Envar’s report on degradation of  compostables in full-scale composting trials

 

As part of the series of reports and documents being published by research consortium partners in the Compostable Coalition UK, this REA webpage hosts Envar Composting Ltd’s research REPORT and the coalition’s slides-style SUMMARY.

Envar ran trials on the degradation of compostable intermediate materials and finished products (packaging and non-packaging items) in its full-scale, in-vessel plus outdoor-turned-windrow composting process, located at its flagship site in Cambridgeshire.

 

Report’s abstract

‘Envar Composting Limited has designed and undertaken a suite of operational experiments and collected data to better understand the degradation profile of intermediate materials and finished products certified as “compostable” under one of the independent certification bodies’ certification schemes. Most of the materials and finished products supplied were finished packaging products and intermediate materials (polymer films) used for making packaging products, while at least one product supplied was a format not classed as packaging. To ease readability, this report refers to these intermediate materials and finished products as ‘compostable packaging’ where talking about them collectively.’

‘The main trial and data collection took place over a period of three months, beginning in late December 2022…The material provided data which shows that compostable packaging does break down in an industrial composting setting with a steady degradation profile over time. The degradation profile is affected by how the material is managed and the extent it is spread throughout the composting mass.’

‘Despite some of the materials remaining visible at the final stage of the composting process, it was found that contamination levels of the final compost, as per the industry standard tests, showed the screened compost was compliant with quality requirements set in PAS100*.  Analysis looking at all types of microplastics also showed that compostable material microplastics were not present in sampled, screened compost, indicating a full breakdown.’

‘The analysis concluded that through the operational control of the composting process, compostable materials independently certified compliant with standards (EN 13432, EN 14995 or ASTM D6400) are compatible with the desired environmental outcomes of our society.’

* The fourth (and current) edition of PAS 100, published in September 2018.

 

Summary of Compost Testing, Analysis and Degradation Trials

The slides-style summary of Envar’s trials says key findings were that:

• materials with larger surface areas break down faster, e.g. coffee pods, and pre-treatment methods like shredding can enhance breakdown efficiency;
• proper compost management reduces waste and enhances material breakdown; and
• high surface contact with the compost mass improves degradation, this meant that the mesh bag experiment gave a worst-case scenario as it did not allow the material to spread as it would in a typical composting process.

Conclusions were that:

• the trial showed effective breakdown of compostable packaging, supporting plant growth and meeting PAS 100 compost standards;
• compostable packaging reduces compost contamination by non-compostable plastics and is less carbon intensive versus traditional plastics; and
• the products of compostable material breakdown are stable organic molecules such as lignin, cellulose, bacterial biomass, water, and CO2.

 

Management of Compostables for Organic Recycling

As part of the same project, section 2 of the REA’s report on Management of Compostables for Organic Recycling includes a summary of Envar’s full-scale composting trials and findings.

 

Research funding
The research was funded by Innovate UK and was part of the Compostable Coalition UK’s project titled Capturing and Processing Compostable Packaging – Behaviour Change Interventions and Infrastructure Considerations. Project number 10020315.

Contact: Emily Nichols