Increased resource efficiency through selective fragmentation of bottom ash

Research Project, 2022 – 2023

Sweden´s municipalities annually process approximately 5 million tons of waste, of which approximately half goes to energy recovery, which provides electricity and heat but also a residual product, bottom ash. Today, metals are recovered from the ashes, while large parts of minerals and other residual products are placed in landfills. The project idea is to test a new and more efficient method to release minerals and metals through selective fragmentation, which could increase metal recovery from 8 to 14% and create a new mineral fraction that could be used in concrete production.

The project is expected to generate acceptance for the method and results of selective fragmentation by sending samples of bottom ash from Swedish bottom ash to Selfrag´s facility in Switzerland for processing and analysis. In addition, the project is also expected to generate a business model where the mineral component becomes another part that can be recycled. A successful project can lead to significantly reduced carbon dioxide emissions and that the metals and minerals, already in the cycle are used to the highest degree.

After initial planning, material samples are taken from Renova´s and Sysav´s incinerators. These are sent to Selfrag in Switzerland for processing by selective fragmentation. The clean fractions that are produced are used for tests to set them against guideline values that apply in Sweden regarding contaminated land, levels for free use and acceptance criteria for inert landfill. Analyzes of the results are done in collaboration with Chalmers to adapt the technology and develop a business model that, in addition to metal recycling, also includes circulation of the mineral fraction.