Environment | Waste and tailings management
All operations reuse, recycle or properly dispose of waste generated, minimising waste sent to landfill and maximising recycling and reuse opportunities, including within the operation, for example using waste rock for backfill.
Tailings dam at Minera Alumbrera, Argentina
Xstrata’s operations generated 959 million tonnes of waste in 2006 compared to 638 million tonnes in 2005. Every managed operation has an active waste management plan to reduce the production of waste at the source and optimise the reuse and recycling of wastes. Waste management practices at the former Falconbridge operations will be consolidated into the formal waste management plans by the end of 2007. Waste from mining operations consists primarily of overburden rock, stripped from open cut mines to expose ore or coal. The development of new mines in 2006 increased the amount of overburden removed, which accounted for 98% of the total year-on-year increase in waste produced.
Tailings, coarse reject and slag accounted for 99.7 million tonnes of waste in 2006, of which 3.6 million tonnes were recycled. Hazardous waste, as defined by the Basel Convention 1992, (including hydrocarbons, heavy metal contaminated sludges, medical waste and vehicle batteries) rose to 1.4 million tonnes in 2006, up from 1 million tonnes the previous year. Over 54% or 767,000 tonnes of hazardous waste generated were reused or recycled, an increase of 495,000 tonnes from 2005, and 4,800 kilolitres of waste oil were reused in blasting or recycled through off-site facilities. A small proportion of waste (18,900 tonnes) was disposed of in off-site regulated facilities and the remainder (630,000 tonnes) was disposed of in regulated on-site facilities.
General waste to landfill increased 11% on 2005, primarily due to increased waste from Xstrata Alloys. This was due to the commissioning of the Lion ferrochrome smelter, rehabilitation of the closed Vantech site and Thorncliffe mine, and increased production at Helena mine and the Mototolo platinum joint venture. Waste disposed of in landfills also increased at Las Bambas, due to the construction of an onsite facility, allowing previously stockpiled waste to be disposed.
Acid rock drainage is a particular issue for water management and overburden and tailings disposal facilities or emplacements. When exposed to water and air, potentially acid-forming rock (containing sulphide-bearing material) may form sulphuric acid which can leach heavy metals such as lead, zinc, cadmium and mercury from the ore enabling it to enter ground and surface water. We manage this risk, identified at Alumbrera mine in Argentina and Collinsville coal mine in Queensland, through capping waste rock to prevent water infiltration and ensure its integrity through regular monitoring.
Other strategies include submerging waste in water to prevent the formation of acid through contact with air, in place at a number of former Falconbridge operations. Where waste has been submerged in wetland, this can also reverse the process of acid formation and remove metals and acid from solution.
A particular issue for the zinc industry is the management of jarosite waste, created in the smelting process. Jarosite is rich in iron and is defined as a hazardous waste product. At most zinc smelters, jarosite is disposed of in tailings ponds, which require ongoing close monitoring and management to minimise environmental impact. Xstrata Zinc’s San Juan de Nieva smelter and the former Falconbridge CEZinc operations both use a patented technology to convert jarosite into ‘jarofix’ – an inert, solid material which can be reused as aggregate or infill. In Spain, Xstrata Zinc has used jarofix from its operations to rehabilitate a government-owned disused quarry in partnership with the municipal authorities.
Field technicians Ronnie and Doning Puli monitoring water levels along the Lawit river, Tampakan copper project, Philippines