Optical Sorter Buying Guide for Recycling
By Meadoworks | April 2026 | 11 min read
Key Takeaways
- Four sensor types: NIR (polymers), RGB (color), X-ray (density/atomic), induction (metals)
- Modern sorters process 1-15 tons per hour at 90-99% purity using compressed-air ejectors
- Top brands: TOMRA, Pellenc ST, Bühler, Steinert, Sesotec, MSS — most have multi-sensor configurations
- Used pricing: small NIR sorters $80k; multi-sensor X-ray combinations $750k+
- Critical inspection: sensor calibration, ejector valves, compressed-air supply, and software version
Optical sorters are the heart of every modern materials recovery facility (MRF) and plastics recycling plant. They turn mixed waste streams into mono-material commodities that command premium pricing — and they do it at speeds that no manual picking line can match. This guide explains how optical sorters work, the major sensor technologies, the leading brands on the used market, and the inspection points that matter most when buying a pre-owned machine.
Four Optical Sorter Sensor Technologies
NIR (Near-Infrared)
Identifies polymers and other materials by their molecular spectral signatures. The standard sensor for plastics sorting.
Best for: Polymer separation: PET, HDPE, LDPE, PP, PVC, PS, ABS, PLA. Paper grade separation. Bone-from-meat separation in food.
RGB (Visible Color)
Full-color line-scan cameras identify particles by visible color, shape, and texture. Often combined with NIR.
Best for: Color sorting (clear vs colored PET, glass cullet by color), paper grade sorting, and removing visually distinct contamination.
X-Ray Transmission
Sees through particles to identify density and atomic number. Distinguishes materials with similar surface appearance.
Best for: PVC removal from PET (chlorine), heavy metals from cullet, treated wood, PCBs in e-waste, zorba aluminum alloy separation.
Induction Sensor
Electromagnetic sensors detect conductive metals, both ferrous and non-ferrous, regardless of color or shape.
Best for: Stainless steel removal, aluminum recovery, copper identification, mixed-metal stream separation in scrap and e-waste.
How an Optical Sorter Works: A Process Overview
Acceleration & Spreading
Material is delivered onto a vibrating chute or high-speed belt that spreads it into a single layer moving at consistent velocity.
Sensor Detection
Sensors above (and sometimes below) the stream identify each particle in real time — material type, color, shape, and position.
Decision Logic
On-board software determines which particles match the target rule set and computes the precise timing for each ejection.
Compressed-Air Ejection
A bank of high-speed pneumatic valves fires bursts of air that deflect target particles into one stream while the rest fall through to another.
Common Recycling Applications
Single-stream MRF
Combination NIR+RGB sorters separate paper, plastics by polymer, glass by color, and metals from a mixed residential recycling stream. Multiple sequential sorters achieve material-grade purity.
PET Recycling (Bottle Plants)
Sequential NIR sorters separate PET from HDPE/PP, then RGB sorters separate clear PET from colored. X-ray PVC-removal sorters protect downstream extruders from chlorine contamination.
HDPE Color Sorting
RGB sorters separate natural (translucent) HDPE from colored (pigmented) HDPE for high-value reprocessing. Natural HDPE commands a premium for clear bottle and pipe applications.
Plastic Film Recycling
NIR and induction sorters in film washing lines remove labels, metal contamination, and incompatible polymers before pelletizing. Critical for film-to-film recycling.
E-Waste & Metals
X-ray and induction sorters separate copper, aluminum, brass, and stainless from shredded e-waste and metal scrap. NIR identifies plastic housings for separate processing.
Glass Cullet
RGB sorters separate clear, green, and amber cullet to industry color specs. X-ray and laser sensors remove ceramics, stones, and metal contamination that damage glass furnaces.
Top Optical Sorter Brands
TOMRA
Models: AUTOSORT, AUTOSORT FLAKE, X-TRACT
Norwegian global leader in optical sorting. AUTOSORT line is the most installed sensor-based sorter in MRFs and plastics recycling worldwide. Strong service network and continuous software updates. Premium pricing reflects benchmark performance and uptime.
Pellenc ST
Models: MISTRAL+, COMPACT+, XPERT
French builder with strong installed base in European MRFs and growing in North America. Combines NIR, RGB, and induction sensors. Known for high-resolution sorting on smaller particles and excellent purity.
Bühler
Models: Sortex (food), TotalSense, plastics sorting
Swiss multi-industry leader. Bühler optical sorters dominate food sorting (rice, nuts, coffee) and have a growing footprint in plastics recycling and recovered material classification. Known for engineering precision and global support.
Steinert
Models: UniSort PR, KSS combination, X-ray sorters
German specialist in metal recovery and combined-sensor sorting. KSS series combines NIR, RGB, induction, and X-ray in a single platform — particularly strong in zorba and e-waste applications.
Sesotec
Models: FLAKE PURIFIER, VARISORT+, PIKKA
German builder focused on plastics flake sorting and contamination detection. FLAKE PURIFIER is a recognized standard for sorting PET flake before extrusion or food-grade reprocessing.
MSS / CP Group
Models: ADR, FiberMax, PlasticMax, GlassMax
American MRF equipment specialist with a full optical sorting product line. Strong in single-stream MRF retrofits and U.S.-based service. Often paired with CP Group's screens and conveyors.
