During zinc production Nyrstar - a global, integrated mining and Zn processing company - produces residual products 'goethite' and ‘neutra’, which is released in sediment form. The goethite and neutra sediments were stored in basins at its site in Balen, Belgium. However, the company no longer had the capacity to store the sludge, therefore another solution had to be found.
At a production level of 260,000 tonnes of zinc a year at the time, Nyrstar Balen produces some 75,000 tonnes of goethite per year. The process also yields 40,000 tonnes of neutralised flotation sludge a year. Based on a Build, Own, Operate, Transfer (BOOT) contract, Nyrstar wanted to tackle this problem.