To Flush or Not to Flush – disposing of pet waste

By Green Dog Pet Supply

Not long after we first opened the store, we found a product that we thought sounded like a no-brainer for a green store – doggie poop bags that broke down quickly in water so that they could be safely flushed. It seemed quite logical that pet waste would be best disposed of in a system already in place to treat sewage, so we bought them. However, it occurred to us that we had only worried about the safety of the home sewer system before we bought them, and had not considered to ask what happens to the water supply when pet waste was flushed. We were already selling flushable cat litter and advocating the flushing of litter. Is flushing really the best way to dispose of pet waste?  We contacted the city of Portland about this issue, as we wanted to make sure that it would truly be a good idea on all sides. They vehemently opposed the idea at the time, and we ended up not reordering those bags again (and they weren’t selling that well anyway, so we left it at that).

We heard recently that a few of our distributors were probably bringing in flushable bags, which concerned us a bit, as it means  they would then be actively promoted to local retailers and therefore marketed more widely to the public. As some years had passed and I knew that Portland has made some upgrades to the system in recent years, I called again to discuss the issue. I spoke to Mike Ciolli, Wastewater Manager for Operations in Portland (Columbia Facility). The essence of what he said was similar to what we had heard in the past – They are “Strongly Discouraging” the disposal of any animal waste into the system. He said the facilities are so overtaxed already with human waste, and the facilities cannot be expanded any more than they already have been. As Portland grows, they are very challenged to figure out a way to accommodate this growth from a sewage treatment perspective, which is why they’ve invested so much in bio-swales to divert storm water overflow from the system. The issue of volume is a significant one, when it comes to dog poop. The Environmental Protection Agency estimates that the typical dog excretes three quarters of a pound of waste per day — or 274 pounds per year. This means that for every 10 dogs, more than one ton of poop is generated annually! A seemingly small increase in flushing dog poop would actually generate a very significant problem for a city’s waste management system.

The other issue he brought up is that the bacteria that they use to break down the sewage is chosen to be quite specific to human waste, and pet waste is not broken down as easily by it, causing big problems on that end (he also mentioned that pet waste seems to be much higher in “inert” ingredients that aren’t broken down as easily). Combined with the fact that pet waste can be contaminated with things like parasites, bacterial diseases such as leptosporosis, and toxoplasmosis (toxo. is transmitted through cat feces) that are transmissible to humans, this complicates the problem. If the system is overwhelmed and the pet waste is not broken down properly, these things can slip through. This has happened already on the west coast, as wild sea otters are commonly testing positive for toxoplasmosis, which comes from cat feces being flushed and from storm runoff contaminated with cat feces being implicated. A National Marine Sanctuaries study done ten years ago in Washington state stated that blood tests revealed that 60 percent of the otters tested positive for Toxoplasma, which has been proven as a significant cause of mortality in Southern sea otters in California. There has also been a documented outbreak of human toxoplasmosis in British Columbia, shown later to have been caused by contaminated drinking water, presumably from cat droppings. This is just one pathogen – others could follow the same pattern.

What to do?

  • We encourage people to compost flushable/biodegradable cat litters (minus the poop) at home. Please note: biodegradable cat litter is not yet accepted into the food waste composting program in Portland. It can also be scattered under bushes to break down on its own. When landfilled, it would be best to use biodegradable/compostable bags.
  • Always pick up dog feces from the ground to avoid it being washed into rivers and streams via storm drains – this is a critical step to protecting fresh water from contamination.  We recommend biodegradable or even better, compostable bags. Most landfills in our area have, or will be soon switching over to capturing methane, using it to generate electricity on site, so even landfilling poop is a greener option than it used to be. Though materials take ages to break down in a landfill, encasing poop in a regular plastic bag will ensure it’s preservation forever! (though reusing a plastic bag saves energy vs. the manufacture and transport of compostable bags – AACK! It’s all very complicated.) Picking it up is the critical part of course.
  • There are also home composting kits (Bokashi Pet) that are designed to provide pathogen free fermented poop compost that can be buried or used to fertilize ornamentals/trees etc.  Bokashi tells us that in-ground composters that you bury and add water and enzymes to are inefficient at eliminating pathogens, which can be pushed into the groundwater quickly by all of the flushing with hose water into the soil.

If retailers sell flushable bags in Portland or in other cities with a challenged sewer system and are advocating to customers that this is the greenest option, we worry that the amount of pet waste in the water treatment facility will spike. Mike Ciolli said that he’s aware of a mention by the EPA in an article that says flushing is the best way to dispose of of pet waste, but says that he doesn’t know anyone in his field that has ever advocated the flushing of animal waste, and that there has never been any effort/memo etc issued by the EPA to people in his field that would support this practice.

This is an issue with no perfect answer, but clearly every effort should be taken to keep pet feces from contaminating our streams, rivers, oceans and drinking water. If you live outside of Portland, call your city administrators and ask them whether it’s OK to flush the poop.

2 Responses to “To Flush or Not to Flush – disposing of pet waste”

  1. Brenda Christiansen

    Thanks so much for publishing this message. It is easy to want to do the right thing, but sometimes very difficult to do.

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