A green dispenser filled with dog poop bags is affixed to a wooden post along with a blue sign reminding people to pick up after their pets. The forest is behind it.
A sign at the entrance to Sackville Lakes Provincial Park on July 10, 2023 in front of a garbage receptacle reminding people to pick up after their pets. Credit: Yvette d’Entremont

After picking up 50 discarded bags full of dog poop in just 10 minutes of walking along a neighbourhood trail, Dr. Tony Walker took matters into his own hands. 

In addition to collecting the bags and disposing of them in a garbage receptacle, the Dalhousie University professor sat down and penned an article, “What not to do with dog poop.” His piece was published in the latest edition of the journal Science of the Total Environment. 

Walker’s research includes a focus on plastic and microplastic pollution and the policies that can reduce it. He believes many people mistakenly believe so-called biodegradable bags are compostable. They’re leaving dog waste-filled bags on trails with the expectation they’ll eventually disintegrate.

But in the absence of industrial composting facilities only available in a few jurisdictions, these bags aren’t compostable and lead to environmental and human health problems.  

“Because I’ve worked on these plastic policies for so long, I’ve done a lot on human behaviour and human perceptions, consumer perceptions, of using plastic products… Many are pitched as biodegradable, whether that’s plastic packaging, grocery bags,” Walker said in an interview Monday afternoon.

“And I’ve reviewed a lot of global studies where people are interviewed. It’s one of the common misperceptions with consumers. So, I made the assumption that that was also the same confusion with the poop bags.”

‘Persist for decades’

What many consumers may not realize is that biodegradable or conventional petroleum-based plastics in the environment “will persist for decades or even longer and contribute to the global plastic and microplastic pollution problem.”

“They do degrade at normal temperatures. But because they’re biodegradable, one of the flaws in marketing, one of the loopholes, is they’re allowed and permitted to contain up to 25% fossil fuel plastics,” Walker explained. 

“So, even if the other 75% is plant-based and bio-based, that’s wonderful. But there’s no guarantee that they’re 100% bio-based, in which case 25% of the material could be releasing microplastics.”

On its website, HRM reminds pet owners of the following:

  • Animal waste is toxic, the bags are disposed of as garbage, no other circumstances. They are not organics or fertilizer and pet waste does not go into the green cart
  • Do not use bags marketed as biodegradable or compostable. These types of bags are never accepted at municipal compost facilities and must go into the garbage

‘Not unique to Halifax’

During the trail walk that sparked his journal article, Walker took a series of photos showing several multicoloured bags full of feces festooning his local trail. He included them in the piece when he submitted it to the scientific journal. 

Photos of blue, yellow, and green bags filled with dog poop and discarded on grassy ground.
A few of the 50 single-use plastic bags of dog feces Tony Walker found on a trail walk that sparked his recent article. Credit: Tony R. Walker

“I know it’s not possibly the readership I was aiming for. But at least now news and media have picked up on it and hopefully it’ll get a broader readership,” Walker said. 

“I think together we could hopefully raise the bar of awareness, certainly in this municipality. But (from) everyone I spoke to at an international plastics conference a few weeks ago in the U.K., I learned it’s not unique to Halifax. It’s a widespread problem, unfortunately.”

In addition to being a source of plastic and microplastic pollution, the dog feces in these littered plastic waste bags also pose human health and ecological risks.  

“Dog poo not in a bag doesn’t belong in the environment because of the parasitic tapeworm (toxocara) that can cause blindness,” Walker said. “In addition to those parasitic tapeworms in dog waste, they also contain e. coli.”

Harmful to people and aquatic ecosystems

That dog waste can also make its way into rivers and lakes, resulting in harmful algal blooms and eutrophication. 

“And then ultimately fish kills, because of the lack of oxygen,” Walker said. “It’s a problem. And the problem is that it’s going to make people and the aquatic ecosystem ill.”

