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Belgian recycler enhances recovery using bacteria

Belgium РFollowing three years of research and close collaboration between metallurgists and microbiologists from the GeMMe laboratory at the University of Li̬ge, Belgian recycling specialist Comet Traitements and Biolix have developed a new process that enables optimal recovery of metals by adding bacteria into the equation.

The process is currently in its pilot stage and is tailored specifically to shredder waste. It revolves around the bacteria thiobacillus ferrooxidans and leptospirillum ferrooxidans which ensure a bioreactor-driven ‘€˜selective recovery’€™ from various waste products of copper, zinc, tin and lead as well as a fraction rich in precious metals. These include ferrous and non-ferrous metals, plastics, recoverable mineral materials (such as sand) and recoverable iron oxides (such as substitute ores).

These bacteria allow the energy and reagents required for efficient separation of the metals to be minimised. For every tonne of copper treated using the novel process, 72 kg can be produced, for instance – with precious metals concentrate boasting a 98% recovery rate, resulting in a total of 87 kg. The lower recovery rates are represented by tin-lead and zinc concentrate, both of which average 91%, producing respectively approximately 533 kg and 35 kg per tonne. This far exceeds the European average, which has not yet reached 84%.

It has been a long-time challenge to acquire a satisfactory output from the finest shredder waste down to just tens of micrometres. This is a missed opportunity, Comet concludes, as these particulates make up approximately 50% (or 5 million tonnes) of all shredder waste sent to landfill each year across the EU.

The recycler notes: ‘€˜The metal content of the fine polymetallic concentrates gives them an economic potential that is by no means insignificant but is often underestimated. This advanced process now finally allows us to exploit most of their intrinsic value.’€™ The potential of this ‘€˜low-cost solution to recycling’€™ has already earned the project the 2012 Prix Zénobe for Research and Innovation.

Based on the performance of the pilot unit to date, Comet is optimistic about its application for EU funding, which would help towards the construction of a first industrial-scale facility by early 2014. The annual capacity of such a unit is predicted to be around 4000 tonnes.

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