Copper production & environmental impact

 copper solar control facade

 

Key points

• Copper is malleable, ductile, and an extremely good conductor of both heat and electricity.

• A computer contains around 1.5 kg of copper, a typical home about 100 kg and a wind turbine 5 tonnes.

• Copper has low chemical reactivity. In moist air it slowly forms a greenish surface film called patina; this coating protects the metal from further attack.

• Copper is easily alloyed with other metals. Currently, there are around 570 copper alloys listed.

• Brasses and bronzes are probably the most well-known families of copper-base alloys. Brasses are mainly copper and zinc. Bronzes are mainly copper along with alloying elements such as tin, aluminum, silicon or beryllium.

• Useable copper reserves are subject of debate. Some predict 'peak copper' will be reached somewhere 2025-2030; Others claim there is much more available. See below.

• Around 95% of all copper ever mined and smelted has been extracted since 1900.

• Copper’s use averages out at around 140-300 kg per capita in developed countries

• Copper along with oil and gold are among the most traded commodities.

• Copper doesn’t break down in the environment, leading to its accumulation in plants and animals.

• Absorption of some copper into the body is essential for human health.

• Occupational exposure to copper can result in relatively minor conditions

• Acute industrial exposure to copper fumes, dusts or mists can result in chronic copper poisoning.

 

 

How much copper is there left to go?

• Some argue that the industry is rapidly approaching maximum extraction (aka ‘Peak copper’). Whereas, theoretically copper is finite resource and extraction will reach a peak, the timing is subject of debate. Confounding the imminent 'peak copper' argument is the fact that continually discovered reserves combined with increasing efficiency of extraction means that, for now, known and speculated quantities of copper far extend beyond current consumption.

• World production of copper amounts to 12 million tons a year and exploitable reserves are around 300 million tons. About 2 million tons a year are reclaimed by recycling. (source EPA)


growth in copper consumption

World copper production 1900 - 2012

• “We are at a time where putting two or three mega-mines into production does not even keep up with demand of almost 1Mt per year growth “(Gianni Kovacevic

  of Petaquilla Minerals)

• The US Geological Survey estimated that, as of 2013, there remained 3.5 billion metric tons of undiscovered copper resources worldwide in porphyry and sediment-hosted type deposits, two types which currently provide 80% of mined copper production. This was in addition to 2.1 billion metric tons of identified resources. Combined identified and estimated undiscovered copper resources were 5.6 billion metric tons, 306 times the 2013 global production of newly mined copper of 18.3 million metric tons. (Wikipedia)

 

Percentage of known copper reserves by country

 

Copper history

• Copper’s earliest use is recorded in Anatolia in around 7250 BC in the form of coins and decorations. Evidence of copper smelting has been found in Serbia from around 5000 BC – though it is thought that smelting occurred in a variety of locations in Asia and Europe at about the same time.

• Copper tools started to emerge as early as 3500 BC in Israel. Its property of alloying with other metals (particularly tin) was discovered about 500 years later and heralded the Bronze Age, which started in southern Europe between 3000 and 2500 BC.

• Copper has been found used in buildings from an early age. Doors to a temple in Karnak were clad in copper, whilst the earliest examples of copper piping were found in other ancient Egyptian temples and palaces.

• The roof of the Pantheon in Rome was copper-clad in 27BC. Subsequently, the most apparent use of copper up until the present day, has been in the roofing of buildings such as churches, palaces and other prestigious public buildings.

 

Copper Alloys

There are around 570 copper alloys, each with a unique combination of properties, to suit many applications, manufacturing processes and environments.

• Copper + Zinc = Brass

• Copper + Tin = Bronze

• Copper + Nickel = Cupronickel

• Copper + Alumium = Aluminium Bronze

• Copper + Arsenic = Arsenical Copper

• Copper + Tungsten = Copper Tungsten

• Copper + Tin + Zinc = Gunmetal

 

1 Mineral Extraction

 

Common ores

• Usually found in combination with sulphur, iron, carbon and oxygen.

