The Green Lantern

Dirty Dogs and Carbon Cats

The greenest ways to care for your pet.

This piece was originally published in September of 2008.

This one is a little gross, but I have lots of pets at home, and most of my weekly waste is composed of dog and cat poop. What’s the best way to dispose of all that so that I don’t end up hurting the environment?

The Lantern has never been trusted to care for any pet larger than a hamster—rest in peace, Fonzie!—so he’ll admit that this question falls a little outside his comfort zone. But your question raises an important point: To own a dog or cat can significantly increase the ecological footprint of your household. The Lantern hopes to cover other aspects of domestic animal husbandry in the future, but today let’s focus one of the most important ways you can manage your pet’s “pawprint”: responsible waste disposal.

Whether you have a dog or a cat, you’ll have two problems to deal with: How do you collect your animal’s poop, and what do you do with it once you have it in hand? Most dog owners have been conditioned to clean up after their pets when they walk on public streets and sidewalks. But it’s just as important to dispose properly of dog waste in your own backyard. Pet waste contains bacteria that can contaminate local waterways if it washes from your lawn into storm drains. In large enough quantities, this pollution can remove oxygen from streams and rivers and contribute to algal blooms, threatening marine life.

What should a dog owner do to prevent this from happening? Experts recommend one of several options. First, you can dump the waste down the toilet, since most sewage-treatment systems can filter out the harmful bacteria. You can also bury the waste in your yard at least 12 inches deep and then cover it with soil. Or you can create a special composter for your dog waste—see these instructions from the U.S. Department of Agriculture; just make sure it’s far away from any fruits and vegetables you might be growing.

To move dog poop around, it’s best to reuse old plastic shopping bags. If you’ve made the better move of eliminating polypropylene bags from your diet already, then try to find boxes or bags that are made from bio matter.

For cat owners, things get more complicated. Cats that get infected with a parasite called Toxoplasma gondii can shed that organism’s oocysts in their waste. (Most cats with toxoplasmosis won’t show any symptoms, so you might not know if your cat has the disease.) According to research conducted in California, Toxoplasma appears to have contributed to an uptick in the deaths of wild sea otters in the past few years. (The parasite can be toxic to humans, too, but as long as you wash your hands after dealing with cat poop, you probably aren’t at risk.) And conventional sewage treatment doesn’t appear to be effective in filtering out the nasty bugs.

Skeptics have pointed out that cats haven’t definitively been identified as the culprit. They note that only 1 percent of cat feces samples in one recent study carried Toxoplasma,that indoor cats are especially unlikely to catch the parasite,and that many infected otters may actually be dying of other causes. It’s also not clear how much Toxoplasma affects other kinds of marine life. But pending further research, the Lantern thinks that if your cat ever wanders outside the house, precaution merits keeping its poop out of the toilet and out of your yard. 

You’re better off using kitty litter instead—but be careful about which kind you use. Most is made of bentonite clay or its cousin, fuller’s earth; both materials are extracted through surface mining, an environmentally taxing process. According to the U.S. Geological Survey, about a quarter of all bentonite mined in the United States and over half of all fuller’s earth—nearly 2.5 million metric tons a year between the two—is used as an absorbent for pet waste. Mining companies claim they can regrow any vegetation removed during the extraction process, but the scope of reclamation projects for Wyoming bentonite suggests that the effects of strip mining can be significant. Meanwhile, because the litter is nonbiodegradable, there’s no place for it to go but the landfill.

A better option would be litters that come from recycled newspapers, wheat, corn cobs or reclaimed sawdust, assuming you don’t want to go about making your own. These litters—along with the cat waste—can be composted, as long as you use the right precautions, and they provide a good use of recycled material. If you use liners for your litter box, you can find ones made from biodegradable plastic. (Some owners complain about their cats’ reactions to green litters, so try them on a small scale first and see what happens.)

Is there an environmental quandary that’s been keeping you up at night? Send it to, and check this space every Tuesday.