How to Compost Cat Litter

Composting is the most environmentally friendly way to dispose of biodegradable cat litter. It reduces the amount of waste we send to our landfills and creates a nutrient-rich humus that can be used to nourish ornamental plants. But it’s not as simple as composting yard waste or food scraps.

Can You Compost Cat Litter?

Some types of cat litter can be composted. Any biodegradable cat litter that is free of additives can be composted. Plant-based litter containing chemical additives and clay litter can’t be composted.

Before you begin, it’s important to understand the risks.

You’ve probably heard about the dangers of cat litter to pregnant women and their unborn children. But it’s also potentially dangerous for individuals with compromised immune systems.

This is because cat poop can contain any number of pathogens and parasites, including Toxoplasma gondii. And unfortunately, compost doesn’t often reach the required 165° F temperature to kill Toxoplasma gondii.

By using humus containing cat waste on or near edible plants, you risk spreading harmful pathogens and parasites. It should only be used for ornamental plants.

What Types of Litter Can Be Composted?

Any biodegradable, plant-based cat litter with no additives can be composted. Including wood, paper, wheat, grass, corn, tofu, and walnut shell litter. Clay and crystal cat litters can’t be composted.

Compostable Cat Litters

Non-Compostable Cat Litters

Composting Cat Litter Isn’t for Everyone

Unfortunately, composting cat litter isn’t realistic for everyone.

It should only be done outdoors and in an area with plenty of space. Avoid placing your compost pile near any structure like buildings, fences, and sheds. Avoid placing near water sources like streams, wetlands, and drains. And, of course, avoid placing near any food growing area.

This makes composting unrealistic for those of us in apartments and with smaller yards.

Also, try to be mindful about the process. Your neighbors may not appreciate you stockpiling cat waste too near their property.

The composting process stops below 40° Fahrenheit. If you live in a climate where temperatures rarely reach this, composting isn’t an option.

Folks who live in an area where temperatures only drop below this threshold for portions of the year can continue to add to their compost pile throughout the winter. When the weather warms enough for composting, the process can be restarted by adding water and turning the pile.

And finally, many cities and towns have restrictions and regulations regarding composting. Many cities ban outdoor composting because of issues with rats and other rodents. Check with your local Department of Public Works to be sure.

Is it Safe to Compost Cat Litter?

Composting cat litter is safe when done responsibly. But if you’re not careful, you may end up doing more harm than good. A misplaced or mismanaged compost pile can spread pathogens, Toxoplasma gondii, and other parasites.

Before Getting Started

To get started with composting you’ll really just need an area to compost and a shovel or pitchfork to turn the pile. Though not mandatory, we find a long-stemmed moisture meter and a compost thermometer quite helpful.

A compost pile on bare earth is ideal. It allows worms and other organisms to aerate the compost pile and move valuable nutrients throughout your lawn and garden.

This method is most appropriate for yards with plenty of space and no dogs, children, or wildlife who may tamper with the pile. Either way, it’s strongly recommended to screen off the area containing your compost to keep out unwanted visitors.

If not possible, a compost bin will still work just fine. A digester is a type of compost bin enclosed on the top and sides, but open to the earth on the bottom. Tumblers are fully enclosed compost bins that can be turned to aerate the compost. While either will work, a digester shares many of the same benefits as an unenclosed compost pile.

To save a few bucks, making a homemade bin isn’t very difficult either. Just build a wood box at least 3 cubic feet in size, or slightly larger. Be sure to use non-treated, non-composite wood.

Alternatively, a large plastic trash can with a few half-inch holes drilled into the bottom, or the bottoms completely removed, will work as a functional and inexpensive starter bin.

Composting 101

Composting requires four main ingredients to be successful. Carbon, nitrogen, oxygen, and water. The key to a healthy compost pile is maintaining a good balance between carbon and nitrogen while allowing the pile an appropriate amount of air and moisture.

Carbon Sources

Carbon-rich matter, or brown material, provides compost with a source of energy. Examples include branches, dried leaves, eggshells, straw, and biodegradable cat litter.

Avoid using sawdust or wood chips that have been chemically treated or may contain machine oils. Avoid lawn or plant trimmings that have been treated with insecticides or herbicides. And try to avoid using perennial weeds as you may end up spreading seeds.

Nitrogen Sources

Nitrogen-rich matter, or green material, provides compost with the microorganisms needed to oxidize carbon. These include food scraps, fresh lawn clippings, green leaves, and cat poop.

