Steps Towards Protecting Scotland’s Soil Health

In Scotland, around 60% of the country’s treated sewage sludge is applied to agricultural soils.1 Sewage sludge contains a cocktail of complex chemicals and microplastics, inevitably impacting soil health. Therefore, to protect the health and productivity of Scotland’s agricultural soils we need to stop the application of sewage sludge to land in its current contaminated form


The wastewater from industry, businesses and our homes all goes to wastewater treatment works where it is filtered and cleaned. Yet, this clean water comes at the expense of an increasingly contaminated sewage sludge product. As water is filtered, solids settle out and are left behind, and it is this solid that is known as ‘sewage sludge’ or ‘biosolids’. Currently, sewage sludge acts as a sink for persistent contaminants removed from wastewater, with the level of contamination being dependent on that in the influent to the treatment works.2  

Organic contaminants such as PFAS are almost impossible to remove and therefore contaminate the sludge. One disposal route for treated sewage sludge is the application to productive agricultural soils. Once applied to land, nutrients, organic matter and closely associated contaminants can be transported from the soil, into rivers and the wider environment, ultimately ending up in the oceans.  

Potentially toxic elements and pathogens in sewage sludge are regulated, but synthetic chemicals (i.e., PFAS, bisphenols, parabens) and microplastics are not. Fidra appreciate sewage sludge’s potential value as a resource but are concerned that contaminants from treated sludge are being transferred to agricultural soil with potential, unknown impacts. As a strong supporter of the precautionary principle, we believe this pillar of environmental protection needs to be upheld. If we are to protect our soils and the wider environment, the application of sewage sludge to agricultural land in its current contaminated form needs to be avoided. Precautionary action needs to be taken by Scotland and the rest of the UK to avert legacy contamination of its soils and the wider environment. By doing so, we will ensure our soils are healthy, biodiverse, and continue to be productive for generations to come.  

Fidra seek to work collaboratively with multiple stakeholders involved in sludge and wastewater production, management and utilisation, and will work to protect the health of Scotland’s agricultural land until sewage sludge is proven to be a clean, safe resource for the future circular economy. 

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[1] Materials to Land Assessment – Sustainability, Availability and Location
[2] Sewage sludge and the circular economy,
European Environment Agency, 2021