Salvaging treasures from waste

Resources are becoming more scarce. Metal prices are rising steadily. Reason enough to find new sources of raw materials. A team of scientists and engineers from industry and various research institutions is now beginning to hunt for "treasure" in bottom ashes from waste incineration.

These ashes contain about eight percent iron and up to two percent of more valuable non-ferrous metals, especially copper and aluminium. Currently, using magnets and eddy current technology, these metals are only partially recovered during processing of bottom ash into gravel substitutes.

The goal of the team is to double the metal yield. This is to be achieved by using enhanced impact crushing technology. The technique by which smaller metal particles also become accessible, was developed by Tartech eco industries AG from Berlin. Metals contained in the ash in the form of chemical compounds can also be recovered using procedures normally found in the mining industry for processing ores.

"The concentrations of copper and lead in bottom ash are higher than in some ores which are mined elsewhere in the world, often under questionable conditions. This waste is a domestic source of raw materials", says Franz Simon, waste expert at the Federal Institute for Materials Research and Testing.

The ATR project "Digestion, separation and recovery of resource-related metals from thermal process residues using innovative methods" has nine project partners, a term of three years and is coordinated by BAM. It has a total budget of 3.5 million EUR and is funded by the Federal Ministry for Education and Research (BMBF) with 2.2 million EUR within the "r3 - Innovative Technologies for Resource Efficiency" research programme.

Source: Federal Institute for Materials Research and Testing (BAM)