Shredding In Focus

Aluminum is everywhere. From soda cans to car parts, from home siding to the siding of airplanes, its durability, unique properties, and impressive strength-to-weight ratio have made aluminum a favorite material for manufacturers. Yet, the most important property of aluminum is its recyclability.

Where most materials degrade over time with each recycling cycle, aluminum can be melted down and reformed infinitely without losing its original strength and integrity.

“It’s just a perfect material to be recycled,” says Dave Wilson from behind his desk at Shredding Systems Inc (SSI), where he has been providing recycling systems to the aluminum industry for nearly four decades, an industry that is expanding with growing demand.

Although aluminum is the most abundant metal in Earth’s crust, it remains costly and complex to produce.

Most often, aluminum starts as bauxite ore, a mineral-rich sedimentary rock. Mining bauxite poses serious environmental hazards, including carbon emissions, water pollution, and habitat destruction. Extracting aluminum from the bauxite requires a series of energy- and chemical-intensive processes.

It takes approximately 15,000 kwh to produce one ton of new aluminum, enough energy to power an electric car for 60,000 miles, or nearly two and a half laps around the world. In contrast, recycling aluminum requires only 5% of that energy and eliminates the need for bauxite mining.

The State of Aluminum Recycling in the U.S.

The modern interest in aluminum recycling began in 1904 when the first dedicated recycling facilities opened in the US. During World War I and II, the US government encouraged citizens to donate old pots and pans, farm equipment, and cars to aid the war effort.

Despite the economic incentive and environmental benefits of recycling aluminum, the United States still only recycles about 45% of its aluminum, with the other 55% (equivalent to approximately 61 billion aluminum cans) ending up in landfills. This represents $1.2 billion in value thrown in the trash each year.

The United Kingdom and Japan recycle 82% and 71% of UBCs respectively and Germany is the global leader in UBC handling, collecting, and recycling 99%.

Why does the US lag so far behind?

One significant factor is the lack of bottle bill laws, legislation requiring consumers to make a refundable deposit for beverage containers at the point of sale, which can be redeemed by returning the used containers to a recycling facility.

Over the decades, bottle deposit laws have proven to be highly effective, yet only 10 US states have them. Of those 10 states, 8 rank in the top 10 for aluminum recycling rates in the US. Despite these successes, attempts to pass bottle bills in other states have failed due to staunch opposition from large beverage companies.

Curbside recycling inefficiencies also contribute to the problem. Most municipalities use single-stream curbside recycling, where all recyclables are mixed in one bin for collection. While this system is convenient for consumers and encourages participation, it creates challenges in sorting and contamination. Commingled materials require costly sorting, and contamination reduces the amount of aluminum that is actually suitable for recycling.

Aluminum in the Pre-Consumer and Post-Consumer Economy

The aluminum recycling ecosystem extends beyond blue bins and beverage cans. In manufacturing, capturing, and recycling pre-consumer aluminum scrap, such as extrusion heads and tails, slitter trim, or stamping scrap, is an easy step towards a zero-waste aluminum economy. Because pre-consumer scrap is typically clean and sorted by alloy, it requires minimal processing before being reintroduced into the production cycle.

To achieve the desired properties in their products, manufacturers use aluminum alloys, blends of aluminum with metals like copper, magnesium, tin, and nickel.

“Most manufacturers, especially automakers, haver their own alloy, their own secret sauce,” explains Lee Sage aluminum specialist at SSI, “it's up to the recyclers to figure it out.”

Scrap yards recover aluminum from diverse sources, including automobiles, household appliances, construction debris, and industrial waste. To maximize its value, aluminum must be cleaned of contaminants and sorted by alloy, a process best achieved through shredding.

Once sorted and graded, aluminum moves to smelters, usually large facilities supported by a network of smaller, independently owned scrap yards and suppliers.

Transportation efficiency is critical for scrap yards, which typically bale aluminum to reduce cost. While baling benefits scrap yards, it poses challenges for smelters as bales must be broken apart before smelting, a process that requires specialized equipment.

“Bales are getting denser,” notes Dave Wilson, “to combat that, SSI designs and builds

Considerations in Aluminum Smelting

“Smelters are primarily concerned with two things,” shares Sage, “Safety and efficiency. And shredders help with both.”

Shredders address these concerns by liberating materials instead of trapping them, making it easier to remove contaminants and produce a clean, high-value feedstock.

Additionally, high-impact design of hammermills combined with increased production of fines threatens workplace safety.

The type of furnace a smelter operates determines aluminum processing requirements, and shredding plays a key role in ensuring an efficient melt.

Smelters typically use reverberatory, rotary, or induction furnaces, each requiring different levels of pre-processing.

Reverberatory furnaces, common in large-scale operations, can handle mixed and coated scrap but perform best when materials are pre-shredded to remove contaminants and ensure consistent feedstock size.

Rotary furnaces, which process dross and lower-grade scrap, benefit from shredding that exposes clean metal surfaces, improving flux efficiency and metal recovery.

Induction furnaces, which require high-purity aluminum, are particularly sensitive to contamination, making precise shredding and sorting essential to prevent impurities and ensure uniform melting.

Smelters rely on advanced shredding technology in producing clean, high-value material that enhances both safety and efficiency in the melting process.

Advancements in Shredding Technology

Rotary shredders have become the industry standard for processing aluminum scrap, replacing older hammermill-based methods.

While hammermills offer high throughput, their high impact and rotary speeds produce excessive fines, small aluminum particles lost as waste during smelting.

During the melting process, these lightweight fines float on top of the molten aluminum, forming waste material known as dross. Shear shredders, in contrast, produce fewer fines, improving metal recovery during smelting.

Additionally, hammermills create wads of aluminum that trap contaminants, which results in more dross.

Since its inception in 1981, SSI has been a leader in developing shredders for the aluminum recycling industry. SSI incorporates decades of customer feedback and hundreds of thousands of hours of in the field equipment runtime into the design of its aluminum shredders, primary reducers, and grinders.

“The neat thing about aluminum is that our whole product line can be employed in various stages of the process depending on the needs of the customer," says Sage.

SSI designs their PRI-MAX® line of primary reducers, implemented to break and open baled aluminum, with unique features for aluminum processing. The large cutting chamber and the ability to reverse allows the agitation and reorientation of dense bales until it breaks them apart.

For applications requiring greater shear force in their primary shredder, DUAL-SHEAR® two shaft shredders are a good option due to their low speed, high torque design.

The versatility and power of the QUAD® four-shaft shredders make them an ideal secondary shredder capable of accepting pre-shredded material and creating a uniform particle size. Achieving a manageable particle size is an essential element of efficiently sorting, cleaning, transporting, and smelting aluminum. Depending on the application, QUADs® can function as a primary shredder or a bale breaker for low density bales.

SSI's UNI-SHEAR® single-rotor shredders excel as secondary shredders for aluminum applications, offering cost-effective particle size reduction. When paired with a QUAD®, UNI-SHEAR® shredders deliver the highest thruput potential and most consistent output.

Looking Towards the Future

The success of the aluminum recycling industry depends on efficient scrap processing and smelting practices. With global demand for aluminum projected to double by 2050, sustainable recycling practices are more critical than ever.

By advancing recycling technologies, improving collection rates, and enhancing material handling, we can meet growing needs while minimizing environmental impact.

The future of aluminum recycling rests in our hands, and our shredders.

Want to watch some shreds? Check out some of our Aluminum Shredding Videos.