Update on the progress

A1. Feasibility study. Selection and characterization of specific wastes from REYDESA to be bioleached (origin, shape, suitable pretreatments, etc.) and study on possibilities to use available waste streams from nearby other industries for nutrients solution.
1. Preparation of inoculum for the bioleaching cultivation experiments.
Figure 1a
Before placing into the bioleaching experiment, the Inoculum CELMS No EEUT ARGCON5 is pre-cultivated in test tubes in a thermostated shaker at t=37°C.
Photo by S. Sipp Kulli.
After pre-cultivation the remarkable haze in test tubes with inoculum demonstrates the growth of bacteria.
Photo by S. Sipp Kulli.
Figure 1c
The BiotaTec coworkers of Kärt Ukkivi, MSc and Anne Menert, PhD are examining the quality of inoculum CELMS No EEUT ARGCON5. The Inoculum has grown up and is ready to be added to the non-metallic fraction of PCBs of WEEE.
Photo by S. Sipp Kulli.
2. Study of microbial biodegradation potential of indigenous species of ARGCON5 with bioleaching cultivation experiments in microcosms with OxiTop AN measuring system.
Figure 2a
The flasks of OxiTop AN measuring system with PCBs of WEEE in growth medium inoculated with ARGCON5 and with growth medium and inoculum, 100th day of experiment. The flask with PCBs of WEEE is remarkably darker.
Photo by A. Menert.
Figure 2b
The flasks of OxiTop AN measuring system with PCBs of WEEE in growth medium inoculated with ARGCON5 adapted to e-waste, with growth medium and inoculum only and with PCBs of WEEE in growth medium (without inoculum), 10th day of experiment. In the flask with all components added, gas bubbles indicate degradation of organic matter.
Photo by A. Menert.
The flasks of OxiTop AN measuring system with PCBs of WEEE in distilled water. The liquid phase is crystal clear without haze typical to bacterial growth.
Photo by A. Menert.
Figure 2d
The flasks of OxiTop AN measuring system are maintained in thermostated shaker at t=37°C during the whole experiment.
Photo by S. Sipp Kulli.
Figure 2e
Pressure increase recorded on data logger indicates the start of methane production.
Photo by S. Sipp Kulli.
3. Principal scheme for microbiological treatment of PCBs of WEEE.
Figure 3a
Crushed Printed Circuit Boards (PCBs) of WEEE in the Reydesa facility in Legutio, Spain, 17 July 2018.
Photo by A. Menert.
Figure 3b
Milled and densitometrically separated PCBs of WEEE from Reydesa, magnification 10X.
Photo by S. Kuuse.
Figure 3c
Bioleached e-waste (Estonian origin), magnification 10X.
Photo by S. Kuuse.


B1. Optimisation of bioleaching process. Different bioleaching tests will be carried out with WTW OxiTop systems and Erlenmeyer flasks with conditions and waste stream selected in task 1 in order to perform bench scale tests at 20 L.

B2. Pilot building and operation. Pilot building of the bioreactor will be carried out in REYDESA´s facilities in Spain and 10-20 semi-industrial batches will be developed.




The PCB waste is categorized into three groups (A, B, C) based on precious metals concentrations. This categorization is not a strictly defined selection system, but it is commonly used in WEEE management systems. Those categories identify each PCB batch:

Category 1/A/High printed circuit boards contain more than 400 ppm of gold (mainly electronic printed circuit boards).

Category 2/B/Medium contains PCBs with 100-400 ppm of gold.

Category 3/C/Low covers PCBs with less than 100 ppm of gold, mostly segregated from devices like CRT displays, power supply, radios, and TV.

Therefore, it was stated that there is no common international standard for grading PCBs, rather grades are agreed in advance with the end markets and are based on:

- Physical composition of the PCBs (presence of visible gold, aluminium parts etc.).

- The prevailing market value of the metals contained.

Standard types of PCBs are often used in the manufacture of electrical items so the grades of PCBs recovered can frequently be determined based on the WEEE category from which they are recovered. But some Companies do not refer to grades at all, especially if they handle only one category of WEEE.

The following table is an overview of three primary grades of PCBs segregated by treatment facilities:




EEE Product

Grade 1/A/High

Generally, these will contain processors, semiconductors, gold pins and connectors containing precious metals which can be recovered

IT base units, hard drives & laptops, Display screen equipment, including flexible PCBs

Grade 2/B/Medium

Whilst not as valuable as Grade 1 type boards, these will still contain some semiconductors, gold pins and connectors containing precious metals which can be recovered

IT equipment, set top boxes, Display screen equipment, Small mixed WEEE

Grade 3/C/Low

These will generally only contain little, if any precious metals and are mostly valuable for their copper content

Small mixed WEEE, CRT TVs, Large domestic appliances


BIOTAWEE project was focused in the treatment of PCBs grade 1, mainly from computers due to the higher level in precious metals.



Processing PCBs includes several steps of crushing and separation until a non-metallic fraction to test by bioleaching technology is obtained. Next figure shows the three steps of the global
process where the material has to pass until the final fraction is achieved:

Figure 1. Material through each step of the process.


1st STEP: The process begins with the crushing of the material in a shredder.

2nd STEP: The material is introduced in the mill during continuous cycles.

3rd STEP: The aim of this step is to separate the metallic fraction from the non-metallic one. 


MATERIAL FOR BIOLEACHING: The non-metallic fraction obtained in the previous step is the one selected to be used in the bioleaching process that will be carried out by BIOTAWEE consortium. 

B3. Post-processing. Leach-solvent extraction-electrowinning (SX/EW) and other extraction technologies will be applied to obtain pure raw materials, or metallic concentrates of known composition, from pregnant solutions and the cost effectiveness of the solution will be assessed in order to develop the replicability and transferability plan as well as the business plan.