Worms: A Sustainable Solution to Pet Waste

Sustainable Materials Management—being responsible from sourcing to recovery and disposal—extends to all aspects in our lives, and dealing with cat waste is no exception. Most of us in the GreenBlue office have canine and/or feline companions—both of which regularly visit the office—and we have often discussed pet waste and the associated environmental impacts. Now that I have enrolled into a local government-sponsored program, the Rivanna Regional Stormwater Education Partnership (RRSEP), to test pet waste vermicomposting (or composting using worms), the time seemed right to delve further into the sustainability journey of the feline kind.
One widely adopted option is to allow cats to use the great outdoors as their bathroom. However, outdoor cats can cause a number of unavoidable problems, ranging from the threat to a child’s sandbox health to the devastation to local bird populations. Flushing and burial aren’t ideal because of the potential introduction of the parasite Toxoplasma gondii into waterways.
That leaves the litter box as the most widespread solution for cat waste. Most commonly used litter types include clay or silica gel, and there are a diversity of bio-based and biodegradable types made from newspaper, corn, wheat, and pine. This article by Carol Frischmann summarizes well the different types of litter and the associated attributes and drawbacks. While a full analysis is lacking, the negative impact of sodium bentonite mining that produces clumping clay litter renders this material the least sustainable.
Given the volume of cat waste produced annually, including the used litter, which currently goes to landfill—estimated to be at least two million tons—it seems intuitively obvious that composting is the best option for disposal. Enter the RRSEP, who provided us with a “Worm Factory” composter to get started. We were excited when the red wigglers (Eisenia fetida) arrived at the office from Uncle Jim’s Worm Farm! They have just been placed into the bin, and we’ll keep you posted on how the experiment with cat, and occasional dog, waste goes. We’ve named the squirm “Vern” (I actually looked up the name for a collective group of worms, and indeed it is squirm).

The internet has many examples of successful composting of all kinds of waste, even including “humanure.” All indications are that composting systems that maintain certain conditions, including a curing phase, take care of potential pathogens. There seems to be much more information available on composting cat litter than on the litter itself, particularly this excellent paper that examines the tradeoffs associated with various composting methods. Using the finished material on non-edible plants and trees is an easy, conservative approach. I think most of us are more interested in responsibly disposing of the material, rather than creation of food-grade compost, and so we feel quite good about our wormy endeavor.
Another aspect of this issue that gets little attention is the extensive use of plastic bags to collect and dispose of litter. Many plastic bags and films are easily recycled at retail stores, which is the preferential route for disposal of bags. A mere second use of a bag en route to the landfill is maybe thrifty, but not a smart use of resources
The most awesome option is to train your cat to go in the toilet—we had a cat once who we almost had trained to do it, I swear! Whatever option you choose, it is likely that we all have room for improvement when it comes to managing pet waste sustainably.