NEW YORK – Americans own around 90 million dogs. They provide companionship, reduce stress and help people stay active.

They also produce about 12.2 billion kg of waste a year. Most of it ends up in landfills, where it generates planet-warming methane. And poop bags can shed microplastics into the environment.

Here is 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 takeaway food and deliveries. Since these bags are usually destined for a landfill anyway, reusing them to pick up dog poop is “a great option”, said Associate Professor 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.

“Plant-based” 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 chemical engineer and professor Ramani Narayan at Michigan State University.

It is the same for bags sold as biodegradable. There is no guarantee that they will break down safely in nature or a compost bin.

Biodegradable is a marketing label, and all it means is that the bags have additional ingredients that may or may not help them break down. Those ingredients “could be organic or could be anything”, Prof Narayan said. “To call it biodegradable is a purely misleading claim.”

Compostable bags, on the other hand, are 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.

But in the United States, no such seal of approval exists.

America’s leading certification group, the Biodegradable Products Institute, does not assess poop bags because the va...