Reuse of vegetation removed from highways explored in new partnership

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

Biochar is created through the process of pyrolysis when 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 removed from large highway schemes can be processed on site using a mobile pyrolysis plant, with the aim of using the resulting biochar in the landscaping programme, which takes place once construction has been completed.

TerrAffix Managing Director 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% reduction in traffic journeys that remove vegetation from sites.”

The study will outline how best to use the biochar to gain maximum benefit from the overall scheme. 

The benefits of this approach include reducing carbon emissions and costs.

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

The vegetation is then processed, creating a slow carbon dioxide release to the atmosphere, contributing to climate change. 

RSK and Kier embarked on this new partnership after sharing ideas and aspirations at the Highways UK event. Kier then engaged RSK to undertake a study to provide further information on the process and its application.

Matt Tompsett, Kier Highways head of environment & sustainability, said: “We’ve commissioned TerrAffix to complete a feasibility study, as we are committed to doing all that we can to complete our work as sustainably as possible. 

“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, while using a carbon capture and storage technique which means the carbon absorbed by the vegetation will be locked away, instead of releasing it back into the atmosphere.”

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

This will allow TerrAffix and Kier to collect further data and understand the added benefits associated with the project. 

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