Put a synthetic material in a river or on a seabed for decades and someone will reasonably ask what it sheds into the water. On a submittal in a sensitive water, that question is close to guaranteed.
The honest answer is uncomfortable, and it is the one this page gives.
The position
All polymer geosynthetics shed to some degree, and claiming otherwise would be wrong.
No published ISO or EN standard measures that release for a geosynthetic in service, as far as can be established.
Therefore no supplier — FES included — can put a defensible number on the comparison. Any percentage you are shown by anyone in this category should be traced to its method before you rely on it.
The standard most often cited for this is an apparel textile method for material loss from fabrics during washing. The rock bag FAQ sets out in full why it does not apply to a bag armouring a riverbed, and that answer is the site’s single reference on the point. There is no correct substitute: none exists for geosynthetics in service.
What this site got wrong
Worth publishing rather than quietly fixing, because it is the clearest available evidence of how the rest of the material claims are handled.
A microplastics testing claim appeared on 21 pages, with a trust badge on 17 and a “~30% fewer microplastics” hero stat on 7. The FAQ went further and described the method as measuring emission from geosynthetic materials, which is not what it measures.
The 30% figure had no published basis. It also contradicted the policy written at the top of the site’s own test standards file: no measured values, because a plausible-looking figure on a page a DOT reviewer may rely on would be invented.
All of it came down. The badge was removed rather than replaced, because a new trust marker is a marketing decision and this was a correction.
What survives, and it is the good part
The argument for virgin polyester over recycled polymer is sound. It just rests on different ground than the claim did.
Recycled polymer is reprocessed material: more heat history, variable feedstock, and generally shorter polymer chains than virgin material of the same nominal type. For a product whose whole job is to not degrade while submerged for decades, that goes directly at the property that matters.
The properties that support the choice are the ones that are actually testable:
- Hydrolysis resistance to EN 12447
- Weathering to EN 12224
- Oxidation resistance to BS EN ISO 13438
- Consistent, specifiable strength properties
That is a narrower case than “30% fewer microplastics” and it is one that survives a reviewer checking it. See virgin vs recycled polymer and which test standards apply.
What to say in a submittal
If a reviewer asks about microplastics or polymer shedding:
- All polymer geosynthetics shed to some degree
- No published ISO or EN standard measures it for a geosynthetic in service
- FES therefore publishes no comparative figure
- The virgin-polyester specification rests on hydrolysis, weathering, oxidation, and consistent strength, each with a named method and an independent laboratory
- Reports are issued per project on request
Saying “there is no standard for this” is unusual enough in this category to be worth something. It is the same move that makes when not to use rock bags the most quotable page on the site.
The wider environmental picture
Microplastics is one question among several:
- Construction-phase water quality and turbidity — construction turbidity control
- End of life — end of service life and recovery
- Habitat effects of a permeable face — what colonises an installation, where the data is qualitative and says so
- Working in designated critical habitat — working in critical habitat