A Deeper Dive Into The Sorting Process
Waste Management’s sorting process is a sophisticated, multi-step operation designed to maximize the recovery of
recyclable materials while minimizing what ends up in landfills. Here’s a detailed breakdown of how the sorting process
typically works, specifically in Phoenix, AZ:
1. Collection and Transportation
It all begins with the collection of waste from residential, commercial, and industrial sources. In Phoenix, Waste Management
uses specialized trucks to gather recyclable materials, organic waste, and non-recyclable garbage, often in separate bins
provided to residents and businesses. These trucks transport the waste to a Material Recovery Facility (MRF) for sorting.
2. Pre-Sorting
Upon arrival at the MRF, the waste is first subjected to a pre-sorting phase. This initial step involves manually removing
large, non-recyclable, or hazardous items (like plastic bags, textiles, or electronics) that could damage sorting equipment.
Workers may also remove any contaminants that could interfere with the recycling process.
3. Mechanical Sorting
Once pre-sorting is complete, the remaining materials enter a series of highly automated, mechanical sorting systems
that use various technologies to separate recyclables based on their properties.
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Trommel Screens: These large, rotating drums are used to sift materials by size. Smaller items like glass shards
or dirt fall through holes in the screens, while larger items like cardboard, plastic bottles, and cans continue on for
further processing.
•
Air Classifiers: Air streams are used to separate lighter materials, such as paper and plastic, from heavier items like
metals and glass. The lighter materials are blown into a separate area for further processing, while the heavier ones
are sorted downstream.
4. Optical Sorting
Next, Waste Management employs optical sorters, which use infrared sensors to identify different types of plastics
based on their chemical composition. These machines can precisely sort materials like PET (from water bottles) and
HDPE (from detergent bottles), ensuring that each type of plastic is separated for recycling.
•
Near-Infrared (NIR) Technology: NIR scanners detect specific wavelengths reflected by different plastics, allowing
for high-speed sorting of multiple plastic types in seconds.
•
Color Sorters: Some optical sorters also use color recognition to separate materials, like distinguishing between
clear, green, or brown glass for recycling.
5. Magnetic Separation
For metal separation, the facility uses powerful magnets to extract ferrous metals like steel from the waste stream. This
method ensures that metal cans, appliances, and other steel-based materials are pulled away for recycling.
•
Eddy Current Separators: Non-ferrous metals (like aluminum and copper) are separated using an eddy current system,
which creates a magnetic field that repels non-magnetic metals, pushing them into a separate bin.
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DTPR MAGAZINE #15-5: September - October 2025