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The advancing technology should also benefit the environment

Environmental risks and benefits of some of the technologies discussed in Chapter 3 were also addressed there. This chapter describes research opportunities and technologies that would lessen the environmental impacts of mining.

The creation of large-scale surface disturbances, the generation of large volumes of waste materials, and the exposure of previously buried geologic materials to the forces of oxidation and precipitation are intrinsic to the mining industry and may continue to present complex environmental problems even when the best available practices are conscientiously followed Chiaro and Joklik, 1998.

Even with all of the recent advances in environmental protection, the mining industry still cannot completely and effectively predict, prevent, or treat releases from mine sites during and after operations.

Six Ways Tech Is Helping the Environment

Technologies that predict, prevent, mitigate, or treat environmental problems will be increasingly important to the economic viability of the mining industry. With new and effective environmental technologies new mining operations may be permitted that might otherwise have been rejected because of unacceptable environmental risks. New technologies may also result in reduced costs for environmental compliance and facility closures.

Improved environmental technologies related to mine closures have the greatest potential for increasing overall productivity and reducing overall energy consumption because costs of long-term maintenance will be factored into the analysis. Closure procedures usually affect the quality of drainage water from the mine and thus, productive use of the land. Long-term in perpetuity treatment of drainage water from mines now requires capitalization by interest-bearing funds.

Today, perpetual treatment or maintenance often appear to be economically preferable to expensive permanent treatments. Moreover, permanent solutions prevent problems from becoming exacerbated over time rather than simply managing their impacts.

The industry now generally recognizes that planning for closure must begin when the mine is in the planning phase. Some are common to all mining sectors; others are specific to one sector or even to one commodity within a sector Sidebar 5-1. For example, environmental planning in surface coal mines and surface areas of underground coal mines must meet the performance standards of the Surface Mining Control and Reclamation Act of 1977, which the advancing technology should also benefit the environment established standards for closure and reclamation.

Even before the federal law was passed, several coal-mining states, particularly in the eastern United States, had long-standing, mining-specific legislation requiring the reclamation of disturbed lands. As a result of this long history of mandated standards, industry and governmental agencies have made considerable efforts to address the problems specified by the regulations, specifically air quality, water quality, land use, and noise.

Industrial-minerals operations in close proximity to communities have been subject to local zoning regulations, which has had a major influence on planning, including environmental planning. Even if the problems facing all mining sectors are similar e. Evolutionary and Revolutionary Technologies for Mining. The National Academies Press. The production of phosphate generates 5 tons of phosphogypsum for every ton of phosphate product manufactured.

In Florida alone nearly a billion tons of phosphogypsum have been generated. This by-product is generated when phosphoric acid is manufactured using sulfuric acid, an inexpensive reagent. The resulting phosphogypsum must be managed as a waste.

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Other acids could be used to manufacture phosphoric acid; however, the by-products of these processes are an insoluble calcium salt, which also raises disposal issues. Although potential uses for phosphogypsum have been identified, its use is prohibited by the Environmental Protection Agency because of the presence of radium at a concentration greater than 10 picocuries per gram present in Florida phosphogypsum.

The role of science and technology in future design

Potential uses of phosphogypsum include material for road bases, agricultural fertilizer to supply sulfur and calcium, and a supplement in landfills and sewage treatment plants to enhance the microbial decomposition of organic waste.

Research to identify or develop uses for phosphogypsum that contains radium could reduce the amount of material that must be managed as waste, as well as limit its potential environmental impact.

Research should also focus on the development of a phosphate manufacturing technology that does not produce phosphogypsum as a by-product.

Nevertheless, all mining sectors would benefit from new technologies to reduce or eliminate adverse environmental impacts caused by mining operations.

Accelerating climate action

Water-quality issues related to mine closures are often the most challenging and costly to address for all types of mining. They also present significant opportunities for research that could increase overall productivity.

New technologies for managing other materials of environmental concern, such as innovative, cost-effective solutions to managing slimes, could also increase productivity in the mining industry. Acid-Rock Drainage 1 The most common water-quality problem associated with metal and coal mining is the release of metals, acidity, and sulfate from reactive rock surfaces, particularly when pyrite is present University of California, 1988.

