The disposal of waste has environmental and social implications including land disturbance, emissions to the environment and contamination of soil and groundwater. Rio Tinto generates two main types of waste during mineral extraction. These are mineral and non mineral wastes.

Mineral Wastes include the mined rock that contains no economic ore; tailings, which are the fine sand like residue after the mineral has been extracted from the rock; and slag, the solid residue from the smelting process. Most of Rio Tinto's mineral wastes are disposed of on site; they are either put back into the pit or underground workings from which they were originally extracted, placed in adjacent areas (in engineered stockpiles and rock dumps) or placed in engineered structures, such as dams.

Rio Tinto produced 1,641 million tonnes of mineral waste in 2003. That accounts for over 99 per cent of the total waste produced by the Group. The majority (85 per cent) of mineral waste is waste rock. More on mineral waste performance.

A significant issue with the management of mineral wastes arises from the presence of sulphur in some minerals. Exposure of this material to oxygen and water can in certain circumstances, generate an acid or sulphate containing liquid, commonly called acid rock drainage. More on acid rock drainage.

Non mineral waste primarily consists of auxiliary materials that support mining and mineral processing such as oils, tyres, batteries, refractory lining, and domestic rubbish. Non mineral waste may or may not be hazardous. The management of non mineral waste includes re-use, recycling, incineration, storage or disposal to in pit back fill or landfill. Rio Tinto produced 312,000 tonnes of non mineral waste in 2003. More on non mineral waste performance.

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