Urban mining is the practice of recovering elements, compounds and materials from products, buildings and waste. Many metals can be mined, including, aluminum, copper, magnesium, titanium, lead, tin, and zinc and rare earths.
Little research exists about urban mining, and the method is one that hasn’t been exceedingly exposed to the public. The best way to clarify urban mining is to provide a paradigm.
Many everyday items contain elements that can be reused. For example, aluminum cans, or used beverage cans (UBC), are a very “refined form of bauxite ore”. Bauxite is an ore that is our key resource for aluminum. Our ecosystem is limited, decreasing and materially closed; and consumers are often unaware of how valuable this metal is, and the environmental and economic repercussions that can occur if we do not properly recycle UBCs.
Although the US aluminum can recycling rate is improving, it still hovers around 55%. This implies that almost half of all cans produced are lost to the recycle stream and end up in a landfill. It is practical for us to explore urban mining concepts to recover lost and buried aluminum cans. Our current efforts to gather aluminum UBC waste include the collection of “clean” UBCs; the collection of UBCs as commingled waste; and mining a preexisting landfill. Urban mining only supplements and complements these methods, and can help produce a desirable recycling rate of 95%.
Much research and preliminary testing needs to be done before attempting to mine a landfill. First, we must seek a site with practical and profitable exploration, and recovery potentials; in order to fully exercise our methods, the landfill must contain an above average amount of UBC. Best methods and costs to loosen and separate material from soil still needs to be researched. In addition, we need to find solutions to:
- the degree of packing and overburden in the landfill;
- the amount of drying and cleaning required for UBC;
- the landfill timeline and the potential capital and operating costs;
- the potential value of the recovered aluminum;
- the economic, environmental and legal requirements and costs for opening and resealing the landfill following the recovery process.
Economic and Environmental Impacts
It is estimated that, nationwide, there are 20 million tons of UBCs that are sitting in landfills. Assuming a metal price of $2,500 per ton, this signifies a loss of $50 billion. If these cans were recycled, then the aluminum industry would gain 909,000 tons of metal per year. The advent of this metal would prevent the aluminum industry from having to build new bauxite mines, alumina refiners and aluminum smelters that extract metal from its ore through a process of mining, refining and smelting. Additionally, recycling will lower capital and energy costs, as well as environmental releases of CO2.
The aluminum industry—the use of smelters—leaves a large carbon footprint; contrarily, recycling only uses 5% of this energy.
All options should be explored in order to lessen the aluminum industry’s carbon footprint, and ensure better carbon neutrality for the global aluminum industry. Urban mining is currently one of our best unexplored options which must be rigorously bolstered with more in-field research.
Conceived, Developed and Written by Dr. Subodh Das and Tara Mahadevan , May 3, 2012
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