Salt, the multifunctional element

‍A story of flavour and tears

Fernando Pessoa is credited with the romantic idea that much of the salt in the sea comes from Portugal's tears, in a poetic reference to Portugal's maritime adventures. But the facts also establish a link between our country, the Discoveries and salt production, which dates back to the Bronze Age, according to archaeological findings.

In writing, there is evidence of its exploitation in the oldest document referring to Portuguese salt: the document is dated 959 and is a record of the donation of land and salt marshes in Aveiro. The annals of history then confirm that the activity was already so important in the 16th century that King João I authorised, for the first time, the exportation of sea salt produced by solar evaporation. This salt, due to its quality, was worth more than that produced in the mines of Central Europe. But it wasn't just its economic importance that contributed to the country's maritime development. Salt – which scientists later named sodium chloride – also played an essential role in preserving food at this time, an asset when travelling on long journeys.

Man's relationship with salt was already many millennia old. Prehistoric man obtained the salt he needed – and our bodies need around 100 grams for every 40 kilos of weight, as sodium is essential for cell function – by eating animals. Then, when humanity turned to agriculture, it soon realised that the salt found in the sea and in salty inland lakes gave vegetables a taste similar to meat.

By the 6th century BC, salt was already being mined in various parts of the world and the possession of this precious commodity, nicknamed "white gold", began to justify even armed conflicts. The first Roman road was even called Via Salaria, linking Rome to the Adriatic Sea, where salt was collected, and the empire's soldiers and civil servants were paid partly in salt, which is where the word salary comes from. Salt was a bargaining chip that remained in various parts of the world until the 19th century.

Throughout this time, and up until the Industrial Revolution, salt was mainly used to preserve food during the winter months, but the white crystals were also used for religious rituals (as a symbol of purity), to heal wounds or to tan leather, and are believed to have been the first traded goods.

In the 18th, 19th and 20th centuries – with the advent of the Chemical Revolution – the salt industry, extraction processes – salt can be obtained from seawater, natural salt pans or salt rock deposits (formed by the evaporation of ancient oceans) – and refining processes underwent some innovations. Science has also led to the discovery of new uses for the mineral as an industrial raw material, which have had a significant impact on humanity’s development and quality of life.

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A well-seasoned business

Throughout history, salt has been the subject of state monopolies and special taxes. Currently, the global salt market, according to projections in the Fortune Business Insights report, is expected to grow from 34.1 billion dollars in 2023 to 48.6 billion in 2030.

In 2022, statistics showed a global production of 290 billion metric tonnes of salt, with China leading the world supply, followed by the United States and India. The three countries combined produced a total of 151 billion metric tonnes of salt that year.

Although the Portuguese salt industry has been declining since the time of the Discoveries, in 2022 our country generated 117.700 tonnes of sea salt, according to the latest data from the "Fisheries Statistics 2022" yearbook, drawn up by the INE – National Statistics Institute and the DGRM – Directorate-General for Natural Resources, Safety and Maritime Services. The figures show that production grew by 30.3% compared to 2021 and that the total number of functioning salt pans increased by 44.4%, amounting to 52 units. Tradition, however, is not what it used to be: around 83% of salt was extracted by mechanical processes, "fleur de sel" accounted for 0.2% of production and "traditional sea salt" only 16.8%.

Although the world's average daily salt intake is estimated at 10.8 grams per person (in China the figure rises to 17.7 grams and in Portugal it is 8.9 grams, which is twice the amount recommended by the World Health Organisation), the truth is that the food industry is not among the top five consumers in the global salt market. It is the chemical industry that has by far the largest share, which in 2021 was 47%.

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‍The salt you can't see

There are thought to be more than 14,000 uses for salt, which go far beyond simply adding it to our food or to homemade cleaning recipes.

The chemical industry's growing demand for this inorganic compound is mainly stimulated by the increase in the production of chlor-alkali (chlorine, caustic soda and other derivatives) through electrolysis of brine solution (a technology that uses electric current to induce the reaction of sodium chloride, transforming it into other components.)

The resulting compounds are essential raw materials for more than half of the chemical industry's end products, as well as for the competitiveness of various other sectors, such as energy, construction, sanitising products, cosmetics, textiles, plastics, glass and paper, among many others.

But as well as being the source of most of the products that surround us, salt processed by the chemical industry takes on a new life when it is transformed into products that also serve to protect human and animal health and the entire food chain.

Chlorine-based phytopharmaceuticals, for example, are substances used in agriculture to protect crops from diseases and pests. And chlorine is also the basic component of 85% of medicines used to treat diseases such as hypertension, cancer, AIDS, pneumonia, allergies, diabetes and meningitis, as well as playing a key role in drinking water treatment, which makes human life safer.

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