Posted by Kevin Vollquartz
on 28 August 2026
Some are, but only in the conditions they were tested for. A bag certified to the industrial standard needs a commercial facility running at 55 to 60°C to break down. A bag certified home compostable is tested for a garden heap at ordinary temperatures. Put either one in a general rubbish bin and it behaves a lot like ordinary plastic.
That gap between the label and the bin is where the confusion sits, and it is worth understanding before you buy anything with a leaf printed on the packet.
What does "compostable" actually mean on a bag?
It means the material passed a test against a named standard, and the standard specifies both the conditions and the time allowed. That is the entire value of the word. The European standard EN 13432 covers packaging recoverable through composting, and certification schemes such as TÜV Austria's OK compost INDUSTRIAL sit on top of it. Those schemes assume an industrial composting plant: a controlled environment with heat, moisture and regular turning.
"Biodegradable" carries none of that. Everything biodegrades eventually, a car tyre included, so the word on its own tells you nothing about how long or under what conditions. Our older explainer on biodegradable versus compostable works through the difference, and we take the wider label question apart in how to read eco labels.
Industrial and home composting are not the same test
The difference is mostly temperature. TÜV Austria describes products that are only OK compost INDUSTRIAL certified as ones that compost only in industrial facilities at 55 to 60°C, while OK compost HOME covers material that will break down at the lower, far less predictable temperatures of a garden compost heap.
A heap in a Copenhagen or Manchester back garden rarely holds 55°C for any length of time. In winter it may barely get above ambient. Home certification is therefore the harder one to earn, and an industrial-only bag in your garden bin will probably still be recognisably a bag next spring.
Why do some "compostable" bags survive a real compost heap?
Because a certification test is a controlled experiment and a garden heap is not. This is not a theory. Researchers at UCL ran the Big Compost Experiment, a citizen science study published in Frontiers in Sustainability in 2022, surveying 9,701 UK participants, 1,648 of whom ran home composting tests on real packaging.
The results make uncomfortable reading for anyone selling compostable products, us included. Of the items carrying home compostable certification, 60% did not fully disintegrate. In a randomised sample of 50 item photographs, 46% showed no identifiable compostability certification and 14% showed industrial composting certification only. The authors concluded that home composting is not currently a viable or environmentally beneficial route for compostable plastics in the UK.
Two separate things are going on there. Some of those bags were never certified for a home heap and were bought by people who assumed otherwise. And even properly certified material struggles when a heap is cold, dry, badly turned or too small to hold heat. Certification tells you the material can break down in home compost conditions. It cannot promise your particular heap provides them.
Can you put compostable bags in your council food waste bin?
Usually not, and this catches almost everyone out. The government's Simpler Recycling guidance for household collections in England draws a line between liners and packaging: caddy liners used to hold food waste can be collected, while plastic packaging or non-packaging items labelled "compostable" or "biodegradable" do not have to be. A zip bag counts as packaging whatever it is made from, so it falls on the wrong side of that line.
The reason is operational rather than ideological. Food waste runs through a fast processing cycle, often anaerobic digestion, and anything still intact at the end is screened out as contamination. Nobody on a moving belt can tell a certified compostable bag from an ordinary plastic one, so both get pulled. Check your own council's page before you assume, because the rules vary between authorities.
What happens if a compostable bag ends up in general rubbish?
Very little that helps. Compostable materials are certified for composting conditions, which means oxygen, moisture, warmth and an active microbial population. Buried under compacted waste in landfill, most of that is missing, so the bag sits there far longer than the label would lead you to expect. If your waste goes to incineration instead, the bag burns like any other packaging.
So the compost claim only pays off if the bag reaches somewhere it can actually compost. Most never do, and that is the industry's problem rather than the consumer's.
What to look for on the label
Look for a named certification and a named scheme rather than a green leaf and a friendly adjective. Four marks account for most of what turns up on a shelf.
- The Seedling is European Bioplastics' registered trademark for EN 13432. Their logo guidelines require the valid registration number (it takes the form 7PXXXX) to be printed below the mark, with the words "industrially compostable" under that. A Seedling is pointing you at an industrial plant, not your garden heap.
- OK compost HOME is TÜV Austria's mark for material tested at garden heap temperatures. That is the one worth hunting for if you compost at home.
- DIN CERTCO certifies home and garden composting too, and does the same job as the TÜV mark.
- A leaf, a globe or a swirl of arrows with no scheme name beside it has not been certified by anybody.
The two home marks name the certifier on the mark itself and carry a certificate number, and you can look that number up in the certifier's public database. A symbol with no number to check is decoration.
The table below is roughly how we sort bags ourselves.
| What the bag says | What it is certified for | Home compost heap | Council food waste bin | General rubbish |
|---|---|---|---|---|
| "Biodegradable", no standard named | Nothing verifiable | Unlikely to break down usefully | Not accepted | Behaves much like plastic |
| EN 13432 or OK compost INDUSTRIAL | Industrial facilities at 55 to 60°C | Often still visible months later | Not accepted as packaging | No meaningful benefit |
| Certified home compostable | Garden heap conditions over months | Designed for it, though a cold heap slows it right down | Not accepted as packaging | No meaningful benefit |
| "Plant-based" or "bio-based" | The feedstock only, not the end of life | Depends entirely on the polymer | Not accepted | Depends entirely on the polymer |
Vague green wording is getting riskier for the companies using it, too. The Competition and Markets Authority's Green Claims Code sets out how consumer law applies to environmental claims: they must be truthful, substantiated and account for a product's full life cycle. A big claim with no standard named is a signal in itself.
So are compostable bags worth buying at all?
They are, if you buy them for the right reason. That reason is not that they dissolve into soil the moment you have finished with them. It is that they take single-use plastic film out of your kitchen, and they give you a defensible end of life if you keep a working compost heap.
That is how we designed our compostable zip bags. They are certified home compostable, PFAS-free and BPA-free, and they are safe in the freezer and the microwave. The part that matters most day to day is the zipper, because it means one bag handles sandwiches, batch prep and freezer portions many times over before it goes anywhere near a home compost heap. A bag reused many times and then composted beats a bag used once and composted perfectly. The end of life route is your own compost heap, not the council food waste bin.
They come in four sizes, and the 140-bag set of compostable zip bags covers all four if you want to replace cling film and freezer bags across a whole kitchen at once. You will find them with the rest of our household range. If you are weighing up the alternatives more broadly, our comparison of beeswax wrap and cling film covers where each format genuinely wins.
One last piece of advice, and it applies whoever you buy from. If you do not compost at home and your council will not take compostable packaging, buy for reuse and durability instead, because the compost claim will not be the part you ever use.
