Potash is any of various mined or manufactured salts that contain potassium in water-soluble form. The name derives from pot ash, which refers to plant ashes soaked in water in a pot, the primary means of manufacturing the product before the industrial era. The word potassium is derived from potash.
The world’s largest commercial potash deposits come originally from evaporite deposits and are often buried deep below the earth's surface. Underground or solution mining of solid evaporite deposits of Potassium Chloride, chemical formula KCl, also referred to as common Potash, Muriate of Potash (MOP), or Sylvite (the name of the common mineral), accounts for the majority of potash production today. However, mining of other potassium minerals is also significant, including Sulfate or Potassium (SOP or Potassium Sulfate), Potassium-Magnesium Chloride, Sulfate of Potash Magnesium (SOPM or Potassium Magnesium Sulfate), and Potassium Nitrates, as is the production of potassium salts from surface and near-surface brine deposits (including salt and brine lakes). Projects to produce potash from seawater have been proposed and piloted in multiple countries including India, but have not yet reached commercial-scale production.
The United States Geological Survey has estimated that the world produced approximately 39 million tonnes of potash in 2015 on a K2O equivalent basis, of which over 60% was produced in just three countries that also hold over 60% of the world’s reserves: Canada, Russia, and Belarus. The majority of production from these countries is from underground and solution mining of Potassium Chloride.
To estimate product tonnages of KCl divide K2O equivalent tonnages by 0.61.
2015 Global Potash Production
Underground mining, which accounts for a majority of global potash production today, extracts solid potassium salt mineral resources using a variety and combination of techniques including shafts and tunnels, room and pillar, as well as cut and fill mining.
Solutions mining is generally used when potash deposits are located too deep for underground mining. The process typically injects a liquid solution (generally water and salt) into the underground potassium salt mineral, which then dissolve. This dissolution process forms underground caverns from which the resulting brine solution is pumped to the surface, where the potassium salts are crystalized and processed into an end product ready for sale.
Surface and Near-surface Brine Deposits
The natural deposits of salt rich brines are pumped from shallow depths beneath the surface and fed into a series of large, shallow ponds or large mechanical crystallisation installations to ultimately form saleable potash via multiple process steps. The biggest salt brine production of potash in the world is located at the Dead Sea. Other notable operations are located at the Great Salt Lake in Utah, in the Atacama Desert in Chile, and at multiple salt lakes in China.
GrowMax’s Bayovar concessions host a significant near-surface potassium rich brine deposit.
Common Potash Processing
Common potash ore generally consists of sylvite (KCl), halite (NaCl – common salt) and occasional inclusions of carnalite, anhydrite and insoluble matter including silicate and carbonate.
The processing of these ores to produce relatively pure Potassium Chloride is typically done by mechanical flotation, which produces standard grade potassium chloride. In flotation, process reagents added to the potash, salt and brine mixture attach only to the Potassium Chloride crystals. These reagents enable the Potassium Chloride crystals to attach to fine air bubbles that are introduced into the bottom of flotation devices. The potash particles rise to the surface for collection and the common salt remains on the bottom, where it is discarded.
Chemical processing is employed to produce higher purity industrial grade and specialty fertilizer grade (white muriate) potash, and generally involves hot leaching and further crystallization of potash salt from saturated salt brines.
Solution Mining and Lake Brine Crystallization Processes
Brines produced from solution mines or brine deposits require evaporation of water content and crystallization of minerals. In colder climates this is achieved with relatively high energy consumption in vacuum evaporation and crystallization processes. However, where climate conditions allow, solar evaporation and crystallization in a series of ponds is typically the preferred method, as has been trialed by GrowMax at its Bayovar operations.
Approximately 90% of all potash production is consumed as a fertilizer or as part of a complex fertilizer. Potassium Chloride also has a range of other applications in aluminium recycling, in the production of potassium hydroxide, in metal electroplating, in oil-well drilling fluid, in snow and ice melting, in steel heat-treating, in medicine as a treatment for hypokalemia, and in water softening, whereas other potassium salts (including sulfate of Potassium, SOP) are used even more exclusively as fertilizers.
Potash demand is distributed and has been growing in a manner similar to the other main fertilizer nutrients.
Global Potash Consumption by Region (mm mT of K2O)
However, it is worth noting the extent to which Latin America is a growing and significant net importer of potash.
Potash Net Imports by Region (‘000 of mT of K2O)
Source: International Fertilizer Association (IFA)
Potassium Sulfate or Sulfate of potash (SOP), chemical formula of K2SO4, is the second major form of potash. It is priced at a premium to common potash (MOP), and is particularly useful in the cultivation of higher value crops including fruits, vegetables, potatoes, tobacco and tree nuts. It is also generally sought after in climates and agricultural environments where build-up of chlorides from long-term application of Potassium Chloride can cause issues.
Global production of SOP is estimated at approximately 3 million tonnes K2O (6 million tonnes SOP). Approximately 50% of global SOP production and consumption occurs in China, where production has grown rapidly from effectively zero in 1990. High export tariffs have effectively isolated Chinese fertilizer production from international markets.
Outside of China, SOP production is largely attributable to a small number of producers that convert MOP to SOP in Europe (Tessenderlo in Belgium and K+S in Germany), as well as from lake Brines in Utah (Compass Minerals) and Chile (SQM).
However, in part due to a significant increase in recent years of the relative market price premium for SOP over MOP, various new projects to produce SOP have been proposed.
Further, an almost direct competitor to SOP is Potassium Magnesium Sulfate, also called Sulfate of Potash Magnesium (SOPM), the largest production of which comes from mining of Langbeinite mineral deposits in the United States.
Local demand for SOP (and SOPM) is significant in Peru, where irrigation projects have led to the development of substantial fruit and vegetable production in the arid coastal regions, and fruit and coffee/cacao production is also growing in the Andean and Amazonian regions. As a result, SOP and SOPM account for a much higher percentage of total potash demand in Peru than is the case globally.
Peru Potash Imports (metric tonnes)
Source: Peru Ministry of Agriculture
Both MOP and SOP can be produced in different grades, defined by the purity and particle size of the product. For SOP, the grades are typically classified as follows:
Standard SOP: Fine crystals with typical particle size of 0.2 mm to 1.7 mm that can be applied directly on hardy crops or used in the manufacturing of compound fertilizers.
Granular SOP: Small granules with typical particle size of 0.8 mm to 3.4 mm that can be used in bulk blends, for mechanized or manual spreading. Granular SOP is the most common can be produced from Standard SOP by mechanical compression or using a binding agent. This is the most widely used grade in North America and Europe.
Soluble SOP: Fine powder with a typical particle size range of 0.1 mm to 0.3 mm. used in open field fertigation, foliar feeding, and greenhouse and hydroponic systems. This form of SOP likely accounts for a small proportion of SOP sales globally, but may account for a substantial and growing portion of the local SOP market in Peru, and typically sells for a premium to the other SOP grades.
GrowMax is currently evaluating the possibility of producing premium-priced soluble SOP from its potassium-rich brine resources on its Bayovar concessions