The U.S. Department of Energy (DoE) recently announced $39 million in funding for 16 projects to develop market-ready technologies that will increase domestic supplies of critical elements required for the clean energy transition. The projects, said DoE, aim to develop commercially scalable technologies that will enable greater domestic supplies of copper, nickel, lithium, cobalt, rare earth elements, and other critical elements.

Selected projects will be funded and managed through DoE’s Advanced Research Projects Agency-Energy (ARPA‑E) Mining Innovations for Negative Emissions Resource Recovery (MINER) program. The program funds technology research that increases mineral yield while decreasing required energy, and subsequent emissions, to mine and extract energy-relevant minerals. Specifically, the program investigates potential CO2 reactive ores to unlock net-zero or net-negative emission technologies.

Among the selected projects are several that focus on recovering value from tailings or waste. These include the following, with project descriptions provided by DoE:

• $2.95 million for Columbia University to develop new processes with lower environmental impact to obtain energy-relevant metals from mines that are olivine-rich at lower cost than state-of-the-art processes. Olivine is a CO2-reactive waste product that can be returned as tailings after capture carbon from the air. Columbia will improve the yield of nickel and copper from its partner mining operation, simultaneously increasing the amount of carbon captured per kilogram of metal. Innovations are based on a recent discovery of rapid mineral-leach kinetics with reagents that can be regenerated by an electrochemical process inspired by flow-battery technologies. The chemistry and process may enable the replacement of smelters for processing sulfide minerals. The technology has been proved for copper-sulphide minerals, which will improve the yields of Cu and ultimately Ni.

• $2 million for a Travertine Technologies program described as ex situ tailings leaching and lateritization with electrolytic acid recycling for critical metal concentration and mineral carbon sequestration – a process that integrates strong acid treatment of mining waste or tailings with electrolytic acid recycling. Leached critical elements are recovered as oxides, while carbonate minerals are precipitated using CO2 from the air. Travertine will develop the design basis for a 1 ton/day CO2 removal system to demonstrate the technical feasibility and commercial viability of this concept, taking it from proof-of-concept to field-ready.

• $1 million for Pacific Northwest National Laboratory’s investigation into re-mining red mud waste for CO2 capture and storage and critical element recovery (RMCCS-CER), which involves in-situ and ex-situ techniques to determine the solubility and thermodynamic properties of various sodium rare earth element (REE) carbonates, REE (hydroxy) carbonates, REE phosphate, and REE (oxy) hydroxides in various solutions and pressures and temperature conditions, with or without the presence of CO2. The team will use the results to construct a data-base for optimizing conditions that efficiently recover energy-relevant minerals in red mud waste.

• $2.04 million for Missouri University of Science and Technology’s program aimed at reducing comminution energy and improving energy-relevant mineral yield using carbon-negative oxalatization reactions, which aims to establish a novel pathway to extract energy-relevant minerals, such as nickel and cobalt, from CO2 reactive and low-grade silicate feedstock (e.g., lean ore, mine waste, and geologic formations) via a novel pretreatment using a CO2 or biomass-derived organic acid that can dissolve silicates efficiently and liberate metals. The progressive dissolution will be followed by the precipitation of oxalate products, turning the bulky silicate rocks into micron-sized crystal particles and amorphous silica. The micron-sized crystal particles reduce the need for energy-intensive comminution during mineral beneficiation, and the separated crystalline oxalates will be further processed using hydrometallurgical approaches to separate the desired energy-relevant minerals.

• $2.5 million for a Michigan Technological University project for energy reduction and improved critical mineral recovery from low-grade disseminated sulphide deposits and mine tailings, aimed at achieving a decrease of 10 wt% CO2 equivalent per ton of ore processed compared with the current methods for primary nickel extraction by storing CO2 in CO2-reactive minerals and recovering 80% of energy-relevant minerals from both sulphide and nickel-bearing silicate minerals in mine tailings. MTU will demonstrate (1) 200 kg of CO2 storage per ton of magnesium-rich and iron-rich silicate minerals in mine tailings within 4 hours after processing with 10% energy reduction compared with state-of-the-art; and (2) recovery of 50%-80% yield of nickel from domestic low-grade disseminated sulfide ores. An estimated 2.2 million tons of CO2 per year will be sequestered in mine tailings that are permanently and safely stored with a decrease of 100 kg of CO2 equivalent per ton of ore processed.