Optical Sorters in Recycling & Composting: What You Need to Know

Material only has value within a recycling or composting system when it can be separated to a quality that makes it suitable for future use. A bale containing too much of the wrong polymer can lose value, just as finished compost containing mixed pieces of plastic or glass can have limited end-use potential. Contamination reduces the marketability of recyclable commodities and finished compost, with effective separation being key to ensuring high-quality output.

Optical sorters are only one part of a wider processing line and are not a piece of machinery intended to replace every other separation method. Instead, optical sorters may work alongside screens, shredders, magnets, eddy current separators, air separation, and other waste recycling equipment to address the specific sorting needs of the facility.

Mechanical waste management systems separate material according to size, weight, density, and form. An optical sorter makes it possible to identify other properties, including polymer composition or color, and to remove non-organic contamination when composting.

An optical sorter is an automated sorting system that uses sensors or cameras to identify materials moving through a processing line, then separates selected items from the wider stream. The exact capability of an optical sorter will depend on the machine’s technology, with modern systems usually utilizing a combination of hyperspectral imaging, visual cameras, and near-infrared (NIR) sensors, along with software to distinguish between materials.

The operating process for an optical sorter is relatively straightforward.

Systems are moving beyond identifying broad polymer types and towards recognizing specific products. Current developments in waste management technology are focusing on AI-assisted recognition, enabling sorting technology to become more capable at recognizing specific products using a combination of visual information, including shapes, colors, and logos.

An optical sorter works best when it has a clearly defined role within the wider sorting line. An MRF may operate an optical sorter alongside shredding, screening, air separation, magnets, eddy currents, and other automated sorting systems.

Optical sorters should be placed within the sorting line where they can address a specific separation problem. At this point, the material should reach the sorter suitably prepared and distributed so that individual objects can be detected and separated effectively.

Our MRF solutions take an integrated approach with equipment selected and positioned according to the needs of the incoming material and the commodities the facility wants to recover. Upstream preparation is crucial for achieving this, including using screening and equipment like Westeria windsifters to separate light and heavy fractions.

Manual sorting carries significant ongoing labor costs, with optical sorting providing greater automation, reducing the reliance on manual intervention. It also removes the stress of recruiting and retaining employees for repetitive sorting roles, but the financial case for optical sorters goes beyond this.

More accurately separated commodities can produce more valuable bales, improving revenue while reducing operating expenditure. Labor cost, throughput, material recovery, bale purity, and commodity value all account for the return on investment (ROI) that MRFs can make from optical sorters.

An optical sorter can be configured to recover desirable material from the wrong stream or remove unwanted material from the target stream, depending on the objective of your sorting line. Its polymer identification is particularly valuable when visually similar plastics need to be separated.

Better separation can increase bale purity and reduce the amount of valuable material lost to residue. Using an optical sorter enables the recovered commodity to deliver its full value by ensuring it is sufficiently clean for a downstream processor to use.

Organic and composting streams can contain plastics and other non-organic contaminants that need to be removed before the finished material reaches its intended end use. Optical sorters help with the initial separation but are also useful for quality control and during the polishing stage by targeting contamination that earlier processing stages may have missed.

Optical sorters can work alongside other composting equipment to remove the final pieces of contamination that can make a genuine difference to the quality of the finished product.

Poor contamination removal can leave an organic fraction unsuitable for its desired application. More effective sorting enables processors to produce cleaner, more consistent, and more marketable finished compost.

An optical sorter can be the difference between an organic fraction that nobody wants in their garden and a product suitable for the consumer compost market. Better sorting leads to higher quality control and potentially more commercial opportunities.

Better sorting can recover commodities that might otherwise leave the recycling process as residue. Higher-purity recovered materials can also be more suitable for downstream processing and reuse, making it easier to adopt circular economy practices.

As a result, optical sorting can help facilities keep more usable material circulating within viable markets. At eFACTOR3, our plastic recycling solutions work to turn mixed waste into cleaner material streams that have a realistic route back into production.

Optical sorting helps to reduce landfill waste in an MRF by recovering recyclable material that could otherwise become residue. Similarly, it reduces waste in composting by removing contaminants so organic material remains suitable for productive use.

While optical sorting can’t solve landfill dependency by itself, it can contribute to its reduction when incorporated into an effective wider processing system by recovering more usable material.

The process for successful waste management starts by identifying the majority commodity streams and where valuable material is currently being lost. A detailed mass balance can show where good material is being lost and where contamination is entering finished bales.

The next step is to pinpoint the sorting gap to determine whether optical sorting technology can identify and separate the problematic material. It’s best to identify the point within the existing process where an optical sorter could address this loss the most effectively. The right positioning will help maximize the commodity value and bale quality for a higher ROI.

For many MRFs, it’s best to work backwards by considering the point of view of the customer to determine if better sorting could create a viable new commodity stream or fill a product gap.