Long-term contaminant accumulation in farm soils from repeated applications of contaminated sewage sludge is a growing concern – and current decision-making does not fully account for environmental and societal costs. New research by environmental economics experts eftec (at Fidra’s request) investigates the socio-economic risks of applying contaminated biosolids to farmland. It recommends that UK sludge policy should take a precautionary approach that protects soils as a long-term national asset, weighing the full costs of land application and prioritising alternative treatments that destroy contaminants and recover resources.
(Source: iStock, xiepe)
Read the full report or our one-page summary here
The research
Eftec’s research compares current UK biosolids land application against alternative sludge treatment options (including incineration, pyrolysis and gasification). Costs associated with unregulated contaminants (microplastics, PFAS and pharmaceuticals) are assessed over a 20-year period.
Key findings
- Long-term contaminant accumulation remains a key concern and soil should be managed as a long-term national asset
- Contaminant mixtures will increase long-term risks
- Current decision-making does not fully account for environmental and societal costs
- Further evidence is needed, but uncertainty should not delay action
- Alternative treatment technologies warrant greater consideration
- Recovery of strategic resources could improve environmental outcomes
Future UK sludge policy recommendations
There is no single optimal solution, and the findings support a precautionary approach that protects soils as a long-term national asset while recognising the continuing uncertainties surrounding emerging contaminants. Recommendations include:
- A precautionary approach due to the persistence of many contaminants and the potential for long-term public and environmental health effects.
- Prioritising research on contaminant mixtures and their long-term impacts on soils, biodiversity and human health.
- Appraisal of sludge management options that consider wider costs of land application, such as biodiversity loss and health burdens.
- Further evaluation of alternative treatment technologies, including their scalability, costs, integration with existing infrastructure and implementation timelines.
- Maximising nutrient and other resource recovery alongside contaminant destruction to reduce dependence on synthetic fertilisers.
Impact pathways from biosolid application to agricultural land to ecosystem services potentially at risk
Stop it at source – prevention beats clean-up
Fidra believes that the most effective and economically efficient way to protect both the value of sewage sludge as a circular resource and the UK’s precious soils, is to prevent contaminants entering wastewater systems in the first place. Once contaminants become concentrated in sludge, treatment becomes more expensive and resource recovery becomes more challenging. Improving industrial source control and reducing pollution should be central to a long-term strategy for protecting public and environmental health. Source control will complement other cost-effective policy measures to manage contaminants that cannot readily be prevented at source, such as legacy substances. Overall, this important research contributes to the discussion around choices we face in managing contaminated sludge today.
Support our call for stronger safeguards
The UK must mitigate risks and phase out the application of contaminated biosolids to farmland. The current outdated regulations do not protect human and environmental health fully from contaminant risks. Fidra are calling for urgent reform of the sewage sludge regulatory framework across the UK with the list of regulated contaminants in sludge expanded to include microplastics, PFAS and pharmaceutical residues.
In England and Wales, the agricultural use of sludge must be brought into the environmental permitting regimes. Stronger enforcement and streamlined regulations for waste materials is needed with flexibility for further safeguards against other emerging contaminants in the future, tackling regulated, known and emerging contaminants of concern.