Sustainability website / Environment / Waste and tailings management

Policy and approach

Policy and approach / Performance and goals / Waste rock and tailings

We reduce wastes and the toxicity of our wastes, as set out in our revised Sustainable Development Policy. All operations re-use, recycle or properly dispose of waste generated, minimising waste sent to landfill and maximising opportunities for recycling or reprocessing waste to reduce costs and generate additional revenues.

In addition to its environmental impact, waste produced by Xstrata’s operations has cost implications, from the cost of producing the waste initially (e.g. the cost of removing overburden to enable mining of metalliferous ores or coal) to costs associated with responsible waste disposal or storage (e.g. waste stored in tailings dams, disposal of hazardous waste). We aim to progressively reduce the volume of waste disposed to landfill and for 2006 and 2007 we have estimated the greenhouse gas emissions from waste to offsite landfills, included in reported CO₂-e emissions.

Xstrata’s mining operations generate a large volume of waste rock from the removal of overburden to expose ores or coal, which is replaced in open cast or underground operations, re-used or stored in waste rock facilities. Processing wastes include tailings, course reject and slag and are generated from the processing of ore. Where possible processing wastes are recycled or re-used, and are otherwise stored in specially constructed tailings storage facilities and dams. Non-mineral waste is split between hazardous waste as defined by the Basel Convention 1992, including hydrocarbons, heavy metal contaminated sludges, medical waste and vehicle batteries, and non-hazardous or general waste. Tailings dam storage facilities are constructed according to international standards and are subject to regular external audits and risk assessments. No Xstrata operations dispose of tailings into rivers or the ocean.

(see SD Management Standard 10: Environment, Biodiversity and Landscape Functions and SD Management Standard 13: Life Cycle Management)

Performance and goals

Policy and approach / Performance and goals / Waste rock and tailings

Xstrata’s operations generated a total of 1.03 billion tonnes of waste in 2007, 8% higher than in 2006. Excavated rock and overburden, non-processed waste, accounted for 90% of waste generated.

Processing waste (including tailings, course reject, slag and sludges) accounted for 10% of total waste or 119 million tonnes in 2007, of which 7% or 7.8 million tonnes were recycled. The graph on this page shows the various processing wastes that were recycled in 2007, many of which were used to recover additional metal content.

Hazardous waste and general waste together comprise less than 0.1% of total waste generated. Hazardous waste reduced to 784,782 tonnes from 853,977 tonnes (restated from 1.4 million tonnes1) the previous year. Over 81% or 639,558 tonnes of hazardous waste generated was reused or recycled, compared to 90% in the previous year, and 14,000 kilolitres of waste oil was reused in blasting or recycled through off-site facilities.

General waste to landfill increased by 60% compared to 2006 to 958,500 tonnes. On a like-for-like basis, excluding Falconbridge, general waste to landfill increased by 7%. A small proportion of general waste was disposed of in off-site regulated facilities with the remainder disposed of in on-site regulated landfills.

Waste management plans were implemented at all Xstrata operations in 2006. We are on track to meet our target for all operations acquired in 2006 and 2007 to develop and maintain waste management plans including hazardous waste management and tailings disposal by the end of 2008. Over 95% of tailings dam facilities at managed operations were externally audited during 2007 to ensure integrity.

Recycling

Xstrata Recycling operates precious metal sampling facilities in East Providence, Rhode Island and San Jose, California. It also has commercial offices in Penang, Malaysia, Toronto, Canada and Zug, Switzerland. These facilities are part of Xstrata Copper’s worldwide precious metal recycling network and are world leaders in the sampling of precious metal-bearing recyclable materials containing gold, silver, platinum, palladium and copper. After sampling at either East Providence or San Jose, materials are smelted and refined at Xstrata Copper’s Horne Smelter and CCR Refinery respectively, both of which are in Canada. Over 120,000 tonnes of various metal-bearing materials are recycled through these facilities annually and in January 2008, Xstrata Recycling announced it would double the Horne Smelter’s annual capacity to process electronic scrap to 100,000 tonnes. This responds to the growing supply of electronic scrap due to higher usage of electronic products, together with changes in waste regulations including the EU’s Waste Electrical and Electronic Equipment (WEEE) Directive which requires all electronic scrap to be recycled.

