NIR sorting is an automated sorting technology that uses near-infrared light to identify materials. As items pass under a sensor on a fast conveyor, each polymer reflects a characteristic spectrum, and the machine recognises PET, HDPE, PP, LDPE and others in milliseconds.
Precisely timed air jets then blow the selected items off the belt into a separate stream. NIR sorters process several tonnes per hour with high purity, and can be combined with cameras that sort by colour. Their main limitation is black plastic coloured with carbon black, which absorbs the infrared signal and goes undetected. Heavily soiled or multilayer items are also difficult. NIR is a core part of mechanical sorting in a modern MRF and in plastic recycling plants.
