How plastic waste could one day be used to build roads

SEVERAL experiments are currently underway in the United States to make roads more environmentally friendly by incorporating waste plastic into their surface. For this purpose, various mixtures of asphalt and plastic have been developed and are now being tested on many road sections.

In recent years, about half a dozen US states have been testing a new mix of materials for road construction, using plastic recycled from shopping bags, bottles, printer ink cartridges and a host of other sources.

The idea is to build roads from waste that often ends up polluting, whether in landfill or in the natural environment. In all cases, the recycled plastic is combined with asphalt (composed of sand, stone or gravel and hydrocarbons) before this savvy mixture is applied to the road.

As a result, a certain number of pilot programs have been launched in several states. One of the reasons for this is new federal legislation encouraging the use of sustainable materials. In California, for example, a mixture of 90% asphalt and 10% plastic from ink cartridges was used on a construction site near Sacramento.

In Hawaii, near Honolulu, a section of road was created from a mixture containing recycled plastic polymers. Virginia, Pennsylvania and Missouri are also conducting experiments of this kind.

The question now is whether these roads built with recycled plastic are economically viable for US states, whether they are durable in the long term (more so than traditional asphalt) and whether they are safe for drivers (not causing potholes or ruts). For that, states are still waiting to see how these roads will hold up to extreme temperatures or weather conditions like frost.

There is also the question of the impact microplastics contained in the mixture could have on the environment. This aspect is being closely monitored to ensure that the microplastics do not seep into nearby waterways, for example.

The US Department of Energy's National Renewable Energy Laboratory (NREL) estimates that 44 million metric tons of plastic waste was dumped in landfill (2019 figures). Only 5% of such waste was recycled.