Scooping up poop might be one of the worst parts of walking the dog. The only thing slightly more annoying? Using a brand-new plastic bag — one that you know will linger in landfills for centuries — just to hold poop.
Maybe this frustration has piqued your interest in “compostable” or “biodegradable” dog waste bags. But odds are, whatever you think will happen with eco-friendly poop bags isn’t panning out. “Biodegradability is the most used and abused term,” says Ramani Narayan, a chemical engineer at Michigan State University. The word carries little regulatory oversight, and when slapped on products, it can leave customers thinking their purchase — whether it be plastic cups, forks or dog poop bags — leaves a smaller impact on the environment than it does.
When people envision a biodegradable bag, Narayan asks, what do they picture? Generally, consumers want a product that melts away into the environment as if it was never there. In a way, that’s what scientists want, too. A biodegradable product is something that microbes take apart and turn entirely into fuel, with no bits and pieces, molecules or potential contaminants left behind.
When researchers engineer a biodegradable product — like a to-go container or a plastic-like film — they generally design the material to break down in a specific environment, such as saltwater or soil. If the product isn’t immersed in the right surroundings, the degradation doesn’t happen as it should.
If a company — say, a dog poop bag manufacturer — is serious about their product biodegrading, it will put disposal instructions on the package to make sure the product reaches the correct final destination. If a product only says “biodegradable” with no disposal protocol and no timeline saying when the product will break down by, “it is not good marketing and it’s misleading,” says Debra Darby, the manager of organics and sustainable solutions at Tetra Tech, an engineering and environmental consulting firm.
The word is misused often enough that California banned the sale of any product labeled “biodegradable” without providing disposal guidelines and a timeframe on how long the item takes to break down. And the Federal Trade Commission has gone after companies in the past for deceptive marketing around biodegradability claims.
If you’re reading your “biodegradable” dog poop package more thoroughly, you might see the label states that the bags supposedly meet ASTM standards, or metrics put out by an international organization that help measure biodegradability. Bags boasting these claims sometimes only partially align with those guidelines, Narayan says.
“That standard is a test method for how to measure biodegradability, but it doesn’t tell you what a pass or fail is.” For example, microbes might consume 10 percent of a bag or container the way the ASTM standards dictate. But manufacturers might still claim their product “meets” those rules, without disclosing that 90 percent of their product lingers too long or is never consumed by microorganisms.
What About Compost?
Some doggie bags might skip over the word biodegradable and say the product is compostable. If you like the idea of your dog’s poop heading off to a commercial compost facility to get churned into a rich soil additive, check on two crucial pieces of information before buying the product. First, look for a seal from the Biodegradable Products Institute. This third-party organization uses independent labs to determine whether a product might be accepted by commercial composting facilities in the U.S.
Second, figure out if your local composting company actually accepts the bag — or dog poop, period. Many composting facilities don’t accept dog feces or kitty litter because of concerns about diseases or unwanted bacteria, Darby says. Some avoid all kinds of bags, compostable or not, because of the way the material interacts with their machinery. Other facilities only accept bags made of certified organic materials.
Checking all these boxes might be impossible. If that's the case, you'll end up with a solution Darby thinks is most likely. “Primarily, pet waste should be put into the trash,” she says. And in that scenario, the bag material you choose likely doesn’t make much of a difference, as the poop and its bag will slowly degrade and release methane or — depending on where you live — get sent to incinerators.
Even if you can’t find a way to compost your dog poop, know that it’s a good step to be picking it up in the first place, as the pathogens it might carry could linger in the environment otherwise. And please — bring the bag all the way to the trash can and don’t chuck it elsewhere. As Darby points out, “most times when I see them, dog waste bags are hanging from a branch.”