Processing of low-grade ultramafic nickel ores: A critical review

•Nickel demand to rise 350% of 2017 by 2050.•High-grade nickel deposits rapidly depleting.•Abundant ultramafic ores offer alternative source of nickel.•Serpentine separation is a major challenge in processing ultramafic nickel ore.•Emerging new technologies helping develop low-grade nickel deposits. Nickel (Ni) is used to fabricate a variety of products, including various alloys- stainless steel being a prominent one, batteries, and catalysts. Global Ni demand is projected to increase by up to 350% by the year 2050 relative to 2017, while the high-grade Ni sulfide ore deposits have largely been depleted. The increasing demand for Ni from emerging markets such as electric vehicles and energy storage requires newer sources of nickel. In addition, the systemic exploration of nickel sulfide ores has led to resources that are more challenging to process due to the higher impurities. The processing complexity necessitates the development of new technologies and pathways to sustainably process globally abundant low-grade Ni sulphide ores. This work systematically reviews and compares various Ni resources in terms of their composition, occurrence, challenges, and opportunities. The conventional processing methods of low-grade ultramafic Ni ore are discussed along with emerging technologies. Key challenges remaining and future perspectives that tie together fundamental and applied research are also provided.