As communities strive to increase recycling rates and reduce landfill waste, many municipalities have adopted co-mingled recycling—a system where recyclable materials like paper, plastics, and metals are collected in a single bin. This approach makes recycling easier for households and can boost participation rates. But how does co-mingled recycling actually work behind the scenes? From curbside pickup to complex sorting systems, here’s a detailed look at the entire process.
What Is Co-Mingled Recycling?
Co-mingled recycling, also known as single-stream recycling, allows residents to place all accepted recyclables into one container without the need to separate materials. This differs from dual-stream or source-separated systems, where paper products must be kept separate from containers like glass, metal, and plastic.
The primary advantage of co-mingled recycling is convenience. It reduces the effort required from the public and can increase the volume of recyclables collected. However, it also introduces challenges, especially in the sorting phase, due to the potential for contamination.
Step 1: Curbside Collection
The first step in co-mingled recycling begins at the curb. Municipal or private waste management services collect recyclable materials from households using specially designed trucks. These trucks often feature divided compartments to keep co-mingled recyclables separate from landfill waste or organics.
Drivers follow designated routes and collect bins placed outside homes or businesses, usually once a week. It’s important that residents follow local recycling guidelines, as incorrect items in the recycling bin—such as plastic bags, food-soiled containers, or non-recyclable plastics—can contaminate an entire load.
Step 2: Transportation to Material Recovery Facilities (MRFs)
Once the recyclables are collected, they are transported to a Material Recovery Facility (MRF). These facilities are designed to receive, separate, and prepare recyclables for processing into new products. There are two main types of MRFs: clean and dirty. Co-mingled recycling typically goes to clean MRFs, which only accept recyclables that have not been mixed with general waste.
The contents of the trucks are tipped onto a large floor area, known as the tipping floor, where operators conduct an initial visual inspection. Large or hazardous contaminants may be removed manually at this stage.
Step 3: Pre-Sorting
Before the automated sorting process begins, human workers often conduct manual pre-sorting to remove large non-recyclables, tanglers (like plastic bags or hoses), and contaminants that could damage equipment. This step is critical in maintaining the efficiency of the overall sorting system and preventing downtime caused by jams or equipment failure.
Step 4: Mechanical Sorting Processes
Once pre-sorting is complete, the co-mingled recycling materials pass through a series of mechanical separation technologies, each designed to isolate specific materials:
Screening
Rotating disc screens separate items by size and shape. For example, cardboard and paper are lifted over the discs while smaller items fall through.
Air Classifiers
Air jets or fans blow lighter materials like paper and plastic film away from heavier ones such as glass and metal.
Magnetic Separation
Ferrous metals, such as steel cans, are removed using strong magnets.
Eddy Current Separators
Non-ferrous metals like aluminum are repelled by a rapidly rotating magnetic field, allowing them to be separated from the waste stream.
Optical Sorters
Advanced facilities use optical sorters equipped with near-infrared sensors to identify and separate different types of plastics based on their polymer composition.
Glass Cleanup Systems
Glass, which often breaks during collection and transport, is sorted by size and color, often using vibrating screens and density separators.
Step 5: Baling and Shipping
After separation, the cleaned and sorted materials are compressed into bales—compact cubes of a single material type. These bales are easier to store, transport, and sell to manufacturers.
The materials are then shipped to specialized processing plants, where they are re-manufactured into new products. For example, aluminum cans may be melted down to create new cans, and cardboard can be pulped and turned into packaging materials.
Challenges in Co-Mingled Recycling
While co-mingled recycling offers many benefits, it also has drawbacks. One of the biggest issues is contamination, which occurs when non-recyclable or food-soiled items enter the recycling stream. Contamination reduces the value of recyclable materials and increases the cost of processing.
Another challenge is material degradation. For example, broken glass can mix with paper fibers or become embedded in plastics, making them harder to recycle. These challenges underscore the importance of public education and improved recycling sorting technologies.
Conclusion
Co-mingled recycling simplifies the process for households and can significantly increase participation rates. However, the behind-the-scenes process is complex and relies on a combination of human labor and advanced technology to ensure that materials are properly sorted and prepared for reuse. From curbside collection to high-tech recycling sorting systems, the efficiency and success of co-mingled recycling depend on both infrastructure and community cooperation.
