Sustainable dog poo bags: how to choose the right option
The most sustainable dog poo bag depends mainly on how you dispose of your dog’s waste. If your dog poo bags go into general waste or dog poo bins, the...
Welcome to poo bags 101
An evidence-led guide to poo bags
For pet owners who want to make better everyday choices without greenwashing or guesswork.
There's more to poo bags than meets the eye
With over 20 million poo bags used every day in the UK, they're one of the largest sources of physical waste linked to dog ownership.
It's no wonder so many turn to compostable or cornstarch bags. They're often the first solution people turn to – because they sound like the better choice.
There's a problem, though. It's not quite as straightforward as that.
The marketing often skirts around what truly matters
With many "cornstarch" bags, you're not being shown the full picture:
- 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.
You'll learn how poo bags really work, what trade-offs exist, and how to think about them clearly.
What actually happens to dog waste in the UK
In the UK, dog waste is not composted.
It's disposed of as general waste, and mostly incinerated with a minority potentially ending up 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 for their benefits to be actualised
- Compostable cornstarch poo bags cause harm in landfills. The incorrect conditions cause them to release methane, a powerful greenhouse gas, instead of biodegrading. The same reason why we don’t want food waste to end up in landfills.
Key takeaway: compostable cornstarch poo bags offer no end-of-life benefits because dog waste is incinerated or landfilled after disposal.
What poo bags are really 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.
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.
They are made of cornstarch-derived polymers that have been chemically altered to become plastic and PBAT (polybutylene adipate terephthalate).
About PBAT:
- A fossil-fuel-derived plastic polymer
- Commonly makes up 50–80% of the material
- Required for strength and flexibility
Recycled Plastic Poo Bags
These are made from plastic waste already on the planet.
No new plastic is created. Waste plastic is reused before disposal.
This doesn’t make the plastic disappear. It won’t biodegrade and will still go to the same waste streams as other poo bags. However, it reduces 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 from recycled plastic waste have been shown to have the smallest eco-footprint.
Common eco-friendly poo bag myths
❌ “Cornstarch poo bags aren’t plastic”
It’s easy to think this, since their marketing suggests it.
However, to work as a poo bag, cornstarch needs to be chemically converted into plastic polymers.
This is why these bags are still legally and scientifically classified as plastics, unlike the cornstarch in your kitchen cupboard.
❌ “Compostable bags break down in landfill”
Landfills stop biodegradation by limiting oxygen and moisture.
In these conditions:
- Food waste doesn't compost well
- Paper breaks down slowly
- Compostable plastics don't work as they should
So, compostable poo bags do not reliably biodegrade in landfills.
They need to go to a composting facility. However, such facilities for dog waste don't exist, making compostable poo bags ineffective.
❌ “Cornstarch poo bags stop plastic entering landfill”
These poo bags are still plastic, which means they can end up in landfill.
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 break down in nature"
These bags need very specific conditions to biodegrade properly.
Their certifications check how well they break down in compost settings. Different compost environments, like industrial and home, have their own certifications.
Several factors influence how well a compostable poo bag biodegrades, such as:
- Oxygen levels
- Moisture levels
- Temperature
- Living microorganisms
Without controlled conditions, these bags do not biodegrade reliably or safely in nature.
❌ “Cornstarch poo bags reduce poo bag littering"
This is a dangerous misconception.
Research shows the opposite: more people litter poo bags when they think they will “break down” over time.
As mentioned in the previous myth, these bags do not biodegrade in nature. In fact, they are likely to shed microplastics more easily.
All these statements are false.
Landfill & incineration
What you need to know...
Many people worry about their poo bags sitting in landfill “forever.” That's a valid concern.
Sadly, landfill conditions prevent successful biodegradation, regardless of the type of poo bag.
However, two key points are often overlooked:
- Most dog waste in the UK is incinerated
- The environmental impact varies based on the material being burned
Incinerating virgin plastic is not equivalent to incinerating existing plastic waste.
Using existing, recycled plastic means:
- No new plastic is made
- Existing waste is reused
- Demand for materials is lowered.
Incinerating a “cornstarch” poo bag isn’t better either. As noted, these bags contain 50-80% fossil-derived polymers. They are virgin plastics.
Key takeaway: There’s no perfect outcome – only less harmful ones.
What actually makes a difference?
We won’t sugarcoat it. A “perfect” solution doesn't currently exist.
The most useful question we can ask 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
- Virgin vs recycled materials
- Performance
- Total material footprint via a full Life Cycle Assessment
Our approach
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 do 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 use.
Want to learn more?
Check out our videos below. You can also read our official whitepaper, LCA, and blog posts. Don’t forget to view our ReSEAcled Poo Bags.
Let's make a poo bag expert out of you
Understanding the truth about compostable & “cornstarch” poo bags
Why “waste-based” poo bags are currently better for our planet
You're officially a poo bag expert!
No, we can't give you a certificate. We're proud of you all the same, though.
Pet Impact's official white paper on eco-friendly poo bags
Further reading
Can you flush dog or cat poo down the toilet?
In the UK, it is generally not advised to flush dog or cat poo down the toilet. Pet waste can contain parasites, bacteria and veterinary medicine residues that our sewage...
What the science says about home composting dog poo
Dog poo composting: what the science actually says. We explore what we know, what we don't, and why it matters for your health and the environment.
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'...