When is a pack genuinely compostable, and who decides?
ISO 18606 is the international standard that answers that, setting out when used packaging can be classed as recoverable by organic recycling, the technical name for industrial composting and anaerobic digestion.
In its 2013 edition it turns compostable into a test scheme with pass marks. It is one of six standards in the ISO 18600 packaging and environment series, under the umbrella standard ISO 18601.
Compostable does not mean a pack breaks down wherever it lands. ISO 18606 measures what happens inside an industrial composting plant, and it leaves out your garden heap and a dropped wrapper on purpose.
The essentials of ISO 18606
The reference details first, for anyone who only needs those.
- Number and title ISO 18606, packaging and the environment, organic recycling
- Edition The 2013 first edition, published on 15 January 2013 and still current
- What it does Sets the requirements and the test scheme for classifying used packaging as recoverable by organic recycling
- Type A requirements standard you assess yourself against, not a certification you hold
- Who wrote it ISO/TC 122 (Packaging), subcommittee SC 4 (Packaging and environment)
- Where it sits One of six standards in the ISO 18600 series, under the umbrella ISO 18601
- Words it treats as equivalent Organically recyclable, organically recoverable, compostable, and biodegradable during composting
How organic recycling actually works
ISO 18606 defines organic recycling as the controlled biological treatment of the biodegradable parts of used packaging by microbial activity, producing compost and, where anaerobic digestion is used, methane as well.
Two routes count and two do not
Industrial composting is the first. It runs aerobically, with oxygen, and the output is compost.
Anaerobic digestion is the second. It runs without free oxygen and turns the input into a methane rich biogas plus a digestate, and that digestate is usually stabilised by composting afterwards anyway.
The standard rules the other two out inside the definition itself. Landfilling is not organic recycling. Neither is littering.
Ultimate biodegradability is the bar being set
Ultimate biodegradability means micro-organisms break the material down into carbon dioxide, water and mineral salts where there is oxygen, or into carbon dioxide, methane and mineral salts where there is not, plus new microbial matter.
In other words the material is gone, not merely broken into pieces too small to see. That is why the standard tests disintegration separately, and defines it plainly as the physical breakdown of a material into fragments.
Why one bad component sinks the whole pack
ISO 18606 judges packaging at the level of its parts, and it is strict about it. Packaging is recoverable by organic recycling only if every one of its individual components meets the requirements. Some but not all is a fail for the whole pack.
One exception softens that, and in practice it does most of the work. Where the components can be easily and physically separated before disposal, each separated component is assessed on its own, so the tray and the lid get their own answers instead of one shared one.
So one distinction is worth knowing. A component is a part you can separate by hand or by simple physical means, so a lid, a sleeve or a sticker. A constituent is a part a component is made from, and cannot be separated that way, so a coating, an ink or an adhesive.
Constituents never get their own verdict. They are tested inside the component they belong to, which is why a compostable fibre tray with a thin plastic barrier coating fails outright.
A separable part is a different story, as the two ways of assessing the same tray show.
So a compostable tray sold under a plastic film lid is not compostable packaging as it stands. Peel the lid off and the tray passes on its own. That makes a compostable claim a claim about a pack plus an instruction, and the instruction has to reach the person holding it.
The five checks a pack has to clear
Getting to organically recyclable means running five assessments as a minimum. The standard names all five, and a pack has to clear every one.
| Check | What it looks at | The bar |
|---|---|---|
| Characterization | The constituents, hazardous substances, organic carbon, dry and volatile solids | At least 50 per cent volatile solids |
| Biodegradation | Whether micro-organisms break the material down completely | 90 per cent of the organic carbon to carbon dioxide, within 180 days |
| Disintegration | Whether the pack physically falls apart during treatment | Breaks into fragments with no observable harm to the process |
| Compost quality | What the pack leaves behind in the finished compost | Inside the Annex A limits on regulated metals, no ecotoxic effect on plants |
| Recognizability | Whether the end user can tell it belongs in the bio-waste bin | Recognizable as organically recyclable by appropriate means |
The standard names the test methods too. Biodegradation runs under controlled composting conditions to ISO 14855-1 or ISO 14855-2, and disintegration to ISO 16929 or ISO 20200.
Fifty per cent volatile solids is a plain way of saying the pack has to be mostly organic matter rather than mineral filler. Biodegradation also allows a relative pass, reaching at least 90 per cent of what a microcrystalline cellulose reference manages over the same period.
The two checks that get underestimated
Compost quality has no single global table, because the limits that apply are the ones for the country where the pack is placed on the market or disposed of. The standard puts the job of finding the right national or regional rules on whoever is applying it, not on the test lab.
Recognizability is a design requirement rather than a paperwork one. It is the clause behind marks like the seedling logo, because a pack nobody recognises as compostable ends up in the wrong bin however well it tested.
