Closing the gap in optical plastics sorting

Sesotec has begun testing its VARISORT+ CARBON BLACK sorting system on real-world waste streams. 

The VARISORT+ CARBON BLACK bridges a critical technological gap in optical plastic sorting. This system detects black plastic parts at a relatively coarse grain size after pre-shredding and reliably sorts them by material type — before the final grinding into fine granulate. 

The difficulty of sorting black plastics could be a thing of the past 

Previously, sorting black plastics was often only possible at much smaller grain sizes during the granulate stage, which meant material separation occurred later in the process, requiring significantly more sorting effort.

The main component of the innovation is Mid-Wave Infrared Technology (MWIR), which allows Sesotec to strategically expand its sensor portfolio into the wavelength range essential for reliably detecting carbon-black-containing plastics. While black plastics largely absorb visible light and the Near-Infrared range (NIR), making them difficult for conventional optical systems to detect, they exhibit distinctive spectral signatures in the MWIR range. This enables precise material classification.

The material is illuminated with mid-wavelength radiation. An MWIR sensor captures the material-specific spectra, which are then analyzed using intelligent software, established AI models, and Sesotec's extensive expertise in spectral analysis. This enables reliable differentiation of plastic types such as PE, PP, or ABS — even with highly absorbent carbon-black-containing plastics.

Sesotec supports established recyclers 

The key advantage of this technology is its seamless integration into the existing Sesotec platform. Users can continue to leverage proven software, algorithms, and AI models, ensuring high classification accuracy with minimal implementation effort.

"By transferring the system to our technical center, we've reached a crucial milestone," says Tobias Eder, head of Technologies Sorting and Plastics at Sesotec. "The feedback at IFAT highlighted the significant demand for a reliable solution to sort black plastics. With the combination of MWIR technology, intelligent software, and our extensive experience in spectral analysis, we can tackle this challenge early in the recycling process. Once integration is complete, we will deploy the system with our customers under real-world conditions and fine-tune it based on practical insights to perfectly suit each application."