Quality control by hyperspectral imaging in solid waste recycling: Fundamentals

A fast, reliable and low cost characterization of solid waste products as fed to a recycling process, and/or resulting from different processing actions, represents one of the most challenging targets in the recycling sector. Today, thanks to the strong technological development, different techniques are available according to different sampling strategies and analytical principles to detect specific physical-chemical attributes of solid waste particles. They represents the key factor to perform a full process monitoring and/or to apply specific control/tuning actions on the process itself. The attributes can be determined off-line (e.g. sample collection and laboratory scale analyses) or on-line (i.e. direct collection of the information of interest from the particle flow stream). In this paper the principles and the possibilities offered by the adoption of specialized devices allowing to develop on-line acquisition/processing strategies, based on HyperSpectral Imaging (HSI) and finalised to perform solid waste streams characterization, inspection and quality control actions, are investigated and discussed.