Frequently asked questions

• What are biosolids?

  Biosolids are a treated material derived from sewage sludge, which is produced during wastewater treatment. After the wastewater is treated, the remaining solids (sewage sludge) are further treated to produce a material called biosolids that can be recycled to agricultural land under regulatory controls and the Biosolids Assurance Scheme (BAS).

• Why recycle biosolids to land?

  Recycling to land is one of several management options and aligns with the waste hierarchy, which prioritises recycling over disposal.
  When managed in accordance with regulation and defined standards, recycling biosolids to agricultural land returns nutrients and organic matter to the soil.

• Why are biosolids used in agriculture?

  Biosolids provide nutrients such as nitrogen and phosphorus, along with organic matter that supports soil structure and function. When recycled to agricultural land in accordance with regulation and best practice, biosolids support crop production and contribute to long-term soil management.

• Do biosolids improve soil?

  Biosolids improve soil condition by providing valuable organic matter and nutrients that contribute to soil structure, crop growth, water retention, nutrient supply and soil biological activity.
  The extent of these effects will vary depending on soil type, climate and management practices.

• Do biosolids increase crop yields?

  Biosolids provide nutrients such as nitrogen and phosphorus that support crop growth as part of a planned nutrient management approach. They also provide organic matter that contributes to soil structure, water retention and soil biological activity. Crop performance depends on multiple factors, including soil condition, weather and overall farm management.

• How are biosolids applied to land?

  Application is controlled and typically includes:

  • Setting application rates based on soil and crop need
  • Following timing and crop restrictions
  • Using appropriate spreading methods
  • Keeping records of applications
• Are biosolids widely used?

  Recycling biosolids to agricultural land is a long-established practice in Great Britain and forms one of several established routes for managing sewage sludge. Each year, around 3.6 million tonnes of biosolids are recycled to approximately 150,000 hectares of agricultural land in Great Britain.

• Can farmers choose whether to use biosolids?

  Yes. The use of biosolids is a farm management decision, based on factors such as soil condition, nutrient requirements and crop rotation. Each year in Great Britain, biosolids are recycled to approximately 150,000 hectares of agricultural land as part of planned nutrient management approaches, contributing an estimated £50 million in nutrient value to the farming industry.

• What is the Biosolids Assurance Scheme?

  The Biosolids Assurance Scheme is a standards-based scheme operating in Great Britain.
  It sets requirements for the treatment, storage, transport and recycling of biosolids, with conformance independently verified through third-party audit.

• Does BAS certification guarantee safety?

  No. Certification does not imply a guarantee.
  It demonstrates that defined activities meet the requirements of the Biosolids Assurance Scheme (BAS) Standard, as verified through a third-party independent audit.

• Are biosolids regulated?

  Yes. Their use is regulated under environmental and agricultural legislation, including controls designed to reduce and prevent diffuse pollution from nutrients. In addition, the Biosolids Assurance Scheme (BAS) provides a defined set of requirements for the treatment, storage and recycling of biosolids, with conformance independently audited.

• Do biosolids contain contaminants?

  Wastewater reflects modern life and can contain a range of substances from domestic, commercial and industrial sources. Regulation sets controls for specified materials, and systems are in place to monitor, assess and manage potential risks, including for substances under ongoing research.

• What are PFAS?

  PFAS are a group of chemicals used in many consumer and industrial products. They have received media attention due to their persistence in the environment.
  Research and regulatory review are ongoing to better understand their presence and behaviour in wastewater and biosolids and in the wider environment.

• Are biosolids safe?

  The use of biosolids is regulated and monitored, with controls designed to manage and reduce potential risks to the environment, soil and the food chain.
  The Biosolids Assurance Scheme (BAS) provides independent verification that defined requirements for treatment, storage and recycling to agricultural land are being met.