While researching his article, Walker did learn of the existence of 100% bio-based dog waste bags. However, they’re not going to appeal to everyone. 

“They’re akin to a very thick paper bag, but they’re not going to be ideal. You think of wet weather, you think of even the consistency of the dog waste. You’re not going to be able to pick up everything without getting your hands messy,” he said. 

“So, they are available. But they’re few and far between, and they have obvious limitations because they’re not structurally sound.”

Messy problem

If all we have are biodegradable or conventional plastic bags, Walker said it’s critical that owners collect their dog waste and bin it at home or in a garbage receptacle along their walking route. 

“Some jurisdictions even have special dog poop bins with lids on. In an ideal world, that would be the best place for it because it will be dealt with by that municipality. But at the very least, people should be bringing these bags home,” Walker said.

“They will not degrade in the environment. And if they do, it will take decades and then they’ll only release microplastics…They will not break down, and they will continue to release the harmful bacteria and parasites eventually.”

Walker wrote that to increase awareness and change the behaviour of pet owners, “all plastic waste bags should clearly indicate appropriate waste disposal instructions.” Additionally, if they are biodegradable, additional instructions should indicate the bag can only safely be composited in an industrial composting facility.

“So, to all responsible pet owners, please deposit your biodegradable or conventional petroleum-based plastic dog poop bags in an appropriate waste bin, not in the environment,” he wrote.

Looking out his home office window facing a popular Halifax trail, Walker expressed dismay over the knowledge that there are many discarded bags full of dog poop festering there.

“It turns my stomach because somebody, probably it’s going to be me, will have to go around and collect those up and bin them. I’m just gearing myself up for that eventuality,” Walker said. “But if we can raise awareness, then then at least we’re turning the tide on this messy problem.”

Yvette d’Entremont is a bilingual (English/French) journalist and editor who enjoys covering health, science, research, and education.

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  1. Hello! I was glad to read this article, and I would be curious for Dr. Walker to in fact talk to the dog walkers who leave the bags, to find out if indeed, the majority of them think they are biodegradable, or rather if they intended to pick it up on their way back, and forgot. (Or maybe they were going to pick it up that day and Dr. Walker beat them to it!). I honestly have no idea, but my thinking is, if people go to the trouble of putting it in a bag, it’s because they do plan to dispose of it. But– I do think it is perfectly normal and acceptable for people to bag it on the way out, with the plan to pick it up on the way back. Why carry stinky gross poop with you on a two-hour out-and-back walk if there are no trash cans along the trail and you know you’ll be passing that way again on the way home? Unfortunately the plan to pick it up on the way back leads to a chance of forgetting it, and that is why I believe Dr. Walker found so many bags on his walk. But I think there are things we could do to address that (see my suggestions below).

    If the dog owners are in fact of the mind that poop is natural and compostible as Dr. Walker suggests, I would think they would just leave it in the woods and not go to the trouble and yuckiness of picking it up. (I have spoken to a few dog owners about why they let their dogs poop in the woods without picking it up, and they all have told me it’s because they see it as “natural”- and seem oblivious to the issues of water and soil pollution, and the fact that it’s nasty to look at/smell/possibly step in for their fellow hikers).

    But I’m genuinely curious and it would be great if Dr. Walker did some first-hand research (he says in the article he only based his assumption about why people leave poop bags on the fact that people use plastic bags in their compost bins thinking they are biodegradable, but I think that’s quite a different situation!)

