Co-mingled recycling, also known as single-stream recycling, has become an increasingly common method of collecting recyclable materials in many municipalities and commercial settings. Its appeal lies in simplicity: residents and businesses place all recyclable materials—paper, plastic, glass, and metals—into a single bin, which is then collected and sorted at a centralized facility. While convenient for users, co-mingled recycling presents unique challenges and requires sophisticated processing systems.

This article explores the full journey of co-mingled recycling, from the moment recyclables are placed in curbside bins to their processing at a materials recovery facility (MRF).

What Is Co-Mingled Recycling?

Co-mingled recycling refers to a system where different types of recyclables are collected together without being separated by the consumer. These materials typically include:

• Paper and cardboard

• Plastics (e.g., PET, HDPE)

• Glass bottles and jars

• Aluminum and steel cans

This system contrasts with source-separated recycling, where consumers sort recyclables into different bins based on material type. While co-mingled recycling increases participation due to its convenience, it also leads to increased contamination and greater reliance on technology at the sorting stage.

Step 1: Collection from Curbside Bins

The process begins at the curb, where recycling trucks—often equipped with compacting mechanisms—collect co-mingled recyclables from homes, businesses, and institutions. These trucks are designed to transport mixed materials without excessive compaction to prevent damage that would complicate sorting.

In many municipalities, collection occurs on a weekly or biweekly schedule, depending on population density and infrastructure. Once collected, the materials are transported to a nearby MRF for sorting and further processing.

Step 2: Delivery to a Materials Recovery Facility (MRF)

Upon arrival at a materials recovery facility, co-mingled recyclables are unloaded onto a tipping floor. From here, the materials enter the sorting system via conveyor belts. MRFs are designed to handle massive volumes—sometimes hundreds of tons of recyclables per day—and must quickly separate materials by type and purity.

There are two main types of MRFs:

1. Clean MRFs, which process recyclables collected from residential or commercial sources with relatively low contamination.
   
   

2. Dirty MRFs, which handle recyclables mixed with non-recyclable waste and require more intensive sorting.

For co-mingled recycling, clean MRFs are typically used.

Step 3: Initial Manual Sorting

Before automated systems take over, facility workers perform a pre-sort to remove contaminants such as plastic bags, electronics, or non-recyclable materials. These contaminants can damage equipment or degrade the quality of recycled output.

This stage is critical, as contaminated loads can result in higher rejection rates later in the process.

Step 4: Mechanical Separation Technologies

After pre-sorting, materials move through a series of mechanical and automated sorting processes. These technologies are key to making co-mingled recycling viable at scale. Major sorting technologies include:

• Screens: Rotating or vibrating screens separate materials based on size and shape. For example, paper and cardboard are often lifted over disc screens, while heavier items fall through.

• Air classifiers: These use air jets to separate lighter materials (like paper or plastic films) from heavier ones (like metals and glass).

• Magnets and eddy currents: Magnets remove ferrous metals (iron and steel), while eddy current separators are used to eject non-ferrous metals like aluminum.

• Optical sorters: Using infrared sensors and cameras, these machines identify different types of plastics and fibers, then direct air jets to separate them accurately.

• Glass cleanup systems: Broken glass is separated by size and density, and often cleaned of labels and debris before being sent for reuse.

The goal is to sort the materials into clean, uniform streams that can be sent to specialized recycling processors.

Step 5: Baling and Shipping

Once the materials are separated, they are compressed into bales—large, dense blocks that are easier to store and transport. Each bale consists of a single material type, such as PET plastic, cardboard, or aluminum. These bales are then sold to recycling companies and manufacturers that turn the materials into new products.

Markets for these bales vary in quality and price depending on contamination levels, demand, and global market trends. Higher purity leads to better marketability and environmental outcomes.

Challenges with Co-Mingled Recycling

While co-mingled recycling increases convenience and participation, it does introduce several challenges:

• Contamination: Materials like greasy pizza boxes, plastic bags, or unwashed containers can render entire loads unrecyclable.

• Material degradation: Glass often breaks during transport and sorting, making it harder to recover cleanly.

• Equipment damage: Non-recyclable items can jam or break automated machinery, increasing maintenance costs and downtime.

Education campaigns and clearer labeling on recyclable products can significantly reduce contamination and improve system efficiency.

Conclusion: The Importance of Efficient Recycling Sorting Solutions

The success of co-mingled recycling hinges on advanced processing technologies and public cooperation. While it simplifies collection, it shifts the complexity to the sorting stage—requiring precise systems and well-managed facilities. As urban populations grow and recycling goals become more ambitious, investing in smarter recycling sorting solutions is essential to ensure that co-mingled recycling remains both effective and sustainable.