New Horizons — The wasteless mine

Mine waste is gaining great importance in mine management. The need to protect the environment, combined with increasingly strict environmental legislation, calls for efficient waste management methods.

These methods may involve high costs, not only during operations, but also after mine closure.

For instance, the reclamation of the mill tailings area of a sulphidic mine, troubled with acid mine drainage, may take a hundred years and cost between 25 cents and one dollar for each tonne of tailings per year. The total amount of tailings can be millions of tonnes.

To solve the waste problem of mainly sulphidic mines, Outokumpu has started a research program called “Wasteless Mine.” The objective is to develop processes that minimize the amount of environmentally harmful waste and yield final mill tailings that do not endanger the local environment. Waste is no longer seen as an outcome of the ore-to-metals chain, but as an integral aspect of every operation, from mine geology to concentration. Accordingly, a waste management plan is initiated with mine geology, and all processes are designed to conform to the objectives of a wasteless mine.

The program makes use of Outokumpu’s mine backfilling know-how for the development of methods to dispose of mill tailings underground. Another goal is to develop economical methods for the dewatering of tailings and treatment of solids for integrated backfilling processes.

Backfilling will not, however, remove the problems associated with mill tailings altogether; this is because only about 60% of the material hoisted from a mine fits back into it. A great deal of the tailings have to be disposed of by other means. Some can be used as construction material, while a portion has to be stored on surface at the mine site.

To prevent mill tailings from causing acid mine drainage, some operators endeavor to isolate the reactive portion of the tailings by means of processing. To that end, Outokumpu has conducted a study aimed at reducing, by flotation, the amount of sulphidic sulphur in tailings from its Pyhasalmi mine in central Finland.

The goal of the Wasteless Mine program is to develop a waste management plan that extends from the feasibility study stage to mine closure.

–From a recent issue of “Outokumpu News.”