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rosario efficient environmental gold mine mineral processing production line price

gold mining processing, gold washing plant, gold processing, gold mining equipment, gold mining recovery

gold mining processing, gold washing plant, gold processing, gold mining equipment, gold mining recovery

With the rising gold prices in recent years, it further stimulated the rapid development of gold industry. As the exhaustion of high-grade gold ore, researching on middle-low grade and refractory gold ore and strengthen the traditional gold mining process undoubtedly have become the main trend in global gold beneficiation industry.

Under the new situation, Xinhai Mining has paid long-term attention to gold recovery process, technology and equipment research & development. After 20 years of continuous studies, according to the different types of gold ore characteristics and user requirements, Xinhai has formed three gold beneficiation systems:

PrincipleAccording to the difference of gold ore surface in chemical and physical properties, after the flotation reagents, the gold mine is attached to the bubbles selectively, achieving the separation

Xinhai has make Class B design Qualification, set up mine design institute and mineral processing research institute, more than 200 professionals provide the technical support service for gold processing plant, Since its establishment 20 years, Xinhai has been committed to gold processing service the development and innovation of equipment, and has formed the complete gold processing system. Xinhai concentrates on providing the Turnkey Solution for Mineral Processing Plant that is research and design- complete equipment manufacturing and procurement- commissioning and delivery, striving for building the international leading enterprise in gold processing plant industry.

"Create a global brand, based on global gold markets " has been one of the strategic thought of Xinhai, depending on its professional gold processing service, Xinhai has got the EU certification, and ISO9001:2008 quality management system certification as early as in 2008, Xinhai is classified as the assured brand with advanced products and standard quality!

Xinhai currently has 112 patents technologies, the gold dressing plant projects spread among China, Southeast Asia, South America, Africa, Iran, Russia, Mongolia, North Korea and other places, and Xinhai has established offices around the world.

energy efficiency energy intensity in copper and gold mining
 - mineral processing

energy efficiency energy intensity in copper and gold mining - mineral processing

Summary: Mines are faced with numerous challenges, such as falling raw material prices, declining metal grades in the ores and higher energy prices. Especially because ore processing is particularly energy-intensive, the industry is again focusing on the saving of energy. This report shows what are the key energy saving considerations in the copper and gold mining sectors.

In recent years, many mining companies have been able to reduce their specific energy requirements in the ore processing of base metals, gold, silver and platinum group metals, thereby improving their competitiveness. The reasons are complex and involve, for example, the closure of unprofitable mines, technological improvements such as modern grinding processes or improved energy management. But there are also opposing tendencies. For example, the electricity demand for Chiles copper production is expected to increase by 53.5% between 2015 and 2026, although the planned increase in copper production over that period is only 7.5%. An analysis of the reasons for this reveals that the contributing factors are not only the type of ore dressing process, but also the declining ore head grades and the supply of water to the mines.

After iron ore, the leading places in the global sales ranking for mineral raw materials are occupied by copper and gold. Despite an interim sales crisis, the demand for copper and gold is unbroken. Fig.1 shows the development of copper mine production over the last 10 years. Production has risen at average annual growth rates (CAGR) of 3.0% to 20.2milliont (Mt). The annual growth fluctuations were between 8.9% and -0.2%. In the case of gold production, the situation is similar (Fig.2). The CAGR of gold production was 3.6% in the last 10years. In 2016, 3260tonnes of gold were produced, after 2350tonnes in 2007 and a relatively small slump in gold production during the financial crisis of 2008.

In principle, it is clear that higher productions can only be realized with a greater energy expenditure. This technical paper will particularly consider the electrical energy input in more detail. The electrical energy input and the fuel requirements are roughly the same in the gold and copper production sectors. Of particular interest is the specific energy input per ton of recovered copper or gold. The relevant data are provided primarily by the mining companies. To a lesser extent, data are available from individual mining associations. Further data sources are energy audits and the project descriptions of consulting companies for mine expansions and new copper and gold mining projects. The situation is fundamentally similar in the case of other mineral raw materials.

