PROJECT DESCRIPTION
BACKGROUND
Waste electrical and electronic equipment (WEEE) is one the fastest growing waste streams in the EU (3-5% per year) and is expected to reach more than 12 million tonnes per year by 2020.
WEEE is made up of complex mixture of materials, including potentially toxic substances such as lead, mercury, cadmium and beryllium. These pose considerable environmental and health risks if not treated properly. Rare, precious and expensive metals are also used to make electronic goods, for example, 10% of the world's gold. For the EU, which accounts for less than 1% of global gold output, this means depending on imports.
Collection, treatment and recycling of WEEE is essential to improve environmental management, enhance resource efficiency by making more secondary raw materials available, and contribute to the development of a circular economy.
OBJECTIVES
LIFE BIOTAWEE piloted a new technology for recovering gold, silver, copper, and platinum from the non-metallic fraction of printed circuit boards (PCBs) found in electrical and electronic waste. These valuable metals are currently incinerated because they cannot be recovered from the circuit boards.
The two-stage 'bioleaching' process initially was planned to combine aerobic and anaerobic treatments and produce methane, which could be used as a source of power. The new solution would reduce energy consumption and processing costs in comparison with other treatment processes (pyrometallurgy, hydrometallurgy, and one-step bioleaching). It also would made use of available waste from other industries (food and animal feed) as an additional nutrient booster for microorganisms.
The project was to evaluate whether two-stage bioleaching could be used to cost-effectively process other waste streams with a high plastic content (such as batteries and end-of-life vehicles). Results were to be communicated to relevant stakeholders across Europe.
LIFE BIOTAWEE aim was to contribute to the implementation of the EU Regulation on copper scrap end-of-waste, The Waste Incineration Directive and the Integrated Pollution Prevention and Control Directive.
RESULTS
The project had to change the proposed bioleaching technology combining aerobic and anaerobic treatment with two consecutive aerobic steps (the first one for base metals and the second one for precious metals) due to the difficulties experienced with the anaerobic step.
The beneficiaries were finally able to recover copper and gold, whereas silver recovery was insignificant and therefore, not profitable. In the same way, it was proved that the two bioleaching stages (anaerobic and aerobic) were not interesting either, having finally remained with the aerobic step only. The main reason is that the anaerobic step was intended as a pre-treatment to transform the organic matter and obtain methane. But the project proved that this pretreatment was not working well for PCBs, because no methane flow was obtained.
The aerobic process performed in the 50L pilot plant showed a recovery of 86 - 95% Cu and 1-4% Ag. Other metals contained in the waste in very small quantity have also been extracted with a recovery, around 76-88.5 % Al, 98% Zn, 53- 55% Ni.
Reydesa is currently engaged in a research project aimed at extracting lithium from End-of-Life Vehicle (ELV) batteries, based on the results and equipment of the LIFE BIOTAWEE project. The project is still ongoing and has not yet reached completion. If the results are successful, the process will be implemented at commercial scale.
