I. What is Mixed Waste?
In daily life, a typical garbage bag might contain beverage bottles, waste paper, leftover food, and broken glass. This combination of waste of different types is a typical example of “mixed waste.”
Mixed waste refers to a state where recyclables, organic waste, hazardous waste, and other waste of different types are mixed together without proper sorting or sorting. Based on its source, it can be categorized into household waste, commercial waste, construction waste, etc. Its typical characteristics include:
– Complex composition: Diverse physical forms (solid, liquid), chemical properties (organic, inorganic), and hazards (harmful, harmless)
– Cross-contamination: Mixing of dry and wet waste leads to contamination of recyclables; for example, oil stains on paper reduce its recycling value.
– High processing difficulty: Direct landfilling or incineration may result in resource waste or secondary pollution.
II. Mixed solid waste management: Waste Sorting System
– Pre-treatment unit: Bag-breaking machine tears open garbage bags, trommel screens are preliminarily grouped by size, and magnetic separators extract ferrous metals.
– Near-infrared separator: Utilizes differences in molecular vibration frequencies to accurately identify plastic types (e.g., PET, PP).
– Eddy current separator: Generates electromagnetic repulsion against non-ferrous metals, achieving the separation of aluminum and copper.
– Optical separator: Separates glass and specific plastics through color recognition.
– Air separator: Separates lightweight plastics from heavy materials based on differences in specific gravity. In intelligent control, Sensor networks monitor sorting parameters in real time, and AI algorithms dynamically optimize equipment coordination.
Taking a demonstration project as an example, mixed waste enters the system and undergoes a progressive process of “coarse screening – crushing – multi-stage sorting”: first, large foreign objects are removed by a drum screen; then, a shredder homogenizes the material; near-infrared equipment identifies PET bottle flakes; an optical system sorts transparent glass; and finally, an airflow device separates thin-film plastics. The entire process is carried out in a closed negative-pressure environment, with a dust and odor collection rate exceeding 95%.
III. From Sorting to Recycling: Resource Regeneration
Sorted materials enter specialized recycling channels, forming a closed loop of “waste-raw materials-products”:
Plastic Recycling Line: PET bottle flakes, after deep cleaning and melt granulation, can be converted into textile fibers (such as recycled polyester fabric). One ton of recycled PET is equivalent to saving 6 tons of petroleum.
Metal Remelting: Aluminum cans are compressed into ton bags and sent to smelters for remelting, consuming only 5% of the energy required for ore smelting.
Paper Remanufacturing: Deinked pulp removes ink particles through flotation technology, and recycled paper achieves up to 90% of the strength of virgin paper.
Organic Matter Utilization: Organic waste undergoes anaerobic fermentation to produce biogas, and the residue is used to make biochar to improve soil.
Data from a circular economy park in Beijing shows that through meticulous sorting, the resource utilization rate of mixed waste has increased from less than 20% to 65%, reducing carbon dioxide emissions by approximately 80,000 tons annually.
The brilliance of the mixed solid waste management system lies in weaving these overlooked “end-of-life materials” back into the resource recycling network. In the journey of building an ecological civilization, ensuring that each type of waste is properly disposed of is not only a sign of respect for nature but also a responsibility to civilization.