WRAP supported research investigates digestate RBP and PTE issues
Recent feedback received via the Biofertiliser Certification Scheme (BCS) and through the PAS 110 & AD QP workshops in December 2011 has included comment on both the Residual Biogas Potential (RBP test) and the limits for Potentially Toxic Elements (PTEs).  Over the next 3 to 6 months WRAP are undertaking two projects that seek to address many of the concerns highlighted. 

Residual Biogas Potential project
Feedback received regarding this test has highlighted how some AD facilities are experiencing difficulty with achieving the required digestate stability.  To address this and other concerns noted at the December workshops, WRAP have commissioned an RBP test application review. 
The aim of this work is to establish the validity of the current Residual Biogas Potential (RBP) test as a means of assessing how effectively an anaerobic digestion plant has digested its waste feedstock, and therefore of establishing that the input waste materials have been recovered.  A supplementary aim is to consider whether alternative methods for demonstrating recovery of input materials are available (and more cost-effective) and whether they have any advantages over the RBP test. 

To undertake this work our appointed contractors will need to undertake laboratory work requiring the analysis of new (and completely anonymised) samples from AD plants around the country.  They will be in touch with AD operators soon to identify plants willing and able to take part in this study. 
Click HERE to read WRAP's tender invitation document.

Potentially Toxic Elements project
The main purpose of this project is to examine current UK AD industry data on PTE concentrations in digestate and to determine whether other limits could be set (either on a dry matter basis or utilising alternative approaches) that are equally protective of the environment as the current PAS 110 approaches.  For this work our contractors will also contact AD operators shortly, asking for their permission to access any their data on digestate PTE concentrations (liquid and solid fractions), which will be reported on an entirely anonymous basis.  No additional sampling is required for this review. 
Click HERE to read WRAP's tender invitation document.
Use of project outputs and collaboration with industry
Outputs from both these projects are also intended to contribute evidence towards the ongoing consultation on the EU proposals to develop cross EU End-of-Waste (EoW) Criteria following the methodology guidelines established by the Joint Research Centre’s Institute for Prospective Technological Studies (JRC-ITPS).  The RBP project will address the current suggestion within the JRC’s working document regarding the 1500 mg L-1 Organic Acid (OA) total and whether UK AD operators will be able to comply.
These two projects complement the ongoing activity led by Kate Lister for the AD operating companies working group gathering relevant data, where available, to ensure any refinement of the PAS or development of the EoW is in line with UK practice.  Our aim is to coordinate the collection and collation of data and to ensure that the results are open and available for use by all.  By working closely with Kate we will aim to maximise efficient use of resources and enable WRAP and industry to collect an improved evidence base.
It is WRAP’s intention to present to the industry the outputs from these two projects, both for discussion and input, ideally in the late summer and/or early autumn and to utilise the outputs from the work in the upcoming review of PAS 110.  If you have any questions regarding these projects please do contact me (in the first instance), or David Tompkins at WRAP. 
Kind regards,

Dr Sarah Macnaughton, Interim Manager, WRAP.

Email, Mobile 07985 790923, Website
Published on AfOR website: 9th March 2012
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