In an economy which is becoming increasingly focused on being environmentally friendly and finding more sources of renewable energy, recycled tire rubber is making its way into industries as one such source for the creation of both “green” products and more cost-effective fuels. This being the case, there is a strong emergence of recycled rubber products, especially recycled rubber sheets, which have a plethora of applications, anywhere from the streets you drive on to the homes you live in. There is no limit to the ways in which these products can be used in every aspect of life. Research is constantly being conducted on how to recycle rubber, so that the methods involved may produce the most bountiful, cost-effective, and harmless products and bi-products. Not to mention the fact that over 260 million tires are discarded yearly. The durability of tires makes them difficult to keep in landfills. As a result, states have started campaigns subsidizing the development of tire derived products (TDPs). California and CalRecycle are at the forefront of strategies to reduce tire buildups. The California Department of Resources Recycling and Recovery (CalRecycle) is a state agency that promotes the importance of reducing waste.

While some methods have already been perfected and deemed completely trustworthy, there are still methods which will require more investigation before they are widely promoted for use. Nonetheless, these processes may provide an exciting look into the future of recycling! This piece will be a look into just how discarded rubber materials can be reformed into products that are available for our everyday use.

There are multiple processes used to properly reuse tires. Essentially, these processes involve separating what is rubber from what is not rubber; for the most part, it is the separation process that differs from method to method. Some of these processes are mechanically based, others are chemically based, but they all come down to isolating the rubber in the recycled tire rubber so that they may be utilized as TDPs and other applications.

First, the rubber is broken down by mechanical processes so that the non-rubber products, such as steel and nylon, may be removed. The tires are shred into strips which are then placed into granulators to be milled into assorted sizes and consistencies. Sometimes, machines use magnets to further aid in the separation of metals from the compound. A less-common step that is involved in this is to actually freeze the tires with liquid nitrogen to a temperature of -60®C, then, the frozen material is crushed and milled in a similar manner. These methods are fairly standard and simple, not having to use complex steps, making them the preferred ways on how to recycle rubber. Sometimes, the recycled tire rubber need not even undergo any of these processes, as old tires can simply be refurbished and used again for automobiles, or used for applications such as creating barriers, garden beds, and in some special cases, entire homes! We know that retreaded tires may at one time have conjured up images of unsafe vehicles, but that is no longer true. Do you know that most jet engine planes land on retreaded tires? That most commercial and public transit vehicles use retreaded tires? The largest portion of the discarded tires is converted into Tire Derived Fuels (TDFs) and is burned in cement or brick kilns as a fuel source.

But there is a recycling process that is a bit more complex than any of the ones previously explained, and in turn, the yields of this method are even more interesting! The method is called pyrolysis, and it involves heating materials in an oxygen-free environment. The process occurs under pressure and at temperatures above 430®C. Pyrolysis is used for the chemical decomposition of organic (carbon-based) materials. Unfortunately, research on pyrolysis has not been completed and is yet to be determined as commercially viable. Nonetheless, the process yields some interesting results, decomposing the recycled tire rubber into oils, gases, and char. The oil that is produced, called bio-oil, is being investigated as a replacement for petroleum-based fuels, and it can be used as boiler fuel or upgraded to renewable transportation fuels. The char (called bio-char, unsurprisingly), can be used on farms as soil amenders and can increase soil’s ability to retain water and nutrients, and prevent water contamination and soil erosion. Perhaps most astonishing is that the use of bi-char can help to alleviate global climate change through carbon sequestration. The syngas can also be converted into chemical compounds used in fueling. All of these are amazing developments in the field of recycled rubber products!

After the rubber has been isolated, and the “crumb” or “mesh” produced, it must then be reclaimed. The waste rubber is heated and treated with chemicals, and then processed mechanically into sheets. The mesh may be either treated with hot sulfuric acid to destroy the fabric in the tire, and heat treatment renders the scrap rubber useful as filler. Alternately, the compound may be heated with the use of alkali, an ionic salt, for periods of time ranging from twelve to thirty hours. The produced recycled rubber sheets are then used for a multitude of applications.

Promoting the use of recycled tire rubber to produce recycled rubber products is helpful in many ways. For one, using discarded materials is more cost-effective and more energy-efficient than producing new ones. Saving money and saving energy are both high on this country’s priorities, and recycling rubber does just that! Furthermore, by creating rubber that is perfectly fine for usage, the demand for new natural rubber is decreased, thus helping to keep down the expansion of Para tree farms, preserving still-untouched pieces of land in the tropics. This reduces the cost of products overall, including the cost of recycled rubber sheets. Not to mention the fact that Tire Derived Products are produced and sold at far lower prices than their so-called virgin counterparts. Lastly, discarded materials are kept from taking up space in landfills, leaving more room for other waste and reducing chances of pollution from landfill fires. Not only do you now know how to recycle rubber, you know the ways in which these processes can contribute to a greener, cleaner, more affordable future for all of us!