Most chlorine today is produced by separating the chlorine and sodium ions of a salt brine in an electric field. This process is called electrolysis. One ton of salt (and water) yields around 600 kg of chlorine, 680 kg of sodium hydroxide (caustic soda) and 17 kg of hydrogen.
Electrolysis plants consume a substantial amount of energy but despite this, PVC production uses less overall energy than most alternatives; this is quantified by eco-profile data. Consequently, greenhouse gas emissions related to PVC production are lower as well.
Some 9 million tons of chlorine are produced in Western Europe and used in more than half of all chemical activities.
The electrolysis of salt therefore is a basic process to get important raw materials used in the chemical industry. Some 34% of chlorine is used to produce PVC, 23% to produce isocyanates for the production of polyurethanes, chlorine is also used in the production of polycarbonates or silicones and low amounts to keep 98% of Western Europe’s drinking water safe and produce other chemicals. Sodium hydroxide is important for the manufacture of paper, soap and textiles and other applications. Hydrogen is either used chemically or to generate energy.
Since both chlorine and sodium hydroxide are produced in a highly efficient way, they are also a good basis for low cost materials. Products made from them, e.g. PVC-products therefore are also low cost products, a very important point in a sustainability assessment.
In summary, electrolysis yields in the end products requiring relatively low energy and being low cost, an important environmental, economic and social contribution to sustainable development! (for more information on chlorine, see www.eurochlor.org )