At present, copper production is stagnating in Chile (Fig.3). In 2013, a peak mining output of 5,776Mt was reached, while in 2016 the production figure was 5.553Mt, corresponding to a share of 27.5% in the worldwide mining output of 20.2Mt. Starting from 2015, the Chilean Copper Commission (Cochilco) is planning to increase the annual mining output by 0.5% in order to achieve about 6.2Mt by 2026. In 2015, Cochilco published a study on the future electricity demand of the Chilean copper mining industry. This study covers all current and future projects. Fig.4 shows how the future electricity demand is forecast to change from 22.1terawatt hours (TWh) in 2015 to 34.1TWh. The various consumers are also shown.

The largest consumer is the conventional ore dressing process with a concentrator as used for sulfidic ores, consisting of crushing, grinding and subsequent flotation. This is followed by processes for oxidic copper ores with heap leaching, solvent extraction and electrowinning (LS-SX-EW). The share of ore production by concentrator processes will increase from 72% in 2015 to 89% in 2026. Correspondingly, the electricity demand for the concentrator processes will increase by 69% from 13.2TWh to 22.3TWh in 2026 while that of the LS-SX-EW processes will decrease by 40% from 4.5TWh to 2.7TWh. Also interesting is the increase of almost 460% for seawater desalination/pumping. The increases in mining (+38%), refining (+30%) and services (+26%) within the framework of the planned additional mining output are somewhat more moderate, but clearly exceed the planned production growth.

For many years the copper ore grades have been declining as exploitation of the higher-grade deposits progresses. On a worldwide scale, the mined ores contain an average of less than 1.0%Cu (Fig.5). In Chile, the copper grade of the ores is significantly lower than even that. In 2015, the average copper grade in the ores was only 0.65%. For the year 2026, it is expected that the ores in Chile will have copper grades of less than 0.5%. This will naturally increase the amount of run-of-mine ore that has to be processed. In international comparison, the Chilean copper ore mining industry is steadily deteriorating. While about 35% of the worldwide copper mine output had higher copper grades than the product of Chilean mines in 2010, this figure will rise to 43% in 2020.

Fig.6 shows the development of the electricity demand for concentrator and LS-SX-EW processes. While in the case of concentrator processes the specific electricity demand per t of material has increased by 4% from 79.3MJ/t to 82.5MJ/t, the power demand for the LS-SX-EW processes has decreased by almost 23% from 43.2 MJ/t to 33.3 MJ/t. The figure also shows that the power demand per t of material is significantly lower in the case of LS-SX-EW processes. However, in the concentrator processes this disadvantage is compensated by higher yields. As depicted in Fig.7, the specific electricity demand per ton of produced copper is currently about 12.0GJ/t of copper (Cu) in both the concentrator and the LS-SX-EW processes. However, in the case of plants equipped with concentrators, this value has increased at a faster overall rate over the past 10 years.

The mineralogical properties of the ores are increasingly influencing the required processing methods. In the production of copper, sulfidic ores are enriched into concentrates by grinding and flotation, followed by pyrometallurgical processes for the production of pure copper. Oxidic ores are treated with sulfuric acid in a heap leaching process after the grinding stage and are subsequently processed into cathode copper by SX/EW methods. On a worldwide scale, concentrate production dominates with a market share of about 85%. In the production of gold, the cyanide leaching or CIL (carbon-in-leach) processes have gained a market share of almost 90%. For the worldwide energy demand of these processes only estimated figures are currently available.

Fig.8 presents a simplified overview of the energy input for the different processes and process stages in the production of copper based on a copper ore grade of 0.5%. The energy inputs are expressed in kJ/t of material and kJ/lb (pound of copper). The so-called run-of-mine (ROM) leaching followed by a SX/EW process has the lowest energy demand, while the process with SAG/ball mills and subsequent flotation and pyrometallurgy has the highest energy demand. For each respective process, various possibilities for reducing the energy input are shown. Fig.9 additionally shows how the energy demand for the different processes varies depending on the copper grade of the ore. Correspondingly, the respective theoretical energy inputs range from less than 10MJ/lbCu up to more than 80MJ/lbCu.