Two rules that sit around the testing
Anything known to be, or expected to become, hazardous during biological treatment must not be deliberately introduced in the first place.
Organic constituents present at between 1 and 10 per cent of dry mass are assessed on their own, while anything under 1 per cent needs no biodegradability data, as long as all such constituents together stay under 5 per cent.
Two ways to skip part of the testing
Running a pack through the full scheme is slow and expensive, so ISO 18606 builds in two exemptions. Both are narrower than they first appear.
Materials of natural origin need no biodegradation test
Chemically unmodified materials and constituents of natural origin are accepted as biodegradable without testing. The standard's own list is wood, wood fibre, cotton fibre, starch, paper pulp, bagasse and jute.
The exemption covers the biodegradation test and nothing else. Those materials still have to be chemically characterized, and they still have to clear disintegration and compost quality.
Chemically unmodified is the load-bearing phrase. A coated, laminated or chemically treated version of the same fibre does not inherit the exemption.
One proven form covers the lighter versions of it
Once a material has been shown to be organically recyclable in one form, it is accepted in any other form with the same or a smaller mass to surface ratio or wall thickness.
In practice you test the heaviest version and the lighter ones come with it. A film proven at 60 microns needs no retesting at 30 microns. Testing the 30 micron film first proves nothing about the 60.
What ISO 18606 deliberately leaves out
Three exclusions are written into the scope, and each one answers a question producers actually ask.
Home composting is out. The standard does not apply to biological treatment carried out in small installations by householders. Everything it measures assumes an industrial plant or a digester, so a pass says nothing about a garden compost heap.
Litter is out. ISO 18606 sets no requirements for the biodegradability of packaging that ends up in soil as litter, and it gives a blunt reason. Littering is not considered a recovery option.
Residual product is out. The standard covers the used packaging. It does not address the rules on whether the food or liquid left inside it is recoverable.
Put together, that draws a hard line around where a pass under ISO 18606 means anything at all.
Those first two exclusions come back later in this article, because the EU has turned both of them into wording that has to be printed on the pack.
Who needs to care about ISO 18606
The standard is written for whoever has to stand behind a compostable claim rather than simply print one.
- Packaging developers choosing a compostable film, tray or liner, who need to know the coating and the adhesive get judged as well.
- Fillers and brand owners putting tea, coffee or fresh produce on the market, whose packs sit closest to the categories the EU is regulating first.
- Material suppliers selling a compostable grade, who generate the biodegradation and disintegration data their customers lean on.
- Compliance and sustainability teams who have to produce that data when a regulator, a retailer or a scheme asks for it.
There is no ISO 18606 certificate to hold. The standard calls itself a framework for self-assessment, and the series states plainly that third-party certification is not required to show the requirements have been met.
That is not the same as saying an outside check is pointless. Schemes such as the seedling logo and the OK compost label exist because a buyer normally wants somebody other than the seller to have looked.
PPWR and the narrow list of packs that must be compostable
The EU's Packaging and Packaging Waste Regulation, or PPWR, does something unusual with compostability. It makes it compulsory for a very short list of packaging, and steers everything else away from it.
Three dates carry the whole thing, and they arrive close together.
Article 9 names the packs that have to compost
The list is short and specific, and it splits into what the EU mandates everywhere and what each country may add.
| Packaging | What Article 9 says | Who decides |
|---|---|---|
| Permeable tea, coffee and other beverage bags | Compostable by 12 February 2028 | EU-wide |
| Soft pod-style single serve beverage units | Compostable by 12 February 2028 | EU-wide |
| Sticky labels on fruit and vegetables | Compostable by 12 February 2028 | EU-wide |
| Rigid capsules for a machine, anything but metal | May be required to be compostable | Each member state |
| Lightweight and very lightweight carrier bags | May be required to be compostable | Each member state |
| All other packaging | Designed for material recycling by the same date | EU-wide |
That is what puts tea bags and coffee pods at the front of this queue. A country can only add to the list where it already collects similar waste with bio-waste and has the treatment infrastructure for it.
The regulation words the requirement as being compatible with the standard for composting in industrially controlled conditions in bio-waste treatment facilities. In plain terms, the pack has to survive a real municipal or industrial composting plant, not a lab.
Everything else has to be designed for recycling
That last row of the table is the one people miss. It explicitly covers packaging made from biodegradable plastic polymers, so biodegradable plastics get no special treatment.
Read the two halves together and the message is hard to miss. Biodegradable is not an exit from recyclability, and moving a pack to a compostable material outside the Article 9 list creates a recyclability problem rather than solving one.
The EU label repeats what ISO 18606 leaves out
Compliance with Article 9 has to be shown in the Annex VII technical information behind the EU Declaration of Conformity, so this is evidence a producer has to hold rather than a design choice they can just make.
From 12 August 2028, Article 12 then requires the harmonised label on Article 9 packaging to say three things. That the material is compostable, that it is not suitable for home composting, and that it is not to be discarded in nature.
