The Resin Identification Code (RIC) with a number inside a triangle does not guarantee an item is recyclable. This code was originally created for plastic manufacturers to identify resin content, not to serve as a consumer recycling guide. The actual recyclability of plastic depends on its chemical structure, physical form, manufacturing method, and local economic conditions for processing. Many plastics are rejected because they are incompatible with the existing machinery and market demands of Material Recovery Facilities (MRFs).
Plastics Rejected Due to Chemical Composition
The inherent molecular structure of certain plastics makes them chemically incompatible with standard recycling processes. Polyvinyl Chloride (PVC), identified by RIC 3, contains high levels of chlorine atoms. When PVC is heated during reprocessing, it releases hydrochloric acid (HCl) gas. This corrosive gas severely damages recycling equipment and contaminates batches of valuable polymers like polyethylene terephthalate (PET) or high-density polyethylene (HDPE).
Plastics under the RIC 7 category, labeled “Other,” are often complex resins or various chemically distinct polymers that cannot be easily separated. This category includes materials like polycarbonates and new bioplastics, which have different melt temperatures and processing requirements than common plastics. Introducing these mixed polymers into the recycling stream results in a finished material with unpredictable and low-quality physical properties, often making it structurally weak or brittle.
Polystyrene (PS), designated by RIC 6, presents a challenge due to its low density and high volume. Expanded Polystyrene (EPS), often known as Styrofoam, is mostly air, making it difficult and uneconomical to transport the vast quantities needed for profitable recycling. Polystyrene often contains residual styrene monomer, a chemical compound that can leach out. This raises concerns about its use in food applications and makes it less attractive for high-quality recycling.
Physical Forms That Clog and Contaminate
Many plastic items are rejected because their physical properties cannot be handled by the sorting equipment at a typical MRF. Flexible plastic film, such as shopping bags, dry cleaning wraps, and bubble wrap, are a primary example of mechanical failure. These lightweight, pliable materials are called “tanglers” because they wrap around the rotating screens and gears used to separate material sizes. This entanglement frequently shuts down the sorting line, requiring costly and time-consuming manual removal by workers.
Very small plastic items also pose a problem due to their size relative to sorting technology. Items smaller than two inches, such as loose bottle caps or small pill containers, are typically too small to be accurately detected by optical sorters. These small pieces often fall through the mesh of sorting screens designed to filter out fine contaminants like dirt. Consequently, these plastics are diverted into the residual waste stream or contaminate other fractions, preventing their recovery.
Even items made of otherwise recyclable plastic, like PET or HDPE, can be rejected if their shape is incompatible with the machinery. A whole plastic bottle is easily identified and sorted by an optical sorter. However, if that plastic is shredded or crushed into a flat shape, the screens may misidentify it as paper or cardboard. Small, round containers that roll easily on the conveyor belt are also difficult for optical sorters to detect and direct precisely.
Multi-Layer and Composite Materials
Modern packaging is often engineered to combine multiple materials for superior performance, which renders them unrecyclable through traditional methods. Multi-layer packaging (MLP) consists of two or more different polymer types, or plastic combined with materials like aluminum foil or paperboard, bonded together. This fusion creates effective barriers against light, moisture, and oxygen, preserving products like chips or pet food. However, the different layers cannot be separated economically once they are fused.
Composite packaging examples include laminated pouches, which may combine polypropylene (PP), polyethylene (PE), and aluminum. Since these different polymers melt at radically different temperatures and are chemically incompatible, melting them together produces a weak, impure material. The process of delaminating these layers to recover pure polymers is energy-intensive and cost-prohibitive for most recycling facilities.
Blister packs and certain yogurt cups also fall into this composite category, often sealed with a foil-based lid or a dissimilar plastic. The presence of even a small amount of non-plastic material, such as metal from the foil or the adhesive, is considered a contaminant. Because the technology and infrastructure to separate these materials at an industrial scale are not widely available, these composite materials are typically sent to landfills.
Processing and Market Limitations
A plastic item may be technically recyclable but still rejected due to limitations in the recycling infrastructure, dictated by local economics and technology. Many older municipal sorting facilities struggle to accurately separate dark or opaque plastics. The common Near-Infrared (NIR) optical sorter relies on reflecting infrared light to identify a plastic’s chemical signature. Black pigments, particularly carbon black, absorb this light, making the object invisible to the NIR scanner and causing it to be incorrectly shunted to the residual waste stream.
The economic viability of recycling significantly constrains what materials are accepted. Recycling is a business, and processing costs must be lower than the market value of the resulting product. Virgin plastic, made from cheap, subsidized fossil fuels, often costs significantly less than recycled plastic. This disparity reduces market demand for recycled material and removes the financial incentive for facilities to invest in machinery required to process lower-value polymers.
A lack of consistent end-market demand for certain polymer types means that even successfully sorted material may have no local facility willing to buy and process it. This forces MRFs to ship material over long distances, increasing transportation costs and negating environmental benefits. If a consistent, profitable market for a specific recycled plastic does not exist nearby, local programs often exclude that material to maintain cost-effectiveness.