Solid waste refers to solid and semi-solid materials discarded during human activities—both in production and daily life—and is commonly known as "solid waste," or simply "SW." This includes solid particles separated from wastewater and exhaust gases. In essence, any solid or semi-solid substance generated throughout all human activities that has lost its original utility value for the owner is classified as solid waste. In production processes, the solid waste typically produced is referred to as "waste residue," while the solid waste originating from household and daily-life activities is called "garbage." However, it's important to note that the term "solid waste" is defined specifically from the perspective of the original owner. In fact, during various production or consumption processes, owners usually extract only certain valuable components from raw materials, products, or consumer goods. Yet, the majority of solid waste—though no longer useful to the original owner—often still contains valuable substances that could be repurposed. With the right technological processes, these materials can be transformed into essential raw materials for relevant industries—or even directly reused. Thus, the concept of solid waste is inherently relative, evolving with changes in time and space. Promoting the societal recycling of resources aims to maximize resource utilization, boost both social and economic benefits, and minimize the volume of waste requiring disposal, ultimately contributing to sustainable societal development.

Application

The dual pressures of dwindling natural resources and solid-waste pollution threatening the environment are putting human survival and quality of life at risk. Comprehensive utilization of solid waste stands out as an effective strategy for conserving resources and preventing environmental contamination. Many countries are actively engaged in both the practical implementation and research of solid-waste resource recovery. In China, however, resource utilization faces significant challenges, characterized by "three lows": low per capita availability—despite the country ranking third globally in total mineral reserves, its per capita share remains just half the world average; inefficient resource use, with a predominantly "resource-intensive" and wasteful approach; and a low rate of solid-waste recycling, typically below 20%, while the remaining 80% is discharged as waste, contributing to widespread environmental pollution. As a result, the integrated management and sustainable utilization of solid waste—aiming for both resource recovery and harmlessness—has increasingly become a priority for society.

Generally speaking, solid waste often holds significant potential for development and utilization. In China, the annual emissions of industrial slag and mine tailings amount to 600 million tons. These solid wastes contain valuable resources such as metals, rare metals, and construction materials, which remain highly recoverable and can still be put to productive use. Additionally, society has accumulated as much as 600 million tons of scrap metal resources, with at least 35 million tons available for recycling each year—resources worth over 220 million yuan. Cities generate vast amounts of municipal solid waste, rich in recyclable materials like paper, fiber, metal, and glass. Some types of solid waste can even be incinerated to produce heat, which can then be used for electricity generation and heating. Moreover, organic-rich waste—such as sewage sludge—can be fermented to efficiently capture biogas, which can be utilized either for power generation or as a renewable gas source.

In the area of solid waste resource utilization, China adheres to the principles of environmental harmlessness, economic efficiency, and technical feasibility, ensuring that solid waste recycling progresses toward achieving "three simultaneous outcomes"—environmental, economic, and social benefits—while also yielding initial successes.

Environmental Recycling Method for Hazardous Lead-Containing Solid Waste

Tin-lead alloy solder is widely used in the manufacturing of electronic information products. During the soldering process, high-temperature oxidation generates significant amounts of oxide slag. This oxide slag primarily consists of tin and lead oxides, classifying it as a hazardous solid waste containing lead. If disposed of improperly, it poses severe risks to both human health and the environment, making it a category of hazardous solid waste subject to strict national regulations.

Processing Procedure

1. Waste solder paste

The waste solder paste undergoes a physical heating process that separates the flux from the solder material. During this treatment, the temperature is carefully maintained below 240°C—specifically within a lower range—and kept under flux coverage, ensuring no lead fumes or other harmful gases are produced. After the waste solder paste containers are thoroughly cleaned with solvents, they can be disposed of as regular plastic products. Additionally, the cleaning solution can be distilled and recycled for reuse.

2. Remove Welding Slag

The use of heating, liquid covering, and reduction techniques not only reduces tin-lead oxides but also avoids the generation of lead fumes or other harmful gases, as the processing temperature matches the previously mentioned warm-up temperature used for waste solder paste treatment.

3. Preprocessing

Classify the solder paste and solder residue based on inspection results. The pre-processing steps for the solder involve removing the packaging material, ensuring no residual solder residue remains on the packaging. For the solder paste, the process includes taking it out of the plastic container and thoroughly cleaning the container with a solvent.