The greatest energy input in copper and gold production is required for the comminution and grinding processes. The energy audit of mainly Australian copper and gold mines shows that 36% of the overall energy consumption is attributable to comminution [1]. Previous studies had shown values between 18% and 50%. Fig.10 shows that the specific comminution energy is a function of the copper grade of the ore, but also a function of the throughput of the mine and thus of the technology employed. Therefore, on the one hand, the declining copper grades require higher specific energies of more than 4MWh/tCu, while on the other hand, so-called scale effects occur in the case of larger mines and partially compensate for poorer copper grades, making specific comminution energies of less than 1MWh/tCu possible.

The classical grinding process employing SAG and ball mills (Fig.11) is progressively losing ground [2,3] against high-pressure grinding rolls (HPGR), which are increasingly being used for the grinding of both copper and gold ore. The first noteworthy HPGR application was at the Cyprus Sierrita copper mine in the USA in 1995[4], even though the extremely abrasive ore prevented the achievement of economic grinding roll service lives. This changed with the Cerro Verde project, a copper-molybdenum mine in Peru in 2006 and later in 2011, when the SAG mills were completely replaced by 4HPGRs, each with a capacity of 2100t/h[5]. In 2014, the largest HPGR that has been implemented so far was installed in Freeport-McMoRans Morenci copper mine in Arizona/USA, achieving throughputs of up to 5400t/h (Fig.12). Pilot studies had demonstrated that the HPGR can achieve energy savings of 13.5% compared to grinding processes employing SAG mills. By 2014, more than 35HPGR had already been put into operation in the copper grinding industry.

A further important area for power consumption reductions is the after-grinding of products from the flotation stage [3, 6, 7]. Here, the fineness requirements are in the broad range of 2 to 75m, the feed particle sizes are smaller than 200m and the throughput rates are usually below 100 t/h, so that due to their high energy requirements ball mills do not represent a reasonable solution in this range of fineness. With the IsaMill horizontal stirred media mill (Fig.13), it is possible to achieve energy savings of 20-30% compared to conventional ball mills[10] in various applications. High energy savings are also achieved with vertical flow stirred media mills (Fig.14). Due to their relatively low energy requirements, both these mill types are also being increasingly used for secondary and tertiary grinding as replacements for ball mills [8, 9, 10].

The decreasing mineral grades in the ores have also led to increased throughput rates in the flotation stage (Fig.15). In order to accommodate higher flotation volumes, plant manufacturers have undertaken a scale-up of the flotation cells. So-called supercells are now available with volumes of up to 600m3[11]. It is of particular interest in this context that the larger cells provide an improved hydrodynamic performance compared to small cells using conventional technology, a factor which reduces energy costs by up to 40%. However, the amount of savings thus achieved for the entire processing line must be put into perspective, since the flotation stage usually accounts for less than 10% of the energy costs for the grinding stage.

Two other areas that are also among the notable energy consumers are the mechanical handling of the material and the pump conveyance of liquids and slurries. Mechanical conveyor systems (Fig.16) are indispensable for feeding the processing equipment. In addition, there are various mechanical conveyors in the mine itself. The consumed electrical energy amounts to less than 5% of that of the total ore processing line. The energy consumption situation for pumping is somewhat different. In particular, when seawater desalination plants and long-distance water supply are included, the electrical energy consumption can rise to over 15% of the total. High energy losses occur, in particular, when slurry pumps suffer premature wear. This problem can be reduced by special designs, such as wear rings in the pump.

Australian scientists have evaluated the energy consumption of a total of 68 copper and gold mines covering all such mines in Australia as well as 24% of the worlds copper mines and 15% of the worlds gold mines[1]. While complete data for SAG and ball mills were available, only partial data were obtained for crushers and post-grinding, so that some results were estimated. Fig.17 presents the results for the specific comminution energy for the grinding of copper ore. The average consumption is 1.223MWh/t Cu. On the abscissa, the cumulative copper production quantity of the analyzed mines is shown. A corresponding graph also exists for the analyzed gold mines (Fig.18). This represents mines with a production of 11million ounces(Moz). The average specific comminution energy is 353kWh/oz.

