Acrylonitrile Butadiene Styrene (ABS) is a common plastic polymer used in durable goods, such as LEGO bricks, automotive trim, and computer casings. ABS is technically recyclable because it is classified as a thermoplastic material. Despite this, ABS is rarely accepted by typical residential, single-stream recycling programs. This exclusion from curbside collection is a central challenge in managing this high-volume plastic waste.
The Material Science of ABS Recycling
The ability to recycle ABS stems from its nature as a thermoplastic polymer. This property allows the material to be repeatedly melted and reformed into new shapes without significant chemical degradation. ABS is a terpolymer synthesized from three distinct monomers: acrylonitrile, butadiene, and styrene.
Each component contributes specific characteristics that make the material valuable for recycling. Acrylonitrile provides chemical resistance, butadiene adds impact strength, and styrene contributes rigidity and a glossy finish. The retained integrity of these properties after melting allows recycled ABS to maintain a good market value.
Practical Barriers to Curbside Collection
The primary obstacle preventing ABS collection in curbside programs is the lack of reliable identification at the Material Recovery Facility (MRF). Unlike high-volume plastics like PET (#1) and HDPE (#2) that have dedicated sorting streams, ABS is typically grouped into the ambiguous “Plastic #7 Other” category. Automated optical sorters cannot reliably isolate pure ABS because the #7 category contains a heterogeneous mix of various resins. Processing an unsorted blend is economically unfeasible for recyclers and results in low-quality end products.
The contamination risk is substantial, particularly with ABS sourced from electronics. ABS items often contain non-plastic contaminants that destroy the integrity of a recycling batch. These include metal inserts, glues, dyes, and, most critically, hazardous additives like brominated flame retardants (BFRs) or heavy metals.
When ABS containing BFRs is melted, the resulting recycled material is legally restricted from use in new consumer products like toys or food containers. This contamination renders large volumes of otherwise recyclable material unusable, which is why residential facilities typically decline ABS items.
Specialized Recycling Pathways
Since municipal programs largely exclude ABS, specialized pathways are necessary to capture this material stream. Mechanical recycling remains the most common method, involving the collection of pre-sorted industrial scrap or high-volume items like electronic casings.
In this process, the collected ABS is first shredded into flakes, washed, and thoroughly dried to prevent the polymer chains from degrading when heated. The clean flakes are then fed into an extruder, where they are melted, homogenized, and pushed through a die to form continuous strands or pellets. This pelletized material serves as a high-quality raw input for manufacturers.
Closed-loop and take-back programs, often facilitated by electronics companies, provide another specialized route. These manufacturer-driven programs ensure that a product’s ABS casing is returned to a controlled facility for processing. Because the source material is known and relatively uniform, these systems can easily dismantle, clean, and mechanically recycle the plastic into new components for similar products.
A unique, decentralized pathway exists within the 3D printing community. Dedicated desktop extruders allow hobbyists and small businesses to shred clean, single-source ABS waste, dry the flakes, and melt them into a fresh spool of filament. This process creates a self-contained, small-scale circular economy.