A kitchen worktop with unbranded plain packaging, a paper cup and a clear plant-based food tray beside a small food waste caddy, in soft morning light
AI-generated image, not a photograph of a real person or place.
doodlebio

WHAT THE RESEARCH SAYS

Read the label,
then the bin.

CHECK FIRST before you compost it

  • Bio-based is not biodegradable
  • Compostable usually means industrial
  • Check your council's guidance
  • Three words, three meanings

Green-sounding packaging is not all the same.

Bio-based, biodegradable and compostable describe different things. UK research shows many of these plastics do not break down in a garden heap, and most councils ask for them in the general waste bin.

Updated

Decode a label

THE SHORT ANSWER

Compostable rarely means
your compost heap.

The labels describe a material,
not the bin you have at home.

LABELS

Three words, three meanings

The UK government defines bio-based plastics as made from plants, and says they can be biodegradable but are not necessarily. Compostable is a narrower claim than biodegradable.

Decode a label

HOME COMPOST

The heap is not hot enough

In a UCL citizen science study, 60% of certified home compostable items were still clearly visible when participants checked their compost.

See the numbers

LITTER

Not a licence to drop it

University of Plymouth researchers found biodegradable bags could still carry a full load of shopping after three years in soil or the sea.

What to do instead

DECODE A LABEL

What does the
word promise?

Pick a word you have seen on packaging. The bar shows how specific the claim is: how much it tells you about where and how fast the material breaks down.

Label decoder

Choose a word on the pack
Bio-basedMade from plants

Made from polymers derived from plant sources such as starch, cellulose or lignin. It says where the material came from, not that it will break down.

BiodegradableNo time or place

Can be broken down by living things, but the word does not say under what conditions or how long it takes. That depends on temperature, moisture, microbes and oxygen.

Oxo-degradableUnproven

Plastics with additives meant to speed up breakdown. Responses to the UK call for evidence agreed these are unproven and likely to be a source of microplastics.

Home compostableNo single standard

There is no harmonised international or European standard for home compostable plastics, only national schemes. In a UK study, most certified items did not fully disintegrate.

Industrial compostableTested standard

The EN 13432 standard asks for 90% of the carbon to become CO2 within six months under industrial composting. Those conditions run at 55 to 70 °C.

Sources: GOV.UK, Standards for bio-based, biodegradable and compostable plastics (2021); Purkiss et al., The Big Compost Experiment, Frontiers in Sustainability (2022).

Based on the UK government's 2021 response on bio-based, biodegradable and compostable plastics and UCL research. Always follow your own council's bin guidance.

TWO NUMBERS WORTH KNOWING

Labelled to vanish,
built to last.

One figure from UK home compost bins,
one from bags left in soil and sea.

60%

Certified home compostable items still clearly visible

Across 1,307 results from UK households, 60% of items carrying a home compostable certification were still clearly visible, and only 27% had fully gone.

HOME COMPOST · UCL 2022

3 years

Biodegradable bags still able to carry shopping

Biodegradable, oxo-biodegradable and conventional bags still worked as carrier bags after more than three years in soil or the sea.

SOIL AND SEA · PLYMOUTH 2019

Sources: Purkiss et al. (2022), Frontiers in Sustainability; University of Plymouth news release, 29 April 2019, on a study in Environmental Science and Technology.

WHAT TO DO WITH IT

Four habits
that help.

A crumpled pale plastic carrier bag lying half buried in damp soil among fallen leaves
AI-generated image, not a photograph of a real person or place.

The guidance from UK councils and the government points the same way: check the label, check the bin, and prefer things that can be reused or recycled.

  1. Check your council first

    Councils such as East Sussex and Greater Manchester ask for compostable and biodegradable packaging in the general rubbish bin, not recycling or food waste.

  2. Keep it out of the food bin

    Greater Manchester's food and garden waste becomes compost in 6 to 10 weeks. Compostable packaging can take much longer, sometimes years.

  3. Do not count on the heap

    UCL researchers concluded that home composting is not an effective way to deal with compostable packaging in the UK, even when it is certified.

  4. Never treat it as litter

    Plymouth's study found biodegradable bags intact after three years outdoors. A green label is not permission to leave it behind.

WHY THE BIN MATTERS

Where it goes
is the real test.

An open garden compost bin full of dark compost and vegetable peelings, with a few pale scraps of film packaging still visible on top
AI-generated image, not a photograph of a real person or place.

Compostable plastics are designed for controlled industrial composting. UCL researchers note they are incompatible with most anaerobic digestion and recycling systems in the UK, so they usually end up in landfill or incineration.

Telford and Wrekin Council says its green waste is composted outdoors at temperatures and timescales too low for even the thinnest compostable packaging. The UK government's stated preference is that most plastics are reusable or recyclable.

Questions

Questions people ask

Is bio-based plastic the same as biodegradable?

No. The UK government defines bio-based plastics as made from plant-based sources such as starch, cellulose or lignin. They can be engineered to be biodegradable, but are not necessarily.

Can I put compostable packaging in my food waste caddy?

Check your council's guidance. Recycle for Greater Manchester asks people not to, because its food and garden waste is composted in 6 to 10 weeks and compostable packaging takes much longer.

Will home compostable packaging break down in my garden bin?

Often not fully. In UCL's Big Compost Experiment, 60% of certified home compostable items were still clearly visible, and the researchers say typical home composting takes 3 to 12 months.

What temperature does industrial composting need?

The UK government describes optimal industrial composting conditions as 55 to 70 °C with high humidity and oxygen. A garden heap is largely unregulated and usually cooler.

Is it fine to drop a biodegradable bag outdoors?

No. University of Plymouth researchers found biodegradable bags could still carry shopping after three years in soil or sea, and the government noted concerns that the label could encourage littering.

Sources

Where the facts come from

  1. Purkiss et al. (2022), The Big Compost Experiment, Frontiers in Sustainability
  2. GOV.UK: Standards for bio-based, biodegradable and compostable plastics, summary of responses and government response (2021)
  3. University of Plymouth: Biodegradable bags can hold a full load of shopping three years after being discarded
  4. Recycle for Greater Manchester: Compostable packaging
  5. East Sussex County Council: What you can recycle and where
  6. Telford & Wrekin Council: Compostable packaging

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