Aqua Enviro AD expertise secures REAL project to evaluate the Residual Biogas Potential test for PAS110 digestates

The PAS110 specification for digestate quality is key to market confidence in UK biofertilisers. First established in 2010, the specification is designed to meet the needs of digestate users, regulators and producers – by including quality controls that limit everything from E. coli to plastics.

Digestate stability is an essential element of PAS110, included to satisfy the requirements of regulators that waste materials have been adequately processed. Stability is demonstrated through compliance with the Residual Biogas Potential (RBP) test.

BMP test

The RBP test is time-consuming and requires specialist laboratory equipment. Over time, a number of AD operators have grappled with invalid RBP test results, which creates challenges for digestate certification – as well as adding cost and delays to operators.

These issues are now under investigation by Aqua Enviro, which has been appointed by the Renewable Energy Assurance Ltd (REAL) Research Hub to undertake its fourth research project, ‘Evaluation of the potential for the improvement of the Residual Biogas Potential test and investigation of alternative test procedures for PAS110 biofertilisers’.

Aqua Enviro, a SUEZ company, was selected for its extensive knowledge and experience in the sector, having delivered multiple projects on food-based anaerobic digestion and digestate. Having recently upgraded its in-house laboratory capabilities, the collaborative Aqua Enviro team was well-placed to explore the RBP test and its alternatives.

Working in close collaborLab technician doing BMP testation with Biofertiliser Certification Scheme (BCS) operators, REAL, and their approved laboratories, the Aqua Enviro team is analysing the performance of the RBP test using whole, separated liquor and separated fibre digestates from different operators. Other commercial tests of digestate stability are also being examined, alongside a deep-dive into BCS data. Overall, a good understanding of the RBP test, its limitations and alternatives will be synthesized into recommendations for REAL. The project is expected to be completed in June 2023.

”We, as Aqua Enviro, have brought together an experienced team with extensive experience working across PAS110 sites. Our internal laboratory gives us the analytical expertise and flexibility needed to deliver the project’s aims and objectives,” said Dr. David Tompkins, Head of Knowledge Exchange and Innovation for Aqua Enviro.

REAL, a subsidiary of The Association for Renewable Energy and Clean Technology, is dedicated to ensuring participants of their certification schemes comply with the scheme requirements, providing assurance to consumers that certified digestate (and compost) is safe and of high consistent quality. This is especially relevant in light of the UK government’s Resources and Waste Strategy under its 25-year Environment Plan, which pushes for more efficient energy recovery from residual waste using innovative technologies.

“We are pleased to work with Aqua Enviro on this important project to inform future developments to the RBP test method. We understand that the test impacts operations for AD plants under BCS, which was a key motivator for funding this work to explore viable alternatives and improvements to the test. REAL eagerly anticipates the results of the project later this year,” REAL said in a statement.

For an overview of the project, visit

Learn more about Aqua Enviro’s BMP test facilities

Posted 17th January 2023
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