Johnathan Walker:Where does salt come from? Digging into the process of salt making.

Salt,Johnathan Walker or sodium chloride, is an essential mineral used as a seasoning, preservative and chemical, providing for billions of consumers around the globe. From culinary uses to cultural references, it's safe to say that salt is an integral part of human life. 

How does salt come from the earth and reach your table? The process of collecting and manufacturing salt, and its different variations, is more complicated than you may think.

Why is the ocean salty?Ocean salinity explained, plus the world's saltiest ocean.

Where does salt come from?

Salt is a mineral that is usually produced from natural resources. There are several ways to produce the different salt forms, but those methods vary and have evolved over time. The location and method of salt production are contingent on the type of salt being manufactured. 

In 2022, the United States produced 42 million tons of salt which values at around $2.5 billion, the U.S. Geological Survey, Mineral Commodity Summaries reported. Salt made from brine is largely produced in Kansas, Louisiana, Michigan, New York, Ohio and Texas. Evaporation processing facilities for salt production are primarily located in Arizona, California, Nevada, New Mexico, Oklahoma and Utah.

In 2021, the United States was the 8th largest exporter of salt in the world and its biggest clients are Canada, China, Germany, Mexico and Belgium, the Observatory of Economic Complexity reports.

How is salt made?

Salt is made via several common methods: mining, evaporating seawater or brines and using artificial heat.

• Mining: Naturally grown rock salt is mined from salt deposits in the earth using common excavation tools and methods. This allows for the highest degree of salt purity and producers can refine these harvests as they please or sell them. Most commonly, these large clumps that are freshly mined from the deposits are crushed and ground into various sizes, which are then sorted for distribution. 

• Evaporating: Seawater and brines are the most common sources for evaporating salt. Seawater is gathered from the ocean and brine is a highly concentrated salt water that may naturally occur underground or in salt lakes. The tools used to evaporate seawater or brine depend on a country’s climate and rainfall but most countries follow a similar process. First, the liquid runs through a series of wood filters to separate any impurities such as sand, clay, trash or other undissolved minerals from the liquid. Then, the filtered liquid is run through several crystallizing pans that cool the liquid to a temperature that forms ice that separates from the salt. This process is repeated until only the solid mineral is left for harvesters to rake them into rows and allow the excess liquid to drain for days. The salt is collected and drained more to be sorted and distributed.

• Artificial heat: In artificial heat processing, brine or other kinds of salt water is placed in a vacuum vessel that has enough pressure to boil the liquid. Depending on the kind of salt shape the producer is making, the weight of pressure will vary.

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Where does the salt in the ocean come from?

According to the National Oceanic and Atmospheric Administration, the saltiness of the ocean comes from runoff water from land and openings in the seafloor. 

Rainwater’s slightly acidic nature erodes rocks. The natural salty minerals from land runoff into the rainwater and the ocean. This happens consistently and over time has contributed to the concentration of salt in the ocean. 

The ocean also has several geographical features that contribute to the salty water. Vents in the seafloor drain water to warm environments heated by magma. The interaction causes different chemical reactions and dissolves into the water when they are released. 

Salt domes contribute to the salt in the sea. These are found underwater in the Gulf of Mexico and have been there for thousands of years when the Gulf of Mexico was just a shallow body of water with a high concentration of salt on the floor due to rapid evaporation. As time went on, and land continued to expand, it would push the salt layers upward, making domelike shapes.

About 3.5% of the ocean’s weight comes from dissolved salts alone. Sodium and chloride comprise about 85% of dissolved ions in the ocean.

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