In February this year, FIREFLY partners were publishing a scientific paper presenting a critical evaluation between best available physicochemical and electrochemical approaches for metal recovery of elements which form part of spent catalysts or other sources such as wastewater, mining waste and spent batteries.
This study laid the groundwork for the next step, researchers at VITO taking the comparison further, by “pitting” FIREFLY’s electrified metal recovery technologies directly against these state-of-the-art [SoA] processes.
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This recent comparative study included a set of technical, economic and environmental key performance indicators (KPIs), looking, among other outcomes, at the metal recovery efficiency, selectivity, energy consumption and chemical usage, but also waste production, scalability and compatibility with renewable energy resources [RES].
The benchmarking exercise shows that various FIREFLY processes – ETOS, GDEx, ESLX/ESX, ETMS, achieve high recovery yields and selectivity, all while reducing the environmental impact. Additionally, they demonstrate compatibility with renewable energy integration, making them even more appealing from an environmental perspective. While other FIREFLY processes, such as MCP, ELX, or ERMS, feature adaptability to complex feedstocks, the ability to reuse input chemicals, and generate less waste.
The study avoids biases and recognises there is room for improvement. Selectivity, feedstock flexibility, and by-product valorisation remain areas for further development. And, as always, economic competitiveness at industrial scale will be the ultimate test.
An incursion into existing processes for catalyst recycling
In industry, catalysts containing precious metals are often incinerated to recover metal ash, which is then treated with corrosive chemicals for leaching. This incineration process is highly energy-inefficient and releases hazardous air pollutants; the subsequent recovery of metal parts often relies on toxic chemicals.
Pyrometallurgy, while efficient for high-grade materials, remains unsuitable for low-grade residues due to its high energy consumption and pollutant emissions. Hydrometallurgy, on the other hand, can process lower-grade materials at lower temperatures, but requires large volumes of hazardous acids and solvents. Both methods depend on fossil-based energy and reagents, produce significant CO2 emissions, and do not fully utilise the circular potential of spent catalysts.
Comparative performance matrix of the state-of-the-art technologies for metal recovery across various analysed KPIs | © VITO
Electrification presents a promising approach in reducing the environmental impact of spent catalyst recycling, lowering processing costs and mitigating supply risks. Building on this potential, the FIREFLY project aims to electrify a significant portion of the chemical value chain by developing a sustainable power-to-chemicals method centred on (electro)chemical catalyst recycling. By recovering critical metals from waste, spent and off-specification heterogeneous and homogeneous catalysts, and reusing them to synthesise new (electro)catalysts, FIREFLY seeks to reduce dependence on primary resources and support a circular, low-carbon economy. The core of FIREFLY’s approach is a flexible, predictive, renewable-energy-powered electrochemical toolbox that integrates complementary electrified systems.
Snapshot of FIREFLY technologies’ benchmarking results
The reported values are based on qualitative or quantitative data from the technology providers and reflect the performance of each process as implemented or tested for different waste streams within the FIREFLY project. It is important to clarify that the information presented here is not meant for direct comparison between FIREFLY technologies. Instead, it offers a consolidated snapshot of each technology’s self-reported performance, which fed the benchmark exercise against the SoA technologies.
- MCP, with a solution-phase output that involves high metal dissolution, highlights its role in preparing or conditioning material for subsequent recovery steps.
- ESLX/ESX achieves high selectivity under mild operating conditions, emphasising its potential for high-purity separations in well-defined feed streams.
- ETMS demonstrates high efficiencies in challenging matrices, supported by its ability to operate at elevated temperatures with precise control of process parameters.
- ETOS is known for functioning in non-aqueous media, producing high-quality products and maintaining strong selectivity, which can be advantageous when targeting sensitive or high-value metals.
- GDEx is characterised by low reagent consumption, selective recovery, and significant product valorisation potential, which is still being optimised for specific feedstocks.
- ELX exhibits broad applicability to diverse metal portfolios, flexibility with complex feed matrices, and strong prospects for modular and automated deployment, making it suitable for both centralised and decentralised systems.
- ERMS stands out for its ability to operate effectively in complex matrices and at high temperatures, using two complementary methods: selective chlorination and consumable anodes.
Each technology demonstrates unique strengths within the KPI framework, providing complementary capabilities for various recovery scenarios.
Normalised heat-map comparing the performance of FIREFLY (black rows) and state-of-the-art (grey rows) metal recovery technologies across 18 technical, environmental, and economic KPIs. Color intensity increases with higher normalised scores (0 = lowest, 1 = highest) | © VITO
