What is a single-stream recycling system?

The US recycling industry processes over 69 million tons of material a year, and the majority of it comes from single-stream curbside recycling programs. A single-stream recycling system describes the network of conveyors, sort stations, screens, magnets, optical sorters, and balers that separate the unsorted material into sellable commodity streams.

What is single-stream recycling?

Single-stream recycling (or single-sort or commingled recycling) is a collection method in which all accepted recyclables go into one bin or cart instead of being separated by material type before pickup. The mixed stream is collected by truck and delivered to a materials recovery facility (MRF), where equipment and personnel sort it into individual commodity streams: fiber, plastics, ferrous metals, non-ferrous metals, and glass.

Single-stream recycling is the dominant collection model in the US because it lowers collection costs and increases participation rates. The tradeoff is that it concentrates contamination risk and processing complexity at the facility level, which is where conveyor layout, sort station design, and equipment choices influence output quality.

How a single-stream recycling system works

The process follows a defined sequence from inbound delivery to baled output:

Step

Action

Equipment involved

Mixed recyclables arrive at the MRF

Tipping floor, loader

Material feeds into the sort line

Infeed conveyor

Large contaminants and hazards are removed

Pre-sort station

Fiber and containers are separated

Screens, disc screens, OCC screen

Ferrous metals are recovered

Belt magnets

Non-ferrous metals are recovered

Eddy current separators

Plastics and containers are refined

Optical sorters, manual quality control

Sorted material is prepared for market

Baler, discharge conveyors

What materials move through a single-stream system?

A single stream system handles the full range of common residential and commercial recyclables in a single mixed flow:

Paper

Mixed paper, newspaper, and other fiber

Cardboard

Old corrugated containers (OCC) and other corrugated material

Plastics

PET bottles, HDPE containers, and other accepted plastic types by resin code

Ferrous Metals

Steel cans and tin cans

Glass

Bottles and jars, where accepted by the local program

A recycler’s equipment capabilities determine which materials are accepted and recovered.

Contamination enters alongside accepted material. Plastic bags, garden hoses, textiles, food waste, e-waste, batteries, and bulky items create processing problems at the sort line. Pre-sort stations are the first line of defense.

The role of conveyors in a single-stream recycling system

Conveyors are the connective tissue of single-stream recycling systems. Every separation stage depends on a conveyor to receive material, present it at the right rate, and transfer it to the next stage.

The conveyor system controls flow rate, which affects how much material sorters can process per shift and how consistently screens and optical sorters can perform. An infeed conveyor that dumps too much material at once creates a pile-up at the sort station. A transfer conveyor running at the wrong speed creates gaps that reduce optical sorter accuracy. Belt width, speed, elevation changes, and discharge geometry affect downstream performance.

Roller chain conveyors

Handle the heavy, abrasive, and high-impact material that enters at the infeed: mixed recyclables with glass shards, dense cardboard, metal cans, and wet contamination.

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Equipment used in a single-stream recycling system

A complete single-stream MRF uses a coordinated set of equipment specific to its operation. This list covers the major equipment types used in single-stream processing systems:

Infeed conveyors move mixed recyclables from the tipping floor into the sort line.
Sort stations give sorters safe, ergonomic access to the moving stream.
Transfer conveyors move material between screens, separators, sorters, and balers.
Pre-sort stations remove bulky contaminants and hazardous materials before mechanical separation.
Screens and disc screens separate 2D fiber from 3D containers and size material.
Belt magnets pull ferrous metals from the stream.
Eddy current separators eject non-ferrous metals such as aluminum.
Optical sorters identify and eject material by type using sensor technology.
Ballistic separators separate 2D and 3D material by trajectory.
Glass breakers process glass for separate handling or removal.
Baler infeed conveyors deliver sorted commodity material to the baler.

All Fluent custom recycling sort systems can be designed to coordinate with any combination of the above equipment. Fluent's conveyor designs account for elevation, transition geometry, belt speed, and discharge points to ensure each component in the line feeds cleanly into the next.

Sort stations

Sort stations are the manned section of the line where personnel remove oversized contaminants, QC sorted streams, and pull problem materials that automated equipment misses. Fluent builds standard recycling sort stations in 4, 6, 8, 10, and 12-man configurations for manual sort operations. Standard systems ship faster and suit facilities with defined throughput needs and established sort line layouts.

Custom sort systems are available for facilities that need a different footprint, higher throughput, or integration with automated separation equipment. Custom systems can be manual, semi-automated, or fully automated depending on the facility's labor model and commodity targets.

Screens

Screens are the workhorses of fiber and container separation. A disc screen or OCC screen uses rotating discs or stars to let fines and smaller material fall through while 2D fiber rides over the top. Screens operate continuously and require even material distribution from the infeed conveyor to function at capacity.

Magnets and eddy current separators

Belt magnets suspended over the conveyor line lift ferrous metals out of the stream without interrupting flow. Eddy current separators use a rapidly rotating magnetic field to repel non-ferrous metals (primarily aluminum) off the belt and into a collection chute. Both are passive once installed and rely on consistent material presentation from the conveyor feeding them.

Optical sorters

Optical sorters use near-infrared sensors and air jets to identify and eject specific material types at high speed. A single optical sorter can make thousands of ejection decisions per minute. The accuracy of those decisions depends on how well the material is presented: single-layer depth, consistent speed, and even distribution across the belt width.

What is the difference between dual-stream and single-stream recycling?

In a dual stream system, residents separate fiber (paper and cardboard) from containers (plastics, metals, glass) before collection. The MRF receives two already-separated streams and does less separation work. In single stream, the MRF receives one mixed stream and must perform all separation internally.

Single stream is better when collection cost reduction and participation rate are the primary goals, and the MRF has the equipment to manage contamination. Dual stream is better when fiber quality is a market priority, and the collection operation can support the added complexity.

What is the difference between dual-stream and single-stream recycling?

Contamination and material quality

Contamination is the central operating challenge in single-stream recycling. When non-recyclable material enters the stream, it degrades the purity of sorted bales, increases residue, raises processing cost, and in some cases makes material unsaleable. Common contaminants include plastic bags, hoses, wires, textiles, food-soiled containers, e-waste, and batteries.

The contamination rate in US MRFs averages under 20% of inbound material by weight, according to a nationwide survey of MRF operators published by researchers at the University of Wisconsin–Madison. Contaminated material enters the facility and must be removed or disposed of without generating revenue.

Conveyor layout and sort station design are the two primary engineering levers for managing contamination before it reaches mechanical separation:

Pre-sort station placement:

A pre-sort station early in the infeed line removes the largest and most problematic contaminants before they reach screens or optical sorters, where they can cause jams or cross-contaminate separated streams.

Material presentation speed:

Materials must move slowly enough for manual sorters to work efficiently but fast enough to maximize throughput.

Belt width and load distribution:

Wider belts and even load distribution across the sort face reduce the chance that sorters miss problem material bunched at one edge of the stream.

Commodity buyers set purity thresholds for accepted bales, and material that falls below those thresholds is either downgraded, rejected, or returned at the facility's expense. Facilities that invest in better sort station and conveyor design recover the cost through improved bale revenue and reduced residue disposal.

How Fluent Conveyors supports single-stream recycling

Fluent builds conveyors and sort systems for single-stream recycling facilities across the US. Our systems are designed for the material handling demands of commingled recyclables.

Our single stream offerings include:

We design and build custom conveyor systems and sort lines to order, with all fabrication done in the US. Our engineering team works from your facility layout, material characteristics, and throughput requirements to configure a system that fits your space and hits your output targets.