Urban Mining and its Potential: In Relation to Aluminum Recovery

Urban mining and Landfill Mining are two terms that are used interchangeably to represent the extraction and processing of wastes from landfills.?However, urban mining is a broader concept compared with landfill mining.?

Landfill mining denotes the extraction and processing of wastes that have been dumped in particular kinds of deposits such a municipal landfill, mine tailings, etc. Urban Mining is an extensive term that covers the process of reclaiming materials from any kind of anthropogenic stocks, including buildings, infrastructure, industries, products (in and out of use), Electrical and Electronic Equipment (EEE), etc., and an environmental media receiving anthropogenic waste.

Both the concepts are an integral part of the circular economy principles. The circular economy rejects the linear ‘‘take-make-waste” business models. It promotes longer use of products by reusing and repairing them, reducing waste generation, and using more secondary raw materials in production cycles.

Urban Mining is a practical concept that must be strongly structured within a Circular Economy strategy. The concept needs further discourse regarding the technical and scientific community, terminology, targets, technologies, challenges, and opportunities. The extraction and processing of materials during urban mining are strongly based on economic feasibility. There is a standard mechanism for enhancing the concentration and extraction of given elements. Therefore, the process needs a pragmatic approach rather than an ideological one.

In our article, we will focus primarily on the landfill mining process regarding the recovery of aluminum from UBC cans.?

Current Industry Practice

Landfill mining is a process whereby landfills are excavated, and the buried resources are processed for environmental, economic, or social benefits. The key objectives of landfill mining are:

• Conservation of landfill space and soil recovery
• Reduction in the landfill area
• Expanding landfill lifetime
• Elimination of a potential source of contamination
• Mitigation of an existing contaminated source
• Energy recovery
• Recovery and processing of materials buried in landfills
• Site redevelopment

The process is complex and requires a sequence of processing machines laid out in a functional conveyor system. The landfill material is excavated, sieved, and sorted with the help of the machinery. Processing involves a series of mechanical processing operations designed to recover the resources buried in the landfill.?Basic equipment used in LFM operations are excavators, screens, and conveyors. Complex landfill mining operations require additional equipment to recover and process the materials.

History

Several landfill mining projects have taken place in various parts of the world in the last 50 years with different objectives, some being successful, and others abandoned because of cost factors. The first reported landfill mining project was an operation in Tel Aviv, Israel in 1953, which was carried out to improve the soil quality in orchards.?It was later employed in the US to generate fuel for incineration and energy recovery.?

Urban mining and the metal sector

The metal economies are the most significant beneficiaries of landfill mining and urban mining, supported by the fact that the metals are often 100% recyclable and most of the landfilled and discarded wastes contain metals. With the growing awareness about a circular economy and reclamation of waste, the concepts of landfill mining and urban mining are gaining ground concerning metal and rare earth element recovery.

The vast quantities of metal buried in landfills can be suitable for use as potential secondary resources. Nonferrous metals contribute the most to the revenues from landfill mining (LFM). However, metals in landfills undergo stronger degradation compared to that of their normal use, which might lead to a difference in scrap quality compared to end-of-life scraps.??NFM can be recovered, segregated, and processed as separate metals and can also be commercialized directly from the landfill as a mixed nonferrous scrap. In both ways, non-ferrous metals continue to dominate the landfill mining and urban mining space.

Potential reclamation of aluminum from landfilled UBCs

Aluminum is one of the highly recycled non-ferrous metals and has the maximum potential to be reclaimed through landfill mining and urban mining.

EPA releases data on aluminum packaging waste generation based on Aluminum Association industry statistics. As per the latest data, in 2018, aluminum waste generation was 1.3% of total MSW generation at 3.9?million tons. This included 1.9 million tons of aluminum?containers and packaging and two?million tons in?durable?and?nondurable?goods.

Further, as per the EPA data, in 2018, the total recycling rate of aluminum containers and packaging was 34.9%. Within this number, the most recycled category of aluminum was beer and soft drink cans, at 50.4% or 0.67 million tons.

In 2018, landfills received about 2.7 million tons of aluminum or about 1.8% of all MSW landfilled that year.