Oxide copper minerals

- malachite

- azurite

- chrysocolla

Sulfide copper minerals

- bornite

- chalcocite

- chalcopyrite

 

Occurrence

• Copper is distributed in many parts of the world

• Copper minerals are divided up into three groups

            - Primary or hypogene minerals found at great depths

            - Oxidised copper minerals commonly formed by copper sulfides exposed to erosion

            - Copper secondary sulfides formed from leaching of sulphides exposed near the earth’s surface

• The most common commercial minerals are:

-  Chalcocite (Cu2S) containing around 80% copper

-  Chalcopyriet (aka copper pyrites) (CuFeS2) containing around 34% copper

 

The top 5 copper-producing countries in 2013 (source USGS)

1 Chile: 5,700,000 tonnes

2 China: 1,650,000 tonnes

3 Peru: 1,300,000 tonnes

4 USA:  1,220,000 tonnes

5 Australia: 990,000 tonnes

 

2 Manufacture of Copper

 

Extraction of copper from minerals

• Involves a series of chemical, physical and electrochemical processes.
• Depending on whether an ore is sulfide or oxide, the process follows one of two routes.

 

Beneficiation

• Beneficiation is the concentration of ore through separation into desirable mineral-the part of the ore that is useable; and gangue (pronounced ‘gang’) – the part of the ore that is commercially worthless.

• Rocks are crushed in a series of crushers.  Sulfide ores are further reduced through a ‘wet grinding’ process that ensures a particle size suitable for the flotation process.

 

copper leaching

Copper leaching

Sulfide ores and froth flotation

Sulfide ores are mixed with water and a surfacant creating a slurry. The slurry, when agitated causes the copper sulfide minerals to float at which point they are skimmed off the surface dried. The dried material is then sent to the smelter.

Oxide ores and leaching

Oxide ores (and certain sulfide ores) are placed onto a leach pad and saturated with weak sulfuric acid solution that dissolves the copper mineral content. The resulting copper-bearing solution is collected and pumped to a solvent extraction plant.

 

Smelting and Extraction

Sulfide Ore

The dried copper concentrates are sent to the smelting operation where it is reduced and melted in several operations. At the end of this smelting process the copper is about 99% pure..

Oxide Ore

The copper-bearing solution is collected and pumped to the extraction plant where it is purified. It progresses through a number of steps that combine an organic solvent or sulfuric acid to the solution until the copper concentration is high enough for effective electro-plating.

 

Refining

Sulfide Ores

After smelting, the 99% copper rich material is poured into molds as "anodes" using a casting wheel and transported to the plating house. In this form, they are ready for the next step, which involves dissolving and re-plating the copper to increase its purity level.

Oxide Ores

The copper-bearing solution, from the solvent extraction operations, is plated into pure copper cathodes using a process called solution exchange electrowinning (SX-EW). Stainless steel blanks are added to the plating tanks to act as cathodes and copper is plated onto them by electro-chemical deposition. It takes about a week before the cathode is ready to be removed from the tank so the copper can be stripped off the blank. The cathodes are now 99.99% pure copper and ready for product manufacturing.

 

( Extraction details provided by the Copper Development Association)

 

Extraction and Beneficiation Wastes and Materials

Waste Rock

Waste rock is typically hauled from the mine site to waste dumps for disposal. Waste rock piles may have high permeability to both air and water. Oxygen and sulfide minerals may be contained in the dump. The quantity and composition of waste rock generated at mines vary greatly by site. This material can be classified as either oxide or sulfide, with varying solubilities, depending on the composition of the ore body. Sulfur-bearing minerals, such as pyrite and pyrrhotite, can oxidize to form sulfuric acid. Factors that influence acid generation by sulfide wastes include: (1) the amount and frequency of precipitation, (2) the design of the disposal unit, and (3) the neutralization potential of the rock. Constituents of concern for waste rock include sulfur-bearing minerals that may generate acid and leach metals contained in the ore body and surrounding rock. (Mining Industry Profile: Copper)

 

Tailings

Tailings are generated during flotation. Tailings are made up of very fine host rock (i.e., gangue) and nonmetallic minerals separated from the values during beneficiation. The physical and chemical nature of tailings varies according to the ore characteristics and the beneficiation techniques used. Tailings are a slurry of fine-grained rock material and process water. Liquid is removed from the tailings slurry in thickeners and the thickened tailings are discharged to the tailings impoundment. Water is usually reclaimed from the thickeners and recirculated to the mill to be used in beneficiation and dust control (Mining Industry Profile: Copper)