Used Optical Sorter Pricing
| Configuration | Price Range |
|---|---|
| Small NIR sorter (1m wide, single-sensor) | $80,000 – $200,000 |
| Mid-size NIR sorter (1.4-1.6m) | $150,000 – $350,000 |
| Wide NIR sorter (2-2.4m) | $250,000 – $500,000 |
| Combination NIR + RGB sorter | $200,000 – $600,000 |
| X-ray transmission sorter | $200,000 – $700,000 |
| Multi-sensor combination (NIR + X-ray + induction) | $400,000 – $750,000+ |
Compressed Air: The #1 Forgotten Cost
An optical sorter can consume 100-300+ scfm at 90-100 psi. Inadequate or unclean compressed air supply is the most common reason a properly specified sorter underperforms. Always verify your compressor, dryer, receiver, and filtration are sized for peak ejector demand — and budget for an upgrade if not. Many used-sorter buyers report their machine never matched its expected throughput because of supply-side air problems.
What to Inspect on a Used Optical Sorter
Sensor Bank Condition
Inspect NIR/RGB sensor windows for scratches, dust, and age-related drift. Verify sensor calibration to manufacturer reference cards. Sensor replacements run $10,000-$40,000 each.
Ejector Valves & Air System
Test every ejector nozzle through the diagnostic mode. Sticky or slow-firing valves cause missed ejections and reduce purity. Air consumption under load should match nameplate; high consumption indicates leaks.
Vibrating Feeder & Acceleration Belt
Verify feeder produces consistent, single-layer presentation. Worn belts cause overlapped particles that defeat the sorter logic. Listen for vibratory motor or belt drive problems.
Compressed Air Supply
Verify the compressor, dryer, and receiver are sized to peak ejector demand. Wet or oily air contaminates valves and sensors. Inadequate supply causes ejector lag and missed targets.
Software Version & Updates
Confirm software version matches current support. Material profile libraries are continuously updated; outdated software may not recognize new packaging types. Upgrade costs vary widely.
Wear Liners & Chute Surfaces
Inspect material-contact surfaces for wear and abrasion. Worn chutes affect material trajectory and sorting accuracy. Replacement liners are a routine consumable.
Frequently Asked Questions
What is an optical sorter and how does it work?
An optical sorter is an automated machine that identifies and separates materials based on their optical and physical properties. Material is fed onto a vibrating conveyor or chute that spreads it into a single layer at controlled velocity. Sensors above and/or below the material stream — near-infrared (NIR), visible light (RGB cameras), induction, or X-ray — identify each particle in real time. A bank of compressed-air ejector nozzles fires precisely timed bursts that deflect target items into one stream while the remainder falls into another. Modern sorters process 5-15 tons per hour with 90-99% purity at the eject side.
What is the difference between NIR, RGB, and X-ray optical sorters?
NIR (near-infrared) sorters identify polymer types by their molecular spectral signatures — perfect for separating PET, HDPE, PP, PVC, and PS in plastics recycling. RGB or full-color cameras identify materials by visible color and shape — used for sorting paper, glass by color, or removing colored bottles from clear PET. X-ray sorters detect material density and atomic composition — used for separating heavy non-ferrous metals, removing PVC from PET (chlorine signature), or identifying lead in glass cullet. Many modern sorters combine multiple sensor technologies in a single machine for higher purity.
How much does a used optical sorter cost?
Used optical sorter pricing depends on width, sensor configuration, and age. A small 1-meter NIR sorter typically runs $80,000 to $200,000 used. A 2-meter NIR sorter ranges from $150,000 to $400,000. Combination NIR+RGB sorters run $200,000 to $600,000. Multi-sensor X-ray plus NIR systems can exceed $750,000. Total cost of ownership includes air consumption (compressed air is the largest operating cost) and periodic sensor calibration.
What materials can optical sorters separate?
Plastics: PET, HDPE, LDPE, PP, PVC, PS, ABS, and even biopolymers like PLA. Color sorting can separate clear from colored PET or natural HDPE from mixed-color HDPE. Paper: separating cardboard from mixed paper, removing contamination. Glass: by color (clear, green, amber) and to remove ceramics or metals. Metals: distinguishing aluminum, copper, brass, stainless, and zorba alloys with X-ray or induction sensors. E-waste: PCB recovery, plastic-housing separation. Wood: separating treated from untreated lumber, removing painted board.
How should I size an optical sorter for my MRF or recycling plant?
Sizing starts with infeed throughput (tons per hour), particle size distribution, and target purity. Small in-plant sorters (1-meter wide) handle 1-3 tph. Mid-size MRF sorters (1.4-1.6 meters) handle 3-8 tph. Wide MRF sorters (2-2.4 meters) handle 8-15+ tph. Compressed-air supply must be sized to peak ejector demand — 100-300+ scfm at 90-100 psi depending on sorter width and rejection rate. For plastics recycling lines, plan for 2-3 sequential sorters (single-stream → polymer-specific → color-specific) to achieve 99%+ purity.
Sourcing or Selling Optical Sorters?
Meadoworks works with MRF operators, plastics recyclers, and metals processors to source used optical sorters and complete sorting lines. We can help you scope a system or sell surplus equipment from facility upgrades.
Browse recycling equipment or contact our team. Call 800-323-0307.
