Indonesia is expected to continue expanding its nickel production in the coming years, especially through increasing its high-pressure acid-leaching (HPAL) capacity, but the lack of readily available sulphuric acid and proper management of the tailings waste could pose challenges to this plan.

Production is expected to rise despite an anticipated surplus in the supply of nickel in the market.

Sulphuric acid is used in the HPAL process to separate nickel and cobalt from nickel ore to produce mixed hydroxide precipitate (MHP), which is the feedstock for the downstream processing of nickel sulphate, cathode and battery.

Indonesia is expected to produce 325,000-345,000t of MHP this year, up from around 269,000t of in 2023, according to market sources. But with several MHP projects planned to come online in the next few years, MHP output for the next three years is projected to treble to 800,000-900,000t, according to the country's deputy minister for the co-ordinating ministry for maritime and investment affairs Septian Hario Seto on 2 October at a metal event in London. As this would require a lot more nickel ore and sulphuric acid, there are concerns that the availability of limonite ore could deplete as fast as the saprolite ore supply, which is mainly used for nickel pig iron and matte production. There were also discussions that the Indonesian government will convene with nickel market participants to discuss about the supply situation of limonite ore.

There are currently four HPAL facilities operating in Indonesia. This includes Huayou's Huayue and Huafei projects, GEM's QMB project and Lygend's HPAL project.

Others were also concerned that the availability of sulphuric acid could be a limiting factor to Indonesia's rapid expansion of HPAL production, as sulphuric acid demand from Indonesian HPAL projects is expected to reach 7.12mn t in 2025, almost 40pc increase from this year's demand at 5.17mn t, according to Argus estimates.

Indonesia has been importing sulphuric acid from mainly China and South Korea to meet the growing demand for its production units at Obi Island and Sulawesi. But a ramp-up in sulphur-burning operations has pushed several MHP producers like Halmahera Persada Lygend to switch to buying lower-cost sulphurinstead. For most sulphur burners, 1t of sulphur produces around 3t of sulphuric acid.

The startup of Freeport McMoran's Manyar smelter in Java integrated industrial and port estate in East Java's Gresik, coupled with mining firm Amman Mineral Nusa Tenggara's (AMNT) copper smelter in the West Sumbawa regency of Nusa Tenggara province, is also expected to alleviate some supply concerns, with the two expected to add at least 3mn t/yr of acid capacity by the end of 2025.

Proper disposal of tailings waste could pose another challenge to Indonesia's planned HPAL expansion, particularly with increasing scrutiny on the environmental, social and governance (ESG) standards by Indonesia's mining industry.

The HPAL process generates a large volume of tailings, with energy consultancy Wood Mackenzie estimating an output of 1.4-1.6t of waste from every 1t of nickel produced through HPAL.

There are three common ways to dispose tailings waste – tailings dam, deep sea tailings and dry stacking. Dry stacking is more widely used because it is considered as the more sustainable option. But dry stacking also comes with its own environmental and biodiversity risks, as Indonesia's seasonal wet weather and seismic activity of the site could be a problem for waste storage.

To ensure a smooth expansion in HPAL production, it is crucial for Indonesia to find ways to secure the necessary sulphuric acid supplies and to adopt appropriate methods for tailings waste disposal.