Rubber Recycling

Yes, all rubber is recyclable but not all rubber is recycled. This is either because individuals or companies do not bring rubber to collection stations, or because not all authorities accept rubber. This could lead to rubber ending up in landfills. Maintaining the characteristics of the rubber can pose a challenge when recycling.

Most rubber for the rubber recycling industry comes from waste tires. The rubber recycling industry turns waste rubber products into usable material, that can be applied to make new rubber products. Waste rubber can also be turned into fuel.

Waste rubber is a hard product to recycle due to:

• The durability of the material,
• The large volume of waste rubber,
• The hazards that are involved with handling and storage of waste rubber.

Until recently, the technology to deal with waste rubber did not exist. Rubber stockpiles were the standard, despite the (economic, health, and flammability) risks and hazards.

Fortunately, decades of coordinated effort have resulted in effective and efficient rubber recycling programs.

Also, newer technologies such as pyrolysis and devulcanization have made recycling of waste rubber easier.

Rubber is used in a variety of products, from tires on vehicles to disposable surgical gloves. Increasingly both manufacturers and legislators are realizing that rubber recycling is crucial for environmental sustainability. Rubber recycling can also improve the cost of manufacture.

The large volume of rubber waste produced globally makes it difficult to manage as accumulated waste rubber, especially in the form of waste tires, can pose a significant fire risk. Recycling rubber not only prevents this problem but can produce new materials with desirable properties that virgin rubbers don’t have.

However, recycling rubber presents challenges. The main challenge is to maintain the characteristics of rubber during the devulcanization process, which involves high heat and toxic chemicals.

Rubber recycling process

There is a complete industry dedicated to the rubber recycling process.

In the typical rubber recycling process, rubber is collected, shredded, sorted, and finally devulcanized to transform waste rubber into raw material.

Collection of rubber waste

Rubber waste is collected from deposits by individual households and from landfills whereafter it’s sent to recycling centers. In most cases, this rubber waste is in the form of a waste tire (ELT), the major rubber product.

Size reduction of rubber waste

To reduce rubber products into smaller particles a shredder/granulator is often the machine of choice. Reducing the size of rubber into smaller particles allows for easier processing during the sorting and devulcanization processes.

Click here for manufacturers of shredders for this application.

Crumb rubber

Rough crumb rubber is more manageable than whole waste tires but is not very useful. The rough crumb rubber still contains fragments of reinforcing fabric and wire.

Depending on the end market, additional processing may be necessary to remove those impurities and create a finer crumb size, or mesh.

Sorting of rubber waste

Sorting of rubber waste often occurs during the size reduction process. During this sorting process, steel fibers are removed from the rubber waste stream by means of a magnet.

Textile fibers are separated from the waste stream by using (shaking) screens, (wind) sifters, (low vacuum) suction equipment.

Devulcanization of rubber waste

Devulcanization of rubber waste is a process that reverses the “vulcanization” of rubber, recycling it so that it can be vulcanized again. This process converts waste rubber into a new “virgin” raw material.

Definition Devulcanization: A process that causes the selective breakup of the sulfur-sulfur (S-S) and carbon-sulfur (C-S) chemical bonds without breaking the backbone network and without degrading the material.

The devulcanized rubber can be mixed with virgin rubber or with other kinds of matrices to give new compounds without generating a significant decrease in mechanical and physical properties.

Many devulcanization process types are presented: chemical, microwave, ultrasound, thermomechanical, etc.

Other waste rubber processes:

Beyond this, there are other options for the processing of the waste rubber. They include:

Freezing

This concerns the freezing of the waste rubber to process its recycling. While this process is less common, it’s still as effective as devulcanization. In this process, the rubber gets frozen with the use of liquid nitrogen.

After the rubber is frozen, it gets processed in mills where it is grounded to create granules. These granules then become suitable to create new rubber products.

Pyrolysis of rubber waste

Pyrolysis of rubber waste offers an economically and environmentally beneficial method for transforming waste rubber into useful products, heat, and electrical energy.

Pyrolysis is a recycling method that involves heating (thermal decomposition) whole or shredded waste rubber in an oxygen-free reactor to break the polymers down into molecules.

These molecules vaporize into gases that travel from the reactor to a condensing system where the gas transforms into liquid oil.

Non-liquified gases return to the combustion system as fuel. The liquid oil collected by pyrolyzing rubber waste is often required for processes in the metal, alloy, or chemical industry.

Innovations in rubber recycling have increased the quality of materials produced through rubber recycling processes. These rubber recycling innovations have also reduced the need for chemicals used in the rubber recycling process.

Innovations continue to be of significant importance as the need for new sustainable, circular end-use markets.

Recent innovations include the innovative use recycled rubber into rubber pavement that repairs itself when it rains.

Another recent innovation by EcoTech converts shredded rubber from used tyres into an ultra-fine rubber powder that is filtered to remove impurities and then re-formed into rubber sheets.

Rubber recycling news and rubber processing news provides in-depth coverage of actionable examples of how rubber recycling professionals process irreparably or worn-down rubber products into reusable rubber materials.

Rubber recycling news and information topics include updates on product and equipment manufacturing, legislative news, original research, and material innovations.

