What the science says about home composting dog poo

Dog waste in the UK is incinerated (burnt) or landfilled, which has led many dog owners to ask - there must be a better way!

Many have turned to composting their dog's poo, turning 'waste' into something useful. 

We agree that we should change our attitude to and perception of dog poo. Instead of viewing it as waste, we should view it as a valuable resource that could be used to improve our soil or even power our streets (1)! In fact it can create a more nutrient-rich fertiliser than livestock manure (2). 

So what makes dog poo different, why isn't it widely composted like livestock manure and why do so many people caution against composting it altogether?

Well, first and foremost, compared to livestock manure, when it comes to dog poo - we still know so little. There are very few good quality studies specifically looking at the safety and utility of composting dog poo at a household level. 

And secondly, we know dog poo is much riskier than livestock poo - dog poo can contain comparatively higher levels of pathogens (disease causing bacteria, parasites and viruses) that can infect livestock, wildlife and humans.  

So let's dive a little deeper.

What do we know? 

1. Composting dog poo can be done
We know that from a practical perspective it can done, with several studies doing so on a larger scale (3-5). Composting dog waste is established in many parts of North America (6) and many people are already doing it at home in UK. With regards to home composting, very little research exists but it has recently received its first rigorous scientific validation in Australia (7) showing that properly stabilised dog waste compost can meet WHO safety guidelines without reaching high temperatures (although how long this takes in the UK, what happens to parasite eggs, veterinary drugs and antibiotic resistant genes were not confirmed - more on this later!). 

2. Landfilling and incinerating dog poo is environmentally detrimental 

Landfilling dog waste is environmentally detrimental because, when sealed in plastic bags, it undergoes decomposition without oxygen which produces methane, a potent greenhouse gas. Pathogens, excess nutrients and microplastics from landfilled dog poo (and poo bags) can contaminate the soil and waterways, contributing to long-term environmental pollution. Whilst modern incineration methods can use advanced filtration and generate energy, it is still considered an environmentally harmful practice by experts. This is because it still releases toxic air pollutants—including dioxins, heavy metals, and greenhouse gases—and hazardous ash that causes cancer, respiratory illnesses, and climate change, often disproportionately affecting nearby low-income communities (8).

3. Dog poo (even from healthy dogs) contains disease causing pathogens

As mentioned, we know that dog poo (even from perfectly healthy dogs) can contain a wide variety of pathogens such as Toxocara, Giardia, Salmonella, Campylobacter, Clostridia, Enterococcus, E. coli, Cryptosporidium, Ancylostoma and Echinococcus, all of which have zoonotic potential (i.e. can cause disease in humans) (9 - 11). From a public health perspective, Salmonella, Campylobacter, E coli and Toxocara the top concerns, with the World Health Organization and Centers for Disease Control classifying toxocariasis among the top six parasitic infections of priority to public health (12). Parasites like Toxocara, are extremely resilient and can survive for years in the soil, with one adult worm producing 12500 eggs a day (13)! Children, pregnant women and immunocompromised individuals are more susceptible to these pathogens.

Age is the single strongest predictor for shedding pathogens: dogs under 12 months shed significantly more of almost everything (14). Raw-fed dogs carry significantly more Salmonella, Campylobacter, Clostridia and antibiotic resistant bacteria (15 - 18). Kennelled and rescue dogs have the highest Campylobacter rates (19, 20). Rural and farm dogs face greater exposure to Echinococcus. Regular deworming reduces parasite shedding but adherence to recommended worming schedules in the UK remains inadequate (21).

The prevalence of each of these pathogens varies but can range up to 75% (11, 12, 15-20) so the bottom line is that collectively, it's highly likely there'll be at least one pathogen of concern in one dog poop. Due to the seriousness of this risk, when it comes to composting we should plan for the worst case, not the average.

4. Dog poo can contain antibiotic resistant bacteria

Perhaps more worryingly, dog poo can contain antibiotic-resistant bacteria (15, 21, 23). These bacteria can pass their resistance genes to bacteria in the soil, which then can contaminate crops and waterways - eventually finding their way into humans. When these resistance genes spread to disease-causing bacteria in humans, they can cause serious, untreatable infections. Antibiotic resistance is fast becoming one of the defining global health issues of our time. If left unchecked, it could mean common infections, like UTIs, could become fatal in the future.

5. Dog poo can contain veterinary drugs that are extremely ecotoxic 

Flea, tick and worming treatments are now widely used and many drugs (like the isoxazolines) are predominantly excreted in the faeces, often in their active forms. These drugs can continue to be excreted in the faeces for months after treatment (24) and can be highly persistent in the environment (one study showed they can persist for up to 1000 days in soil (25)). However, the ecotoxicity of these drugs is almost completely unstudied. What little evidence we do have paints an alarming picture - studies show they can be extremely toxic to insects (26) (imidacloprid is over 7000 more toxic to honey bees than DDT) and have already widely contaminated our environment (27). Many other veterinary drugs can be excreted in the faeces, such as antibiotics which contribute to the antibiotic resistance problem discussed above. 