4. Process Flow for Regeneration Treatment of Lead-Containing Solid Solder Waste

Table 1 shows the process flow for the recycling and treatment of lead-containing solid waste solder. As indicated in the table, the first step involves inspecting and classifying the waste solder, followed by separate recovery processes tailored specifically for waste solder paste, waste oxidation slag, and pot-dump materials.

Table 1: Process Flow for Recycling Lead-Containing Solid Solder Waste

Processing steps

5. Recycling and Processing of Lead-Free Solder Residue

The recycling process for lead-free solder dross can follow the treatment method outlined in Table [2]1; however, it’s important to note that cross-contamination is a significant issue with lead-free solder materials, making proper sorting and screening absolutely critical. If handled improperly, the recovered solder will end up as a mixed product, severely diminishing its value for reuse.

Other issues

1. Safety Protection

To ensure electrical safety when using an electric heater for the regeneration of lead-containing solid waste, operators must wear insulated shoes and gloves during the process. When heating and stirring, take care to prevent liquid from splashing out of the heater, as this could cause burns. Additionally, exercise caution when dispensing and pouring molten solder to avoid high-temperature liquid splashes. Before pouring molten steel into molds, make sure the molds are completely dry—there should be no standing water on the floor, and oil or grease is strictly prohibited. During feeding operations into the heater, carefully avoid mixing explosives or moisture with the material. Regularly schedule maintenance of the heater by qualified personnel to guarantee safe operation and eliminate potential hazards. Finally, keep the work area clean, well-ventilated, and free from clutter.

2. Environmental Measures

During the handling, loading, and transportation of lead-containing solid solder waste, it is essential that the packaging used be robust enough to prevent solder from spilling and contaminating the environment. Each operation should be conducted with iron drums and other specialized tools on hand, ensuring that effective measures can be swiftly implemented should any solder residues accidentally scatter. In the recycling process of lead-containing solid solder waste, two key factors pose potential environmental risks: lead fumes and residual ash. The ash, a byproduct of solder treatment, typically appears as fine particles or a powdery residue. This material is essentially an oxidized mixture of lead and tin, yet it retains significant value for reuse in professional smelting facilities. To manage this residual ash responsibly during the recycling process, it is collected in iron drums and stored securely. Periodically, the ash is then handed over to smelters for paid processing, eliminating any risk of environmental contamination from these residues.

Solid waste refers to solid and semi-solid materials discarded during human activities—both in production and daily life—and is commonly known as "solid waste," or simply "SW." This includes solid particles separated from wastewater and exhaust gases. In essence, any solid or semi-solid substance generated throughout all human activities that has lost its original utility value for the owner is classified as solid waste. In production processes, the solid waste typically produced is referred to as "waste residue," while the solid waste originating from household and daily-life activities is called "garbage." However, it's important to note that the term "solid waste" is defined specifically from the perspective of the original owner. In fact, during various production or consumption processes, owners usually extract only certain valuable components from raw materials, products, or consumer goods. Yet, the majority of solid waste—though no longer useful to the original owner—often still contains valuable substances that could be repurposed. With the right technological processes, these materials can be transformed into essential raw materials for relevant industries—or even directly reused. Thus, the concept of solid waste is inherently relative, evolving with changes in time and space. Promoting the societal recycling of resources aims to maximize resource utilization, boost both social and economic benefits, and minimize the volume of waste requiring disposal, ultimately contributing to sustainable societal development.

Application

The dual pressures of dwindling natural resources and solid-waste pollution threatening the environment are putting human survival and quality of life at risk. Comprehensive utilization of solid waste stands out as an effective strategy for conserving resources and preventing environmental contamination. Many countries are actively engaged in both the practical implementation and research of solid-waste resource recovery. In China, however, resource utilization faces significant challenges, characterized by "three lows": low per capita availability—despite the country ranking third globally in total mineral reserves, its per capita share remains just half the world average; inefficient resource use, with a predominantly "resource-intensive" and wasteful approach; and a low rate of solid-waste recycling, typically below 20%, while the remaining 80% is discharged as waste, contributing to widespread environmental pollution. As a result, the integrated management and sustainable utilization of solid waste—aiming for both resource recovery and harmlessness—has increasingly become a priority for society.