In January 2008, the construction of a smelter dust treatment plant was completed to allow Altonorte to safely recycle the metallurgical dust that the smelter generates during the copper concentrate fusion process. The project involves an agitated tank leach process that dissolves part of the copper contained in the dust followed by filtration to separate the liquids and solids. The liquid solution (PLS) is transported to Xstrata Copper's Lomas Bayas open pit mine for processing in the SX-EW facility and the solids are re-fed into the Altonorte smelter. The two processes are expected to achieve a global recovery of 94.8% of the copper contained in the dust.

Mount Isa Mines commenced a small scale trial battery recycling programme at the lead smelter in 2007 which recycled approximately 53 tonnes. If this trial is successful, we will investigate expanding the programme further in 2008.

Waste rock and tailings

Policy and approach / Performance and goals / Waste rock and tailings

Xstrata’s SD Standards and Guidelines set stringent expectations for the management of tailings and waste rock facilities. Acid rock drainage is a particular issue for these facilities and occurs when potentially acid-forming rock is exposed to air or water and forms sulphuric acid which leaches heavy metals such as lead, zinc, cadmium and mercury from the ore contained in waste rock. Left unchecked, acid rock drainage causes heavy metal contamination of land and water sources close to waste rock storage and tailings disposal facilities. This has been identified as a key risk at a number of operations where waste rock dumps are capped to prevent contact with the air or water, for example from rainfall.

Management processes in place at all managed operations to manage tailings disposal facilities include:

• Engineering designs of tailings facilities which comply with international standards regardless of location;
• Regular external inspections and audits of tailings dams;
• Regular physical stability control, risk assessments and monitoring;
• Leaching control, groundwater monitoring;
• Effluent treatment, for example seepage collection systems;
• Progressive rehabilitation or reclamation; and
• Planning including worst case scenario weather and geological conditions (e.g. seismic activity, 100-year floods, prolonged heavy rainfall, landslides).

At Raglan, tailings are stored in permafrost and temperature is therefore critical to the tailings placement and stability. Temperature monitoring equipment has been installed on the tailings stack to monitor thermal trends and progressive rehabilitation is performed annually and supervised by external experts to provide quality assurance. Raglan’s Climate Change Steering Committee meets regularly to review the performance of the tailings stack, as well as to identify impacts with regards to global warming. This group has reviewed the tailings design assumptions against actual field conditions and forecast climate change trends and recommends improvements to planning and storage design to ensure the integrity of the tailings facility.

Black Star Open Cut (BSOC) zinc-lead mine at Mount Isa has commissioned and sponsored significant research into the cover system design and role of vegetation in the capping of waste rock dumps. This research includes mathematically modelling of potential moisture store and release cover system options. In early 2008, a field study will commence to identify the most economically and environmentally beneficial moisture store and release cover system option for the mine’s waste rock dumps. BSOC has also sponsored the University of Queensland’s Sustainable Minerals Institute research programme into the role that vegetation plays in cover systems in preventing moisture percolation into waste rock dumps. Currently very little is known about the role of vegetation in cover systems and the results of the research will help to ensure environmentally safe waste rock dumps and improved rehabilitation outcomes at Xstrata sites world wide.

In many regions, slag is used by Xstrata’s operations or sold commercially as substrate for road construction, building aggregate, to make bricks or for landfill purposes. However, in South Africa, slag from chrome mining is classified as a hazardous substance (class 2) and its use for these purposes is prohibited. Xstrata Alloys is currently in discussions with the Department of Environmental Affairs and Tourism (DEAT) to reclassify slag. Slag samples are currently being tested at the Council for Scientific and Industrial Research (CSIR) in South Africa to ensure that acid is not created when the material comes into contact with rain and through toxicity characteristic leaching procedure tests. Based on the results of these tests, a material safety data sheet for each use will be drafted and presented to the DEAT. There is a very high demand in the building industry for this material, presenting us with an opportunity to realise value from a waste product and reduce our environmental footprint.

At George Fisher zinc-lead mine at Mount Isa, tailings are recycled for use in the Pastefill Plant as a partial substitute for concrete for backfilling mined out voids in underground operations. Surface stockpiles of granulated slag, produced from historical smelting operations at Mount Isa, have properties that allow them to replace up to 50% of the cement consumed in backfilling underground voids. Approximately 3,700 tonnes of cement was replaced by slag grinding for underground fill in 2007. Concrete is an energy intensive product to manufacture and reduced cement production in 2007 has resulted in greenhouse gas savings of approximately 1,980 tonnes of CO₂-e together with associated cost savings from lower energy use.