6. Compostable poo bags should not be used in home compost

There's very little research into the home composting of compostable plastics in the real world. However, the few studies we do have show even properly certified home compostable plastics in well managed composts do not biodegrade as expected (28, 29), releasing biodegradable microplastics that are just as harmful as conventional microplastics (30). A new landmark study specifically examined the disintegration of compostable dog poo bags and concluded, 'Due to the potential risks of using home compost contaminated with microplastics in household gardens, dog owners should avoid including compostable plastic bags in their home composts' (28) - a message that aligns with what we've cautioned for several years now. Microplastics are a new and emerging environmental contaminant that can now be found in the food we eat, the air we breathe and the water we drink (31). 

So even if home composted dog poo isn't used on edible plants (as is commonly advised due to the pathogen risks), it could still pose environmental and public health risks by contaminating our wider environment with drug residues, antibiotic resistant genes and microplastics. 

What don't we know about composting dog poo?

1. We don't know what happens to parasites
   While the Australian study showed dog poo 'cold-composted' properly can kill bacterial pathogens (7) - no peer-reviewed study has demonstrated complete elimination of everything, including Toxocara, at household or community scale in a UK climate. 
   
   
2. We don't know what happens to antibiotic resistant genes
   The fate of antibiotics and antibiotic resistance genes in dog poo compost is
   unknown. Most research uses livestock manure which has a different antibiotic exposure profile. Would dog poo compost act as a reservoir for resistant genes and contribute to the spread of this growing global health problem?
   
   
3. We don't know what happens to ecotoxic veterinary drugs

   We simply don't know what happens to common veterinary drugs in dog poo compost - will these chemicals harmlessly biodegrade or will they persist as ecotoxic residues?

4. We don't know what method, temperature or length of time is required to eliminate all risks (pathogens, antibiotic resistance genes and veterinary drugs)
   When it comes to composting, there are a variety of methods (e.g. aerobic vs anaerobic, with or without various microbial or worm 'amendments'), temperatures and time periods that can be used. Each of these variables have the potential to impact compost quality, pathogen loads, veterinary drug residues, and antibiotic resistance gene dynamics and more (9, 32 - 34) but we don't know what combinations are optimal for dog poo.

Conclusion

Our honest take as two veterinarians with a passion for sustainability: the science supports careful, well-managed dog waste composting as far preferable to landfill or incineration. But it's important to recognise that questions about pharmaceutical persistence, antibiotic resistance, parasite kill and long term impacts on soil ecology remain open. Future research should be dedicated to investigating these questions. The evidence shows home composting dog poo has promise but it is not yet strong enough to declare the practice unequivocally safe. These critical data gaps are why we're actively involved in the UK's first scientific dog poo composting pilot in Gloucestershire and we hope to continue contributing to this important topic.

What can you do?

If you are already composting dog poo at home, firstly - good on you! And secondly, check out our how to page to learn about how to minimise the potential risks.

If you cannot compost dog poo - the best (or least harmful) overall solution after weighing up the environmental and public health risks, is to bag it and bin it. Leaving dog poo in nature is a nuisance, hurts fragile habitats, destroys biodiversity, contaminates our soils and waterways, could spread disease and antibiotic resistance to animals and ultimately humans. However, we understand the frustration of having to use a 'harmful' plastic poo bags to do this job. That's why we've dedicated the last 3 years to finding the best bag for the bin. 

Our award-winning solution, ReSEAcled Poo Bags, have undergone the most rigorous environmental assessment that's currently available - a 'cradle to grave life cycle assessment'. This means a third party has measured and independently verified their entire eco-footprint, from raw materials, to manufacture through to disposal, across 16 environmental categories.

We found ReSEAcled performed exceptionally well, and outperformed a standard corn-starch poo bag in 14/16 categories, such as carbon emissions, land and water use. In addition, each bag funds the recovery of one bottle's worth of ocean-bound plastic through our partnership with rePurpose Global. Alternatively, reusing single-use non-recyclable plastic from day to day life is also a brilliant option, as this plastic would be going to landfill/incineration anyway, giving it a second life as a poo bag keeps materials in circulation for longer which is environmentally beneficial.

ReSEAcled Poo Bags allow you to do the responsible thing: clean up after your dog while minimising your eco-impact and stopping plastic entering our ocean. A win for pets, people and the planet!

References:

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