Thermal recycling of foundry waste sand and implementation technology for zero emissions--Porous ceramics conversion process at Tsuchiura (circa 1997)

Thermal recycling of foundry waste sand and implementation technology for zero emissions--Porous ceramics conversion process at Tsuchiura (circa 1997)

In the 1990s, Japan was at a turning point when the concept of a "zero-emission society" and a "recycling-oriented society" began to permeate both policy and industrial practice, and the Law for Promotion of Utilization of Recyclable Resources in 1991 led to a search for ways to recycle by-products and improve recycling rates in various industrial sectors. The adoption of the Kyoto Protocol in 1997 also made the elimination of waste and landfills a national issue.

Against this backdrop, the Tsuchiura City, Ibaraki Prefecture, Japan, facility developed a heat treatment and recycling technology that converts used mold sand into porous ceramics by firing it at 900°C. This technology is used in the casting industry for molding products. The casting industry discards a large amount of mold sand used for molding products, most of which has been disposed of in landfills. The annual volume of this sand waste, which amounts to several million tons, has created an urgent need to redesign the treatment system due to the tight supply of landfill sites and the environmental impact of the waste.

This technology reconstitutes waste sand by high-temperature calcination and recycles it as a porous structural material with excellent specific surface area and water retention properties. The material has a wide range of applications, including water purification material, soil improvement material, and planting foundation material, and is intended to be converted from mere waste disposal to the creation of useful materials. Unlike incineration or landfill, this process does not cause secondary pollution and is highly efficient in terms of resource recycling.

As of 1997, the plant had a monthly processing capacity of 400 tons and attracted attention as a model plant with a "zero waste sand" policy. The Ministry of International Trade and Industry (MITI) participated in the demonstration phase, and as a model for social implementation of recycling technology through industry-government collaboration, it was expected to spread to other regions and materials.

This case represents an ideological turning point in redefining the distinction between raw materials, by-products, and waste by reviewing the end of the material flow in the manufacturing industry. The integration of technology and systems that redefine the function of materials even after their death was an important step toward the future of Japan's environmental and industrial policy.