As per the data from The Aluminum Association and Can Manufacturers Institute (CMI) The current consumer UBC recycling rate in the United States is around 45.2%. The industry recycling rate increased in 2020 to 59.7 percent. However, more than 50 billion cans, around $800 million worth of aluminum -- were diverted from the recycling stream in 2020 to the landfill that could have otherwise been responsibly recycled and made into new cans. This loss has a significant negative impact on the environment as well as on the economy.

As CMI has pointed out, if the aluminum UBC recycling rate were 70% in 2020 instead of 45%, more than 25 billion cans would have been recycled. These 25 billion fresh cans would have generated revenue of more than $400 million for the US recycling system and the saved energy could power more than one million US homes for a year. The figure for the lost value of UBCs gets bigger if we look at the current (2021-22) market price of aluminum.

Aluminum beverage cans contribute just 3% of the weight of all recyclable wastes generated at U.S. homes. Yet, UBCs account for nearly half of the revenue from recyclable materials from single-family homes. These statistics come from the landmark study published by The Recycling Partnership's 2020 State of Curbside report.

Aluminum cans have immense possibilities for end-of-life recycling. The possibilities go beyond that to reclaim all the cans that have been landfilled in the US for decades. As per the last estimate, more than 30 million tons of aluminum scraps are buried in the nation's landfills over the past 3-to 4 decades. If recovered and processed, they can compensate for a large volume of freshly mined metals. As the US is increasingly focusing on secondary sourcing of aluminum and closing most of its primary smelters, the country's landfills can be the next best source for reclaiming the aluminum mostly buried in the form of UBCs.

Challenges

Landfill mining is a complicated process and can be expensive enough to consume about 80% of the project budget.?The cost of excavating trash, sorting out the materials such as metals, and then reburying the rest tends to exceed the revenues from selling recovered materials. This also comes with numerous political, legal liability, and regulation issues.

When a landfill is filled and sealed, decomposition in the sealed volume generates methane, which is combusted for steam generation and to heat large institutional buildings. Boring into a landfill will release methane and this will be counterproductive if the gas is being used as a fuel. Also, the material recovered from a landfill will certainly be more contaminated than end-of-life wastes. They might not be an attractive option to the remelt operators.

Again, then, there is the need to develop technology to clean and beneficiate the waste UBC. Before attempting to mine an existing landfill, it would be important to conduct some surveys of the locality to select a landfill with an above average content of UBC scrap. It is important to assess all related aspects of mining a landfill before embarking on the project. As per an EPA recommendation, the followings steps are to be considered before a landfill mining project:

• Conduct a site characterization study
• Assess potential economic benefits
• Investigate regulatory requirements
• Establish a basic worker health and safety plan
• Assess project costs
• Assess the potential value of the recovered metal

Initial costs of landfill mining cannot be eliminated. However, this cost can be recovered if the waste management communities come up with more innovative solutions for processing and reusing the mined materials. At present, the waste management industry is paying more attention to promoting recycling and diverting wastes from ending in landfills. Landfill mining is still in the experimental stage and needs further research and development to be a normal practice.?

Key takeaways

A planned landfilled mining system can reduce dependence on the import of raw materials, cut carbon emission considerably in industrial production, fortify recycling supply chains and finally strengthen the circular economy goals in the true sense of the term. The claim becomes more relevant for aluminum because the demand for the metal is growing every year and the supply side is under pressure. The primary industry is facing an immense challenge because of the growing energy prices and the strict carbon emission standards. The solution is to develop a strong secondary supply chain through increased end-of-life recycling and reclamation of the aluminum that are buried in the landfills for decades.

Reference

1. https://www.epa.gov/sites/default/files/2016-03/documents/land-rcl.pdf
2. https://www.urbanmining.it/public/documents/simposio/editorial-waste-management-2015.pdf
3. https://eurelco.org/wp-content/uploads/2018/09/p5.pdf
4. https://secat.net/wp-content/uploads/Recovering-Aluminum-from-Used-Beverage-Cans.pdf
5. https://www.rts.com/blog/what-is-urban-mining/
6. LANDFILL MINING: Process, Feasibility, Economy, Benefits and Limitations, July 2009, René M?ller Rosendal
7. 2020 State of Curbside Recycling Report, THE RECYCLING PARTNERSHIP
8. Defining a Closed-Loop U.S. Aluminum Can Supply Chain Through Technical Design and Supply Chain Innovation, JACK BUFFINGTON, RAY PETERSON (TMS)