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POO BAGS 101
What actually counts and why
A clear, evidence-led guide for pet owners who want to make better everyday choices - without greenwashing or guesswork.
Introduction
POO BAGS MATTER
In the UK alone, it’s estimated that over 20 million poo bags are used every single day. They are one of the largest sources of physical waste linked to dog ownership!
Which is why so many turn to compostable or cornstarch bags...
Compostable and cornstarch poo bags are often the first solution people turn to because they sound like the better choice.
Choosing them isn’t naive - it’s a thoughtful response to a genuine problem.
The problem is… it’s not that straightforward
Unfortunately, the way “cornstarch” poo bags are marketed often avoids what actually matters:
- whether the claims on the packaging match real-world conditions
- what the bags are made from
- how they behave after use
- where dog waste really goes
That gap between intention and real-world impact creates confusion and misleads well-meaning pet owners.
This guide exists to bridge that gap.
It explains how poo bags really work, what trade-offs exist, and how to think about them clearly - so you can make a decision that actually aligns with the reason you cared in the first place.
WHAT ACTUALLY HAPPENS TO DOG WASTE IN THE UK
In the UK, dog waste is...
- not composted
- disposed of as general waste
- mostly incinerated, with a minority potentially ending in landfill
This matters because:
- dog waste is not treated like food or garden waste and taken to a composting facility
- compostable cornstarch poo bags must go to composting facilities, NOT general waste
- compostable cornstarch poo bags cause harm in landfills - the incorrect conditions cause them to release methane, a powerful greenhouse gas instead of biodegrading. This is the reason we don’t want food waste in landfills.
Key takeaway: compostable cornstarch poo bags offer no end of life benefits given dog waste is incinerated or landfilled after disposal.
WHAT POO BAGS ARE ACTUALLY MADE OF
Spoiler alert: “Cornstarch” poo bags are NOT plastic-free!
Compostable & Cornstarch Poo Bags
These are often marketed as:
- “plastic-free” or “plant-based”
But in reality, they are bioplastics, a subset of plastic. They are:
- legally classed as plastics
- chemically structured as polymers
- physically a plastic
They are made up of cornstarch-derived polymers (that have been chemically changed to become plastic) and PBAT (polybutylene adipate terephthalate). PBAT is:
- is fossil-fuel derived plastic polymer
- commonly makes up 50–80% of the material
- is required for strength and flexibility
Legally, chemically, and physically, these bags are still classed as plastics. The difference is some cornstarch has been used in their manufacture - not whether they are plastic or not.
Recycled Plastic Poo Bags
These are made using existing plastic waste that’s already on the planet.
No new plastic is created. Instead, waste plastic is reused before disposal.
This doesn’t make the plastic disappear - they won’t biodegrade and will still end up in the same waste streams as other poo bags - but it does reduce the production of “new” plastics and the demand for virgin materials.
Conventional Plastic Poo Bags
These are typically made from fossil-fuel-derived plastics such as polyethylene.
They’re often the cheapest option - but when made from virgin materials, they add new plastic into the system.
Key takeaway: All poo bags are still types of plastic, including “cornstarch” ones.
While not a perfect solution, poo bags made of recycled plastic waste is shown to have the smallest eco-footprint.
COMMON eco-friendly poo bag myths
“Cornstarch poo bags aren’t plastic”
It’s understandable to think this - their marketing strongly suggests it.
But to function as a poo bag, cornstarch must be chemically converted into plastic polymers.
That’s why these bags are still legally and scientifically classified as plastics (and so different to the cornstarch in your kitchen cupboard!).
“Compostable bags break down in landfill”
Landfills prevent biodegradation by limiting oxygen and moisture.
In these conditions:
- food waste doesn’t compost properly
- paper breaks down very slowly
- compostable plastics don’t behave as intended
So compostable poo bags do not reliably biodegrade in landfill. As the name suggests, they need to go to a composting facility. But these do not exist for dog waste, meaning compostable poo bags are pointless.
“Cornstarch poo bags stop plastic entering landfill”
As discussed above, these poo bags are still types of plastic and therefore add plastic to landfill (if they end up there).
