Herriot-Watt announce circular economy project

The project involves a £250,000 Knowledge Transfer Partnership (KTP) funded by Innovate UK and the Scottish Funding Council. Herriot-Watt will partner with Brewster Bros, a Livingston-based recycling business, with an aim of further developing Scotland’s approach to a circular economy.

Part of the project will look at recycled clay which can account for up to 25 per cent of the output produced when excavation waste is recycled via a washing process. This by-product commonly ends up in landfill. Herriot-Watt confirmed that the project will also include the creation of a hazardous soil treatment centre, the first of its kind in Scotland.

Professor Gabriela Medero, a geotechnical and geoenvironmental engineer at Herriot-Watt said: “As pressure mounts on global governments to react to the climate crisis, future regulation and legislation in the waste industry must be shaped to facilitate the adoption of a complete circular economy. 

“Recycled clay is an exciting but currently unexplored material which could significantly reduce the waste we send to landfill each year. However, many barriers remain that prevent waste from major industries like construction being better utilised, including a lack of scientific understanding about material composition and the criteria for its use as set out by governing bodies like the Scottish Environmental Protection Agency (SEPA).”

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Medero said that the project will involve rigorous testing of the properties and behaviour of recycled clay to prove it meets building standards for product specification. The team will also investigate the use of spent oil shale and incinerator bottom ash as secondary aggregates, she confirmed, aiming to ‘allay any concerns’ about their future use.

Spent oil shale has been used in road construction for decades, while the use of incinerator bottom ash is currently constrained by regulation. The researchers believe that further research into the materials could provide evidence to allow restrictions to be relaxed. The increase of Energy from Waste incinerators being used in response to landfill bans will cause an increase of incinerator ash as a waste product in the coming years.

Scott Brewster, managing director at Brewster Bros said: “A circular business model eases pressure on our country’s remaining landfill capacity and finite material resources, while helping our customers to avoid paying landfill tax and the aggregates levy. This will be even more important as businesses focus on a ‘green recovery’ in the post-Covid era.”

Brewster Bros’ West Lothian site will host the new hazardous soil treatment centre, which plans to use various remediation techniques to transform hazardous soils into a non-hazardous state so that they can be recycled and reused. According to SEPA, during 2019, 1.17 million tonnes of soils were disposed of, totalling 39 per cent of all landfill waste. As landfill bans, higher landfill tax and tighter regulations are imposed, construction contractors will have greater need for such a facility, researchers said.