Collection, treatment and recycling of WEEE is essential to improve the environmental management, contribute to a circular economy and enhance resource efficiency. In this way, the recycling of WEEE offers substantial opportunities in terms of making secondary raw materials available on the market. Hence, LIFE BIOTAWEE project wanted to demonstrate the possible recovery of valuable metals (mainly Cu, Ag and Au) from the NMF of PCB of WEEE by the application of bioleaching technology. Bioleaching uses direct metabolism or by-products of microbial processes to solubilize a metal sulfidic ore or waste into an aqueous solution.

The project focus was on the necessity of increasing recovery degree of PCB of WEEE, contributing also to reduce European dependence of some high-valued metals with very low EU supply (mainly Au but also Cu and Ag). Moreover, promoting the biotechnology in the recycling processes of PCBs as the future feasible methods which can achieve the recovery objectives, reducing processing cost, CO2 eq. and waste generation respect to a hydrometallurgical process. The achievements of the project have been:

  • Reduce the volume of unused fractions of PCB. From 1 Tn of PCBs, almost 40 % may be integrated in the NMF of PCB (impurities after the mechanical treatment and the suction dust of the process). 
  • Reduction in hazardous effluents waste generation of 3.88 Tn/Tn PCB respect a complete hydrometallurgical process. Bioleaching is more environmentally friendly comparing to the use of solvents needed in hydrometallurgy.
  • Reduce 45 % CO2 eq compared with the hydrometallurgical process. 
  • Materials were recovered per Tn of PCB applying 2 aerobic bioleaching processes: 182 Kg Cu, 0.24 Kg Ag and 0.021 Kg Au. This recovery may be improved due to the optimisation need for the recovery of precious metals. The recovery for Au is stated in 45% and for the Ag 1-4%. So, there is room for improvement.
  • Reduction of 38% in the processing cost respect the hydrometallurgical process. 

Initially, LIFE BIOTAWEE wanted to demonstrate the possible recovery of valuable metals by the application of an innovative more efficient 2-step bioleaching technology, combining aerobic and anaerobic treatment. During project progress, LIFE BIOTAWEE process changed the proposed bioleaching technology for 2 consecutive aerobic steps (the first one for base metals and the second one for precious metals) due to the weak performance of the anaerobic step with the NMF of PCBs. Meanwhile, the project has demonstrated the viability of this 2-step bioleaching technology (anaerobic + aerobic) but applicated to a different waste (suction dust obtained from the mechanical treatment).

As a fundamental aspect of the project, the consortium underpinned the replicability options of the technology with the satisfactory results achieved with the treatment of suction dust from the mechanical processes. The replicability was approved by means of the evaluation of the technological and economic possibilities in widening the usage of the innovative technology on other complex wastes in order to reduce the processing cost.

Not only takes into account technical aspects of the proposed solution, but environmental and socio-economical are key aspects too. In that sense, the determining deliverables were: 

  • Technical aspects, B.1.2 Bench scale and B.2.2 Semi-industrial scale technical reports
  • Feasibility/future, B.3.2 Cost-effectiveness and B.3.3 Replicability and transferability.
  • Environment aspects, C.1.3 LCA and D.1.6 Analysis of synergies with EU policies.
  • Dissemination, D.1.4 Report on technical publications and D.1.7 Layman report.

The project started in July 2018 and the expected end date was December 2020. However, in October 2020, an amendment for the extension of the project was requested and final date for finishing the project was stated in July 2022. The amendment for the extension was necessary due to the delay in action B1. If no extension was agreed, the project would not have been done in a semi-industrial scale. The delay in action B1, has marked the whole project holding back technical results and important decision as the building of the semi-industrial pilot plant.

Covid situation was partially responsible for action B1 delay, and also had strong implications in dissemination actions (conferences, seminars) and in holding face-to-face meetings and in the planned trips.

LIFE BIOTAWEE project helps to achieve the recycling objectives set in the Directive 2012/19/EU, and is in line with the circular economy initiatives, at European and local level. Therefore, this project aims to contribute to reducing supply risk and mitigating significant price fluctuations. It is a priority to reduce external dependency on the supply of metals by innovating in recycling processes and optimizing the management of metal scrap. The project also supports the Directive 2000/76/EC related to Waste incineration, because avoids incineration of 300 t/year of PCBs, reduction hazardous effluents and waste generation. 

Main barriers detected are relative to the European List of Waste, that is not specific enough to detect the CRM in the waste streams, or even the presence of PCBs, as there are classified in a generic classification with “components removed from WEEE”. But REYDESA is participating in a H2020 project to tackle this problem by increasing the traceability of the CRM since manufacturing, improving not only its recovery, as well the overall environmental performance of the equipment as a product. The recently approved POPs regulation could affect the recyclability of plastics recovered from WEEE, as bromine flame retardants are contained in this fraction, and also could entail more cost in the process of WEEE. 

The future of LIFE BIOTAWEE process involves several possibilities. PCB management service within the recycling industry is not common. In cases where the recycling industry treats PCB fractions, the process usually begins with a mechanical treatment to recover the fractions with the highest economic value, but it generates a non-metallic fraction that is difficult to manage, such as the one used in the LIFE BIOTAWEE pilot. The LIFE BIOTAWEE service has been defined to recover metal content in difficult-to-treat waste after certain conditions (>17% Cu or >50ppm Au). 

Apart from the proposed service, the process will be implemented in the recovery of Li by Reydesa through a new project as a part of replicability actions. BIOTATEC will continue developing further strategies for valorisation of e-waste with grant from Estonian Government and EU as well as raising additional capital. The aim is to further develop and improve the bioextraction technology of various metals from different types of e-waste. Additionally, it will be explored the possible ways to increase the overall value of e-waste leaching process through biosynthesis of metallic nanoparticles.