The CRM-geothermal project has recently reached a milestone in its quest to harness microbial capabilities for metal recovery from geothermal fluids. Researchers from the Laboratory of Microbiology at the University of Neuchâtel and Dr. Brill + Partner GmbH performed innovative screening experiments to identify microbes capable of extracting valuable metals like lithium (Li) and mitigating problematic elements such as lead (Pb) which can cause scaling in some geothermal power plants.

Main findings

Biomineralisation of lithium

Li biomineralization was explored by combining two microbial metabolisms: fungal oxalic acid production and bacterial degradation of oxalic acid/oxalate (Palmieri et al. 2019).

The researchers were able to achieve Lithium biomineralisation as Lithium-phosphates (Fig. 1D). The latter also acted as surfaces for the co-precipitation of NaCl, indicating that NaCl concentrations might be an issue to selectively obtain Lithium-only biominerals.

Figure 1: (A) oxalic acid concentrations produced by two fungal strains, Aspergillus niger and Meyerozyma sp., when grown in: water or a CLL raw fluid, supplemented with either Glycerol or Saccharose as a carbon source, both at either a high (30 g/L) or a low concentration (10 g/L). (B) Evolution of the soluble concentrations of Calcium (Ca), Potassium (K), Lithium (Li), and Sodium (Na) within the CRM fluid with the addition of oxalic acid. Measured with an ICP-OES. n=3. Al, Fe, and P were not detected. (C) Evolution of the pH over 9 days induced by the metabolic activity of Pandoraea sp. when grown in a medium with Li-oxalate as a C-source. (D) Scanning Electron Microscopy (SEM) image showing precipitates of Li-phosphate covered with NaCl retrieved from the Li-oxalate medium inoculated with Pandorea sp.

Biosorption studies

Lithium biosorption/accumulation was assessed using the procedure described in Tsuruta (2005), where the aim is to trigger Lithium complexation on the cell wall of Gram-positive bacteria (chelation via teichoic acids).

Lithium was effectively transferred from the fluid to the cells. In addition to this, the researchers identified that the ratio of cells:liquid also influenced the complexation efficacy. As a result, the removal of Lithium from fluid is technically feasible with the help of microorganisms.

Next steps

The research team plans to optimise the conditions for microbial oxalic acid production, aim to precipitate lithium-carbonate instead of lithium-phosphate, and address the impact of NaCl on biosorption processes. These efforts are geared towards enhancing the efficiency and economic viability of metal recovery from geothermal fluids, offering a sustainable pathway to resource extraction and environmental management in geothermal energy systems.

Lead researchers: 

Saskia Bindschedler

Saskia Bindschedler

Laboratory of Microbiology University of Neuchâtel

Florian H. H. Brill

Florian H. H. Brill

Dr. Brill + Partner GmbH