Recycled aggregates are produced from incinerator bottom ash (IBA). When household wastes or wastes of similar nature are incinerated at high temperatures, the organic content is removed and inorganic residues with constituents of similar strengths as natural minerals remain. The residues are then crushed and screened to remove impurities to produce recycled aggregates, which have been used extensively in Japan, Europe and the United States in construction projects, replacing natural aggregates. Currently approximately 800,000 metric tons of recycled aggregates are produced yearly from domestic incinerators’ bottom ash. The overall recycling rate has reached 93%. 

The EPA stated that to ensure that local governments strictly control the quality of recycled aggregates and prioritize their use in public construction projects, the source, use and destination of every batch of recycled aggregates shall be registered online with quality test reports attached for public viewing. In addition, the EPA has subsidized or assisted local governments in setting up six public recycled aggregates plants in recent years with the prospect to gradually optimize processing facilities and raw material quality. It is expected that the aggregates produced by all public processors will amount to 57% of the total production in Taiwan in 2022, which will be more than the amount produced by all private recycling organizations. They are to be used by each county or city in public construction projects within their administrative districts. The EPA also requires local governments to establish cross-departmental implementation teams that are presided by top county or city officials to coordinate the departments in inventorying the needs of public construction projects within their districts and prioritizing the use of recycled aggregates.     

According to the EPA, the processing of IBA recycled aggregates involves multiple quality checking procedures and must comply with strict control standards and regulations to ensure quality. When recycled aggregates are to be used in a construction project, multiple conditions such as the applicability and rationality are reviewed in the project’s design and planning stage before handing them over to the project operator. They can be further processed based on the needs of the project and made into materials of diverse uses. There were concerns raised by the public and environmental groups about a case where recycled aggregates were used on agricultural and pastoral land last year. In reality, those aggregates were used as the base layer of mushroom huts, not affecting any part of planting. Since these aggregates were construction materials that did not affect the quality of agricultural production, the use was compliant with the regulations.   

There were also doubts raised by environmental groups about the differences between the domestic quality standards and those of advanced countries. The EPA stated that with reference to the latest standards of Japan and European countries, the government has reviewed the quality standards and the leaching control methods for IBA recycled aggregates and has placed restrictions on their usage locations and purposes. The latest version of the Management Regulations on the Recycling of Incinerator Bottom Ash was promulgated on 1 January 2021 using the Recycled Aggregate Leaching Procedure (NIEA R222) as the leaching testing method. In addition, with reference to domestic groundwater pollution control standards and regulations, a usage location classification management system was set up making the management regulations the most stringent to date.   

Excerpt from Major Environmental Policies, September 2021