Sulfide-containing rock is oxidized when newly fractured rock comes in contact with oxygen, water, and very often bacteria. The sulfides are converted to sulfuric acid, which in turn can mobilize a variety of metals Alpers and Blowes, 1994; Doyle and Mirza, 1990. The most common metals released are iron, copper, zinc, cadmium, manganese, arsenic, antimony, lead, nickel, and mercury.

The concentrations of metals vary dramatically with the type of deposit and the environmental factors surrounding the site. The pH of the water can also vary, depending on the amount and type of sulfide minerals oxidized, as well as the amount of neutralization capacity present in the rock.

Highly acid-generating rock produces a drainage pH of less than 1; well buffered-rock e. Metal concentrations, and thus the environmental and health impact of drainage water, depend on the pH. Low pH water high acidity has much higher concentrations of metals than near-neutral pH water low acidity.

Some potentially toxic elements, such as selenium and arsenic, are problematic at any pH. Acid generation is an issue of concern for certain types of coal and hardrock mines particularly mines that contain high concentrations of pyrite but low concentrations of pH-buffering materials. Problems are most common for reactive waste-rock dumps, although tailings and waste facilities, low-grade ore piles, highwalls, and precious-metal heaps can also generate acids under specialized conditions.

Acidic drainage into receiving waters can result in severe impacts to the biological integrity of a stream and can change a diverse, healthy biological system into one in which only less-susceptible organisms can thrive or one devoid of higher organisms.

The advancing technology should also benefit the environment to planning a mining operation, the potential for acid generation is generally estimated based on cores, drill cuttings, and bulk samples used to characterize the orebody. The characterization of acid-generation potential is critical for constructing waste dumps in a way that minimizes the release of contaminants by oxidation of sulfidic rock.

For sites where acid generation is a potential problem, characterization of the rock for contaminant release should be conducted concurrent with characterization of the ore potential. Common tests for acid-drainage potential include acid-base accounting and humidity-cell tests. Both 1 Additional information on acid drainage can be obtained from Webbased information sources, including the Acid Drainage Technology Initiative www.

Can technology save the environment?

Page 55 Share Cite Suggested Citation: Predictive tests of acid-rock drainage can be inaccurate if the samples tested do not adequately represent the material that will ultimately be placed on the waste-rock pile or heap. Therefore, careful characterization of the ore and waste rocks is essential. The preferred technique for managing acid drainage is prevention, which can be effected by several existing methods Blowes et al.

Although each of these techniques has been demonstrated in specialized circumstances, none can be applied in all cases. The most common method of treating acid drainage is lime precipitation Kleinmann, 1997. Lime is added to the acidic water and aerated to oxidize soluble ferrous iron to ferric iron, which then precipitates as iron oxide or oxyhydroxide.

As the pH is raised, other metal oxides can also be precipitated. The technology for lime treatment of acid drainage, which is reasonably mature and widely utilized, requires the continuous delivery of lime.

Even if the chemical composition of the sludge is not a concern, this large volume of material can be very difficult to handle.

Other methods of treating acidic drainage, including direct electrowinning of concentrated waste solutions to remove certain metals an emerging technologyreverse osmosis, and ion-exchange technologies, can be used under certain conditions although at present, few of them can compete with lime precipitation. Because acid management is a significant problem in many mines, additional cost-effective methods for treating these fluids are very much needed.

Processes that recover contaminants in a form that can be beneficially used would be particularly attractive. One promising option that could be used either alone or in combination with lime precipitation is sulfate-reducing bioreactors Kleinmann and Hedin, 1993; Lawrence, 1998.

For this treatment an acclimated biological reactor is fed a variety of alcohols, sugars, other organic substrates, or hydrogen to supply reducing equivalents for the bacteria, which are usually a Desulfovibrio species.

Sulfate is reduced to hydrogen sulfide, which then precipitates divalent metals as metal sulfides.

  • The bond between basic research and the development of both novel and current technologies has been and is well in place;
  • Ignoring our impact in the meantime, however, could have disastrous consequences — especially since some scientists are warning we may be nearing a dangerous climate tipping point;
  • Highly acid-generating rock produces a drainage pH of less than 1; well buffered-rock e.