Compostable bags still contain plastic polymers, so while the idea sounds reassuring, it doesn’t reflect how waste systems actually work.
“Compostable or Cornstarch poo bags breakdown in nature"
These bags require very specific conditions to successfully biodegrade. Their certifications assess for their biodegradability in compost conditions - and the environments are very specific - hence why there are different certifications for different compost environments as well (industrial vs home)!
Factors such as:
- oxygen levels
- moisture levels
- temperature
- living microorganisms
all affect the successful biodegradation of a compostable poo bag. The lack of controlled conditions in nature mean these bags do NOT reliably and safely biodegrade in nature.
“Cornstarch poo bags reduce poo bag littering"
This is a dangerous misconception as research is actually showing the opposite - more people litter poo bags when they think it’s simply going to “breakdown” in time!
But as discussed in the previous myth, these bags will not successfully biodegrade in nature, and in fact will likely shed microplastics more readily.
All these statements are false!
LANDFILL & INCINERATION
What you need to know...
Many people are understandably worried about their poo bags sitting in landfill “forever”.
That concern makes sense. Unfortunately, this will happen regardless of poo bag - as discussed above, landfill conditions prevent items from properly biodegrading.
But two important realities often get missed:
- Most dog waste in the UK is incinerated
- The environmental impact depends on what material is being burned
Incinerating:
- virgin, newly created plastic
VS
- existing waste plastic (recycled poo bags)
are not equivalent.
Using recycled plastic means:
- no new plastic is created
- existing waste is used once more
- overall material demand is reduced
Incinerating a “cornstarch” poo bag isn’t better either - as mentioned above, these bags still contain 50-80% fossil-derived polymers and are virgin plastics.
Key takeaway: There’s no perfect outcome - only less harmful ones.
SO WHAT ACTUALLY MAKES A DIFFERENCE?
We won’t sugar-coat it and pretend there’s a “perfect” solution.
The most useful question now is:
Which choice causes the least harm in the systems we actually use, with real-world considerations taken into account?
For poo bags, that means considering:
- real disposal routes (not ideal ones)
- virgin vs recycled materials
- performance (bags still have to work)
- total material footprint - a full life cycle assessment
This isn’t about being perfect.It’s about being honest and pragmatic.
OUR APPROACH AT PET IMPACT
Pet Impact was founded by vets Alice and Gavin, who strive for progress over perfection.
We don’t believe in:
- pretending plastic magically disappears
- hiding inconvenient details
- basing decisions on assumptions
We believe in:
- evidence over ideology
- clarity over buzzwords
- solutions that work in real life, not just on paper
That’s why we chose to make non-biodegradable poo bags using existing waste - and to talk openly about why.
We performed a full Life Cycle Assessment (LCA) on our ReSEAcled Poo Bags so all areas of environmental impact are accounted for.
Recognising they are not a perfect solution, we then set it up so that every ReSEAcled Poo Bag further funds the recovery of one bottle's worth of ocean-bound plastic - meaning tangible, real change is created from their us.
Learn More
Watch our videos below, read our official whitepaper, LCA and blog posts, or view our ReSEAcled Poo Bags!
Videos to become a poo bag expert
1. Understanding the Truth about Compostable & “Cornstarch” Poo Bags
2. Why “Waste-Based” Poo Bags are Currently Better for Our Planet
Congratulations! You are officially a Poo Bag expert.
Learn more with the additional resources below.
Pet Impact's Official White Paper on eco-friendly poo bags:
Further Reading
The Environmental Harms of Dog Poo
Why have Forestry Bodies across the UK switched their advice from "Stick & Flick" to "Bag It and Bin It"? While easily seen as a "natural" waste product, our dogs'...
How To Compost Dog Poo
Understanding how to compost dog poo can be a tricky topic for many dog owners. Don't worry though, we're here to help! Why Compost Dog Poo? Composting dog poo can help...
Do Plant-Based Poo Bags Actually Exist?
There is an overwhelming amount of greenwashing and confusion surrounding 'eco-friendly' poo bags. It's often claimed that compostable 'cornstarch' poo bags are the best option on the market at present...