Energy Transition Metals: Future Demand and Low-Carbon Processing Technologies ^†

Abstract

This paper discusses the importance of the energy transition metals Ni, Co and Li in building Europe’s clean technology value chains and meeting the 2050 climate-neutrality goal. Some emerging metal extraction technologies, investigated in the framework of the Horizon Europe projects ENICON and EXCEED, in order to decrease the carbon footprint of the production of energy transition metals, are also discussed.

1. Introduction

Energy transition requires substantial quantities of several metals, including nickel (Ni), cobalt (Co), lithium (Li) and copper (Cu). Co and Ni demand is expected to be almost 20 times higher in 2040 compared to 2020. Also, Europe is 100% reliant on imports of Li required for Li-ion batteries, which are central to decarbonising the energy and mobility sectors. Australia accounts for 53% of the global supply of Li, China for 33% of Ni, the DRC for 63% of Co, and Chile for 28% of Cu [1]. Li and Co are included in the Critical Raw Materials (CRMs) list, as mentioned in the EU 2023 criticality assessment. On the other hand, Ni and Cu are designated as Strategic Raw Materials (SRMs). The overall demand for energy transition metals in the coming decades may be as high as three billion tons. A typical electric vehicle (EV) battery pack needs approximately 35 kg Ni, 14 kg Co, 8 kg Li and 20 kg Mn. On the other hand, solar panels require Si, Cu, Zn and Ag, while wind turbines require Fe, Cu and Al. The significance of the green transition is emphasised in the strategic initiatives of the EU, such as the European Green Deal [2].

The objective of this paper is to underline the importance of the energy transition metals Ni, Co and Li for Europe in order to meet the 2050 climate-neutrality goal.

2. Geology of Li, Ni and Co Deposits—Occurrences in Europe

The main Li sources are brine deposits with Li grades of ~0.1% Li₂O and hard-rock deposits with Li grades of 0.6–1.0% Li₂O. Brines are found in tectonically active basins that contain Li-rich lacustrine evaporites, mainly in the United States, Latin America and China. Hard-rock deposits comprise several styles of Li mineralisation in magmatic and/or sedimentary rocks and contain several Li-bearing minerals, such as Li-micas, Li-pyroxenes, Li-silicates, Li-phosphates, etc. [3]. Portugal is the first Li-producing EU country; however, most Li produced today is used for the ceramics and glass industries. Europe hosts 27 Li hard-rock (pegmatite and rare-metal granite) deposits, representing vast lithium resources (10–20 Mt Li₂O). However, the identified potential remains, in most cases, untouched, due to a reluctance to carry out primary mining in Europe. The number of the most significant European deposits per country is illustrated in Figure 1.

Europe’s domestic resources of Ni and Co are mainly low-grade and comprise sulphidic Ni/Co ores (incl. hydrothermal, magmatic sulphide and sediment-hosted ores, mainly present in Scandinavia), Ni/Co-containing pyrite and silicate tailings, as well as limonitic/saprolitic laterite Ni(/Co) ores, mainly present in SE Europe [4,5].

3. Emerging Metal Extraction Technologies

Nickel is produced from Ni/Co sulphide ores and laterites (oxides), while Co is a by-product of Cu or Ni mining. In Europe, until recently, Co production was limited to Finland. Although bio-heap leaching may be used for the treatment of low-grade ores (<1 wt% Ni), pyrometallurgy is the main route applied for the treatment of high-grade concentrates (7–11 wt% Ni) from most sulphidic Ni(/Co) ores. Ni/Co concentrates may be converted to a Ni/Co-rich sulphide matte (~70 wt% Ni) that is subjected to hydrometallurgical treatment with solvent extraction and electrowinning to produce battery-grade Ni and Co.

Compared to sulphide ores, Ni/Co-laterites are of a lower grade (saprolites have a slightly higher grade than limonites), with Ni and Co present in silicate and oxide minerals. In Europe, laterites are processed via pyrometallurgy to produce FeNi (Class-II Ni) for the stainless-steel industry [6]. The process has large carbon footprint, is not able to produce battery-grade Ni (Class-I Ni) and also generates metal-containing slag that is currently landfilled in most cases and does not extract Co, which ends up in FeNi (0.6–1.0 wt% Co).

On the other hand, high-pressure acid leaching (HPAL) may be used for the treatment of laterite ores and the production of battery-grade Ni (and Co). The HPAL process uses high pressure (~40 bar) and temperature (~250 °C) during H₂SO₄ leaching and requires chemicals to regulate pH and precipitate the intermediate product Mixed Hydroxide Precipitate (MHP). The use of nitric acid pressure leaching for the treatment of limonitic ores has been also investigated. Under the optimum process conditions (temperature of 194 °C, duration of 75 min, liquid/solid ratio of 3.4 mL/g, and nitric acid concentration of 17 g/L), Ni and Fe extraction were ~90% and ~1%, respectively. The direct nickel (DNi) process, which involves the atmospheric leaching of nickel laterites using nitric acid, may also be a feasible alternative [7].

The ENICON HE project, https://enicon-horizon.eu/ (accessed date on 7 December 2023), exploits the potential of (low-grade) Ni/Co resources in Europe—i.e., sulphidic Ni/Co ores, Ni/Co-bearing pyrite and silicate tailings, and limonitic/saprolitic laterite Ni(/Co) ores—while improving and developing the Ni/Co-refining capacity to process imported ores, concentrates and intermediates. ENICON aims to develop a new, low-pressure, low-temperature, comprehensive hydrometallurgical process flowsheet for sulphide concentrates and laterite ores. ENICON’s HCl route replaces the hydroapproach of continuously precipitating and redissolving metals, which requires lots of chemicals and creates difficult-to-manage waste streams. It does not use expensive solvents, but employs excess HCl, which is recovered, as well as REACH-compliant and easily accessed extractants such as tris 2-ethyl hexyl amine (TEHA), tributyl phosphate (TB)P and Cyanex 301. The HCl-based route can be extended to the downstream processing of FeNi (Class-II Ni); mixed (Ni/Co) sulphide/hydroxide precipitate (MSP/MHP) from the bioleaching of Co-rich pyrite tailings; and Ni/Co-containing silicate tailings. Finally, to achieve (near) zero-waste processing and further reduce CO₂-footprints, ENICON aims to develop advanced mineral-matrix valorisation processes.

Finally, the EXCEED HE project, https://exceed-horizon.eu/ (accessed date on 7 December 2023), aims to develop a new mining paradigm, i.e., zero-waste, multi-metal/mineral mining. This involves sustainable mineral processing to produce additional critical raw materials (CRMs: rare earths, Nb, Ta, W, Be) and industrial minerals (quartz, feldspar and micas), from four lithium mines located in Finland (Keliber), Portugal (Savannah), France (Imerys) and the UK (Imerys). The project adopts a mineral-centric, integrated methodology based on innovative predictive and forensic geometallurgy, with the support of in-line characterisation tools and the development of digital twins. EXCEED’s long-term impact includes the replication of the approach to the other 23 European pegmatite and RMG deposits, thus boosting domestic CRM production.