In 2020, California repaved a highway using recycled materials, including 150,000 plastic bottles per mile; it could last 2-3 times longer than conventional asphalt

What if an old road could help build the next one — while also giving thousands of discarded plastic bottles a second life?

That is what California transportation officials set out to test on a section of Highway 162 in Butte County. Instead of bringing in conventional hot-mix asphalt, crews used recycled pavement combined with a liquid plastic polymer binder made largely from discarded single-use plastic bottles.

The pilot project, carried out on three lanes of Highway 162 near Oroville, marked the first time the California Department of Transportation, or Caltrans, tested a state highway paved entirely with recycled materials. And the numbers behind the experiment are striking: one mile of road using the treatment can consume roughly 150,000 plastic bottles.

How does a plastic road work?

The technology was developed by Redding, California-based TechniSoil Industrial.

Rather than removing the entire roadway and transporting large quantities of new asphalt to the construction site, crews first grind up roughly the top three inches of the existing pavement.

That recycled pavement is then processed and mixed with a liquid polymer binder. A large portion of that binder is derived from recycled plastic bottles, particularly PET — the same type of plastic commonly used for bottled water and soft drinks.

The resulting material is then placed back onto the road surface.

This differs from Caltrans' conventional cold in-place recycling process. That system can recycle several inches of existing pavement, but the resulting material is generally used as a roadway base. A new layer of hot-mix asphalt still has to be transported from a plant and placed on top.

The TechniSoil process was designed to eliminate that additional step.

Why use plastic bottles in asphalt?

California has long faced a major challenge in dealing with plastic waste. According to CalRecycle, Californians used more than 12 billion plastic beverage bottles in 2017. Finding additional ways to reuse some of that material could potentially reduce the amount going to landfills or becoming litter.

But there is another potential advantage: transportation.

Traditional paving can require trucks to haul newly produced asphalt from a plant to the construction site. With the recycled process, much of the material needed for the surface is already at the site. That means fewer truck trips, potentially reducing fuel consumption, greenhouse gas emissions and other pollution associated with transporting asphalt.

Could the road actually last longer?

That is one of the biggest questions behind the experiment. Previous tests of the plastic-asphalt material indicated that it could potentially last two to three times longer than conventional hot-mix asphalt.

If that performance is confirmed on state highways, the implications could extend beyond recycling. A road that lasts substantially longer could require fewer repairs and resurfacing projects over its lifetime. That could reduce maintenance requirements and the disruption caused by repeated road construction.

But Caltrans was careful to treat the Oroville project as an experiment rather than proof that plastic asphalt was ready to replace conventional paving everywhere. The pilot formed part of a larger $3.2 million project covering about three miles of Highway 162. The specific experimental plastic-asphalt section cost approximately $90,000, and Caltrans planned to study how the material performed under real-world traffic and weather conditions.

California was not the first

Plastic-modified asphalt was not a completely new concept when Caltrans began testing it. Similar approaches had already been explored or used in places including India and the Netherlands. In California, earlier applications had been limited to a handful of surface-street projects in Los Angeles and San Diego.

The Highway 162 experiment was different because it put the technology on a state highway and allowed Caltrans to evaluate its performance under the agency's own road standards. The finished surface also looked much like conventional asphalt. One difference noticed during construction was that it produced less steam, while the roadway could be opened to traffic within hours.

What happens next?

For Caltrans, the real value of the Oroville project was not simply paving three lanes with plastic-derived material. It was gathering evidence. Officials needed to determine whether the recycled surface could withstand traffic, how quickly it would wear, whether its claimed durability held up over time, and whether the environmental and economic benefits justified wider use.

California already uses recycled materials in road construction, including crumb rubber made from discarded tires. The plastic-asphalt experiment represented another attempt to turn difficult waste streams into infrastructure. The idea is appealing because it tackles several problems at once: old pavement is reused, plastic waste is diverted into a new application, and the need to transport fresh asphalt can be reduced.

But there was also a question about whether plastic bottles were the best material for this purpose. Some environmental advocates pointed out that PET bottles already have established recycling markets and can be turned into new products. That makes the experiment less about simply finding a place to put plastic waste and more about determining whether using it in roads delivers a meaningful benefit compared with other recycling options.

Highway 162 was therefore more than a road project. It was a test of whether waste that would otherwise enter the recycling or landfill system could become part of the infrastructure people drive on every day.