Pressure leaching processes (HPAL and POX) require significant steam/acid or oxygen addition to promote metal dissolution (or liberation in the case of gold) which drives up operating costs. Temperature, acidity and oxygen addition also affect the output chemistry and, in turn, the cost of downstream refining and the environmental impact of the residue produced. The complexity of the process makes it difficult to model it using chemistry-based models alone. NTWIST tackles the problem by building models based on actual historical data and offering optimal operating setpoints to the operator. An assessment of NTWIST’s optimization solution for Ambatovy carried out by Sherritt Technologies uncovered potential annual savings of US $1.7 mil.