Chlorine and caustic soda are key building blocks that underpin more than half of the Western European chemical industry turnover of EURO 380,000 million. These basic raw materials are made by passing electricity through brine. The majority of Western European plants use mercury as the negative electrode or cathode in this process. The mercury keeps the highly reactive products apart, which is essential for safe and efficient plant operation.
As mercury is a toxic metal, the industry is progressively converting chlorine plants to other technologies when they reach the end of their economic life. This switch is helped by the high cost of power, as membrane technology is more efficient than mercury cells.
Chlor-alkali manufacturing is non-dispersive and depends on the efficient and complete recycling of mercury within the plant. Today, the residual mercury emissions from the chlor-alkali industry are very low. Substantial improvements have been made, with mercury emissions reduced by over 85% in the past decade, to 10 tonnes (1997) and less than that today. This compares with estimated global total man-made and natural emissions of 20,000 tonnes per year
