Tire Recycling

Whole tires are first shredded into rough chips, then passed through granulators and magnetic separators that strip out the embedded steel belt wire, followed by screening equipment that removes fiber reinforcement, leaving behind clean rubber crumb of various sizes. Depending on end use, that crumb may be sold as-is, refined further, or in some facilities sent to pyrolysis to recover oil and carbon black instead.

Tires are vulcanized rubber reinforced with steel belts and textile fabric, a composite structure that resists the same shredders used for plastics or paper and requires multiple staged size-reduction and separation steps to fully liberate the rubber from the metal and fiber. Vulcanization also makes the rubber chemically cross-linked, so unlike thermoplastics it can't simply be melted and remolded — it has to be devulcanized, pyrolyzed, or used in particulate form.

Processing recovers steel wire (roughly 10-15% of a tire's weight), rubber in crumb or granulate form, and textile fiber reinforcement, each separated and sold into different downstream markets. Where tires go through pyrolysis instead, the process additionally recovers pyrolysis oil and a solid carbon black-like residue known as recovered carbon black.

Primary shredders reduce whole tires to rough chips, followed by secondary granulators that further size-reduce the material, with magnetic separators pulling steel wire out along the line and vibrating screens or air classifiers removing fiber to yield clean crumb rubber. Pyrolysis facilities instead feed shredded tire chips into sealed thermal reactors that break the rubber down in the absence of oxygen.

Most US states and many other jurisdictions ban whole tires from landfills because their shape traps methane gas and creates fire and mosquito-breeding hazards, which has been a major driver of dedicated tire recycling infrastructure since the 1990s. Many regions also run tire-specific extended producer responsibility or disposal-fee programs that fund collection and processing.

Crumb rubber goes into playground and athletic field surfacing, rubberized asphalt for road paving, and molded products like mats and mulch, while coarser shredded material is burned as tire-derived fuel (TDF) in cement kilns and industrial boilers as a supplement to coal. Pyrolysis oil can be refined into fuel or chemical feedstock, and recovered carbon black is reused in new rubber compounding or as a pigment.

Shredded tire material is heated in an oxygen-free reactor to several hundred degrees Celsius, thermally decomposing the rubber polymer instead of burning it, which yields pyrolysis oil, a combustible gas that can fuel the process itself, recovered carbon black, and the steel wire left intact for separate recovery. It's positioned as an alternative to crumb rubber production for tires or rubber grades that aren't suitable for mechanical processing.

Passenger, truck, and off-the-road tires differ in size, steel content, and rubber compound, so processing lines are often configured or scaled differently for each category, and giant OTR mining tires in particular require heavier-duty shredding equipment. Severely degraded, waterlogged, or contaminated tires can also foul granulators and screens, and some rubber compounds are better suited to TDF or pyrolysis than to crumb production.

Recycling scrap tires eliminates the fire and vector-breeding risks of tire stockpiles while recovering steel and rubber that would otherwise be wasted, and using tire-derived fuel or rubberized asphalt displaces virgin raw materials in those applications. Crumb rubber markets also provide a viable revenue stream that has made tire recycling one of the more mature end-of-life material recovery sectors in the waste industry.

Devulcanization technologies that partially break the rubber's cross-linked structure are advancing, aiming to let recycled rubber be reused in higher-value applications closer to virgin rubber rather than just crumb. Pyrolysis is also drawing growing investment as tire manufacturers commit to using recovered carbon black and pyrolysis oil in new tire production to meet sustainability and circular-economy targets.