EVs Have a Polluting Secret, and It’s Not Batteries

New research suggests that electric vehicles increase tire waste by up to 30 percent. As the world converts to EVs, the tire industry must change too.

A new study of electric vehicles and tires demonstrates a common problem with game-changing innovations. They come with hidden costs. It turns out that the heavy weight of these battery-carrying vehicles puts more stress on tires.

The problem is simple: Heavier vehicles burn through rubber faster. But what does that mean in terms of environmental impacts? That “lost” rubber (plus additives) doesn’t just “vanish.” Some of it is deposited on roads, washed into soils and waterways.

The vast majority of the rest ends up in landfills. We’re talking about a substantial rise of 20 percent, or just under 400,000 tons of tire material (in the U.S.) entering the waste stream as EVs become the norm.

Not Just Rubber

Aside from the rubber and steel in a typical tire, about 10 percent of a rubber tire can be classified as “additives” or chemical compounds. This suggests that up to 40,000 tons of this industrial pollution could be buried or shed each year.

To be fair, this pollution must be weighed against the vastly greater amount of CO2 pollution that will be avoided by switching from gas dependent cars to EVs (powered with renewably-generated electricity). That doesn’t let tires off the hook, however. These are different types of pollutants, raising different risks to human and ecological health. Both need to be addressed for future generations.

Notes: Sulfur is used in the vulcanization process, which cross-links the rubber molecules to improve elasticity and durability. Antioxidants and antiozonants protect the tire rubber from oxidative and ozone degradation, extending the tire's life. Plasticizers improve the flexibility and handling characteristics of the tire. Accelerators speed up the vulcanization process. Silane coupling agents are used with silica-reinforced tires to enhance strength and durability. Anti-degradants help prevent the rubber from deteriorating over time. Stearic Acid and Zinc Oxide are activators that make the vulcanization process more efficient. Other Specialty Chemicals can include a wide range of substances designed for specific performance traits, such as reducing rolling resistance or improving traction.

EV Weight: Double the Road Damage

Along with tire wear, EVs put more wear and tear on asphalt roads due to their 20 percent higher weight. One way to calculate this impact is to use something called the “Generalized Fourth Power Law.”

To illustrate, let's consider an average weight increase for EVs compared to ICE vehicles. Based on available data, let's assume the following:

Average weight of an ICE vehicle: 4,000 lbs

Average weight of a comparable EV: 4,800 lbs (20% heavier due to the batteries)

The Generalized Fourth Power Law states that the damage to the road is proportional to the fourth power of the axle weight. Based on this calculation, the damage ratio for electric vehicles (EVs) compared to internal combustion engine (ICE) vehicles is approximately 2.07. This means that, on average, an EV is likely to cause over two times more road wear than an ICE vehicle, purely due to its increased weight.

A complete life cycle analysis of EV conversion, then, also needs to take into account the additional impacts of more regular maintenance and replacement of roadways. 

Tire Recycling Blues

Unfortunately, tire recycling in recent years has declined precipitously. The market for scrap tires seems to have shrunk, despite the growth in waste.

I contacted Art Dodge (AD), CEO of Lancaster, Pennsylvania-based Ecore International. Here’s a transcript of what we discussed.

GB: Can you estimate the difference in average lifespan of tires used for EVs versus combustion vehicles for private use?

AD: EVs wear out tires approximately 30% faster than internal combustion engine (ICE) vehicles. This is partly due to their heavier battery weight, making the vehicles about 20% heavier than equivalent gas-powered vehicles. This added weight places greater stress on tires, leading to accelerated wear and tear. Moreover, the instantaneous maximum torque of EVs results in rapid acceleration, which increases friction and further contributes to tire wear.

GB: Can you underline the highlights of the research your coalition just published?

AD: Yes, the Recycled Rubber Coalition—of which Ecore is proud to be a member—recently published this white paper, which examines how the rapid adoption of EVs will lead to an increase in scrap tires. It provides practical solutions for the recycling and reuse of these tires. According to the report, the U.S. currently generates around 315 million scrap tires annually, and the Coalition projects a 12% rise in the quantity of scrap tires produced as drivers shift towards EVs. 