Fig.19 depicts the specific energy consumption of the companies Teck Resources and Barrick Gold in the copper ore processing sector. The specific data are shown in GJ/tCu and thus provide a measure of the energy intensity of the copper production process. In the case of Teck Resources, the data represent 4 mines in Canada, Chile and Peru with a total production volume of 324kt in 2016. Barrick Gold has only the Lumwana copper mine in Zambia with a most recent production volume of 123kt. With both companies there is a trend towards lower energy intensities over the past three years. The energy intensity of 24.5GJ/tCu at the Lumwana mine is significantly lower than Tecks average value of 43.7GJ/tCu in 2016.

Fig.20 shows the energy intensity for the company Gold Fields. Gold Fields operates 3gold mines in South Africa, Australia and Ghana as well as a copper/gold mine in Peru. In 2016, the company produced 2,15Moz of gold (calculated as gold equivalent), which was almost equal to the previous years figure of 2.16Moz. For the 2016 gold production quantity an energy input of 0.063GJ/t of ore material was necessary, after the figure of 0.072GJ/t in 2014. The energy intensity for gold production was 5.27GJ/oz in 2016 after 4.56GJ/oz in 2014. This means that the energy intensity increased over the two years with a CAGR of 7.5%. Such an increase can only be explained by a sharp decline in the grade of gold in the ore.

Fig.21 shows the energy intensity of the company Barrick Gold for the gold production of selected mines. In total, Barrick Gold owns 9gold mines in Argentina (Veladero), Canada, the Dominican Republic, Peru and the USA (Cortez, Goldstrike, Turquoise Ridge and Golden Sunlight). In 2016, the company produced a total of 5.52Moz of gold, making Barrick the no. 1 worldwide, ahead of Newmont Mining and AngloGold Ashanti. The average energy intensity of the 9 goldmines decreased from 5.33GJ/oz in 2014 to 5.11GK/oz in 2016. However, the 3depicted mines have significantly different energy intensity levels and graph bar sequences. Goldstrike is among the Barrick Gold mines with the highest energy intensity, although its energy demand has been reduced. Turquoise Ridge has the lowest energy demand with minor fluctuations in recent years. Veladoros energy demand showed an upward trend.

Lower metal grades in the ores force mine operators to look for solutions in order to further reduce the energy demand of their processing lines. If no efforts were made, the energy demand would rise significantly. Mining companies are increasingly carrying out energy audits in order to identify the largest energy consumers and to see how plant performance can be improved. The main focus is on the grinding process, as it is the largest energy consumer. For new projects, more energy-efficient grinding processes should be considered, employing HPGR instead of SAG mills and vertical and horizontal stirred media mills instead of ball mills. An important role in energy demand reduction is played by the optimization of grinding circuits[13].

In the case of performance enhancements and Brownfield projects, the focus is on adding machines to existing circuits or replacing machines with higher-performance equipment. HPGR mills and stirred media mills also play an important role here as a simple means of achieving higher throughputs with an additional grinding circuit or other machine combinations. This also concerns the post-grinding after flotation and the replacement of existing flotation cells with new, higher-performance and larger cells in order to achieve longer residence times and better yields. In the recent past, ore selection by sensor-based processes has also been intensively discussed. In any case, mine operators today have numerous options for energy saving while simultaneously reducing cash costs.

The top ore layer of an open pit copper mine is easily processed using heap leach in tandem with solvent extraction and electrowinning to produce copper cathodes. The copper mineral most predominate...

ABB was recently contacted to supply the drive system for a new semi-autogenous grinding (SAG) mill at Neves Corvo/Portugal. The contract was awarded in June 2011. Neves Corvo is an underground mine,...

company profile apex mining co. inc

company profile apex mining co. inc

Apex Mining Co., Inc. (the Company) was incorporated and registered with the Philippine Securities and Exchange Commission on February 26, 1970 primarily to carry on the business of mining, milling, concentrating, converting, smelting, treating, preparing for market, manufacturing, buying, selling, exchanging and otherwise producing and dealing in gold, silver, copper, lead, zinc brass, iron, steel and all kinds of ores, metals and minerals. The Company listed its shares in the Philippine Stock Exchange on March 7, 1974 and attained the status of being a public company under the symbol APX.

