daily processing capacity of 20 tons was built at the company’s Kashima Iron and Steel Works in 1998. Sumitomo Metals’ presence in the market grew steadily to the point where the system was approved for sale to other companies in 2000. Sumitomo Metals was able to develop the system because its steel business had a solid grounding in high-temperature process technologies and know-how for blast furnaces and converters. The involvement of its environmental engineering business in interim waste processing and recycling facilities also contributed to the development of the gasification melt system.

	The Ultimate Goal: Zero Emissions
	The gasification melt system developed by Sumitomo Metals is already operating across the nation. The Gasification Recycling Center of Tosu Miyaki Seibu Environmental Facility Union in Saga Prefecture processes general waste products, offers outsourcing services and facilities, and has produced significant results with its all-round technical expertise and know-how. Trial operation of furnaces for processing automobile shredder residue (known as ASR; shredded residue from the process of recovering parts and materials of value from scrapped vehicles, said to be the most challenging industrial waste product to process) is on track in Yamaguchi and Ibaraki prefectures, and the delivery dates are approaching. Says Gotou, “We need to increase the number of resource recycling facilities if we are not to leave a mountain of waste products for the next generation to clean up. Our system is fully capable of meeting this requirement. We expect the business to take off in earnest, based on the experience we’ve acquired from building and operating the current three facilities.” Livestock manure and construction waste were previously considered a serious nuisance, but now they are being transformed by advances in waste recycling technology into new resources and fuel. Effective use of all waste materials would make the dream of a “zero emissions society” a reality—a future where we make dramatic progress toward solving the problem of garbage left over from the 20th century.	Hisao Gotou, General Manager of Environmental Plant Engineering Division, Sumitomo Metals

(Data collected April 2005)