Rubber recycling industry news gives recycling professionals a competitive advantage in the complex and ever-changing rubber recycling market.

Tire recycling can be described as the process of recycling waste tires/end of life tires (ELT) that are no longer acceptable for use on vehicles as a result of irreparable damage or wear. Tire recycling technology is utilized for this process.

Definition End of Life Tire (ELT): A tire that can no longer serve its original purpose on a vehicle. This excludes used tires that are reused, retreaded, or exported in used cars.

Landfill disposal of waste tires

Landfill disposal of waste tires presents serious environmental concerns. Part of the risk lies with the chemical makeup of tires. Toxins released from tire decomposition, incineration, or accidental fires can pollute the soil, air, and water.

The tire recycling industry is very divided and under stress due to increasingly stringent legislation. Although the tire recycling industry is growing steadily and it’s important to recycle waste tires, they are very challenging to break down.

Rubber tire recycling

Rubber tire recycling is the processing of tires dumped in landfills and end-of-life tires into materials reusable for new products. When the functionality of tires decreases due to wear or damage and are not easily reparable, tires are considered end-of-life and are suitable for recycling.

When recycling rubber products, you can reuse the ground rubber that you get after shredding waste tires or use the waste tires as fuel either by burning them or making fuel out of them using pyrolysis. Reusing the ground rubber is the most environmentally friendly way of recycling tires since almost all the rubber is reused.

Failure to recycle waste tires is a missed opportunity to produce the useful secondary raw material. In certain applications, ground rubber has unique properties that are superior to traditional materials:

• Shock absorption
• Sound absorption
• Non-slip
• Lightweight
• Permeable
• Insulating
• Abrasion and crack resistant

There are a lot of tire recycling processes that can be used to recycle waste tires. Tires can be recycled into rubber and steel wires that can be reused or the tires can be recycled using Tire pyrolysis and used as fuel.

Steel wire removing

Tires have steel wires int them to help with resistance. The steel wires need to be removed before the tires can be recycled. The steel wires can be reused for new steel goods and the rubber moves on to the next step in the recycling process.

Whole tire processing

After removing the wires, the rubber tires need to be reduced in size. There are two ways to reduce the size of the tires:

1. Mechanical – A shredder is used to reduce the rubber into smaller pieces, the size of the pieces can be regulated using a granulator.
2. Cryogenic – The tires are frozen with liquid nitrogen. The frozen tires are then smashed to smaller pieces with a hammer mill. All left over steel pieces can be removed with a strong magnet and other materials can be removed with an air classifier.

Screening

At this point in the process all of the rubber is screened and all steel and other fibers that affect the usability of the rubber are removed. During the screening process the rubber is also sorted by the size of the particle and any pieces that are too big are removed.

Cleaning

At this stage, the screened rubber is cleaned using water or other cleaning substances. The rubber can now be used as raw material. Examples of uses of the rubber are in rubber shoes and playground turfs.

Tire pyrolysis

Pyrolysis is a recycling method whereby whole or shredded tires are heated in an oxygen-free reactor. The rubber gets softened and the polymers start breaking down into smaller molecules. These molecules then gasify and leave the reactor.

The gasses can be either burned directly to generate power or condensed into a fluid that can be used as fuel. Not all molecules can be condensed but these smaller molecules can be used as a fuel. Not all parts of the tire can be used for fuel, after the pyrolysis process about 40% (by weight) of the tires can be removed as ashes.

Examples of manufacturers for turnkey tire recycling systems are CM Shredders, Eldan Recycling A/S, Fornnax, Eco Green Equipment, and many more.

Image: CM Tire Shredders / CM Industrial Shredders

Tire recycling innovations continue to be of significant importance as the need for new sustainable, circular end-use markets.

Recent tire recycling innovations include:

Genan  takes in all types of tires – from cars, vans and trucks – and in a highly technological production process separates them into their original elements: rubber, steel and textile fibers. The output consists of 75 percent rubber powder and granulate, 15 percent steel and 10 percent textile fibers.

Australian tire recycler Green Distillation Technologies (GDT) partnered with CarbonScape, a company based in New Zealand, to turn the carbon created in its recycling process into high value graphite.

Wastefront, a rubber waste recycling company, converts disused tyres into useful commodities, including liquid hydrocarbons and carbon black, which can then be reutilised in processes such as alternative fuel manufacturing or ground rubber production.

Danish manufacturer of tyre recycling equipment, ELDAN Recycling A/S, has developed a new sensor-based system to detect foreign objects in tyre shreds and reduce the risk of breakdowns and yearly down time.

Projected to solve a big issue in the mining field, the HYPERTYM™ integrated mobile unit reduces of all OTR mining tires and all oversized tires up to 63”, allowing for easy recycling and disposal of used tires.

The unique Pyrum-Thermolysis is a thermal dismantling of organic substances respectively rubber and plastic waste under exclusion of oxygen.

RubberJet Valley is a chemical specialty company specialized in the production of engineered raw materials (Polymers) called RubberJet Powder (RJP ™) and RubberJet Granules (RJG ™) capable of replacing virgin raw materials (for example Natural Rubber) in a wide range of applications including which mixes new tires.