On October 10 2014, the Company acquired 100% ownership over Monte Oro Resources & Energy, Inc. (MORE) which has mining and non-mining business interests. MOREs mining interests in the Philippines consist of 100% ownership over Paracale Gold Ltd. which, in turn, fully owns Coral Resources Philippines, Inc. and 40% of Bulawan Mineral Resources Corporation, both located in the Municipality of Jose Panganiban, Camarines Norte. MORE has mining interests in other countries consisting of: (a) 100% shareholding in Minas de Oro Mongol LLC (a Mongolian company) which owns 51% equity in Erdenejas LLC, a joint venture company holding a mining license in Khar At Uul in Mongolia; (b) 90% shareholding in Monte Oro Mining Company Ltd., which is engaged in mining exploration in Sierra Leone, and in MORE Minerals SL which is engaged in artisinal mining and gold trading in Sierra Leone; and (c) 3.92% participation in National Prosperity Gold Production Group Ltd. which holds mining claims and license from the government of Myanmar to develop and operate the gold mine located at Moe di-Moe mi Region, Township, Mandalay Division, Myanmar, known as the Maudi Taung Gold Mine. MORES non-mining businesses consist of a 52% ownership over International Cleanvironment Systems, Inc., a company engaged in solid waste management, and a 30% participating interest in Service Contract No. 72 for natural gas in the Sampaguita gas field offshore northwest of Palawan in the West Philippine Sea.

Itogon-Suyoc Resources, Inc. (ISRI) is a 100%-owned subsidiary acquired by the Company in June 2015.. ISRI is the assignee-company in 2002 of the mining assets of the former Itogon-Suyoc Mines, Inc. (ISMI), which consisted of the Sangilo Mine in Itogon and the Suyoc Mine in Makayan, both located in Benguet Province, and the Benit Claim in Labo, Camarines Norte.

Both Sangilo and Suyoc mines have long history of mining operations before and after the Second World War. Post-war operations from 1951 to 1996 recorded combined production of 1,285,242 ounces of gold and 728,063 ounces of silver from 8.2 million tonnes of ore mined, which was quite remarkable considering the less efficient mining and processing methods then as compared to present practices.

A two-stage development program for the Sangilo mine is underway. The first stage commenced in October 2015 is for the construction of a 400-tonnes per day plant capacity with interim phases to reach at 75 tonnes per day while underground development is being pushed through in fresh and old headings. Incidental production to 2016 accounted for 1,547 ounces of gold valued at P P92.1 million. The second stage plan is a separate plant at 1,500 tonnes per day which will bring the mines total installed capacity to 1,900 tonnes per day at the estimated total investment cost of $68.8 million..

The mine is ISO 14001:2015 certified for environmental management system granted by TUV Rheinland in April 2017. The scope of the certification is for exploration, mining and mineral processing, valid until 2020.

The plan for the Suyoc mine is for a 300 tonnes per day operation, to commence plant construction and mine development work after the reserve validation of the mine now in progress is completed. Investment cost for the Suyoc mine is estimated to be $36.8 million.

The mine is ISO 14001:2015 certified for environmental management system granted by TUV Rheinland in April 2017. The scope of the certification is for mining exploration and project development activities valid until 2020.

gold processing 101 - mining magazine

gold processing 101 - mining magazine

Amidst the general fall in metal prices over the last few years, the gold price has remained comparatively stable in the US$1,000-1,250/oz range. Gold bulls were disappointed that the price did not break through the $2,000/oz ceiling; nevertheless the current stable price run has helped to maintain a strong interest in gold projects.

