Is Cat Litter Compostable? How to Dispose of Cat Litter

Is cat litter compostable? The litter itself sometimes is. What your cat leaves in it is the problem. A composting guide from the USDA's Natural Resources Conservation Service puts it plainly: "We do not recommend adding cat waste or cat litter to your compost." The EPA says the same about waste from any meat-eating pet.

If you switched to plant-based litter so you could compost it, that stings. This guide covers what "compostable cat litter" really means, when a city green bin is the exception, what to look for on cat litter bags, and why the toilet is the worst place for any of it.

Can Cat Litter Be Composted at Home?

What USDA and EPA guidance says

Three government sources say no to the backyard pile:

• USDA NRCS guide (2005, hosted by the EPA): it studied composting dog waste only. "Cat and other pet wastes were not studied. Cats may carry parasites that are harmful to human fetuses. We do not recommend adding cat waste or cat litter to your compost."
• EPA pet care fact sheet: waste from meat-eating pets belongs in the garbage, because "the parasites, bacteria, and viruses are not readily destroyed during the composting process."
• Salt Lake County pet waste brochure (EPA toolbox): "Do not put wastes in a compost pile. The pile won't get hot enough to kill disease organisms."

Why heat matters

The parasite that the UC Davis, USGS and CDC sources focus on is Toxoplasma gondii. Its eggs, called oocysts, are tough. In a 1998 lab study in the Journal of Parasitology, oocysts in water died within a minute at 60 C and within two minutes at 55 C. At 40 C they were still infective after nine days. At 10-25 C they showed no marked loss of infectivity after 200 days.

The USDA guide says a well-built dog-waste pile can reach "up to 160 F and greater" in the centre, but the pile has to be turned so the outer material also "reaches the high temperatures needed to kill pathogens," over "a period of six weeks or more." Salt Lake County's brochure says a home pile "won't get hot enough to kill disease organisms." Even a hot pile does not make cat waste compost safe by any source we found.

Never on food crops

Even for dog waste, which it did study, the USDA guide says the finished compost "should not be used on crops grown for human consumption." Cat waste gets a firmer no. Some litter makers say their used litter can go on the garden as mulch or a soil amendment. Those claims conflict with the USDA and EPA guidance above, so we do not pass them on.

How long the parasite lasts

A 2019 review in Food and Waterborne Parasitology found that Toxoplasma oocysts "can persist in moist soil for up to 18 months" and resist detergents and bleach. The CDC adds that the parasite "does not become infectious until 1 - 5 days after a cat shed it in its feces." That is the reason behind the advice to scoop every day.

What "Compostable Cat Litter" Really Means

Litters made from paper, wood, corn or wheat are plant material, and plant material can break down. A "compostable" label on the bag describes the clean litter. It says nothing about what happens once a cat has used it.

The FTC's Green Guides set the bar for that word. A "compostable" claim needs evidence that every material becomes usable compost "in a safe and timely manner." If it can't be composted safely at home, or if few buyers have access to a composting facility, the label has to say so.

Throwing plant litter in the trash does not mean it breaks down quickly either. The FTC says landfills "do not present conditions in which complete decomposition will occur within one year." Our biodegradable cat litter guide goes through which materials break down and what the evidence says. For the materials themselves, see paper litter and wood litter.

City Green Bins: Check Your Own Rules

Municipal compost is not the same as a backyard pile, and cities disagree. Two examples:

• Toronto: the Green Bin accepts "Pet waste (animal droppings, clay and wood pellet cat litter, cage bedding)." Any plastic bag may line the bin.
• Seattle: "cat litter and poop must always go in the trash." Seattle Public Utilities calls pet waste "a leading source of contamination in the compost stream."

Same litter, opposite answers. Look up your own city's organics list before you put anything from the litter box in a green bin.

Cat Litter Bags: Compostable vs Biodegradable

What "compostable" has to mean

Under the FTC rules above, a compostable bag must turn into usable compost in a reasonable time. If it only does that in an industrial facility, the label must say so.

Why "biodegradable" on a trash bag tells you little

The FTC calls unqualified "degradable" claims deceptive for items that usually end up in landfills, incinerators or recycling plants, because "these locations do not present conditions in which complete decomposition will occur within one year." A litter bag tied off and put in the trash is exactly that kind of item.

California's labelling rules

California bans selling plastic products labelled "biodegradable" or anything similar. Plastic sold there as compostable must meet the ASTM D6400 standard, or OK compost HOME for a "home compostable" claim, and compostable bags need a certification logo and green labelling. If you shop elsewhere, those certification marks are still a useful thing to look for.

Which bag to use

Seattle says pet waste goes in the trash "regardless of what kind of bag is used." The parasitology review says to seal it. So the bag that matters most is one that closes. We found no tested breakdown time for any brand of cat litter bag, so we can't tell you which one disappears fastest.

What Not to Flush

Cat litter and cat feces both stay out of the toilet, even when the bag says "flushable." The reasons:

• Treatment plants don't kill the parasite. A UC Davis study of more than 100 stranded sea otters traced fatal Toxoplasma strains to a bobcat and feral domestic cats nearby. The researchers advise putting cat feces "in a bag in the trash, not outdoors or in the toilet because wastewater treatment is not effective in killing oocysts."
• The eggs survive in the sea. USGS researchers found oocysts kept in seawater for six months could still infect mice. They named cat feces flushed down toilets as one possible route to the ocean.
• Otters show the result. A 2002 study of 223 California sea otters found Toxoplasma in 42% of live otters and 62% of dead ones. Otters near heavy freshwater runoff were about three times more likely to test positive.
• It's the law in California. Every litter sold there must carry a statement such as "Please do not flush cat litter in toilets or dispose of it outdoors in gutters or storm drains." That applies to all litter, not just the flushable kind.
• Pipes. Salt Lake County's brochure says not to flush cat litter "to prevent plumbing problems."

More detail, including what the makers of flushable litter say, is in our flushable cat litter guide.

A Disposal Routine That Matches the Guidance

1. Scoop every day, before the parasite has time to become infectious (CDC).
2. Seal the waste in a bag (2019 parasitology review).
3. Put it in the trash (UC Davis, EPA, Seattle), unless your city's organics program lists cat litter by name, as Toronto's does.
4. Never in the toilet, a storm drain, the garden or the home compost pile.

Daily scooping keeps the box clean, but smell can still build between trash runs. One option is an activated carbon additive such as Purrify, sold in bags and added to the litter you already use. See how activated carbon traps litter box odor.