 

Spent Ore from Heap, Dump, and Vat Leaching

Spent ore consists of the material remaining in either dump or heap leach piles when leaching ceases. Spent ore from heap, dump, and vat leaching may contain residual lixiviant and other constituents of the ore. Some operations may refer to wastes from vat leaching operations as tailings. (Mining Industry Profile: Copper)

 

Mine water

The quantity of mine water generated at mines varies from site to site. The chemistry of mine water is dependent on the geochemistry of the ore body and the surrounding area. Water exposed to sulfur-bearing minerals in an oxidizing environment, such as an open pit or underground workings, may become acidified. This potential is greatly dependent on site-specific factors.

 

Sludge

Sludge is the semisolid gelatinous materials (i.e., soft mud, slime, slush, or mire) that can accumulate in tanks. These sludges that cannot be easily settled or filtered.

The solvent extraction process specifically generates a "sludge," or, as it is known in the copper industry, "crud" or "gunk." Sludge is periodically removed from the system, and centrifuged or otherwise treated to remove the organics. The aqueous solutions and the solids are disposed of and the organics are returned to the solvent extraction circuit for reuse. Depending on the characteristics of the ore body, sludges may contain base or precious metals in quantities sufficient for recovery.

 

Spent Electrolyte

Spent electrolyte is generated during electrowinning activities. Historically, electrolyte went through a stripping step and was subsequently discharged to a tailings pond. Today, due to economics, this effluent is recycled to reduce capital costs associated with the electrolytic acids used in these operations.

 

Spent Leaching Solution

Barren solution (raffinate) is an acidic aqueous solution that has been stripped of copper but still has some carryover of the organic extraction/diluent used in the solvent extraction operation. The raffinate generated at hydrometallurgical plants is typically stored in ponds and recycled to the dump leaching operation. As a result, it does not become a waste until after the closure of the mine. Following mine closure, spent leaching solutions must be disposed of.

 

3 Energy

Primary copper production is a major activity in the mining sector. It is highly energy-intensive, ranking third in specific energy consumption (SEC) among the five major basic metals (aluminum, copper, iron, lead and zinc) .

 

Open-pitmining                     0.021 MJ/ton             19-25%

Milling                                     0.045           MJ/ton                                     40-52

Smelting                                 0.007 – 0.024            MJ/ton                        8-21

Converting                             0.001 – 0.007            MJ/ton                        1-6

Gas cleaning                           0.007– 0.009 MJ/ton                        8

Electrorefining                      0.007  MJ/ton                                    6

 

Total                                      0.086 - 0.112            MJ/ton                       100

 

 

SOURCE: Charles H. Pitt and Milton E. Wadsworth, An Assessment of Energy Requirements in Proven and New Copper Processes report prepared for the U.S. Department of Energy, contract no EM-78 -S-07.1 743, 1980.

 

4 Recycling & Reuse

• Copper is 100% recyclable without loss of quality

• Copper is the most recycled metal after iron and aluminium

• Around 40% of the demand for copper within Europe is supplied from recycled copper.

• Recycling a tonne of copper uses 20% of the energy that would be used to mine and extract the same copper.

• The copper recycling process has much in common as that to extract it, but requires fewer steps. High-purity copper is melted in a furnace and then reduced; Low-purity copper is refined through electroplating in sulfuric acid.

 

5 The Environmental Impact of Copper

 

Release into the environment

Some examples of how copper may be released into the environment are through copper mining, agriculture and manufacturing activities. Copper may also enter the environment through natural processes, such as volcanic eruptions, windblown dusts, decaying vegetation, and forest fires. Additionally, copper is found in most sewage due to the corrosion of copper plumbing.

Copper released into the environment usually attaches to particles made of organic matter, clay, soil, or sand.

Copper does not break down in the environment. Copper compounds can break down and release free copper into the air, water, and foods.

 

Aquatic life

Elevated levels of copper are toxic in aquatic environments and may adversely affect fish, invertebrates, plants, and amphibians. Acute toxic effects may include mortality of organisms; chronic toxicity can result in reductions in survival, reproduction, and growth.  (EPA, 2008)

 

Human Toxicity

Copper is a metal that occurs naturally in the environment, and also in plants and animals. Low levels of copper are essential for maintaining good health.