The second is the sustained, and dare I say sustainable, use of cyanide for gold leaching in the last 100 years or more in a world of increasing environmental concerns and general aversion to the use of toxic chemical like cyanide. Alternatives to cyanide are not the subject of this article, but it is suffice to say that recent applications of alternatives to cyanide, e.g. thiosulfate at Goldstrike Nevada, have been driven by technical rather than environmental imperatives. In the case of Goldstrike, this was a double-refractory ore combining sulphide-occluded gold with preg-robbing carbonaceous material that rendered the ore unsuitable for conventional cyanide leaching and carbon adsorption.

In most cases, gold processing with cyanide leaching, usually with carbon adsorption, is still the core technology and the critical thing is understanding the mineralogy in order to optimise flowsheet selection and cost drivers, and get the best out of the process.

Traditionally, the process selection choice was between a conventional, well-tried, three-stage crushing circuit followed by ball milling, or single-stage crushing followed by a semi-autogenous (SAG) mill and ball mill. The latter is preferred for wet sticky ores to minimise transfer point chute blockages, and can offer savings in both capital costs and long-term operating and maintenance costs. However, the SAG route is more power-intensive and, for very hard ores, comes with some process risk in predicting performance.

Now that initial wear issues have largely been overcome, they offer significant advantages over a SAG mill route where power costs are high and the ore is very hard. They can be attractive too in a heap leach where the micro-cracking induced by the high pressure has been demonstrated in many cases to improve heap leach recovery.

The hashing stage (corresponding to metal extraction and recovery stages) is a little more complex for gold ores, as the optimal process flowsheet selection choice is heavily dependent on a good understanding of two fundamental geometallurgical parameters, the gold mineralogical associations, and the gold particle size and liberation characteristics. These are summarised in Table 2, where the processing options that correspond to the various combinations of mineral associations and liberation are shown along with some examples.

This is common in tropical environments (e.g. West Africa) and typically oxidises gold-bearing sulphides down to 50-100m, transforming commonly refractory gold in sulphides to free-milling gold, behaving in a similar fashion to gold associated with quartz.

Refractory ores are typically treated by flotation and the resulting flotation concentrate may be sold directly to a smelter (common for example in China) or subjected to downstream processing by pressure oxidation or bio-leach.

An ore containing 1% sulphur will produce a mass pull of approximately 5% by weight to a bulk flotation concentrate where recovery is the key driver. If this ore also contains 1g/t Au (for GSR =1), and 90% recovery to concentrate is achieved, then 0.90g will be recovered and with a concentration ratio of 20 (5% to concentrate) this corresponds to 18g/t Au in concentrate.

Both smelter treatment charges and oxidation or bio-leach costs are at least $200/t of concentrate and payables/recovery in the 90% range, so a minimum GSR for effective downstream processing is around 0.5. Clearly this is a function of gold price, but in the current gold price and cost environment, a good rule of thumb is that a minimum GSR of 0.5 is required for downstream processing of a gold-bearing concentrate.

A lower GSR can be tolerated if the flotation concentrate is amenable to direct cyanide leaching without the costly oxidation stage to release the gold from the sulphides. And on-site dor production avoids the off-site costs of transport and smelter charges, but usually with lower recovery (flotation recovery then oxidation-leach recovery) so a trade-off analysis is required.

Smelters typically pay >95% (Au) and 90% (Ag) in copper and lead concentrates, but will only pay 60-70% (maximum, depending on degree of Pb/Zn smelter integration) for gold and silver in zinc concentrates.

It can be seen that the key cost elements are: power, cyanide and grinding steel plus, for refractory ores, the costs associated with pressure oxidation or bio-leaching. It should also be noted that, where cyanide destruction is required (increasingly the norm), then cyanide detox unit costs are usually of a similar order of magnitude to the cyanide unit cost.

In summary, and of particular relevance to project screening, an early appreciation of gold mineralogical associations and liberation can provide considerable insight into metallurgical process flowsheet selection and processing costs.

Copyright 2000-2021 Aspermont Media Ltd. All rights reserved. Aspermont Media is a company registered in England and Wales. Company No. 08096447. VAT No. 136738101. Aspermont Media, WeWork, 1 Poultry, London, England, EC2R 8EJ.

greenhouse gas emissions and production cost footprints in australian gold mines - sciencedirect

greenhouse gas emissions and production cost footprints in australian gold mines - sciencedirect

Significant relationships between gold grade and GHG emissions intensity per ounce.Differences in GHG emissions intensity and production costs due to gold ore source.GHG Emissions and production cost footprints differentiated by gold ore source.Forecast declining gold grades will lead to higher GHG emissions intensities.Significant opportunities exist to reduce GHG emissions at Australian gold mines.

