TerrAffix and Kier identify solution to microplastics road runoff challengeLaboratory testing undertaken by RSK Group company TerrAffix and Kier...
Published on by Lisa Templeton
Laboratory testing undertaken by RSK Group company TerrAffix and Kier has demonstrated that a plant-based material used to create a biochar can successfully remove microplastics found in the runoff from our roads.
These are believed to be the first laboratory trials in the world to look at the possibility of removing microplastics from road runoff using biochar.
The trials were carried out at Swansea University and found that there were no traces of microplastics in the road runoff. The next step for the collaboration is to look at how effective the solution is over time and it will be put to the test on Kier and National Highways A417 project, with details of the road trial in design now.
It is the second groundbreaking development to come out of the TerrAffix-Kier collaboration. In June last year, they announced they were embarking on a feasibility study to look at how vegetation removed from highways projects could be reused on site to make significant cuts to carbon.
TerrAffix Managing Director Mark Smith said: “Our companies were well aware of the concern about the impact of microplastics entering the environment from the surface water than runs off from our roads and enters the environment, including our water infrastructure, and we wanted to use our collective expertise to arrive at solution.
“TerrAffix and Kier could immediately see the opportunity to not only use biochar to reduce carbon emissions but to create a second, equally powerful contribution to environmental challenges. Now that the process to remove microplastics has been proven to be successful in the lab, we are, of course, keen to take it on the road to further demonstrate the process in the field. A mobile means of processing vegetation, cutting carbon and tackling microplastics is a huge innovation for the larger infrastructure and development sectors in the UK and, of course, across the world.”
Matt Tompsett, head of environment & sustainability at Kier Transportation, said: “We’ve been aware of the hidden impact of microplastics generated by the highways network for years. Ever since, we’ve been raising awareness of this issue and we know it’s a problem that needs addressing.
“We wanted to focus on a solution that could be deployed at scale within highway drainage systems. I had high hopes that biochar would be effective at removing microplastic, but the fact that there were no traces of microplastic is fantastic. Globally, there are no published papers at all which look at road runoff and microplastic removal using biochar, so this research is breaking new ground. As with all good research projects, they raise questions as well an answer them. We now know that biochar is very effective at removing microplastic from road runoff, but we don’t know if this effectiveness diminishes over time, so the next step will be to use in a real-world scenario on our National Highways A417 Major Project to find out.”
TerrAffix Chief Technical Officer Siôn Brackenbury said that road runoff was composed of a variety of environmentally damaging contaminants including metals (heavy metals including lead, copper, zinc and cadmium), hydrocarbons and microplastics.
“Microplastics enter the water system by collecting in road dust through sources such as tyre wear, polymer-modified bitumen used in road pavement, some road marking paints and road pavement made of recycled plastics. The microplastics in road dust are washed into waterways during storms making runoff one of the primary sources of microplastics in water systems. The ubiquitous nature of microplastics in natural environments, alongside their potential to transmit harmful pathogenic microorganisms and enter the food chain with associated risks to ecosystems and human health have caused global concern.”
The biochar study recently won in the Research category and won the overall award of the night at this year’s national Chartered Institution of Highways and Transportation (CIHT) awards,
Project notes
What is biochar?
Biochar is created through the process of pyrolysis when organic materials are turned into refractory carbon under high temperatures (thermal decomposition) in the presence of little or no oxygen, locking away carbon from the atmosphere for millennia.
Processing vegetation on site significantly reduces vehicle movements in road infrastructure projects.
What did the laboratory test entail?
A microplastic solution was used as a close representation of highway run off. The solution was passed through five water columns (in triplicate. 15 in total) each with a different filter stone/biochar ratio. The microplastics used in this study are commonly seen in field conditions. The solution was added to the columns three times daily over the period of two weeks. This volume was calculated from an average of the highest 30 daily precipitation values in Southeast England during the period 2000 – 2018, to mimic the nature of precipitation in the field. No microplastics were present in the solution once it had passed through the columns, demonstrating that even the lowest biochar/filter stone mix was affective at removing microplastics.