How to Compost Cat Litter

Composting cat litter is as simple as adding alternating layers of carbon and nitrogen sources while monitoring temperature and moisture. Over time, microorganisms will break down organic waste, like food scraps and cat poop. Leaving behind a nutrient-rich humus that can be used to nourish ornamental plants.

Starting Your Compost Pile

1. Prepare the base of your compost pile. For enclosed bins, start with a three to four inch layer of topsoil, sawdust, dried leaves or straw covering the entire bottom of the container. This allows for drainage and improves airflow. For unenclosed compost piles or bottomless compost bins, till soil in the selected area.
2. Add alternating layers of brown and green materials. Try to maintain a nice rounded shape with a flattened top area. Hold off on cat waste initially.
3. Finally, add your initial batch of cat waste. This should be added at the top center of the compost pile, then completely covered by a layer of brown material.

Adding to the Heap

Once your compost pile is going, it’s best to stockpile brown and green materials instead of adding as you go. This ensures that there’s enough of each to layer effectively.

Brown materials can be stored in a dry place in your yard. Most greens can be kept in any container, but should be frozen if left out for more than a week or so. Cat waste should be kept separately in an airtight container. We like to use the Litter Champ, which is an airtight litter disposal bin.

Once you have a sufficient amount of browns and greens stockpiled, add alternating layers of about three to four inches. Always top the pile with a layer of brown material. This top layer can be pulled back and reused, but is vital to the composting process.

If your compost pile begins to get too large, simply repeat the process above and start a second.

Carbon to Nitrogen Ratio

A healthy compost pile has much more brown material than green. Ideally, around thirty parts carbon to each part nitrogen, by weight.

There are helpful charts available if you want to get really scientific about it.

But our recommendation is to not overthink the ratio. The reality is that as long as you add the right materials, with considerably more brown material than green, and allow sufficient oxygen and moisture, you’ll make compost.

You’ll also get more comfortable with each batch you make, as you naturally figure out what’s working and what isn’t.

Managing Moisture

Your compost heap needs to stay moist at all times, but never wet. Too little moisture will limit the activity of microorganisms, slowing or stopping the composting process. Excessive moisture can lead to anaerobic conditions and a foul-smelling compost pile. A moisture meter can help monitor the level of moisture in the middle of your pile, but is far from necessary.

Because temperature is important, water should never be added straight from a hose. Cool tap water can drop the temperature of your pile, disrupting the composting process. Instead, fill a bucket with water and let it warm in sunlight for a day or two before adding.

If you live in a particularly dry climate, you can cover your compost with a piece of rug or carpet. Which will help retain moisture while still allowing the pile to breathe.

For heavy downpours or in very wet climates, loosely cover the pile with a waterproof tarp.

Oxygen and Airflow

Oxygen can be managed by adding sufficient bulky, brown materials to allow air circulation throughout the pile. Coarse brown materials like hay and dried leaves often allow enough circulation that your pile can breathe, even without turning.

If you’re mostly using less-bulky brown materials, like pellet litter or sawdust, you’ll need to turn your compost pile with a pitchfork or shovel once every few weeks to aerate. But don’t go overboard. It’s possible to turn your compost too often.

The Finished Product

Your compost needs to age until dark and soil-like, smells rich and earthy, crumbles when touched, and the original materials have fully broken down. 

How long this takes depends on the size of your compost pile, what materials you’ve used, how well you’ve managed it, and your climate. Typical compost can be ready within three to six months. But compost containing cat waste needs to cure for at least one year and may take up to eighteen months before ready.

Using compost before fully cured can be harmful to plants, and can make you sick if not properly handled.

Summary

Composting biodegradable cat waste is the most eco-friendly way to dispose of litter. It sends less waste to landfills and creates a nutrient-rich humus for lawns and ornamental plants. If you’re intimidated by the process, you can start by bagging and trashing your cat’s poop and composting only the used litter.

Sources

• Cornell Waste Management Institute. (n.d.). Monitoring Compost Moisture. Cornell University. Retrieved May 31, 2021, from http://compost.css.cornell.edu/monitor/monitormoisture.html
• Powell, E. (2014, November 11). Understanding the Greens and Browns of Compost. University of Florida, IFAS Extension. https://nwdistrict.ifas.ufl.edu/hort/2014/11/11/understanding-the-greens-and-browns-of-compost/

About Matthew Alexander

Matthew lives in Maryland with his two cats, Puff and Pancho. He’s been caring for and fostering cats with various special needs for more than fifteen years. He hopes to pass some of the insight and knowledge that he’s gained on to the readers of Pawmore.