Australia has a globally significant gold mining sector for which both greenhouse gas (GHG) emissions data and production cost data are often available on an individual mine basis. Establishing relationships between GHG emissions and production costs has the potential to shape the future of the gold industry in Australia through greater focus upon cleaner, efficient production. GHG emissions data from Australian gold mines reveal consistent, significant relationships between gold grade and GHG emissions intensity per ounce. Higher gold grades are associated with lower GHG emission intensity per ounce. Differences in both emissions intensity and gold grades exist between open pit mines, underground mines and those operations which source ore from both open pit and underground. Open pit gold mines have the highest GHG emissions intensity but lowest costs. Underground mines have the lowest GHG emissions intensity but costs that are above open pit mines. Australian gold mines exhibit declining gold grades that are predicted to continue over the coming decade. These projected lower gold grades will lead to higher GHG emissions intensities in the absence of other GHG abatement interventions. Significant opportunities exist, to materially reduce GHG emissions at Australian gold mines with interventions underway. Broader adoption of solar and wind energy, changing how underground mines are cooled and the introduction of electric vehicles and mining fleet, especially in underground mines, are key impact areas.

using life cycle assessment to evaluate some environmental impacts of gold production - sciencedirect

using life cycle assessment to evaluate some environmental impacts of gold production - sciencedirect

The environmental profile of gold production with regards to embodied energy, greenhouse gas emissions, embodied water and solid waste burden has been assessed using life cycle assessment methodology. Both refractory and non-refractory ores were considered, with cyanidation extraction followed by carbon in pulp (CIP) recovery assumed for non-refractory ore processing. Flotation and pressure oxidation were included prior to cyanidation for processing refractory ores. For a base case ore grade of 3.5g Au/t ore, the life cycle-based environmental footprint of gold production was estimated to be approximately 200,000GJ/t Au, 18,000t CO2e/t Au, 260,000t water/t Au and 1,270,000t waste solids/t Au for non-refractory ore. The embodied energy and greenhouse gas footprints were approximately 50% higher with refractory ore due to the additional material and energy inputs and gold and silver losses associated with the additional processing steps required with this ore. The solid waste burden was based on an assumed strip ratio of 3t waste rock/t ore, but this ratio varies considerably between mines, significantly influencing the estimated value of this impact. The environmental footprint of gold production (per tonne of gold produced) was shown to be several orders of magnitude greater than that for a number of other metals, largely due to the low grades of ore used for the production of gold compared to other metals.

The mining and comminution stages made the greatest contribution to the greenhouse gas footprint of gold production, with electricity being the major factor, and being responsible for just over half of the greenhouse gas footprint. This result emphasises the need to focus on these stages in any endeavours to reduce the embodied energy and greenhouse gas footprints of gold production. However, the significance of the contribution of the mining and comminution stages to the environmental footprint also means that falling gold ore grades will have a major impact on the environmental profile, and this issue is examined in the paper. Some technological developments in gold ore processing that have the potential to reduce the environmental footprint of gold production are also discussed.

Life cycle assessment used to assess environmental footprint of gold production. Mining and mineral processing stages make greatest contribution to footprint. Declining ore grades will significantly increase environmental footprint. Efforts to reduce footprint should focus on mining and milling stages. Technology developments offer opportunities to reduce environmental footprint.

under the microscope: the true costs of gold production

under the microscope: the true costs of gold production

Hass McCook is a chartered engineer and freshly minted Oxford MBA. He has been researching bitcoin over the past several months and recently joined the Lifeboat Foundations New Money Systems advisory board.

This article is the second in a series on bitcoins sustainability.Having previously examined the cost of bitcoin mining, here McCook seeks to quantify theeconomic and environmental factors involved in mining gold.

