Resource utilization of polymetallic solid waste: Practice and challenges in exploring the value of "urban mines"

As a special "mineral resource", polymetallic solid waste is gradually entering the public eye with the advancement of resource utilization technology. These wastes, which contain various metals such as copper, iron, aluminum, and precious metals, may not only become an environmental burden, but also contain enormous value for recycling. In recent years, the resource utilization of multi metal solid waste has made progress in technological breakthroughs and industrial applications, providing a new path to alleviate resource shortages and reduce environmental pollution. However, obstacles still need to be overcome in terms of efficiency improvement and cost control.
Multi metallic solid waste has a wide range of sources, covering various fields such as industrial production scraps, scrapped electronic and electrical appliances, and used automotive parts. According to statistics, in 2024 alone, China will generate over 80 million tons of solid waste containing multi metal characteristics, with a total amount of metal resources equivalent to the reserves of a large mine. Taking scrapped circuit boards as an example, each ton can be disassembled to produce about 300 grams of gold, 20 kilograms of copper, and various other metals, with a much higher metal content than natural ore. A certain electronic waste treatment enterprise uses specialized technology to process waste circuit boards, recovering nearly 500 tons of metals such as copper, gold, and silver annually, which is equivalent to reducing the mining of about 200000 tons of primary ores, demonstrating the development potential of "urban mines".
In terms of resource utilization technology, the treatment of multi metal solid waste is upgrading from single metal extraction to full component utilization. Traditional craftsmanship often focuses on the recycling of high-value metals, neglecting the utilization of other components, resulting in resource waste and secondary pollution. Nowadays, the combination of physical sorting, hydrometallurgy, pyrometallurgy and other technologies has achieved the cascade recovery of various metals. A certain automobile dismantling park adopts a combined process of "crushing magnetic separation eddy current separation chemical purification" to recover metals such as iron, aluminum, and copper from the metal parts of scrapped cars, while also extracting rare metals such as nickel and chromium, with a comprehensive utilization rate of over 90%. In addition, the experimental application of green technologies such as biological leaching provides an environmentally friendly solution for the treatment of low-grade polymetallic waste. A research institution screened specialized microorganisms and achieved an efficiency of 85% in extracting metals from low concentration nickel containing waste compared to traditional chemical methods, greatly reducing the consumption of chemicals.
The industrial value of multi metal solid waste resource utilization is not only reflected in resource recycling, but also promotes the construction of a circular economy industry chain. In industrial clusters such as Guangdong and Zhejiang, a complete industrial chain of "waste collection classification dismantling metal purification material regeneration" has been formed, which has driven thousands of enterprises to participate. A certain recycled metal industrial park produces 200000 tons of recycled copper, aluminum and other metal materials annually through centralized processing of multi metal solid waste, which are supplied to local manufacturing enterprises as production raw materials. The product cost is 15% -20% lower than that of primary metals, which not only reduces the raw material cost of downstream industries, but also reduces carbon emissions in the production process. This "turning waste into treasure" model has transformed solid waste from a difficult point in environmental governance to a growth point for industrial development.
Despite the broad prospects, the resource utilization of polymetallic solid waste still faces multiple challenges.
Firstly, the separation efficiency of complex components has become a technical bottleneck. In many multi metal solid wastes, complex structures are formed between metals and non metals, as well as between different metals, such as metal solder joints in electronic components and plastic substrates, metal intermetallic compounds in alloy materials, etc. Traditional sorting techniques are difficult to achieve efficient separation. When a certain processing plant is dealing with metal waste containing multiple coatings, due to the tight bonding between the coatings and the base metal, the purity of the target metal can only reach 85%, which cannot meet the requirements of high-end manufacturing raw materials and can only be sold as low-end raw materials, reducing the resource value.
Secondly, high processing costs constrain the large-scale development of industries. The pretreatment, sorting, purification and other processes of multi metal solid waste are complex, and the equipment investment and operating costs are high. Especially for small dispersed waste with large component fluctuations, the cost of collection and transportation accounts for more than 30% of the total processing cost. The head of a small and medium-sized recycling enterprise stated that the cost of processing 1 ton of mixed multi metal waste is about 800 yuan, and the sales revenue of recycled metals can only barely cover the cost. The narrow profit margin leads to a lack of motivation for the enterprise to expand production.
Thirdly, the pressure of secondary pollution prevention and control cannot be ignored. Some polymetallic solid waste contains toxic and harmful substances, such as industrial waste containing lead and cadmium. Improper control during the treatment process may cause heavy metal leakage or harmful gas emissions. A small workshop style processing site used a simple acid leaching method to extract metals, resulting in excessive heavy metals in the surrounding soil. The cost of later treatment far exceeded the recycling benefits, highlighting the importance of standardized treatment. In addition, if the wastewater and waste generated during the treatment process cannot be properly disposed of, it will also create new environmental burdens.
In response to these issues, the industry is making efforts from two aspects: technological innovation and policy support. Research institutions are accelerating the development of intelligent sorting equipment, which uses AI image recognition and spectral analysis technology to achieve rapid identification and precise separation of multi metal components. The intelligent sorting system developed by a certain enterprise can identify more than 10 types of metals in waste within 1 second, improving sorting efficiency by 40%. At the policy level, many regions have included the resource utilization of multi metal solid waste in the scope of circular economy support, provided tax reductions and subsidies to enterprises that adopt advanced technologies, and strengthened supervision of illegal disposal activities to promote standardized industrial development. In addition, the promotion of the "Internet plus+recycling" model has reduced the collection cost by integrating and distributing waste resources through online platforms. A recycling platform has reduced the cost of waste transportation by 20% through centralized scheduling.
The resource utilization of multi metal solid waste is a key measure to solve the contradiction between "resource shortage and waste surplus", and its development level is directly related to the deep promotion of circular economy. With the continuous advancement of technology and the continuous improvement of industrial ecology, polymetallic solid waste is expected to truly become a recyclable "urban mine", providing solid support for the construction of a resource-saving and environmentally friendly society.