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Kier trials highways vegetation project

15 June 2023

Kier trials highways vegetation project

In what is described as a UK first, the RSK Group company TerrAffix is undertaking a feasibility study with the Kier infrastructure group to look at how vegetation removed from highways projects can be reused on site to make significant cuts to carbon. 

A material called biochar is created through a process of pyrolysis, the thermal decomposition of materials, whereby organic materials are turned into solid carbon under high temperatures in the presence of little or no oxygen.

The study will assess if the vegetation can be processed on site using a mobile pyrolysis plant, with the aim of using the resulting biochar for landscaping once construction has been completed. 

Often, vegetation on site is removed using lorries and large vehicles which increase a project’s carbon emissions. 

TerrAffix MD Mark Smith said: “The benefits of an on-site solution are immense. These start with the need to remove vegetation from site, achieving lorry loads of carbon savings, but creating biochar also prevents the slow carbon release to the atmosphere that would ordinarily take place through traditional vegetation processing, such as composting or mulching. 

“An additional benefit is the circular economy solution achieved through the reuse of material at a site. This offers soil enhancement opportunities and the promotion of biodiversity.

“TerrAffix believes that for every tonne of woody biomass carbonised, we will produce 250kg of biochar and 650kg CO2 equivalent will be sequestered from the atmosphere. On top of this, the heat generated can be used on-site and there will be a more than 90 per cent reduction in traffic journeys that remove vegetation from sites.”

Kier Highways Head of Environment & Sustainability, Matt Tompsett said: “In major highways projects we dispose of high levels of vegetation, so to be able to reuse this could be a fantastic example of applying a circular economy model to help reduce carbon and waste.”

Following on from the study, the next steps of the project are to identify a site to trial pyrolysis on. 

Photo: Luca Dugaro


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