Nearly 100 nations have salt producing facilities ranging from primitive solar evaporation to advanced, multi-stage evaporation in salt refineries. Humans need salt to live. Prehistoric man obtained salt from the meat of hunted animals. When man developed agriculture, salt was added to supplement the vegetable and cereal diet and the quest for salt became a primary motivation in history . In the mid-1800s, salt's value as an important raw material for the chemical industry was established when the Solvay process in Belgium converted salt to synthetic soda ash.
Salt is, today, the largest mineral feedstock consumed by the world chemical industry.
A summary of a 1997 book, The Economics of Salt , is available online. North America produces more than one-quarter of the world's salt. The U.S. is the world's largest salt producer, producing 41.3 million tons a year, nearly half of that, 21.1 million tonnes, in the form of brines produced by captive brine wells supplying U.S. chloralkali chemical companies. Currently, the U.S. salt industry operates 48 salt production plants with major production sites in Louisiana , Ohio , New York , Kansas , Michigan , Utah and California . All major U.S. salt producers are members of the Salt Institute .