Introduction
In Japan, approximately 4 million tons of aluminum are consumed annually, with about 40% of that being utilized as recycled secondary alloy ingots. Aluminum products have a low melting point of around 660°C, making it possible to cycle through collection, melting, and re-casting in a short time and at a low cost even after being made into products. This resource-circulating process, in addition to the effective use of limited mineral resources, greatly contributes to the suppression of waste from used aluminum, making it an indispensable initiative for achieving a sustainable society.
On the other hand, primary smelting (new smelting) consumes a vast amount of electricity in the process of extracting alumina from bauxite and obtaining pure aluminum through electrolytic dissolution. In contrast, the recycling process almost completely eliminates the need for this electrolytic process, requiring only about 3% of the energy needed for new smelting. In fact, recycled ingots can be produced with about 3% of the electricity of new ingots, providing the dual benefits of a significant reduction in CO₂ emissions and lower electricity costs.
Against this backdrop, aluminum is often called the “star pupil of recycling” and is one of the most noteworthy materials for achieving both environmental load reduction and resource efficiency. In the future, further improvements in recovery rates and sophistication of quality control are expected to lead to even greater energy savings and CO₂ reductions.
The Basic Process of Aluminum Recycling
1. Collection and Sorting
Aluminum recycling begins with the collection of used aluminum that serves as the raw material. The main sources are aluminum cans, dross (chips and shavings from casting), and various industrial scraps. In Japan, the recovery rate for aluminum cans remains high at about 93.6%, with the rate of those being turned back into cans (CAN to CAN) reaching 71.4%. Collection occurs through various routes, including municipal resource recovery, dealer buy-backs, and manufacturer-operated collection stations, where items are sorted by quality and form.
2. Pre-treatment
The collected aluminum scrap is fed into a large shredder for crushing and pulverizing. Here, foreign materials (iron, plastic, paper, etc.) are removed, and oils and dirt are washed off in a cleaning process. By using magnetic separators and eddy current separators in conjunction, magnetic and non-magnetic foreign materials can be removed with high precision, reducing the impurity load in subsequent processes. Pre-treatment facilities range in line capacity from several tons to tens of tons per hour, with continuous operation types being the mainstream.
3. Melting and Stirring
The pre-treated scrap is transported to a rotary melting furnace (drum furnace) or a melting furnace with a burner and melted at a temperature of 660–700°C. The drum-type furnace allows for uniform melting by heating the scrap while rotating it. In conjunction with degassing treatment using the gas solution method, it removes hydrogen and contaminants contained within. Slag (oxides) in the molten metal is continuously removed through a skimming operation to maintain the purity of the aluminum.
4. Casting and Secondary Alloying
The molten aluminum, after melting and degassing, is poured into molds for ingot casting. After casting, it undergoes cooling and flux treatment to obtain billets or ingots of specified dimensions. Furthermore, magnesium, silicon, etc., are added in an electric furnace to produce high-performance secondary alloys (DX10, DX17, DX19, etc.) with enhanced strength and thermal conductivity. These secondary alloys are widely used, especially in fields requiring high functionality, such as automotive parts, electronic devices, and building materials.
Benefits of Recycling
Environmental Benefits
Recycling requires only about 3% of the electricity needed for primary smelting, allowing for a significant reduction in energy consumption. Accordingly, CO₂ emissions are also reduced by a similar amount, and in Life Cycle Assessment (LCA), recycled ingots are evaluated as having an advantage in reducing environmental load.
Economic Benefits
The reduction in electricity usage directly leads to lower electricity costs, reducing long-term operating costs by about 70–80%. The investment recovery period for recycling facilities is generally said to be about 3–5 years, and even retrofitting existing plants can be expected to generate cash flow in a relatively short period, allowing for increased asset efficiency while suppressing management risks. Furthermore, the recent scrap market has been trading at about 250–330 yen per kg, and the stable to rising trend in scrap prices is also a factor in reducing the risk of fluctuations in raw material costs (aipo.xsrv.jp).
Technical and Quality Benefits
High-performance secondary alloys (DX series) based on recycled ingots can achieve about 1.5 times the tensile strength and a similar improvement in thermal conductivity compared to conventional ADC12. For this reason, their application is actively progressing in uses with high-spec requirements, such as automotive engine parts and heat-dissipating components. For EV/HEV components, by achieving both weight reduction and high strength, they contribute to extending cruising range and improving electricity consumption, thereby enhancing product competitiveness.
