Global population growth, coupled with an increasing demand in emerging nations, is straining the supply of metal-containing ores. To meet that demand, mining industry professionals are finding it necessary to develop new ways to garner greater quantities of metals from existing ore stocks. In the past, available mining technologies did not possess the capability of extracting all available commodities from the ore, leaving valuable content simply piled near the existing mining operations. Heap leaching (HL) is currently seen as a viable process for extracting valuable commodities from those stockpiles.
Why Is There a Need to Extract a Greater Percentage of Minerals from Ores Now?
The mining industry is not only facing increasing demand for products, it’s also facing other issues making it difficult to meet demand through initiating new mining efforts. Not only are there fewer high-yielding sites available, environmental and geo-political issues make opening new operations difficult. Heap leaching is seen as a way to circumvent the need to invest in new operations to extract gold, copper, silver and other valuable trace minerals present.
How Did Heap Leaching Enter the Picture?
In a research paper (, researcher Mark Smith suggests the first use of heap leaching occurred at the Bluebird copper oxide mine during in the late 1960s, with other western United States gold mines following suit in the 1970s. Smith goes on to say that, “By 1983 most new leaching operations used modern technology with fully geomembrane lined leach pods.” Since that time, the technique’s use has spread throughout the world to allow mining operations to extract content not obtainable through older, more traditional, mining strategies.
What are the Advantages of Heap Leaching?
The mining industry is attracted to heap leaching for several reasons, and a recent Mining.com ( article focuses on eight advantages. Author Vladimir Basov lists the technique’s advantages as:
- Lowering capital and operating expenses
- Providing a rapid payback
- Elimination of tailing disposal issues
- Simplicity of design and equipment needed
- Having fewer environmental issues than other processes
- Faster construction phase than alternatives
- Reduced energy and water requirements
- Being applicable where low-grade ores and tailings are present
Viewing the listed benefits, it’s easy to see why the industry finds the process attractive. Decreasing the costs of production while extracting materials from existing stockpiles is certainly more attractive than dealing with the costs of start-up projects.
Are There Disadvantages to Heap Leaching?
As might be expected, there are environmental concerns with the use of HL. Researcher Catherine Reichardt ( points out a few of the concerns. Her paper lists issues related to the strategy as:
- Potential issues with water balance
- Possible exposure of the solutions used on the area’s general population, livestock and wildlife
- The costs associated with pollution control and closure efforts
- Societal perceptions of the practice
Each of those issues is valid. Reichardt did not mention another issue brought up in Smith’s article—seismic risks. With many mining operations located in seismically active regions, sites must be designed to withstand the types of seismic events common in those regions.
Does the Industry See a Potential for Future Growth?
According to the Basov article, “HL technology has all the chances to succeed in the future, with plenty of opportunities, including HL application to extract massive amounts of precious and base metals sitting in abandoned tailings and waste management sites.” Indeed, that prediction is likely to come to fruition. However, there will likely be an increasing pressure on the industry to safeguard local residents and the environment.
