In Denmark, salt is extracted from the subsoil for consumption and for use as industrial salt, road salt and chemically pure salt. In Denmark, salt is solely extracted from the Hvornum salt diapir, which is situated about 8 km southwest of Hobro.
Akzo Nobel Salt A/S is the company undertaking the salt production. The company has an exclusive licence for the production of salt from the Danish subsoil. The licence was issued in 1963 and runs for a 50-year period, which means that it will expire in 2013.
On 25 March 2010 the company was granted a new licence to replace the existing one. The new licence is issued for a period of 15 years until 2028 with a possibility for extension for another 15 years. From 2013 the new licence will only comprise the Hvornum salt diapir and an area around the Suldrup salt diapir southwest of Aalborg.
Salt diapir formation
Salt can be found in some parts of the Danish subsoil. The salt was formed during the Permian period more than 250 million years ago. At the time, Denmark was covered by a warm inland sea much like the Dead Sea today. Here, salt was precipitated out of the water as a kilometre-thick layer on the seabed. Subsequently, 4-5 km of clay, sand and chalk was deposited on top of the salt. Because of the weight of the overlying layers, which are denser than the salt, the salt will slowly try to force its way up through the overlying layers where they are weakest. This results in the formation of a salt diapir.
Salt production
The salt diapir from which production takes place is approximately 3,000 m in diameter and 4,000 m deep, and the top is situated at around 300 m below the Earth’s surface. Salt is extracted from depths of 1,000 to 1,500 m. The salt layers are dissolved by pumping water into them. The saltwater is pumped to a plant where the salt is evaporated by heating it. The salt is extracted via six wells, and the plant itself is situated next to Mariager Fiord. The plant has an annual production capacity of approximately 600,000 tons of salt.
State royalties
A royalty is payable to the Danish state. The Danish state receives about DKK 5 million a year in royalties from salt extraction.