About the Biosolids Assurance Scheme
The Biosolids Assurance Scheme (BAS) sets and maintains the standard for how sewage sludge is treated and recycled as biosolids to agricultural land in Great Britain.
The scheme is owned and operated by Assured Biosolids Limited (ABL), a not-for-profit company established by 11 UK water and sewerage companies.
The BAS provides a defined set of requirements for the treatment, storage and recycling of biosolids, with conformance independently audited.
Why the scheme was introduced
Biosolids have been recycled to agricultural land in Great Britain for decades under regulatory control and various codes of practice.
As expectations across the food chain evolved, the water industry worked with stakeholders to develop a single, independently audited standard for biosolids recycling.
The BAS was formally introduced in 2015, bringing together regulatory requirements, industry best practice and independent third-party verification within a single, structured scheme.
The scheme is available to all parties that produce and recycle biosolids.
What the scheme covers
The BAS applies across the full biosolids lifecycle, including controls on:
- Source materials
- Sludge treatment processes
- Testing and monitoring
- Transport and storage
- Land application and records
Organisations must demonstrate that appropriate control measures are in place at every stage.
Conformance is verified through annual audit by a UKAS-accredited, independent Certification Body.
Governance and independence
The BAS is industry-owned, with conformance independently audited.
Assured Biosolids Limited (ABL) owns and oversees the BAS. The BAS Standard sets the requirements against which organisations are audited. This structure combines sector expertise with external oversight.
A full list of organisations holding a current Certificate of Conformity is available here.
BAS certification is subject to ongoing oversight and may be suspended or withdrawn where requirements are not met.
The role of biosolids recycling
Each year in Great Britain, around 3.6 million tonnes of biosolids are recycled to approximately 150,000 hectares of agricultural land. While biosolids represent a small proportion of organic manures applied nationally, biosolids are subject to defined regulatory controls.
When managed in line with regulatory and BAS requirements, biosolids:
- Return nutrients such as nitrogen and phosphorus to the soil
- Provide organic matter that contributes to soil structure and function
- Support the soil nutrient supply as part of a wider nutrient management approach
- Align with circular economy principles
Recycling to agricultural land aligns with the UK waste hierarchy, which prioritises recovery over disposal.
Managing risk
The BAS is subject to periodic review, drawing on regulation and industry research to identify emerging evidence and inform updates to requirements where appropriate.
Organisations recycling BAS Certified Biosolids must demonstrate ongoing conformance through annual independent audit.
Emerging contaminants
The wastewater system reflects inputs from domestic, commercial and industrial sources. Regulation, operational controls and ongoing research are used to assess and manage potential risks, including for substances subject to ongoing scientific study, such as PFAS, microplastics and other trace organic compounds.
UK regulation sets statutory controls for specified metals.
The BAS works alongside regulators, researchers and industry to review emerging evidence and update requirements where appropriate.
Evolving regulatory and environmental context
Environmental expectations and regulatory frameworks evolve over time. The water sector continues to assess long-term bioresource strategies and emerging technologies in response to these developments.
The BAS Standard is subject to periodic review to reflect regulatory changes, research findings and stakeholder input. This provides a structured mechanism to incorporate new evidence into operational practice while maintaining defined requirements and independent verification.