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First commercial use of pressure hydrometallurgical processes in North America started with the invention by Frank A. Forward and subsequent U.S. Patent 2,576,314 (1948) for Extracting of nickel values from nickeliferous sulfide material, using ammonium carbonate solution, and later implemented by Sherritt Gordon Mines Ltd. at Fort Saskatchewan, Alberta, Canada. Acid pressure leaching and sulphide precipitation processes were developed later and implemented at Moa Bay in 1964 for production of mixed (nickel and cobalt) sulphide from laterite ore. The commercial use of pressure hydrometallurgical processes expanded greatly between 1990 - 1995 with the development and implementation of high-pressure acid leaching of laterite ores in Western Australia. This was followed by pressure oxidative leaching of copper sulphide by Phelps Dodge (2003), and chloride-assisted pressure oxidative leaching of nickel, cobalt, and copper sulphides by INCO Ltd. (2005) and Cominco Engineering Services Ltd. (2006). Most recently, the use of these hydrometallurgical processes has been of interest to companies looking to produce high-purity chemicals used in cathode active materials and electrolytes for solid-state electric batteries with a low emissions footprint. This presentation outlines some conventional hydrometallurgical process options to intermediate products, major reagent requirements, unit energy consumption and key CO2 emissions, with of the objective of comparing the overall environmental footprint of such processes relative to conventional smelter/refining operations.