Salt not only enhances the flavor of our daily meals but also ensures the daily intake of sodium, necessary to regulate many internal activities in the human body.
The reason behind the culinary use of salt is its abundance and, of course, low cost. It may be surprising to know that we consume only 6% of the 270 million metric tons of salt produced worldwide.
Of the remaining 94%, a small proportion is used for softening water, de-icing roads, and agriculture, with the largest volume being used for industrial processes including the manufacture of PVC, plastics, and paper pulp.
Salt is used across industries and cultures and has held an important place in society for over centuries. But where does this versatile mineral come from? Let’s find out how three main types of salt are produced worldwide.
Salt Production Methods
There are essentially three methods to produce salt on a larger scale:
● Evaporation of Seawater
● Rock Salt Mining
● Creating salt brines
1. Sea Salt Production
Sea salt production involves one of the oldest and effective chemical methods to extract salt from evaporating seawater using the solar evaporation method.
Solar Evaporation Technique
We obtain roughly 3.5 % salt from the world’s oceans. You can find salt crystals produced naturally on shallow ponds and dried-up bays. The salt production is higher in areas with prevailing winds, especially in warm climates where the evaporation rate is higher than the precipitation rate.
Solar salt production is, typically, the capturing of salt water in shallow ponds where the sun evaporates most of the water resulting in salt crystals and concentrated brine precipitates. Mechanical harvesting machines later gather and harvest this salt and remove the impurities using the following methods before final packaging:
Advanced Sea Salt Harvesting
However, with the advancements in technology, industries use modern sea salt harvesting techniques using two types of ponds.
● Concentrating pond
● Crystallizing pond
Firstly, the harvesters place the seawater in concentrating ponds where the sun and winds collectively increase the evaporation rate. The resultant product, which is concentrated brine, further shifts to the crystallization pond. Consequently, they obtain the final form of sea salt grains after evaporation.
Crystallization ponds range from 40 to 200 acres with a salt floor thickness of around one foot. However, these deposits are formed over several years. During the salt harvesting process, a concentrated solution of brine continuously flows through these ponds. This way, pure salt crystallizes out from the solution after the water evaporates. Sea salt has usually large-sized crystals that can be grounded according to the requirement.
However, this technique is only applicable in areas with less rainfall and higher temperature, such as the Mediterranean countries and Australia.
2. Rock Salt Production
As the name indicates, rock salt is extracted from none other than the Khewra salt mines. Rock salt, commonly known as Himalayan pink salt, is present in abundance under rocky layers covered with lava.
History of Khewra Salt Mines
Located close to the Jhelum river in Punjab, Pakistan, the Khewra salt mines were formed due to the drying up of ancient oceans millions of years ago. Courtesy of natural composition, the Himalayan salt contains additional 84 minerals compared to sea salt, making it more beneficial and healthy. Interestingly, Himalayan pink salt is hand-mined; that’s why it’s the purest form of salt available.
Salt Mining Process
At present, the Khewra salt mines have a tunnel network of around 25 miles through 19 levels. Moreover, the temperature inside the salt mines remains consistent at 64 degrees. Approximately three hundred miners work in salt chambers using mining tools, such as hand drills, gunpowder, and pickaxes.
The first step is to do the drilling using a hand auger. Next, the miners break large pieces of salt. Every day, miners excavate around 1,000 tons of salt.
Room and Pillar Method
The miners use a technique known as “Room and Pillar,” in which they divide the extracted salt rocks into two equal parts. First, the miners extract the rock salt usually across the horizontal plane, creating arrays of pillars and rooms inside the mine.
Half of the salt rocks serve as pillars to support the ceiling of the salt rooms. On the other hand, the miners transport the other half outside the mines for industrial use. Instead of using explosives, the miners use special equipment to extract large blocks of rock salt from the mines.
Rock Salt Processing
This rock salt is then washed and crushed according to the specific requirements. The manufacturers feed the huge salt blocks into the grinder to further break them into smaller grains.
3. Table Salt Production
The most common and widely used table salt is made by brining salt deposits and evaporating salt brines. Manufacturers further process the obtained salt crystals into fine grains that can be easily mixed in food.
First, the drills dig wells at a distance of a hundred to 1,000 feet from the salt deposit. In Hydraulic or solution mining of salt, the machines pump water below the earth’s surface to dissolve salt deposits. This way, it forms a concentrated salt brine. Next, lateral drilling connects these wells to perform further solution mining operations. Heavy machines pump the brine to the surface in storage tanks for further evaporation.
Large commercial evaporators, known as vacuum pans, evaporate salt brine using steam heat. This method offers a higher yield of pure and refined salt. However, before evaporation, the brine goes through a purification process to remove impurities and other mineral content, such as calcium and magnesium.
You can say that the salt produced from salt brine contains pure sodium chloride crystals, perfect as table salt.
Once you know about the production of different types of salt, you can make a well-informed decision to buy the best one for your daily use. We know that rock salt is the purest form of salt, while the salt from salt brines also known as regular table salt is highly processed and contains anti-caking agents. So, the final decision of choosing the salt is up to you!