Most Multipurpose Composts are made using recycled organic materials such as green waste. During processing, small pieces of plastic, glass, or metal can be left behind, especially when the raw materials come from household or garden collections.
Even though UK composts made to PAS 100 and similar standards are screened and quality-checked, these standards still allow a very small tolerance of visible contaminants (measured in grams per litre). This reflects the limits of current sorting and shredding technology — not a lack of care by the manufacturer.
If you’re seeing larger or frequent plastic fragments, it’s usually a sign of:
- Lower-grade green-waste inputs
- Minimal post-screening at the composting site
Premium brands tend to use cleaner feedstocks (such as bark or wood fibre) or in-house composting systems, which greatly reduce the risk of contamination.
Learn more
See ‘Compost Quality: What It Really Means for Buyers‘ for a detailed explanation of PAS 100 limits, contamination sources, and what manufacturers are doing to improve standards.
Disclaimer.
Brand names such as Westland, SylvaGrow, RocketGro, Dalefoot, Carbon Gold, and others mentioned on this site are registered trademarks of their respective owners. MultipurposeCompost.co.uk includes these examples for informational and comparative purposes only and does not claim endorsement, affiliation, or suitability for any specific use. Gardeners and buyers should always check current product specifications and manufacturer guidance before purchase or application.