Those last two are ISO 18606's own scope exclusions, printed on the pack.
Where ISO 18606 stops being enough
PPWR does not name ISO 18606 anywhere. Article 9 asks the Commission to have the European standardisation bodies prepare or update harmonised standards for compostable packaging by 12 February 2026, and those, not the ISO standard, are what will carry legal weight.
What ISO 18606 gives you is the test scheme that asks the same questions in the same terms. The endpoint the regulation wants verified, conversion into carbon dioxide or, without oxygen, methane, plus mineral salts and biomass, is the ultimate biodegradability ISO 18606 defined in 2013.
For a producer the practical shape is familiar. Which packs are compostable, on what test data, and which market's limits applied all become records you keep, alongside the rest of the evidence behind a packaging Declaration of Conformity.
Where organic recycling sits among the recovery routes
Three comparisons clear up most of the confusion around this standard.
Organic recycling is one of three recovery routes
ISO 18601's own map of the series puts three standards side by side at the recovery stage, one for each way a used pack can be recovered.
ISO 18604 covers material recycling and ISO 18605 covers energy recovery. A pack is assessed against the route it is actually meant to take, and nothing stops it qualifying for more than one.
ISO 18606 and EN 13432 cover the same ground
EN 13432 is the European standard for packaging recoverable through composting and biodegradation, and in the EU it is the one schemes and buyers ask for by name.
ISO 18606 is the international standard on the same subject, built around the same four questions of biodegradation, disintegration, effect on the treatment process and compost quality.
So treat EN 13432 as the document that carries commercial weight in Europe today, and ISO 18606 as the same requirements stated internationally.
Compostable is a much narrower word than biodegradable
ISO 18606 treats compostable and biodegradable during composting as equivalent, but only in the narrow sense it tests, which is breaking down inside an industrial process within a set time.
Biodegradable on its own carries no timeframe and no conditions. That is exactly why the standard defines ultimate biodegradability and puts a 180 day clock on it.
The series stops short of the claim you print
One more boundary catches people out. The ISO 18600 series covers the technical side of packaging only, and does not cover what ISO 14021 requires in order to support a public claim or label.
Passing ISO 18606 establishes that the packaging is organically recyclable. It does not license the wording you print on the pack.
Frequently asked questions about ISO 18606
Short, plain answers to the questions people ask most about ISO 18606.
What is ISO 18606 in simple terms?
ISO 18606 is the international standard, first published in 2013, that sets out when used packaging counts as recoverable by organic recycling. Organic recycling is the technical name for industrial composting and anaerobic digestion, so in plain terms it defines when a pack is compostable.
Is ISO 18606 a certification?
No. There is no ISO 18606 certificate and no accredited scheme behind it. The standard calls itself a framework for self-assessment, and the series states outright that third-party certification is not required. Many producers still use a scheme like the seedling logo, because buyers want a check.
What edition of ISO 18606 is current?
The 2013 first edition, published on 15 January 2013, and it is still the current version. It was prepared by ISO technical committee TC 122 on packaging, subcommittee SC 4 on packaging and environment.
Does ISO 18606 cover home composting?
No, and that exclusion is written into the scope. The standard does not apply to biological treatment carried out in small installations by householders, so it says nothing about whether a pack breaks down in a garden heap. It also sets no requirements for packaging that ends up in soil as litter.
Does every part of the packaging have to be compostable?
Yes, if you assess the pack as a whole. Packaging counts as recoverable by organic recycling only if all of its components meet the requirements. Components that separate easily before disposal may be assessed on their own, so a compostable tray under a plastic lid can pass once the lid is off.
What does a pack have to prove under ISO 18606?
Five assessments as a minimum. Characterization including at least 50 per cent volatile solids, biodegradation of 90 per cent of the organic carbon to carbon dioxide within 180 days, disintegration without harming the process, no damage to compost quality, and recognizability to the end user.
What is the difference between ISO 18606 and EN 13432?
ISO 18606 is the international standard for organic recycling of packaging. EN 13432 is the European one for packaging recoverable through composting and biodegradation. They cover the same subject and the same four questions, and in the EU it is EN 13432 that schemes and retailers ask for by name.
Does PPWR require ISO 18606?
No. PPWR does not reference ISO 18606. Article 9 requires a short list of packaging, including tea and coffee bags and fruit and vegetable stickers, to be compostable by 12 February 2028, and the detailed specification will come from European harmonised standards instead.
Working to ISO 18606 still produces much of the test evidence those rules will need.
Does a compostable pack still have to be recyclable?
It depends which list it is on. Packaging covered by PPWR Article 9 is exempt from the general recyclability requirement in Article 6. Everything else, explicitly including packaging made from biodegradable plastic polymers, has to be designed for material recycling by 12 February 2028.