Like lime precipitation, this treatment creates a sludge metal sulfides that is reactive and must be managed to keep it in a chemically reduced state. If the metal sulfides are allowed to reoxidize, the resulting sulfuric acid and metals can again be released. The cost of this option can be either competitive or less expensive than lime precipitation because bioreactors can be operated without electricity, and gravity is used for flow systems.

Passivation technologies that can coat pyrite surfaces to prevent oxidation are also under development. At least three patented methods of passivation are being evaluated. This technology was developed by the DuPont Corporation and recently donated to the University of Nevada. The silica microencapsulation technology of KEECO utilizes an alkaline solution of silicate to cover the reactive pyrite surfaces Mitchell et al.

  • Improved environmental technologies related to mine closures have the greatest potential for increasing overall productivity and reducing overall energy consumption because costs of long-term maintenance will be factored into the analysis;
  • Decisions regarding what research to fund must be based on informed judgments about which projects represent the most meritorious ideas;
  • While technology and the environment might seem like two completely different areas, nature and our most high-tech devices are more interconnected than we may think.

The Envirobond treatment uses a separate proprietary process to form a stable, insoluble compound with pyrite surfaces Gobla et al. Phosphate coating uses a soluble form of phosphate that coprecipitates with iron oxide to form a stable surface coating on the pyrite.

In silicate coating, basic solutions of silicates are allowed to cover pyrite and form a stable silicate surface on the reactive rock. Further development will be necessary to determine how long any of these methods will last, as well as the costs of treatment and, if necessary, retreatment. The economic viability of these methods is still unproven and will have to be compared to continuous treatments in terms of environmental impact and long-term stability.

Closure and Reclamation of Dump-Leaching and Heap-Leaching Operations and Tailings Impoundments Upon the cessation of production, dump-leaching and heap-leaching piles and tailings impoundments must be closed in an environmentally sound manner. In the the advancing technology should also benefit the environment and precious-metal mining sectors and in some types of industrial-minerals operations these piles and tailings can present potential environmental risks.

The released solution may be acidic as discussed above or may contain cyanide or other contaminants, such as selenium, sulfates, radionuclides, or total dissolved solids. Waste piles are also subject to erosion, which potentially contributes sediments directly to surface waters. Over time, erosion may lead to structural instability and potential catastrophic failure.

Moreover, waste piles remain as unproduc-tive disturbances on the land unless the land is reclaimed for postmining use. Page 56 Share Cite Suggested Citation: Diversions are used to prevent run-on of precipitation. In the gold industry, heaps are rinsed or fluids recirculated until cyanide in the effluent is reduced to an acceptable level.

  1. People are more frequently taking notes and managing their schedules on their smartphones rather than physical notepads and calendars.
  2. Ignoring our impact in the meantime, however, could have disastrous consequences — especially since some scientists are warning we may be nearing a dangerous climate tipping point. Methane Gas Methane gas, inherently associated with coal beds, is released as the coal is mined.
  3. In the basemetal and precious-metal mining sectors and in some types of industrial-minerals operations these piles and tailings can present potential environmental risks. The economic return on federally supported funding was the subject of a report by the Council of Economic Advisors to President Clinton.
  4. Page 55 Share Cite Suggested Citation.

Spent ore and tailings may be recontoured to limit erosion and enhance long-term structural stability. Cover material may be placed on the surfaces both to inhibit infiltration and thereby limit leaching and to provide a medium for plant growth.

Alternatively, wastes may be directly vegetated with the addition of soil amendments. In the last decade a number of facilities have run cattle-feeding operations on closed tailings impoundments to create a soil and promote plant growth. Although existing technologies have been successful, each has limitations. Diversion structures require periodic maintenance to continue to function effectively.

Rinsing is typically effective for cyanide, but if contact with air and water is not limited, sulfidic waste materials can continue to oxidize and release contaminants through infiltration of precipitation and subsequent leaching.

Covering with soil is a proven technique for revegetation but is only practical if soil is readily available. If no soil was salvaged prior to construction e. Moreover, the excavation and placement of large volumes of soil can be costly.