By A Saj Mathews:
Rubber recycling is the process of converting end-of-life or worn-out old tyres, tubes etc. into material that can be utilized in new products. New innovations in recycling promises better results and ensure a sustainable future for the rubber industry
According to the tyre industry, tyre recycling is a major success story. The stockpile of scrap tyres has shrunk from over a billion in 1991 to just 60 million by 2017. Several innovations are happening in the field of recycling of late. An Israeli company has developed a rubber recycling process that results in a high-quality recycled material that can be used to make a wide range of products. The method could help create new markets for recycled rubber, which are usually used only for low-grade applications.
The process, developed by EcoTech, a company based in Petah Tikva near Tel Aviv, 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. The resulting rubber can be used, for example, to produce heavy-duty rubber mats used in farming, or to make marine fenders which absorb the impact when ships dock.
The EcoTech rubber recycling process involves cooling the rubber granules to a temperature of -70o Celsius, prior to grinding the material into powder. Freezing of the rubber helps to maintain the natural qualities of the material, but current refrigeration processes are energy-intensive. EcoTech says that its new process uses about 11% of the energy normally consumed in freezing rubber.
In addition, the company says that its rubber recycling process minimises use of chemicals and generates very low emissions. Products made from EcoTech rubber can themselves be recycled using the same techniques, thus in principle closing the loop in the use of recycled rubber.
EcoTech was recognised in January 2015 when the company was shortlisted for a Circular Economy Award at the World Economic Forum, held in Davos, Switzerland. It was noted that EcoTech can produce rubber at substantially lower cost than synthetic rubber, which is synthesised from petroleum by-products.
An attempt to divert waste tyres
EcoTech’s rubber-recycling technology is one of a number of initiatives that have been attempted at to divert waste tyres from landfill or incineration. In the European Union, for example, the SMART project (Sustainable Moulding of Articles from Recycled Tyres, http://www.smart-recycle.eu) has been studying how moulding processes can be improved so that recycled rubber can be used to make products without the addition of resins to bind the rubber, and without the need to add virgin rubber to the mix.
Meanwhile, in South Africa, the REDISA system provides an example of how the collection and recycling of waste tyres can be incentivised through the introduction of a levy on new tyres being placed on the market. It is hoped that, over time, REDISA will result in innovations in the use of recycled rubber by efficiently providing raw material to innovators.
For more info: http://ecotrc.com
Over one billion end-of-life tyres are generated annually worldwide. Around 249.4 million scrap tyres were generated in the U.S. in 2017. Going back 100 years or so into the history of tyres, tyre recycling was a priority, with the price of an ounce of rubber rivalling the price of an ounce of silver. Such economic incentives faded, however. The introduction of synthetic rubber made from cheap imported oil, as well as by the adoption of steel-belted radial tyres made tyres cheaper as well as more difficult to recycle.
As a result, worn-out tyres increasingly found their way to landfills or were often dumped illegally. Fortunately, tyres are now increasingly diverted from landfills, says www.thebalancesmb.com
The urgency of recycling
About 16% of scrap tyre generation is still landfilled. Old tyres provide shelter for rodents and can trap water, providing a breeding ground for mosquitoes. In landfills, tyres consume up to 75% airspace. In addition, tyres may become buoyant and rise to the surface if they trap methane gases. This action can rupture landfill liners that are designed to prevent contaminants from polluting surface and groundwater. Recycling has been assisted through such programs as the Tire Stewardship BC Association and the work of leading recyclers such as Liberty Tire Recycling.
The three largest markets for scrap tyres include tyre-derived fuel (TDF), ground rubber applications/rubberized asphalt and civil engineering applications. About 43% of scrap tyres were consumed as TDF in 2018. TDF offers a viable alternative to the use of fossil fuels as long as proper regulatory controls are in place. Major applications include Portland kilns (46% of TDF), pulp and paper (29%) and electric utility boilers (25%).
Depending on the type of combustion system, tyres can be burned whole or in shredded form. Often times tyres must be reduced in size to fit combustion units, in addition to other preliminary processing. The US Environmental Protection Agency (EPA) notes the following benefits to burning tyres for fuel:
• Tyres produce the same amount of energy as oil and 25% more energy than coal
• The ash residues from TDF may contain less heavy metals content than some coals
• Results in lower NOx emissions when compared to many US coals, particularly the high-sulphur coals.
EPA stresses that facilities utilizing TDF should have a plan for tyre storage and handling, necessary permits for applicable state and federal environmental programs, and be in compliance with all the requirements of that permit.
Ground rubber applications
Ground rubber applications accounted for 25% of scrap tyre usage in 2017. Ground rubber is used to manufacture a number of products, ranging from asphalt rubber, through to track material, synthetic sportsfield underlay, animal bedding, and more.
The largest use of ground rubber is for asphalt rubber, utilizing approximately 220 million pounds or 12 million tyres annually. The largest users of asphalt rubber are the states of California and Arizona, followed by Florida, with usage anticipated to grow in other states as well.
Civil engineering applications consumed another 8% of the US scrap tyre generation in 2017. Such applications can replace other materials such as polystyrene insulation blocks, drainage aggregate, or other types of fill. The EPA notes that significant material for civil engineering applications come from stockpiled tyres, which are usually dirtier than other sources of scrap tyres and can be used as embankment fill and in landfill projects. While tyre recycling has made huge gains, the industry notes that TDF demand has declined modestly in recent years, prompting it to continue to develop other markets such as ground rubber.
Inputs courtesy: www.thebalancesmb.com