    I am also a bit concerned about Dr. Walker’s points here and how it risks discouraging bagging of poop on the trail. As a non-dog-owner nature-lover and enthusiastic berry-picker , I am always dismayed to see dog poop in the woods along the trails I hike, whether in a bag or not – but I must say of the two options, I *greatly* prefer to find it in a bag near the trail. If it is bagged, it at least keeps it off my shoes, out of my nostrils, and off of the plants that I may decide to sample from. It’s much easier to spot and thus avoid. And if I’m not too far from the trailhead, I am often inclined to pick up a bag or two on my way home and dispose of it in the nearest trash can. Having it bagged makes it relatively easy to do so. If it’s loose on the ground, I almost never pick it up even if I happen to have a bag on hand – I have a sensitive nose and the smell of dog poo makes me retch – scooping poop is one of my least favourite things in the world! 🙂

    I also feel that if the poop is bagged, it more easily gives the opportunity to other dog walkers to pick it up – and I know that some if not many of them have the ethos of “everyone forgets poop sometimes, and I know that could be me too – so I will make a point of picking up an extra bag now and then, to make up for the times I’ve forgotten”. I feel that bagging the poop makes it way easier for any well-meaning person to dispose of it.

    I also think that as Halifax continues to grow and more people use the trails, that it’s important for the province and HRM to step up and use some of this taxpayer money to do more to keep the environment free of dog poop. The reality is, people love their dogs here, people love to take their dogs hiking, and people’s dogs are going to poop along the trails in greater and greater numbers. I think there are a few things that are not being done right now which could be done by the city/province for relatively little money, that would make a big difference:

    1. Educational signs at every popular trailhead – I do think many well-meaning people have no idea about the issues of letting dogs poop in the woods – it would be great to have some clear bullets about the bacteria it introduces into the ecosystem. It would be great to present people with numbers- some think, “wild animals poop in the woods so it’s ok for my do to as well” – but they don’t realize how many dogs per day are pooping there compared to how many other top carnivores like coyotes and bobcats are pooping there- a punchy graphic showing amounts of dog poop deposited at the site per day could be really impactful!

    2. Poop bags and trash cans could be provided not only at the trailhead, but also within a 5 minute walk in from every trail head. The reality is, a lot of dogs poop after they’ve been walking for a while. If the city invested in some trash receptacles slightly out along the trail, I think that would make a huge difference in the amount of poop that is thrown out. Let’s face it- nobody wants to carry a bag of poop on their hike. But if you put the trash cans where the dogs are pooping, I think most well-meaning people will be willing to scoop it and place it in the bin. If the city provides extra bags (as they do in a lot of urban parks), it also helps out the folks who forgot their bags. If you make it easy for folks, they are more likely to comply! I would love to have some of my tax dollars go to pay workers to hike along a trail for 5 minutes to empty trash receptacles. I am sure the city could source some sort of narrow wheelbarrow that would work to allow workers to transport the waste out on a narrow trail. I think some workers might actually enjoy a waste-collection job where they get to do some hiking as part of their day 🙂

    3. An educational campaign that encourages dog owners to pick up bags that are not their own would also be a great idea in my mind. Something like, “Let’s face it, we all forget sometimes!” — encouraging all dog owners to be good citizens and help create an environment where dogs are welcome, by picking up other bags when they see them. “if we all pick up for each other, then we all help keep the place clean, and keep our canine friends welcome on this trail”.
    Once again, if the poop is at least in a bag, it makes it way easier for everyone to help out in this way!

    Thanks for considering,
    Katherine Kitching

  2. Leaving dog waste in plastic bags anywhere and everywhere is not because the owners think they are biodegradable.Everyone is well aware that dog feces are toxic and belong in the garbage at your home or in a municipal waste bin.It’s simply a case of irresponsible dog owners………

    1. In areas of agricultural production one sees animal waste being used as a ground enhancement resource with little processing beyond separation and time having happened before application. At garden centres you can buy bags of what is essentially processed poop.

      There is also the idea of biodigesting the dog waste and perhaps finding a use for the resulting biogas. I think that HRM was looking at this for some areas of high dog concentration like parks.

      I am left wondering if cow, sheep and goat feces are intrinsically less toxic than similar dog product or is it that the infrastructure exists to find a use in those instances and we are still looking at how to deal with the doggy bags as a separate stream in municipal collection systems.

      1. jsimonf: I believe carnivore poop tends to have a lot more nasty bacteria in it, than herbivore poop….