News from the Compost Certification Scheme

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New research paper on plastic contamination in compost and digestate instils consumer confidence

Posted: 6 December, 2022. Written by Emma

• REAL has this week released new research on the level of plastic contamination in end-of-waste compost and digestate products in England  
• Research using results from samples tested within the Biofertiliser and Compost Certification Schemes shows the level of plastics in compost and digestate samples is considerably lower than the limits required by the PAS 100 and PAS 110 standards 
• Research will boost consumer confidence in the quality of independently certified compost and digestate applied to land or, in the case of compost only, used for horticultural purposes  

Renewable Energy Assurance Limited (REAL) carried out statistical analysis of a recent dataset showing the level of compliance with the limits required by PAS 100 and PAS 110. The results provide conclusive evidence that the levels of plastic contamination in compost and digestate that has been independently certified to end-of-waste criteria in England are lower than those required by the standards.  

The research paper explains the current Compost Certification Scheme (CCS) and Biofertiliser Certification Scheme (BCS) testing requirements and plastic limits for composts or physical contaminant limits for digestate. 

The analysis in the paper shows 98.5% of compost samples and 98.1% of digestate samples tested were within the limits for physical contaminants. (Any failures must be investigated to ensure that only material compliant with the limits in the standards can be sent to market.)  

In the majority of compost samples, the level of plastic contamination fell below 0.02% mass/mass. In the majority of digestate samples, the level of total physical contaminants (including plastics) fell below 0.039 kg/t.  

Virginia Graham, Chief Executive of REAL, said:  

“I congratulate my colleagues on carrying out this statistical analysis and on preparing this report. Consumers can take confidence that certified compost and digestate consistently meets, and in many cases exceeds, strict limits for plastic content, and that the overall failure rate in England is very low.  

I hope this report will prove useful for Environment Agency in its ongoing process of revising the Quality Protocols for compost and digestate, a process REAL is pleased to support.” 

Jenny Grant, Head of Organics and Natural Capital at the REA, said: 

“Plastics [conventional plastics] are not wanted in food or garden waste collections. Our [REA] members put considerable effort into removing any plastics that do arrive and appropriately managing compostable plastics.  

This research paper from REAL is very welcome, showing that sampled composts and digestates respectively met and in the majority of cases exceeded plastics and total physical contaminants limits set out in the standards. The data will be especially useful when considering any future revisions to limits for plastics and physical contaminants in composts and digestates.” 

The paper can be accessed here.