Client: Fidra
Year: 2026
eftec team: Thea Sletten, Allegra Naldini, Graham Pattle, Oliver Pilkington, Nil Torrebadella Bulta
Service Area: Chemicals Policy
Location: England
Full report: Economic risk of contaminated biosolid applications
Around 94% of the UK’s sewage sludge is recycled to agricultural land, returning valuable nutrients and organic matter to soils. However, wastewater treatment also concentrates contaminants in sludge, creating a pathway for microplastics, PFAS and pharmaceuticals to enter agricultural soils. Many of these contaminants are not routinely monitored or regulated in the UK, and there is growing concern about their potential to accumulate in soils and move through the wider environment.
Fidra commissioned eftec to assess the economic risks associated with contaminated biosolids and to compare the current approach of applying biosolids to agricultural land with alternative ways of treating sewage sludge.
We found that applying biosolids to agricultural land remains the least expensive option from a financial perspective, but these financial costs do not capture important wider costs to society over the longer term. These wider costs could include impacts on soil health, biodiversity and human health, as well as the possibility of future remediation costs.
Alternative treatment technologies can prevent contaminated sludge from being applied to agricultural land, but they come with their own trade-offs. They require new infrastructure, increase treatment costs and can result in higher greenhouse gas emissions.
To assess these trade-offs, we compared the current UK approach with to four alternatives: conventional incineration, high-temperature incineration, pyrolysis and gasification. We considered treatment and transport costs, energy use and recovery, greenhouse gas emissions, the retention or recovery of nutrients and organic matter, and potential contaminant risks.
Key findings included:
There is no single optimal solution. Incineration, high-temperature incineration, pyrolysis and gasification all have different costs and benefits.
High-temperature incineration can destroy persistent contaminants, including PFAS, but is expensive.
Pyrolysis shows particular potential by combining contaminant destruction with the recovery of useful products.
Recovering nutrients matters. Phosphorus is an essential resource, and technologies that can both manage contaminants and recover nutrients could provide wider benefits for the UK.
Putting an economic value on these risks is challenging because contaminants such as PFAS and pharmaceuticals come from many sources, making it difficult to determine how much of the resulting environmental and health impacts can be attributed specifically to biosolids. We therefore traced how contaminants in biosolids could lead to impacts on the environment and human health and used the available evidence to quantify the economic risks where possible. This included potential impacts on agricultural production and the water environment, as well as health risks associated with PFAS and antimicrobial resistance (AMR).
More research is needed to understand how contaminant mixtures affect soils, biodiversity and human health over time, and how alternative sludge treatment technologies could work at scale in the UK. The work shows the importance of considering long-term benefits of protecting soils from contaminants alongside financial costs associated with alternative technologies, even where evidence about their impacts remains uncertain.