The mining of soluble potassium salts (potash) is essential for manufacturing fertilizers required to ensure continuous production of crops and hence global food security. As of 2014, potash is mined predominantly in the northern hemisphere, where large deposits occur. Production tonnage and prices do not take into account the needs of the farmers of the poorest countries. Consequently, soils of some regions of the southern hemisphere are currently being depleted of potassium due to the expansion and intensification of agriculture coupled with the lack of affordable potash. Moving away from mined salts towards locally available resources of potassium, such as K-bearing silicates, could be one option to improve this situation. Overall, the global potash production system and its sustainability warrant discussion. In this contribution we examine the history of potash production and discuss the different sources and technologies used throughout the centuries. In particular, we highlight the political and economic conditions that favored the development of one specific technology over another. We identified a pattern of needs driving innovation. We show that as needs evolved throughout history, alternatives to soluble salts have been used to obtain K-fertilizers. Those alternatives may meet the incoming needs of our century, providing the regulatory and advisory practices that prevailed in the 20th century are revised.

The electrolytic decomposition of metal oxides to metal and oxygen is an extractive metallurgy principle that, when coupled with carbon-free electricity, drastically mitigates the global warming impact of metal production. The present perspective discusses the electrochemical engineering features of an unconventional electrolyte, molten oxides. A survey of its thermodynamic properties suggests exceptional features, both in terms of applicability to multiple metals and operation at high temperature to produce liquid metal. The review of molten oxides’ transport properties indicates that an unprecedented throughput can be envisioned, a promising feature for tonnage production. However, our ability to define the optimal electrolyte composition with regard to energy consumption is rendered limited due to the lack of predictive tools for both of the reviewed properties. A look at the state of the art in electrode materials reveals that quantitative design criteria remain to be developed for both the cathode and the anode. Finally, the applications of electrochemistry in molten oxides are reviewed; thereby confirming most of the anticipated theoretical features.

Molten oxide electrolysis (MOE) is a carbon-free, electrochemical technique to decompose a metal oxide directly into liquid metal and oxygen gas. From an environmental perspective what makes MOE attractive is its ability to extract metal without generating greenhouse gases. Hence, an inert anode capable of sustained oxygen evolution is a critical enabling component for the technology. To this end, iridium has been evaluated in ironmaking cells operated with two different electrolytes. The basicity of the electrolyte has been found to have a dramatic effect on the stability of the iridium anode. The rate of iridium loss in an acidic melt with high silica content has been measured to be much less than that in a basic melt with high calcia content.

The production of iron metal with low greenhouse gas emissions can be performed by electrolysis. However, the electrolytic reduction of iron ore is not a technique that has reached a high degree of knowledge and development. With the aim of getting insight into the electrochemical reaction mechanism, this work shows that the reduction of iron ore to metal at low temperature in alkaline electrolyte is possible and occurs in a solid-state macroscopic mode. Electrochemical reactions take place in the volume of the solid, progressing from its outer surface toward the core, leading to full conversion to metal. A magnetite intermediate phase has been identified and high current efficiency is measured. Such a reaction occurs at high reaction rates, which further stimulates the interest of producing iron metal by the sole use of electricity.