Here are a couple of graphs from that data:

GB: What's happening with the recycling market?

AD: Unfortunately, the U.S. tire recycling secondary use rate has been steadily declining, dropping from 96% in 2013 to 71% in 2021. While current technology allows us to recycle scrap tires for innovative uses, tire production has outpaced the potential markets for recycled rubber. According to the U.S. Tire Manufacturers Association, 22% of the total pounds of scrap tires consumed in the market in 2021 went to produce sports surfaces. Meanwhile, 28% was used for loose mulch and 34% was molded and extruded.

GB: That makes sense. What needs to be done to get more tires into the recycling stream? 

AD: Here’s my list: 

• More R&D: Further investment in research and development for using scrap tires is essential to match the increasing volume of discarded tires.
• Fees: We need tire purchase fees in all 50 states at the state level, to deter illegal tire dumping and promote tire recycling efforts. 
• Federal Enthusiasm: The U.S. EPA and Department of Energy should prioritize grants aimed at broadening the utilization of recycled rubber at the federal level. Recent efforts by the federal government have been notable in encouraging states to consider environmentally friendly materials like RMA, which offer significant environmental benefits and potential cost savings for taxpayers.
• Pro-Recycling Policy: Promoting policies that foster market expansion is a vital measure to facilitate the industry in achieving higher levels of tire reuse and recycling. For example, the Tennessee Department of Environment & Conservation awarded over $2.25 million in grants for recycled rubber initiatives.
• Smart Disposal: At the local level, it is important for counties to host tire collections. Community initiatives like these are great for promoting the responsible disposal of tires by local residents. 

Are Toxin-Free Tires Viable?

To date, alternatives to rubber tires have not gained a lot of traction in the market, but research is underway. The challenge? Tires are essentially life safety systems. Consumers expect products that perform as well or better than current rubber tires. The prospect of tires that contain fewer additives is attractive, however. Here are some of the more promising research angles being explored:

1. Dandelion Rubber : Research into dandelion rubber is promising not only because it offers a renewable source of rubber but also because the process of extracting rubber from dandelions may allow for simpler formulations with fewer toxic additives. The goal is to create a more natural rubber compound that still meets performance standards without the need for as many environmentally harmful chemicals.
2. Silica-Silane Technology: The use of silica-silane as a filler and reinforcing agent in tires can potentially reduce the need for certain additives that are used with traditional carbon black fillers. Silica-based compounds can provide comparable or superior properties, such as grip and durability, with potentially less reliance on harmful chemical additives.
3. Polymer Reinforcement: Incorporating recycled plastics (such as recycled PET) into tire manufacturing not only reduces waste but can also lessen the need for new synthetic additives, as the recycling process can sometimes retain beneficial properties of the materials without additional chemicals.
4. Exotic, Non-Rubber Polymers and Composites: Researchers are exploring entirely new materials that could one day replace traditional rubber compounds in tires. These materials are being designed with environmental impact in mind, potentially requiring fewer toxic additives to achieve the desired mechanical properties and performance.
5. Airless Tires (Non-Pneumatic Tires): While primarily focused on eliminating punctures and improving longevity, the development of airless tires may also offer avenues to reduce the use of harmful additives. The materials and designs used in airless tires can be engineered to minimize environmental impact, focusing on durability and performance without traditional rubber compounds and their associated additives.

Back to Batteries

Another way to head off a “tire-pocalypse” from the EV transition, of course, is to develop lighter batteries. If battery manufacturers succeed (rapidly) in reducing battery weight by at least 20 percent, at least some of the additional environmental harm from excess tire wear can be avoided. This doesn’t negate the fact that low rates of tire recycling remain a huge environmental problem in the United States. But it will at least buy us time to figure out what to do with the millions of scrap tires overwhelming our waste stream now.