Cluster 5: Biorecovery of metals, rare earth elements from metal-contaminated wastes and by-products
Lead:
University of Edinburgh – Prof Louise Horsfall
Partners:
Cranfield: Gabriela Dotro – Prof Bruce Jefferson, Prof Frederic Coulon
Heriot Watt University – Prof Tony Gutierrez
Bangor University- Prof Alexander Yakunin
Challenges:
Metal-contaminated wastes and by-products (e.g., basic oxygen furnace, goethite residues, industrial sludges, mining tailings) can have complex compositions, including various metals, minerals, and organic compounds. Achieving selective bioleaching processes that solubilise target metals while dealing with the complexity of the substrate, low nutrient availability and efficient oxygen transfer is a challenge, especially in large-scale operations. Enhancing the selectivity of microbial activity to target specific metals and rare earth elements requires careful optimisation. Scaling up bioleaching is also a challenge.
Potential solutions:
Enhanced selectivity can be achieved using sequential microbial processes that involve bacteria capable of bioleaching (e.g., Acidithiobacillus ferrooxidans) and metal reduction (e.g., Desulfovibrio alaskensis, Shewanella oneidensis). Furthermore, the separation of these processes enables immediate use of genetically engineered microbes in a contained environment in line with current regulations. The portfolio of microbial strains engineered for improved metal recoveries by nanoparticle synthesis from Horsfall’s laboratory will be optimised for use alongside bioleaching methods for the recovery of critical metals (e.g., Platinum Group Metals, Rare Earth Elements and Cobalt).
Integrating of nanoparticle biosynthesis with microbial bioleaching and bio-derived lixiviants by leveraging a recent Engineering Biology breakthrough award (Edinburgh), focusing on the utilisation of selected deep eutectic solvents as carbon sources for engineered microbial growth. These solvents will not only provide a sustainable carbon source but also enable semi-selective metal leaching, enhancing the overall efficiency of metal recovery from metal-contaminated wastes and by-products.
Establishing a comprehensive and sustainable approach to bioleaching metals and rare earth elements from metal-contaminated wastes and by- products. This involves further refining the integration of nanoparticle biosynthesis, microbial bioleaching, and bio-derived lixiviants. By optimising these processes and technologies, the cluster seeks to contribute to the development of environmentally friendly and economically viable solutions for metal recovery and waste management.
Lead:
Edinburgh: Prof Louise Horsfall
Partners:
Cranfield – Gabriela Dotro, Prof Frederic Coulon, Vinod Kumar
University of Southampton – Yongqiang Liu, Yue Zhang
Newcastle University – Prof Thomas Curtis, Prof Natalio Krasnogor
Challenges:
Low metal concentrations, complex matrix composition, and the presence of interfering substances that hinder efficient metal extraction. For biological recovery of phosphorus, the key issue lies in achieving high phosphorus removal efficiency and avoiding excessive chemical addition. Coagulants used in wastewater treatment to enhance the removal of suspended solids, organic matter, and metals from the sludge impact the performance of biological systems by affecting microbial activity and metal bioavailability; iron-reducing bacteria such as Geobacter metallireducens has slow growth rates, low biomass yield, and sensitivity to environmental conditions, which affect its practical application in metal recovery.
Potential solutions:
Developing and validating a prototype biological system using naturally abundant and culturable iron reducing bacteria to extract iron in a recoverable form.
Domesticating the target strain(s) using refactoring approaches and adaptive laboratory evolution approaches to produce a microbial culture that can withstand changes in feedstock composition whilst delivering high purity extracted iron for coagulant generation and optimising the extraction process, generating soluble iron hydroxides or encapsulating iron precipitates within the cell structures for efficient production of coagulants.
Implementing the biological system in a pilot scale water treatment plant, consistently achieving iron recovery at commercially viable levels.
Lead:
The University of Southampton: Yue Zhang
Partners:
The University of Edinburgh: Prof Louise Horsfall
Cranfield University: Vinod Kumar
Challenges:
Adapting microbial strains to efficiently utilise diverse waste substrates and maintaining consistent performance across different batches; Designing and optimising metabolic pathways in microbial hosts to convert waste substrates into desired value-added products requires a deep understanding of metabolic engineering principles. Balancing precursor availability, pathway flux, and product toxicity is crucial for achieving high yields and productivity and is strongly dependent on effective product recovery. Microbial strains used in fermentation processes need to be robust and stable to withstand harsh conditions and maintain high productivity over extended periods.
Potential solutions:
Engineering mixed microbial cultures using SynBio tools to enhance substrate utilisation, product yield, and tolerance to inhibitory compounds present in waste streams.
Optimising metabolic pathways and flux distribution to maximise the production of value-added products while minimising by-product formation; Developing effective novel in-situ product recovery techniques to improve fermentation efficiency, productivity, and scalability. Developing advanced process monitoring and control strategies to maintain consistent fermentation performance and improve process efficiency.
Establishing standardised protocols and guidelines for microbial fermentation of waste streams, including waste characterisation, strain selection, process optimisation. Implementing advanced bioreactor designs and operational strategies to minimise downstream processing requirements and enhance overall process economics and life cycle sustainability.
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