When Retrofitting Makes Sense vs. Greenfield

Factor	Favors Retrofit	Favors Greenfield
Building/utilities	Existing building is adequate; power, compressed air, and water are in place	Building is at capacity, undersized, or poorly laid out; utilities require major upgrade
Throughput target	Modest increase (20-50% above current)	2x or more throughput increase; existing conveyors and bunkers cannot handle the volume
Material mix	Similar to current feedstock; existing upstream equipment (shredders, screens) still suitable	New material types requiring fundamentally different upstream processing
Permitting	No change to permitted capacity or emissions; retrofit qualifies as like-for-like replacement	New permit required for expanded capacity or changed process
Capital availability	Budget constrained; phased investment preferred	Full capital budget available; long-term economics favor clean-sheet design
Downtime tolerance	Cannot shut down for more than 1-2 weeks	Can accommodate 2-6 month construction period (possibly with alternative processing arrangements)

Common Retrofit Scenarios

Scenario A: Manual Picker Replacement

Before: 8-12 manual pickers on a sorting line removing specific contaminants (e.g., PVC bottles from PET stream, or non-paper items from a fiber line).

After: Optical sorter installed at the same position in the line. Ejection system removes contaminants automatically. 2-4 pickers retained for quality control and oversized items.

Typical result: Purity from 88-92% to 96-99%. Labor reduction of 4-8 FTE per shift. ROI: 10-14 months at developed-country labor rates.

Watch for: Conveyor transition before and after the sorter must provide adequate material singulation. Existing conveyors designed for manual picking are often too wide with poor material distribution — they need narrowing or replacement with vibratory feeders or accelerator belts.

Scenario B: Adding Polymer-Specific Sorting After a Mixed Line

Before: Single-stream processing of mixed rigid plastics with magnetic and eddy current separation, producing a mixed-plastic output sold at low value.

After: NIR optical sorter installed after eddy current, splitting the mixed plastic stream into PET, HDPE, and PP fractions for separate sale.

Result: Revenue increase of $80-200/t (selling sorted mono-polymer bales vs. mixed plastic). ROI: 12-18 months at typical volume.

Scenario C: Purity Polish Before Baling

Before: Sorted material goes directly to baler. Occasional contaminant bales downgraded or rejected by buyer.

After: Compact optical sorter installed as a final purity check between the last sorting stage and the baler. Removes last 1-3% of contaminants.

Result: Downgrade/ rejection rate reduced from 5-15% of bales to <1%. Often the highest-ROI retrofit because the sorter is small (low capital) and the avoided downgrade cost is immediate and measurable.

Retrofit Planning Checklist

1. Audit current line performance: Measure purity, recovery, throughput, and labor for each stage. This is your baseline. Run a material composition audit on samples from each point in the line.
2. Identify the bottleneck stage: The stage where purity drops most or where manual labor is concentrated. This is where optical sorting delivers maximum impact.
3. Map the required conveyor and space modifications: Optical sorters need specific infeed and outfeed conditions — singulated material, specific drop heights, clean air supply, and access for maintenance.
4. Plan the controls integration: New optical sorters need to communicate with upstream and downstream equipment. Plan the PLC/HMI integration before installation.
5. Schedule around maintenance windows: Coordinate installation with planned maintenance shutdowns. Pre-fabricate mounting frames, cable trays, and ducting off-site.
6. Run acceptance tests: After commissioning, run a challenge test with known-feedstock to verify that purity and recovery targets are met at the design throughput.
7. Train operators on the new system: Optical sorters require different operator skills than manual picking lines. Provide training on sensor calibration, recipe management, and basic troubleshooting.

Common Pitfalls in Retrofit Projects

• Underscoping the upstream modifications: The optical sorter is only as good as the material presentation. Inadequate feeding, singulation, or dust control will prevent the sorter from achieving its rated performance. Budget for upstream conveyor and feeder upgrades — they are typically 20-40% of the total retrofit cost.
• Ignoring the reject handling: The optical sorter will generate a reject stream that needs to be conveyed, stored, and processed or disposed of. If the reject handling system is undersized, operators will reduce the ejection rate to avoid clogging — directly defeating the purpose of the sorter.
• Inadequate compressed air: Optical sorters with pneumatic ejection consume significant compressed air (typically 2-8 m³/min per meter of sorter width at 6-8 bar). Existing plant air systems are often undersized for this additional load. Verify compressor capacity and air quality (oil-free, dry) before installation.

Recommended AISORT platforms

Retrofit projects usually work best with modules that can improve classification without forcing full line replacement.

AISORT Multi-Sensor Fusion Sorter

Adds stronger classification capability to plants facing unstable or complex feedstock.

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AISORT High-Speed Vision Sorter

A practical upgrade path where throughput and reduced manual dependence are the main targets.

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