Greenpeace ship SOLO occupying quay where salt is unloaded for Solvay's chlorine factory, Antwerp, Belgium. Salt is the main material used in producing chlorine gas. Solvay is one of the 3 producers of chlorine in Belgium (others are Tessenderlo Chimie and BASF). Most of the chlorine produced is for PVC production. This plastic produces dioxins during production and incineration.