The name "potash" comes from the "ash" of a "pot". Centuries ago people burned wood, mixed the ashes with water and evaporated the solution in iron pots. The remainder was potash.
Potash was used primarily for soap and glass. However, it was noticed pots were having a significant effect on the plants grown where they were thrown. The result was the reason that the importance of potassium was recognised.
In the late 1800s, when Germany started mining for potassium salts and supply increased, a world fertiliser market opened up. After The First World War, brines were used to source potassium.
The name 'potash' basically refers to potassium-bearing minerals or compounds.
Potassium, nitrogen, and phosphorus are the three macro-nutrients vital for plant growth. Potassium helps the 'blood flow' of the plant, enabling sugars and waters to move around. It thickens cell walls, protects against drought and helps the plant defend against disease.
Potassium naturally occurs in soils and is among the most common elements on earth.
Historically wood (and sometimes kelp) was burned to produce potash. Today, potash comes from hard rock or brine.
Potash from brine often produces a Sulphate of Potash (SOP), or K2SO4 (potassium sulphate). Brine is water that is saturated with salts.
Worldwide, many inland lakes are saltier than seawater and have different chemistry. The groundwater underneath the lakes is often similar in chemistry to the water in the lakes.
We use brine evaporated salts for our flagship SOP project at Lake Wells. The brine is contained in a wide, deep and long paleochannel - a long-buried ancient river channel. This palaeochannel has been carved through the Yilgarn Craton, which includes the oldest and some of the most mineral-rich rocks on the planet.
Potash from hard rock generally produces Muriate Of Potash (MOP) or KCl (potassium chloride). Hundreds of millions of years ago, ancient seas evaporated and left behind potassium deposits. Over time these sedimentary salt beds were covered with more soil and rock. When mined this ‘hard-rock’ potassium ore is processed into MOP.
Sulphate of Potash can be produced using three methods; the solar salt brine method, the salt-reaction process and the Mannheim method. We use the first two methods, which are low energy, clean and environmentally safe.
Solar salt method: The sun evaporates water molecules so that a crystallised salt remains.
Salt reaction method: Take a MOP particle, blend it with a sulphate brine and agitate. The potassium bond in the potassium chloride (MOP) molecule is fragile and will break and connect with the sulphate, forming potassium sulphate (SOP).
Mannheim method: Here you take MOP, add sulphuric acid and heat it to 450 degrees Centigrade. This reaction produces potassium sulphate (SOP) and hydrochloric acid. The method is energy-intensive, and hydrochloric acid is difficult to deal with – it needs to be earmarked for another process because disposal is virtually impossible.
Most of the SOP we get in Australia is imported from where the Mannheim process is used. In 2019 it costs approximately US$400 – US$450/t to produce SOP using Mannheim, so by the time we pay for freight and logistics to get it into our country, it's prohibitively expensive for most farmers to use.
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Australian Potash Limited:
Suite 31, 22 Railway Road
Subiaco Western Australia 6008
PO Box 180
Subiaco Western Australia 6904
Tel: +61 8 9322 1003
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