Challenges and Countermeasures of Recycling
Quality Variation in Raw Scrap
Used scrap has significant variations in chemical composition because the alloy types, treatment histories, and usage environments of the original products are diverse. In particular, casting dross and chips may have oil or paint films attached, or other metals mixed in, which increases the risk of hydrogen gas generation and foreign material defects after melting.
Countermeasure Examples
- Quality checks on a batch-by-batch basis using component analysis (OES, etc.)
- Hot briquetting (re-compressing) by alloy type to homogenize the composition
Foreign Matter and Gas Management
Paint films and oils in scrap decompose when heated, generating hydrogen and ammonia gas, which can induce casting defects (pinholes, blowholes). Also, the combustion of organic foreign matter can cause contamination of the molten metal and an increase in slag (orist.jp).
Countermeasure Examples
- Hydrogen removal using a vacuum degassing furnace or argon bubbling degassing
- Development of pre-treatment technology for detoxification by hydrolysis and calcination (to reduce gas generation)
Limitations of Sorting Technology and Latest Trends
While conventional magnetic and eddy current sorting can remove large foreign materials like iron and copper, they have limitations in distinguishing between different aluminum alloys, thin-walled materials, and composite materials. In recent years, technology that combines AI image analysis and near-infrared (NIR) sensing to identify aluminum material types and the presence of surface treatments at high speed and with high precision is entering the practical application stage.
- Advantages: Reduced miss-sorting rates, lower manual labor costs
- Introduction Costs: Costs for adding cameras/sensors to existing lines, costs for preparing AI training data
Safety and Legal/Regulatory Compliance
To operate recycling facilities, a “mid-term treatment business” permit based on the Waste Management Act is required, and compliance with environmental regulations for exhaust gas, noise, and wastewater is also demanded (Ministry of Economy, Trade and Industry). The Containers and Packaging Recycling Law stipulates the obligation to collect aluminum cans, etc., and the establishment of a quality management system compliant with JIS standards (such as JIS H 4000) and ISO 9001/ISO 15270 (though for plastics, the concept is applied) is recommended (Ministry of the Environment, Japan).
Countermeasure Examples
- Regular monitoring of hazardous substances and setting of voluntary exhaust gas regulation values
- Operation of a quality and environmental management system (QMS/EMS) based on ISO standards
As described above, by comprehensively strengthening each point—raw material characteristics, foreign matter management, latest sorting technology, and legal/regulatory compliance—stable operation and high quality of aluminum recycling can be achieved.
Case Studies
Case Study in the Automotive Parts Sector
In recent years, the automotive industry has been accelerating efforts to reuse aluminum parts recovered from end-of-life vehicles (ELVs) in a “closed loop.” For example, UACJ (formerly Nippon Light Metal) conducted a demonstration experiment by collecting aluminum die-cast parts from five car models of a domestic OEM and performing melting and component analysis for each manufacturing method and alloy type. Utilizing XRT (X-ray Transmission Sorting) and LIBS (Laser-Induced Breakdown Spectroscopy) sorting equipment, they sorted ADC12 and magnesium alloys with high precision. As a result of comparing the CO₂ emissions of secondary alloy recycling and direct recycling, it was confirmed that using recycled materials achieved a CO₂ reduction effect of over 90% (j-far.or.jp, Nissan).
Furthermore, Nissan Motor Co., in sorting car body panels with paint and adhesives attached, jointly developed an optimization of the shredder process and LIBS, establishing an advanced sorting process that suppresses the influence of the painted surface. With this, they are proceeding with trial production with a view to closed-loop recycling from recycled materials to new car panels (Nissan).
Effects and Challenges
- Effects: Significant reduction in CO₂ emissions (80–90% reduction compared to primary materials), reduction in raw material costs, improved reusability for OEM structural members.
- Challenges: Removal of organic contaminants (paint films, oils) in scrap, strict tracing for each alloy type, shortening the recovery period for equipment investment costs.
Case Studies in the Construction and Home Appliance Sectors
Construction Sector
According to a survey by the European Aluminium Association, the end-of-life recovery rate for aluminum products in construction in Europe has reached 98.3%, and the recovery and recycling of items such as partition walls, door frames, and window frames are almost completely carried out (european-aluminium.eu, european-aluminium.eu). These are reused as architectural profiles or composite panels after melting, achieving material circulation.