High levels of copper can be harmful. Breathing high levels of copper can cause irritation of the nose and throat. Ingesting high levels of copper can cause nausea, vomiting, and diarrhea. Very-high doses of copper can cause damage to the liver and kidneys, and can even cause death. (U.S. Department of Health and Human Services, 2004

Cancer: There is no evidence that copper is carcinogenic

Alzheimer’s disease: Elevated free copper levels exist in Alzheimer’s disease  (Brewer GJ, Clin Neurophysiol. 2010)

 

Copper, Chromium & Arsenic (CCA) wood preservative treatment

In Europe, Directive 2003/2/EC restricts the marketing and use of arsenic, including CCA wood treatment. CCA treated wood is not permitted to be used in residential or domestic constructions. It is permitted for use in various industrial and public works, such as bridges, highway safety fencing, electric power transmission and telecommunications poles. In the UK waste timber treated with CCA was classified in July 2012 as hazardous waste by the Department for the Environment, Food and Rural Affairs (Wikipedia)

CCA2 wood preservatives are mixtures of the salts or oxides of the elements arsenic, chromium and copper. They are used for vacuum-pressure treatment of timber. CCA is intended to protect wood against pests such as decay fungi, wood boring insects or marine borers that can threaten the integrity of wood products. Copper is used to control fungi and marine borers, arsenic to control insects and some copper-resistant fungi, and chromium to fix the copper and arsenic in the wood. (Report on Copper, Chromium and Arsenic (CCA) Treated Timber by Deborah Read, 2003)

 

6 Copper mining, Production Wastes and the Environment

 

As with other forms of mining, the control of operations varies considerably from country to country. Sadly, third world mining operations continue to present varying degrees of hazard to the health and well being of those working in and living around the mines.

Common ailments include respiratory illnesses such as asthma and tuberculosis as a result of inhalation of the silica dust particles resulting from the mining and processing of copper.  Miners in particular suffer from silicosis or pneumoconiosis.

The smelting process can also create pollution. Smelting often produces large volumes of low concentration sulfur dioxide that is not worth further processing to remove the sulfur. Acid rain resulting from the combination of rain and SO2 can cause damage to crops, trees and buildings for many miles down-wind.

Leaching solutions are typically regenerated and reused continuously for extended periods. On occasion, however, such during temporary or permanent closure, the solutions are disposed as wastes via land application or other means.

 

Land degradation

Copper mine in Canada

Deforestation

Deforestation for copper in Papua New Guinea

Animals 

Habitat destruction is one of the main issues associated with mining activity. Large areas of natural habitat are destroyed during mine construction and exploitation, forcing animals to leave the site.

Animals can be poisoned directly by mine products and residuals. Bioaccumulation in the plants or the smaller organisms they eat can also lead to poisoning : horses, goats and sheep are exposed in certain areas to potentially toxic concentration of copper and lead in grass. They are fewer number of ants species in soil containing high copper levels, in the vicinity of a copper mine. If fewer ants are found, chances are great that other organisms leaving in the surrounding landscape are strongly affected as well by this high copper levels, since ants are a good environmental control : they live directly in the soil and are thus pretty sensible to environmental disruption (Wikipedia)

 

Ground water pollution

Water in mines can contain heavy metals such as lead and cadmium which can leak into the local groundwater.

Surface water pollution

acid mine drainage 1

Acid mine drainage invades a water course

acid mine drainage pond

Acid mine drainage pond in Portugal

Acid mine drainage

‘Acid rock drainage occurs naturally within some environments as part of the rock weathering process but is exacerbated by large-scale earth disturbances characteristic of mining and other large construction activities, usually within rocks containing an abundance of sulfide minerals. The most commonly mined ore of copper, chalcopyrite, is itself a copper-iron-sulfide and occurs with a range of other sulfides. Thus, copper minesare often major culprits of acid mine drainage.’

‘When the pH of acid mine drainage is raised past 3, either through contact with fresh water or neutralising minerals, previously soluble iron(III) ions precipitate as iron(III) hydroxide, a yellow-orange solid colloquially known as yellow boy. Other types of iron precipitates are possible, including iron oxides and oxyhydroxides. All these precipitates can discolor water and smother plant and animal life on the streambed, disrupting stream ecosystems’ (Wikipedia)

 

 

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