What Kind of Dog Poop Bags Should I Use?

Americans own around 90 million dogs. They provide companionship, reduce stress and help us stay active.

They also produce about 12.2 million tons of waste per year. Most of it ends up in landfills, where it generates planet-warming methane. And, all those poop bags can shed microplastics into the environment.

Here’s how you can reduce that environmental poo-print without adding more plastic to the planet than necessary.

Taking care of business

Responsible disposal starts with picking up your dog’s poop. Bags are the most convenient way of doing that, but not all bags are created equal.

Whenever possible, you should avoid bags made from conventional, new plastic, which is derived from fossil fuels. One exception: bags that have already come into your home with things like takeout food and other deliveries. Since these bags are usually destined for a landfill anyway, reusing them to pick up dog poop is “a great option,” said Rebecca Ryals, an environmental scientist at the University of California, Merced.

Bags made from recycled plastic are slightly better than conventional ones, but they still have a fairly large environmental footprint from production and transportation.

Then, there are bags that claim to be plant-based, biodegradable and compostable. If you’re a dog owner, you’ve probably seen them. You might have also wondered which ones are really green in the environmental sense and which ones aren’t.

“Plant-based” just means some of the stuff used to make the bag comes from plants rather than fossil fuels. While this is preferable to conventional plastic, it does not indicate whether the bag will leave harmful microplastics behind, said Ramani Narayan, a chemical engineer at Michigan State University.

It’s the same for bags sold as biodegradable: There’s no guarantee that they’ll break down safely in nature or even in a compost bin. Biodegradable is a marketing label, and all it means is that the bags contain additional ingredients that may or may not help them break down. Those ingredients “could be organic, or could be anything,” Dr. Narayan said. “To call it biodegradable is a purely misleading claim.”

Compostable bags, on the other hand, are specifically designed to biodegrade when the right conditions are met.

In some countries, they carry a certification confirming that they have passed tests in a simulated industrial composting facility. In the United States, though, no such seal of approval exists. The country’s leading certification group, the Biodegradable Products Institute, does not assess poop bags because the vast majority of curbside composting programs in the United States do not accept dog waste, according to Rhodes Yepsen, executive director of the institute.

Americans who want to compost their bags should try to find ones that meet the D6400 standard of the American Society for Testing and Materials. That’s what the certifiers would be looking for. If a company that advertises these types of bags sells other products certified by the Biodegradable Products Institute, that’s a good sign, too.

But even some compostable bags might not break down fully. Emily Bryson, a researcher at Central Queensland University in Australia who studies the environmental effects of pet waste, tested five types of bags that were certified as compostable and found that all of them left behind some microplastic fragments.

Certifications are based on “highly controlled lab conditions,” she said, and “don’t really consider how these bags might perform in any sort of realistic composting environment.”

Even so, compostable bags are probably the best way to avoid microplastics. And, according to Dr. Ryals, their components and manufacturing processes are less environmentally taxing than traditional plastic.

It’s in the bag. Now what?

Ideally, your dog waste should be composted. But in the United States, only a handful of places offer this service. It’s not for a lack of technology, Dr. Ryals said, but because of cultural aversion.

You can compost dog waste yourself, but you’ll have to take a few precautions.

The United States Department of Agriculture says dog-waste compost can be used as a soil additive for things like lawns, flower beds and potted plants, but not on anything grown for human consumption. Here’s the department’s fact sheet and guide.

Whatever you do, don’t compost or flush cat feces. Cats can carry more dangerous pathogens.

If composting is out of reach, then there’s one more possibility: the toilet. If you’re connected to a municipal sewage system, you should check with your local government to see if flushing is acceptable in your area, said Rose Seemann, co-founder of the Enviro Pet Waste Network, a nonprofit group that promotes eco-friendly pet-waste disposal and maintains a list of places where flushing is OK.

If you have a septic tank, don’t flush. Doing so can cause problems, because dog feces don’t break down as easily as human waste.

And don’t put anything down the toilet except tissue and the waste. Especially not bags. Dr. Bryson recommended picking up your dog’s poop with toilet paper and transporting it to the bathroom in a reusable container.

The next step is easy: Dump it into the toilet and flush.