Slow release fertiliser and microplastics

Ive just be told the slow release granules we have been using in pots for fertiliser have a coating of non biodegradable plastic that just turns into plastic dust at the end of its life.
Any idea if this is true?

genuinely livid if so, that we are being sold something the company knows 100% for sure will pollute our soil forever.

Surely there are so many alternatives, like a starch gel or something? Its horribly sad how companies rely on our ignorance to sell us pollution, for even minor profits.

 

Starch gel is probably not stable enough in plant pots to work, the same goes for many other biodegradable materials, maybe something based on cellulose would work.
Perhaps someone else could confirm this for us.
I would think that using, say 50%, soil in your potting mix would provide enough trace elements for most plants.

 

I don't like the sound of that... but I don't use slow release ferts, and having read the AI response, I'll stick with blood, fish and bone

I don't know, so I asked Google AI -

slow release granules we have been using in pots for fertiliser have a coating of non biodegradable plastic that just turns into plastic dust at the end of its life. Any idea if this is true?

**********************************

Yes, this is true. Many common slow-release (or "controlled-release") fertilizer granules are coated with synthetic, non-biodegradable polymers that persist in the soil as microplastics
.

The Role of Plastic Coatings
To achieve a "slow-release" effect, manufacturers often encapsulate water-soluble nutrients (like NPK) in a physical barrier.

• Materials used: These coatings frequently consist of petroleum-based plastics such as polyurethane, polyethylene, polypropylene, or alkyd resins.
• The "Dust" Effect: After the nutrients have leached out through pores in the coating, the empty "ghost shells" remain in the soil. Over time, physical stressors—such as soil movement, foot traffic, or garden tools—break these shells down into tiny fragments or "plastic dust," known as microplastics.

Environmental Impact

• Microplastic Pollution: These particles do not break down naturally and can accumulate to significant levels (e.g., up to 50 kg per hectare annually in commercial farming).
• Soil and Health Risks: Research indicates these microplastics can degrade soil quality, inhibit seed germination, and potentially enter the food chain as crops absorb the smallest particles.
• Regulatory Changes: Due to these risks, the European Union has introduced regulations to phase out non-biodegradable polymer coatings, requiring them to meet strict biodegradability standards by mid-2024 or 2026.

More Sustainable Alternatives
If you want to avoid plastic "dust" in your pots, look for fertilizers that use:

• Truly Biodegradable Coatings: Newer products are moving toward coatings made from natural materials like starch, lignin, cellulose, or bio-based polyurethanes that fully decompose.
• Uncoated Organic Fertilizers: Traditional organic options like hoof and horn, blood and bone, or seaweed meal release nutrients naturally as they are broken down by soil microorganisms without any synthetic shell.
• Sulfur-Coated Fertilizers: While still a physical barrier, sulfur is a natural mineral that eventually integrates into the soil as a plant nutrient, though it is sometimes sealed with a small amount of wax.

 

However -
AI Overview


Yes, the EU has introduced strict rules under the Fertiliser Product Regulation (FPR) for
slow-release fertilizer coatings, requiring them to meet specific biodegradability standards (like 90% breakdown within 48 months of function) by mid-2024, with the full criteria adopted in July 2024 and becoming fully applicable by October 17, 2028, giving manufacturers time to comply and ensuring polymers degrade into CO2, biomass, and water, preventing persistent plastic pollution.
Key Details of the Regulation:

• Regulatory Framework: The new rules stem from the EU Fertilising Products Regulation (Regulation (EU) 2019/1009) and Commission Delegated Regulation (EU) 2024/2770.
• Scope: Applies to polymers used as coating agents (for nutrient release) and water retention polymers in EU fertilising products, and even to mulch films.
• Biodegradability Standard: Polymers must be natural or meet criteria for soil/aquatic environments, achieving at least 90% degradation (mineralisation to CO2) within 48 months after their functional life ends.
• Compliance Timeline:
  • July 15, 2024: Commission adopted the new biodegradability standards.
  • October 17, 2028: The new biodegradability criteria (Annex I & II) become fully applicable, meaning products must comply by this date.
• Purpose: To stop persistent plastic pollution by ensuring these polymers break down and don't accumulate in soil or water.

In essence: Manufacturers must switch to certified biodegradable coatings or face restrictions on placing their products on the EU market, with the 2028 deadline providing a clear target for innovation and adaptation.

 

sad these things need to be enforced by the law. horrible behaviour

to be honest, i always assumed the nutrients were just in a low-soluble mineral form but it seems all nitrates at least are very soluble.

wish we had space for a personal composter. i might bring it up with neighbours if we can find somewhere for a group bin

 

Nitrates make production easier as you have all the nitrates dissolved dispense the required amounts for each formulation. Then the tricky bit dry and coat, or maybe coat and dry.

 

Take your point @Adam I , but in the whole picture of gardening surely those granules are a very small part of a much wider gardening polution from plastics ?

What about plastic plant pots, we see many of them fade in colour and become more brittle which suggests they are breaking down.
Also the low or peat free composts seem contain so much rubbish can only assume that some of it will be plastic that will also be breaking down ?

Be interested to know if there is a soil testing service that can show the volume of micro plastics present and if plants can in anyway absorb them as that is a more immediate threat to aminals and humans.

 

For what it's worth you can't escape polluting the environment with micro plastics, we ALL do it!

We've all read about the micro plastics situation in the oceans, but I read an interesting article some time ago regarding micro plastics (chiefly rubber) which come from the daily wear and tear on vehicle tyres.

Think of the vast network of roads running the length and bredth of the country, like capillaries, all adding to microscopic rubber particles contamination.

I suppose you could just stop using the slow release fertiliser. But knowing what I've just mentioned regarding microscopic rubber particulate, are you going to stop using your car too!!

This microplastics situation is not just confined to the oceans, it's everywhere, and getting worse.

 

I know we are far from when it happened but one of the biggest chemical manufacturers bayer have links to the Holocaust (not suggesting anything other than dubious practices have a long history) and many of the companies today will happily change their formulae to get around legislation, so dangerous stuff will still persist with perhaps a slight tweak in its makeup to get around any law banning them.

 

Bayer were founded in 1863 in what is now the city of Wuppertal.
They discovered Aspirin, Heroin (curiously marketed as a non addictive substitute for morphine) and Phenobarbital.
In 1925 they became part of IG Farben and yes at the end of the 2 nd world war some employees of Bayer were tried in Nuremberg as part of the IG Farben trial. IG Farben was broken up into separate companies with Bayer continuing to produce Aspirin in Wuppertal.

Wuppertal was also the home town of Friedrich Engels who was sent to run his families Manchester operation where Karl Marx scrounged money off Engels. Marx may also have had an affair with Engels' wife. They also co authored the Communist Manifesto.

 

Ohhh.. and I recently bought osmocote 5-6 months to try.
Another issue to be scared of....

 

Agree, even the best PAS100 compost still contains plastic, which will take far longer to break down than the polymer on slow release fertiliser.

Then you have farmers that are widely using PAS100, those microplastics don't even break down in the digestive systems of cattle let alone in the soil.

So, the likes of manure that is used for organic solid conditioners will have MP's, even a tub of poultry manure bought off the shelf is likely to have MP's. According to science direct, chicken manure and sheep manure for example can have hundreds of MP's per kilo of manure.