High-priced sea salts contaminated with plastic waste,
Meike Schulz, RHEWUM GmbH
Fleur de Sel, Aguni Salz or Sel de Guerande – exotic sea salts are increasingly filling the spice racks of gourmet and hobby chefs. In addition to the exclusive taste the expensive noble salts promise to work real wonders for our health.
But not just the ocean is polluted by plastic waste, also the high-priced gourmet salts that are obtained from seawater. Sea salts are produced by evaporation of water whereby the plastic waste that swims in the ocean is being heavily concentrated. As seawater usually has a salt content of 3.5 % the contained impurities are increased by thirty during the production process.
In April 2017, the British journal “Scientific Reports” published a study which examined various salts from eight countries regarding their type, particle size and proportion of impurities. The result: 16 out of 17 samples were contaminated with microplastics and contained a total of 72 different plastic particles consisting of polymers or pigments. Depending on the origin, nylon 6, polypropylene, polyethylene and PET as well polystyrene or polyacrylonitrile were found.
“As these particles of the microplastics are larger than 200 µm (0.2 mm), it would not be a problem from a technical viewpoint to sieve off the undesired impurities before the crystallization and thus preventing that they are consumed with the salt”, says Sigurd Schütz, Managing Director at RHEWUM. “Apparently this is not happening yet”.
From a technical view there is nothing standing in the way of screening off fine foreign materials from seawater as long as the general technical requirements are taken into account. If you would like to separate particles with a size of less than 100 µm (0.1 mm) in order to remove them from the seawater, the problem is to overcome the cohesive forces of the water - otherwise it passes the sieve cloth in droplets together with the microplastic waste. For such special cases RHEWUM develops individual solutions in close collaboration with the customer. We will be pleased to advise you on the implementation of such a cleaning process.
 Karami, Ali, et al. "The presence of microplastics in commercial salts from different countries." Scientific Reports 7 (2017).