Liberty Tire Recycling has published what it describes as the first U.S. company-commissioned lifecycle assessment focused specifically on rubber-modified asphalt products derived from recycled tires, providing quantified greenhouse gas data for crumb rubber and three tire-derived asphalt additives. The assessment, conducted by Boundless using Liberty’s processing and manufacturing data, evaluated crumb rubber, SmartMIX, DOT Additive and TRXP from the end-of-life tire through processing to the point where the product leaves Liberty’s facility. According to the study, all three asphalt additives had production-related greenhouse gas footprints approximately 96% to 98% below an industry-average benchmark for styrene-butadiene-styrene polymer before accounting for additional avoided emissions. Once benefits associated with steel recovery, tire fiber use and avoided landfill disposal were included, all four assessed products produced net-negative modeled greenhouse gas results under each of three regional electricity-grid scenarios. Liberty said the findings provide transportation agencies, contractors and policymakers with additional evidence for evaluating rubber-modified asphalt as both a pavement material and a higher-value tire recycling outlet.

Assessment covers four recycled tire products

The lifecycle assessment examined four Liberty Tire Recycling products: crumb rubber and three asphalt additives marketed as SmartMIX, DOT Additive and TRXP.

The analysis measured greenhouse gas emissions associated with the material from the point an end-of-life tire enters Liberty’s processing system through production of the finished material at the company’s facility.

Boundless conducted the lifecycle assessment

Liberty commissioned Boundless to conduct the assessment using internationally recognized lifecycle assessment methodology.

The analysis incorporated Liberty’s own material, processing and manufacturing data to quantify greenhouse gas emissions per pound of product.

Asphalt additives compared with SBS polymer

The three tire-derived asphalt additives were compared with an industry-average benchmark for styrene-butadiene-styrene polymer, commonly used as a conventional asphalt modifier.

Before accounting for avoided emissions associated with other recovered tire components, Liberty’s asphalt additives were calculated to have greenhouse gas footprints approximately 96% to 98% below the SBS benchmark.

Dry mix additive shows largest modeled carbon benefit

Liberty said its dry mix rubber additive generated the largest carbon benefit among the materials evaluated.

The assessment calculated avoided greenhouse gas emissions of up to 0.577 kilograms of carbon dioxide equivalent for every pound of the product manufactured.

All four products show net modeled environmental benefit

After accounting for additional benefits from tire recovery, all four products evaluated in the study produced net-negative modeled greenhouse gas results.

Liberty reported greenhouse gas reductions ranging from approximately 0.47 to 0.57 kilograms of carbon dioxide equivalent per pound of product.

Steel recovery included in environmental accounting

The assessment considered the environmental benefit of recovering steel wire from end-of-life tires and using that material to replace virgin steel production.

Steel recovered during tire recycling can be returned to metal manufacturing, reducing demand for primary raw materials.

Tire fiber use also included

The analysis also accounted for the use of recovered tire fiber as an alternative to fossil fuel in cement manufacturing.

This recovery pathway was included alongside steel recycling and avoided landfill disposal when calculating the broader greenhouse gas impact of the tire recycling process.

Avoided landfill disposal contributes to results

Liberty and Boundless also incorporated avoided landfill disposal into the modeled environmental benefits.

The approach recognizes that processing end-of-life tires into usable secondary materials can displace disposal and redirect tire components into productive applications.

Three regional electricity scenarios evaluated

The lifecycle assessment modeled the products under three different regional electricity-grid scenarios.

According to Liberty, every product remained net negative in greenhouse gas terms under each electricity scenario after avoided emissions were included.

Independent expert reviewed assumptions and data

An independent expert specializing in waste tire materials reviewed the assessment’s data, assumptions and results.

Liberty said this external review was intended to strengthen transparency around the methodology and provide a more credible basis for communicating the environmental performance of recycled tire materials.

Study targets transportation agencies and contractors

Liberty said the findings are intended to help transportation departments, pavement engineers, contractors, consultants and infrastructure owners compare sustainability impacts when selecting asphalt modifiers.

The company argues that lifecycle data can complement existing information on pavement performance, cost and durability when agencies evaluate rubber-modified asphalt.

Rubber-modified asphalt could expand tire recycling markets

Greater use of recycled tire rubber in roads could create an additional high-volume market for material recovered from end-of-life tires.

This is particularly important as the tire recycling industry seeks to increase material recycling and reduce reliance on disposal and lower-value recovery routes.

Liberty points to pavement durability research

The company also referenced academic research on the performance of rubber-modified asphalt, including work led by Bill Buttlar of the University of Missouri–Columbia.

That research has examined the ability of recycled tire rubber to improve pavement resistance to cracking and rutting and potentially extend road service life.

Longer pavement life could influence lifecycle performance

The newly published assessment focuses primarily on production of Liberty’s products rather than the complete service life of finished pavement.

If rubber-modified asphalt extends pavement life or reduces maintenance requirements, those effects could create additional lifecycle benefits at the road-system level, although such impacts would require broader pavement-level assessment.

Study adds data to rubberized asphalt debate

Environmental benefits have long been cited as one of the arguments for using recycled tire rubber in roads, but product-specific lifecycle data have been relatively limited.

Liberty said the new assessment is intended to provide quantified evidence that can be incorporated into infrastructure sustainability decisions rather than relying solely on general recycling benefits.

Lifecycle assessment supports higher-value tire recycling strategy

Liberty has been working to move recovered tire material toward higher-value end markets including crumb rubber, molded products and rubber-modified asphalt.

Expanding these markets can improve the economics of tire recycling while creating additional demand for material recovered from end-of-life tires.

RMA remains growth opportunity for U.S. tire recycling

Rubber-modified asphalt remains one of the tire recycling industry’s targeted growth markets in the United States, with several states supporting demonstration projects, grants and road specifications involving recycled tire rubber.

Lifecycle data such as the Boundless assessment could give road agencies another tool for comparing tire-derived additives with conventional polymer modifiers as they evaluate future pavement projects.

Source: Tire and Rubber Association of Canada.