In recent years, various business capabilities for resource recycling have been developed and the recycling business market has rapidly opened up. However, there are not a few challenges such as difficulties in technical evaluation and coordination with related organizations, as well as low utilization rates of existing recycled resources. There still remain many wastes that are difficult to process, such as chlorine waste containers, FRP and other thermoplastics, and petroleum sludge. In other words, business opportunities lie there.

In recent years, various business capabilities for resource recycling have been developed and the recycling business market has rapidly opened up. However, there are not a few challenges such as difficulties in technical evaluation and coordination with related organizations, as well as low utilization rates of existing recycled resources. There still remain many wastes that are difficult to process, such as chlorine waste containers, FRP and other thermoplastics, and petroleum sludge. In other words, business opportunities lie there.
Casting Sand Waste. Casting sand is sand (mainly silica sand) used as molds for machine tools, automobiles, and other parts cast in factories. It is classified into raw molds made by adding clay to silica sand, molds made by adding furan resin, shot sand from shot plasters during shot finishing, etc. After use, it is broken down and disposed of. The Japan Foundry Association estimates that approximately 1 million tons are discharged annually.
However, while some large factories outsource the recycling of shot-plaster sand to contractors and reuse it as casting sand after use, small and medium-sized factories often generate only 2 to 3 tons per month, and most of it is landfilled at final disposal sites. In addition, even if the sand is recycled, a certain percentage of the recycled sand is not reusable due to its finer grain size, and this is also disposed of in landfills.
Methods to Recycle Waste Foundry Sand. Currently, there are several methods for reclamation, including the "dry method" for mechanical separation, the "wet method" for removal of fine clay by washing, and the "roasting method" for separation into sand and gas. The "dry" method has a low yield rate, while the "wet" and "roasting" methods are expensive. The cost of recycling varies from region to region, but is in the tens of thousands of yen per ton (excluding transportation costs). In some cases, the recycled ash is used as a material for bricks and blocks in the recycling process.
Coal Ash. Coal ash is generated by the combustion of coal. The electric utility industry alone generates more than 5.4 million tons annually, of which about 4 million tons are reused as a raw material for cement and gypsum. Although the recycling rate has been increasing year by year, domestic demand for cement will inevitably slow down in the future due to the revision of public works projects and other factors, making the disposal of coal ash an issue to be addressed.
Coal Ash Export Policy. In response, the Ministry of Economy, Trade and Industry (METI) has made a major shift in its export policy, deciding to encourage exports and creating guidelines. In particular, it aims to strengthen exports to countries such as South Korea, which is expected to experience a construction boom. In addition, in order to increase the amount of waste accepted into the cement manufacturing process, cement standards were revised and the allowable chloride ion level was raised. However, challenges still remain, and seminars on the reuse of coal ash are thriving. Coal ash is divided into fly ash collected by electrostatic precipitators and bottom ash that falls to the bottom of boiler furnaces. Fly ash is mainly used for cement and building materials, while bottom ash is used for soil improvement materials.
Construction Sludge. Construction sludge is a source of concern among construction-related wastes. Construction sludge includes bentonite sludge and muddy sludge with high water content, which cannot be diverted to other construction projects. Approximately 1 million tons of construction sludge is generated annually.
The bentonite sludge is treated. Bentonite sludge generated from shield construction is particularly troublesome. Bentonite is used as a stabilizing fluid to prevent collapse during excavation, but it is difficult to treat. Currently, it is either dried naturally for several days or dewatered by adding a coagulant, then transported and landfilled. Bentonite sludge itself contains no hazardous substances, so it can be used as backfill or brick material if dewatered, granulated, and solidified. However, construction sites are always moving, and the unstable supply to recycling facilities and the high cost of dewatering onsite are bottlenecks.