Sustainability Initiatives In Tire Recycling
The U.S. tire industry is not only committed to sustainability throughout the lifecycle of a tire, it continues to advance initiatives that prioritize the health and environmental impacts of tire manufacturing and tire use; drive innovation in tire performance and safety and assure scrap tires are managed as valuable, sustainable materials, John Sheerin, director end-of-life tire programs for the U.S. tire Manufacturers Association (USTMA), said during a presentation at the 2018 Rubber Recycling Symposium in Niagara Falls, Canada.
Tire manufacturers recognize the growing importance of sustainable materials and have stepped up their research efforts and use of these materials, Sheerin said.
For example, more tire companies are using micronized rubber powders in new tire production and at the same time, investing in a range of projects designed to develop sustainable material replacements for other tire components, he said. Recovered carbon black from pyrolysis processing of scrap tires and devulcanized rubber are also reaching commercialization stages and being introduced in some tire formulations. Orange and soybean oils are being researched as a replacement for petroleum-based oils, Sheerin said.
Also underway: guayule and Russian dandelions are in development as a domestic source and alternative for natural rubber; bio-isoprene as a replacement for traditional synthetic rubber; wood waste as a replacement for polymer, and rice husk ash to replace silica.
The U.S. Environmental Protection Agency (EPA) has identified and recognizes the biogenic content in tires — 9 percent natural rubber content in passenger and light truck tires, while truck tires are 34 percent natural rubber, the agency said. EPA has also recognized the biogenic content in the tire derived fuel (TDF) citing it in both its 2010 Greenhouse Gas Reporting Rule and the 2011 and 2014 Rules for Emissions from Stationary Sources.
The natural rubber content in TDF is playing out in state incentive programs for biomass, Sheerin said. North Carolina utilities certified as renewable energy facilities for TDF receive and sell credits for the power generated from the natural rubber fraction in tires.
Georgia pulp & paper mills that buy scrap tires for TDF could receive a sales tax credit for the natural rubber fraction in tires, Sheerin said.
In answer to recent questions on zinc in tires, Sheerin said there is a petition in California to review zinc in motor vehicles under the Safer Consumer Products Regulation. Canada also has a study on zinc that is going out for public comment soon.
According to tire makers, zinc is essential for rubber vulcanization and there are no functionally acceptable alternatives under the Safer Consumer Products Regulation.
With many sources of zinc in the environment, the focus on zinc in tire tread is misplaced, Sheerin said.
Tire manufacturers are committed to producing technically advanced tires, Sheerin said. New tire developments are constantly in play with substantial changes every year, he said.
For example, Bridgestone is working on adding a thin polyfoam layer inside the tire to reduce vibration and road noise. “ Such changes in design could affect how end of life tires are processed and recycled,” he said.
Other technical advances including, sensors to measure tread depth, temperature and provide real time alerts to drivers; run flat technologies including self-sealing tires; self-inflating tires; air-free tires; reduced noise or noise dampening tire technology and stone ejection technologies, all contribute to tire safety, performance and sustainability but may present challenges to recycling tires, Sheerin said.
About 81 percent of scrap tires generated in the U.S. are recycled, according to USTMA’s latest tire recycling report. TDF remains the largest volume use for scrap tires, accounting for 43 percent of the 3.4 million tons of tires recycled in 2017, Sheerin said. While rubber modified asphalt is a cost effective proven product that consumed over seven million tires in 2017, it has the potential to be a high volume consumer of scrap tires, Sheerin said. He expects rubberized asphalt to do better in 2019 with new road construction on the upswing and concerted efforts by the tire recycling industry to help educate highway engineers, pavement contractors and others about its benefits.
Ground rubber accounted for 25 percent of the scrap tire market in 2017 and the use of tire derived aggregate in civil engineering applications comprised 8 percent of the scrap tire market, he said.
But, the real success story for scrap tires, is the reduction of the number of scrap tire in stockpiles over the last eighteen years, Sheerin said. Since 1994, the number of tires stockpiled in the U.S. has gone from about one billion to less than 60 million in stockpiles today.
© Scrap Tire News, December 2018