Generally speaking, solid waste often holds significant potential for development and utilization. In China, the annual emissions of industrial slag and mine tailings amount to 600 million tons. These solid wastes contain valuable resources such as metals, rare metals, and construction materials, which remain highly recoverable and can still be put to productive use. Additionally, society has accumulated as much as 600 million tons of scrap metal resources, with at least 35 million tons available for recycling each year—resources worth over 220 million yuan. Cities generate vast amounts of municipal solid waste, rich in recyclable materials like paper, fiber, metal, and glass. Some types of solid waste can even be incinerated to produce heat, which can then be used for electricity generation and heating. Moreover, organic-rich waste—such as sewage sludge—can be fermented to efficiently capture biogas, which can be utilized either for power generation or as a renewable gas source.

In the area of solid waste resource utilization, China adheres to the principles of environmental harmlessness, economic efficiency, and technical feasibility, ensuring that solid waste recycling progresses toward achieving "three simultaneous outcomes"—environmental, economic, and social benefits—while also yielding initial successes.

Environmental Recycling Method for Hazardous Lead-Containing Solid Waste

Tin-lead alloy solder is widely used in the manufacturing of electronic information products. During the soldering process, high-temperature oxidation generates significant amounts of oxide slag. This oxide slag primarily consists of tin and lead oxides, classifying it as a hazardous solid waste containing lead. If disposed of improperly, it poses severe risks to both human health and the environment, making it a category of hazardous solid waste subject to strict national regulations.

Processing Procedure

1. Waste solder paste

The waste solder paste undergoes a physical heating process that separates the flux from the solder material. During this treatment, the temperature is carefully maintained below 240°C—specifically within a lower range—and kept under flux coverage, ensuring no lead fumes or other harmful gases are produced. After the waste solder paste containers are thoroughly cleaned with solvents, they can be disposed of as regular plastic products. Additionally, the cleaning solution can be distilled and recycled for reuse.

2. Remove Welding Slag

The use of heating, liquid covering, and reduction techniques not only reduces tin-lead oxides but also avoids the generation of lead fumes or other harmful gases, as the processing temperature matches the previously mentioned warm-up temperature used for waste solder paste treatment.

3. Preprocessing

Classify the solder paste and solder residue based on inspection results. The pre-processing steps for the solder involve removing the packaging material, ensuring no residual solder residue remains on the packaging. For the solder paste, the process includes taking it out of the plastic container and thoroughly cleaning the container with a solvent.

4. Process Flow for Regeneration Treatment of Lead-Containing Solid Solder Waste

Table 1 shows the process flow for the recycling and treatment of lead-containing solid waste solder. As indicated in the table, the first step involves inspecting and classifying the waste solder, followed by separate recovery processes tailored specifically for waste solder paste, waste oxidation slag, and pot-dump materials.

Table 1: Process Flow for Recycling Lead-Containing Solid Solder Waste

Processing steps

5. Recycling and Processing of Lead-Free Solder Residue

The recycling process for lead-free solder dross can follow the treatment method outlined in Table [2]1; however, it’s important to note that cross-contamination is a significant issue with lead-free solder materials, making proper sorting and screening absolutely critical. If handled improperly, the recovered solder will end up as a mixed product, severely diminishing its value for reuse.

Other issues

1. Safety Protection

To ensure electrical safety when using an electric heater for the regeneration of lead-containing solid waste, operators must wear insulated shoes and gloves during the process. When heating and stirring, take care to prevent liquid from splashing out of the heater, as this could cause burns. Additionally, exercise caution when dispensing and pouring molten solder to avoid high-temperature liquid splashes. Before pouring molten steel into molds, make sure the molds are completely dry—there should be no standing water on the floor, and oil or grease is strictly prohibited. During feeding operations into the heater, carefully avoid mixing explosives or moisture with the material. Regularly schedule maintenance of the heater by qualified personnel to guarantee safe operation and eliminate potential hazards. Finally, keep the work area clean, well-ventilated, and free from clutter.

2. Environmental Measures

During the handling, loading, and transportation of lead-containing solid solder waste, it is essential that the packaging used be robust enough to prevent solder from spilling and contaminating the environment. Each operation should be conducted with iron drums and other specialized tools on hand, ensuring that effective measures can be swiftly implemented should any solder residues accidentally scatter. In the recycling process of lead-containing solid solder waste, two key factors pose potential environmental risks: lead fumes and residual ash. The ash, a byproduct of solder treatment, typically appears as fine particles or a powdery residue. This material is essentially an oxidized mixture of lead and tin, yet it retains significant value for reuse in professional smelting facilities. To manage this residual ash responsibly during the recycling process, it is collected in iron drums and stored securely. Periodically, the ash is then handed over to smelters for paid processing, eliminating any risk of environmental contamination from these residues.