Enhanced cyanide management through ASTER^TM process technology

ASTER^TM is a proprietary Gold Fields technology that offers a safe, efficient and environmentally responsible alternative to conventional cyanide management and process water disposal. ASTER^TM utilises a blend of naturally occurring microbial species to destroy cyanide and thiocyanate present in recycled tailings process water, following the leaching process. ASTER™ negates the need for costly and environmentally harmful chemicals that are commonly used in cyanide destruction, by using bacteria and fungi that are wholly nonpathogenic.

This not only limits ASTER™’s environmental impact, but also offers significant cost savings compared to rival chemical processes. In addition, the operational efficiency of ASTER^TM has now been proven on a commercial scale. During 2011, this was demonstrated at the first ever commercial ASTER^TM plant, operated by Barberton Mines in South Africa. Process water from the plant demonstrated only trace levels of cyanide, as well as thiocyanate concentrations of <1ppm. This is below what most chemical processes are capable of achieving and well within the International Cyanide Management Code (ICMC) cyanide concentration limit of 50ppm.

ASTER™ can be used to further enhance Gold Fields BIOX® treatment technology, which has very low tolerance of cyanide and thiocyanate and thus requires tailings process water to be detoxified prior to reuse. As a result, the growing global demand for BIOX® will also generate marketing opportunities for ASTER™. Several BIOX® operations are already investigating potential application of ASTER™. In addition, it is likely that the market for ASTER™ will be driven by increasingly stringent environmental legislation around the world, as well as a growing number of companies signing up to the ICMC.

Gold Fields is currently investigating opportunities to use ASTER™ to enhance cyanide management at its Cerro Corona mine and Chucapaca project in Peru.