Furthermore, in London, Veolia UK and Red Squirrel Architects are jointly promoting a project to collect about 2 tons of aluminum beverage cans and reprocess them into honeycomb-structured greening exterior wall panels. In addition to their function as exterior wall materials, they also contribute to suppressing the urban heat island effect and improving aesthetics (IDEAS FOR GOOD).
Home Appliance Sector
In the home appliance industry as well, major players are strengthening the introduction of recycling. According to a report by APPLiA (European Home Appliance Manufacturers’ Association), trials are underway in home appliance production lines to blend up to 25% recycled aluminum into components such as heat exchangers and compressor casings for refrigerators and dishwashers, and it has been pointed out that this has the potential to reduce CO₂ emissions over the entire product life cycle by 30–40% (MDPI, applia-europe.eu). Also, ensuring the traceability of recycled materials through IoT integration has become key to quality control and supply chain efficiency.
Effects and Challenges
- Effects: Stabilization of raw material procurement costs, strengthening of market competitiveness with product eco-labels, improvement of waste reduction rates.
- Challenges: Maintenance of product safety standards (electrical insulation, corrosion resistance), response to the risk of contamination by different metals, cost of homogenizing recycled materials.
From these case studies, it is clear that in each of the automotive, construction, and home appliance sectors, aluminum recycling is achieving significant results in terms of both material costs and environmental load. On the other hand, there are still technical and managerial challenges to overcome for commercialization and mass production, such as quality control, sorting accuracy, and legal/regulatory compliance. In the future, improving sorting accuracy through the use of digital technologies like AI and IoT, and optimizing the entire supply chain through the development of legal regulations and corporate collaboration will hold the key to further expansion.
Data Box (List of Indicators)
| Title | Data | Source |
| Aluminum Can Recovery Rate | 93.6% (CAN to CAN 71.4%) | Shisaku.com: Aluminum Can Recycling Rate 93.6%, CAN to CAN 71.4% |
| Recycled Power Reduction Rate | 97% | 3R Promotion Council: CO₂ load of recycled aluminum is 1/35 of smelting (3r-suishinkyogikai.jp) |
| Domestic Secondary Ingot Ratio | Approx. 40% | Nippon Light Metal HD “Alumirai” |
| CO₂ Emission Reduction Amount | Approx. 10,800 kg-CO₂/ton | METI: 10.2M tons of recycled aluminum production reduces CO₂ by 90.8M tons (Ministry of Economy, Trade and Industry) |
| High-Function Secondary Alloy Shipment Volume | 95,000 tons (First half of FY2020) | Nikkei MC Aluminium: 95,000 tons of product sales in the first half of FY2020 (“Nikkan Sangyo Shimbun,” a specialized paper for the steel and non-ferrous metal industry) |
The figures shown in each indicator are compiled based on the latest publicly available materials. Please verify.
Conclusion
Future Outlook for Aluminum Recycling
In the future, against the backdrop of rising global decarbonization needs and fluctuations in resource prices, the aluminum recycling market will likely expand further. In particular, the demand for secondary alloys that combine high strength and high thermal conductivity is expected to surge for in-vehicle component applications accompanying the spread of EVs/HEVs. Furthermore, by operating closed-loop recycling more efficiently through real-time quality monitoring and strengthened traceability using IoT and AI, it is possible that both recovery and reuse rates will significantly exceed current levels.
Recommendations for Solving Challenges
- Advancement of Quality Assurance Systems
- Strengthen investment in component analysis and degassing treatment facilities to minimize component variations originating from scrap.
- Collaborative Investment in Sorting Technology
- Promote the introduction of AI + NIR sensors jointly within the industry to share and reduce sorting costs.
- Information Disclosure Based on LCA
- Quantitatively disclose CO₂ reduction effects and energy reduction rates to visualize environmental value across the entire supply chain.
Actions for Companies and Government
- For Companies: Collaborate with suppliers to establish scrap collection routes and conclude long-term contracts for the expanded use of secondary alloys. Also, promote the standardization of quality assurance manuals and recycling design guidelines.
- For Government: Continue and expand subsidies and tax incentives for the development of collection infrastructure to supplement weaknesses in local collection networks. In addition, institutionally support corporate efforts by mandating the submission of LCA reports and setting targets for recycled material usage rates.
Through these measures, aluminum recycling can achieve further energy savings and decarbonization, and establish its position as the core of a sustainable material circulation society.
