What's the greenest way to pick up after your pets?

Until genetic engineers develop a dog or cat that doesn't poop, there's no escaping those little piles they leave behind.

Responsible pet owners diligently clean them up. But with so much conflicting information and so many new products to deal with pet waste, it's not as simple as it used to be. More than 60 percent of U.S. households have pets, and our decisions about pet-waste disposal have an enormous impact. Today we'll scoop up the answers to common consumer questions.

Q: Is it really a good idea to just bag dog poop and put it in the garbage?

A: It doesn't seem quite right to entomb dog waste in the landfill. However, a four-year Snohomish County study concluded that putting it in the garbage in a plastic bag is the preferred method. They found it's the best way to protect people and water supplies from disease-spreading pathogens found in dog waste.

Seattle and King County still say dog waste is acceptable, as long as it's at least 8 inches deep and away from vegetable gardens. Some agencies also suggest bringing dog poop inside and flushing it down the toilet, but few dog owners want to do that.

Don't put dog poop or other pet waste in your yard-waste collection container or backyard compost bin. Those new home pet-waste composter or digester units may sound good, but most of them cost a paw and a leg, and they may not reach high enough temperatures to kill hazardous pathogens.

The worst thing you can do is to leave lots of piles of dog poop sitting in your back yard, since it eventually may wash into lakes and streams.

Q: What kind of bags should I use for doggie-do?

A: You don't need to buy biodegradable bags for dog waste (although compostable bags make sense for food waste going to a compost facility). Because modern landfills are so tightly compacted and sealed, neither a biodegradable bag nor anything else will break down in the landfill very quickly. Save money and reduce waste by just reusing your old plastic bags. Long newspaper bags work great, especially when you keep them rolled up in a convenient little bundle.

Q: Since most cats use a litter box inside, it can be convenient to flush their waste down the toilet. Is that OK?

A: Flushing cat waste has been recommended as a disposal method, but concerns have recently been raised about a parasite called Toxoplasma gondii sometimes found in cat feces. Research indicates the parasite could survive the wastewater-treatment process and endanger sea otters and other mammals.

It's rare, but possible, for humans to be infected with Toxoplasma by coming in contact with cat poop. More info is at www.vet.cornell.edu/fhc/brochures/toxo.html.

King County Wastewater Treatment Division officials have begun to recommend that only human waste and toilet paper should be flushed down a toilet, based on concerns about potential health issues and clogged equipment.

Q: Which types of kitty litter are best?

A: Most kitty-litter products, both clumping and non-clumping, come from clay, which is often strip-mined. Instead, try greener kitty litters made from recycled newspaper, sawdust or byproducts from grain harvesting. Never flush kitty litter down the toilet, even the so-called "flushable" types. Put used kitty litter in bags in the garbage.

Q: What about the little guys, such as guinea pigs and rabbits? Their bedding is their litter, and they go through a lot of it.

A: For small animals, choose bedding/litter products made from reclaimed and recycled materials including wood and paper, without chemical additives. As with kitty litter, you may need to try various products before you find a material your pet likes. Like kitty litter, small-animal litter/bedding should be put in the garbage.

A popular children's book, "Everyone Poops," says it all. If everyone also picked up after their pets in the greenest way possible, the world would be a better place.

Tom Watson is project manager for King County's Recycling and Environmental Services.

Reach him at tom.watson@kingcounty.gov, 206-296-4481 or www.KCecoconsumer.com