The Future of Waste Sorting…
By Cyrine Boussabbeh, Researcher, Innofibre
What to do with the growing amounts of municipal, industrial, and commercial waste? This is the question we constantly ask ourselves to find solutions to divert them from landfills, benefit from them (e.g., in the energy sector), or even valorize certain components. These wastes are a major concern today, not only because of their increasing quantity but also due to increasingly stringent environmental limitations, pushing municipalities and industries to constantly seek valorization solutions. An effective recycling process primarily relies on proper sorting to separate valuable materials in the waste and find future outlets for them. Among the most widely used technologies in sorting centres worldwide is optical sorting.
What Is Optical Sorting?
Optical sorting is an innovative technology based on spectral detection in the near-infrared (NIR) and visible (VIS) frequencies, allowing the detection of molecular bond vibrations such as C-O, C-H, O-H, or N-H, to identify and classify materials from a waste stream. With this technology, it is possible to accurately sort solid materials from different waste sources. For example, in municipal waste, plastic bags can be separated from organic waste. In the commercial sector, this technology can separate multi-layer cartons from plastics. In the industrial sector, optical sorting is implemented in construction, renovation, and demolition (CRD) waste, allowing the separation of wood, plastic, and glass. This optical sorting technology is essential to improve the sorting of waste materials, to promote their recyclability, and ultimately, to reduce their environmental impact while fostering the principle of a circular economy.
How Does Optical Separation Work?
The optical separation process is as follows: the materials to be sorted are first spread on a conveyor belt that transports them to the detection system composed of UV-VIS sensors. These sensors analyze the spectral properties of the different materials in real time and send signals to pneumatic nozzles responsible for physically separating the materials according to their nature. These nozzles act instantly to direct the materials to their appropriate compartment.
In most cases, two possible configurations of physical separation can be achieved with the optical sorting system: binary sorting, where materials are separated into two compartments, and ternary sorting, which allows for three compartments (and consequently more advanced separation). The current limitations of the technology using a nozzle system do not allow for a separation beyond the ternary mode—necessarily limiting the diversity of materials that can be sorted simultaneously and/or requiring the series connection of several optical sorting units.
Innofibre’s Position
Innofibre is the only research institution in Canada equipped with an optical sorting system, whose use is highly requested for various research projects and proof-of-concept studies. This optical sorting technology enhances the precision and efficiency of the sorting process in general, leading to a higher recycling rate and a reduction in waste sent to landfills. Thus, it helps to reduce the carbon footprint and aligns with the objectives of the circular economy, which aim to minimize the environmental impact of waste (in accordance with the 2024-2028 government strategic plans). Since acquiring the PellencST Mistral+ optical sorter in 2018, Innofibre has conducted several research projects aimed at identifying and separating compounds such as cellulosic products and plastics. Although satisfactory results have been obtained, some equipment limitations have been identified during various research projects, including black objects. Indeed, materials that are too dark (any black object) are not correctly identified to date.
Improving Optical Sorting Capabilities
To make its optical sorting system more efficient and versatile, Innofibre has acquired a new electronic and software platform FLOW & CNS+ (Central Nervous System). This new system includes a new spectrometer with a wider wavelength coverage and a new algorithm offering more efficient calculations. Moreover, the system is designed to accept new technologies in the future.
This system integrates an improved sorting engine that will provide greater adjustment autonomy through various additional options. This innovative system contributes to reducing operational costs by up to 30% through the integration of the latest lamp technologies (more durable) and a reduction in compressed air consumption. This new module thus offers a significant gain of 2 to 10% in sorting efficiency and purity. Furthermore, sorting parameters can be modified instantly without interrupting the ongoing operation.
Regarding throughput, it has been improved for light bodies, with a speed capable of reaching 4.5 m/s on the conveyor; ensuring a significant increase in separation rates and thus a reduction in costs. Finally, the addition of a “Vision” colour detector will improve the distinction of objects to be sorted.
The new platform, along with the associated module additions to the optical sorting equipment, will serve to offer better yields and increased efficiency for research projects focused on sorting and separating various residual material streams.