As the data below indicates, 52% of all gold ever mined is used for jewellery and palatial adornments. In terms of protection, central banks hold 18% of the worlds gold supply and other investors hold 16% (Hewitt, 2008).

However, the metal also has practical applications, with 10% of yearly demand coming from industry (World Gold Council, 2012). Almost 12% of the worlds supply of gold is contained within technological products, and is lost forever unless recycled which has its own costs attached to it.

Gold is valuable is due to its intrinsic properties: it is highly durable, malleable and never loses its lustre. Most importantly, it is scarce, and becomes increasingly more difficult and expensive to mine so it is safe from inflation.

It is for these reasons, as well as its applications for industry, that the metal has demand, and by extension, value.The following paragraphs seek to quantify the lifecycle of gold, as well its economic, environmental and social costs.

Relative labour costs are also increasing dramatically, which could be a large driver in the metals future mining cost. As most of the energy used in mining comes from non-renewablefossil fuels like diesel, there isnt much hope for reducing its carbon footprint in the near future.

As can be seen from the graphic below (Minerals Council of Australia, 2014) the mining of gold is an intensive process, and the lifecycle of a mine is typically quite long and varied (upwards of 20 years).

Mine construction provides the necessary infrastructure to allow for a productive mine; this includes bulk earthworks and the construction of roads and facilities. It can generally take several years to complete.

Rehabilitation involves returning the land as close to its pre-mining condition as possible to allow plant and animal life to flourish, or the original owner to use it as they please. Although these activities have both impacts and costs associated with them, these pale in comparison to production itself.

Figure 4 shows the process of extracting gold from the ground.Whilst we will not discuss the activities involved in the process chain, you will notice that large volumes of rock, water, and cyanide are used to produce gold.

There is a plethora of peer-reviewed scientific literature and industry-based data on the economic, environmental and social impacts of these processes, and they will be discussed in the following sections of this report.

In early February 2014, the World Gold Council noted that the average industry cost of production is $1,200/ounce, with 30% of the industry becoming unprofitable if the gold price drops below that level (Rudarakanchana, 2014).

Recycling is significantly less energy intensive than mining gold, however, definitive data does not exist as to the exact energy savings (US EPA, 2012). As an indication of how much energy is saved recycling, here are statistics for other metals and products (The Economist, 2007):

The most consistent approach to converting GJ of energy to tCO2 would be to use a weighted average of tCO2 produced by the source of primary energy supply. This is calculated in the table below (Moomaw, et al., 2011), (Sovacool, 2008), (US Department of Energy, 2013):

1GJ is equivalent to 277.77 kWh or 0.2777 MWh, therefore, 25 million GJ results in 4 million tonnes of CO2 produced at 600g/kWh.To sense-check these results, mined gold results in 54 million tonnes of CO2.

Therefore, it can be concluded that carbon emissions are cut by90% if gold is recycled, so long as the above assumptions hold true. This conclusion seems logical, due to not having to deal with huge amounts of waste rock, water, cyanide and other chemical by-products during recycling.

The obvious major social costs of gold mining are native land-owner rights, the human rights abuses involved in obtaining conflict gold, and the unacceptably high worker fatality rates. According to research by Oxfam (2004), 50% of all newly mined gold is taken from native lands.

In a one-off event, BRE-X, a Canadian gold mining scam, cost investors $6.5bn in the biggest mining scandal of all time (Ro, 2012). There are several other documented and undocumented large-scale precious metal frauds that have occurred throughout history, which would be impossible to completely quantify.

Now weve looked at the costs of gold production, its time we compared it with the cost of generating other stores of value. Check back next week for the third article in the series, in which Hass McCook examines the sustainability ofprinting and minting currency. If you missed the first part of the series on the true costs of bitcoin mining, be sure to check it out.

The leader in news and information on cryptocurrency, digital assets and the future of money, CoinDesk is a media outlet that strives for the highest journalistic standards and abides by a strict set of editorial policies. CoinDesk is an independent operating subsidiary of Digital Currency Group, which invests in cryptocurrencies and blockchain startups.

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