Liberty Tire Recycling released findings from a greenhouse-gas assessment conducted by Boundless that gives transportation agencies, paving contractors, and governments new evidence to support wider use of rubber modified asphalt.
Liberty partnered with Boundless to assess Liberty鈥檚 crumb rubber and three asphalt additives鈥擲martMix, DOT mix, and TRXP鈥攗sing Liberty鈥檚 material, processing, and manufacturing data. The study measured greenhouse gas emissions per pound of product, from the end-of-life tire through processing, ending when the product leaves Liberty鈥檚 facility.
The three asphalt additives tested had substantially lower production-related greenhouse-gas footprints per pound than an industry-average benchmark for SBS polymer, a conventional asphalt modifier.
The results can help road builders evaluate sustainability benefits alongside performance and value鈥攕trengthening the case for putting more recycled rubber into roads. Wider adoption could expand tire-recycling markets, conserve resources, and help communities stretch infrastructure budgets through longer-lasting pavement.
鈥淐ustomers are choosing our products because they work, but we also wanted to demonstrate definitively that each product has sustainability imbedded,鈥� said Stratton Kirton, vice president of sustainability at Liberty Tire Recycling.
The study also evaluated the benefits of recovering steel to replace virgin material, using tire fiber as a fossil fuel alternative in cement kilns, and avoiding landfill disposal. After accounting for these benefits, all four assessed products produced net-negative modeled greenhouse-gas results under each of the three regional electricity-grid scenarios.
鈥淏efore counting any avoided emissions, all three of Liberty鈥檚 asphalt additives sit roughly 96 to 98% below the SBS benchmark,鈥� said Patrick McElroy, a Boundless research analyst who helped build the assessment.
An independent waste-tire-materials expert reviewed the study鈥檚 data, assumptions and results. The findings provide a foundation for communicating recycled rubber鈥檚 sustainability value and advancing broader assessments of asphalt mixtures and pavement performance.
The assessment adds new environmental data to a substantial body of academic research and decades of real-world use supporting rubber modified asphalt鈥檚 performance and value. Research led by Bill Buttlar, the Glen Barton Chair in Flexible Pavement Technology at the University of Missouri鈥揅olumbia and director of the Mizzou Asphalt Pavement and聽Innovation Lab, highlights rubber modified asphalt鈥檚 ability to extend pavement life through resistance to cracking and rutting. Those improvements can deliver long-term cost savings while putting discarded tires to productive use.