Are Biodegradable Dog Poo Bags Really Biodegradable?

We sell poo bags, so take this in the spirit it is offered: most of the environmental claims in this category are softer than they look, including some of the ones that have appeared on our own packaging over the years. Here is a straight explanation of what the words mean.

"Biodegradable" is close to meaningless on its own

Everything biodegrades eventually. The word has no legal definition in the UK that specifies how long, under what conditions, or into what. A bag that takes 400 years to fragment into microplastics is, technically, biodegrading. The claim only means something when it is attached to a standard, a timeframe and a set of conditions.

The UK's Competition and Markets Authority has been explicit about this in its Green Claims Code: vague environmental claims without qualification are misleading. If a pack says only "biodegradable", that is the manufacturer telling you very little.

"Compostable" means more — but read which kind

Compostable is a defined standard. In Europe the relevant one is EN 13432, which requires 90% breakdown within 180 days under industrial composting conditions — sustained temperatures around 55 to 60°C. A separate standard, EN 17427, covers home composting, which is slower and much harder to meet.

The distinction matters because industrial composting conditions do not exist in your garden, and they do not exist in landfill either.

The landfill problem nobody mentions

This is the part that undermines most of the marketing in this category. Dog waste bags go in general waste. General waste largely goes to landfill or incineration. Landfill is anaerobic — densely packed, with very little oxygen. Compostable and biodegradable materials need oxygen and warmth to break down, and in an anaerobic landfill they either sit there largely intact, or break down slowly and release methane, which is a considerably more potent greenhouse gas than CO2.

So a compostable bag in landfill is not obviously better than a conventional one, and may be marginally worse. This is not a reason to give up. It is a reason to be sceptical of a bag that claims to solve the problem on its own.

What corn starch blend actually means

A great many bags sold as eco-friendly, ours included, are described as a corn starch blend. The important word is blend. These bags combine plant-derived starch with polymers, which reduces the fossil-derived plastic content but does not make the bag fully plant-based or certified compostable. A blend is a genuine improvement on conventional polyethylene. It is not the same thing as a certified compostable bag, and any brand implying otherwise — including one selling you a bag — is stretching it.

Our bags are a corn starch blend. The roll cores and outer packaging use recycled material. We do not hold EN 13432 certification and we do not claim it.

How to read a pack honestly

• Look for a standard number — EN 13432 or EN 17427, or the seedling logo. No standard means no verified claim.
• Check which composting is meant. "Compostable" with no qualifier almost always means industrial.
• Treat "oxo-biodegradable" as a red flag. These are conventional plastics with an additive that makes them fragment faster into smaller pieces. The EU has restricted them.
• Be suspicious of a specific decomposition figure with no conditions attached. "Breaks down in 18 months" is meaningless without saying 18 months where.

What actually reduces the impact

Less than the marketing suggests, and more than you'd think:

• Use one bag, not two. Double-bagging doubles the material. A thicker bag — ours are 17 micron — means you don't feel the need to.
• Buy in bulk. A 660 pack has a fraction of the packaging and delivery footprint of eleven packs of 60.
• Check your council. A growing number of UK councils accept dog waste in food or garden waste streams, or run dedicated dog waste bins that go to anaerobic digestion. Where that exists, the bag you use genuinely matters.
• Never leave a bagged one behind. A bagged poo hung on a branch is worse than an unbagged one, whatever the bag is made of.

Why we are telling you this

Because the alternative is joining in. This category is full of green claims that do not survive five minutes of scrutiny, and we would rather sell you a good bag honestly described than a mediocre one with a leaf printed on it.

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A note on availability: our own poo bags are out of stock at the time of writing, with no firm return date. We've left this guide up because the advice holds whoever you buy from. Our puppy pads, washable dog nappies and cat litter tray liners are shipping as normal.