Photo Guide to Pet Poop Composting

Kimbo helps keep my garden growing. Over the years, he’s helped make more than 20 wheelbarrows of finished compost. He doesn’t use a shovel or turn the pile. All he does is poop.

Kimbo is an 8-year-old pit bull mix (American bulldog - American Staffordshire terrier cross) we rescued from Town Lake Animal Center in Austin, Texas. He loves fetch, travels very well, and is such a good boy.

I’ve been composting kitchen scraps and food waste since April 2012 with Compost Coalition Austin. The rich organic material helps soil retain moisture, delivers nutrients to roots, and protects plant health while nourishing the microorganisms that thrive in gardens. The following year, I started composting my dog’s poop, too. I also composted cat poop for a short time -- I’ll explain later why I stopped.

Make sure to wash hands thoroughly with a hand scrubber

after handling pet poop compost.

Let’s be clear: compost made from dog or cat poop must not under any circumstances be used to grow plants people will eat. Pathogens, including ringworm, roundworm, salmonella and giardia, thrive in even the healthiest of dog’s poop. Cat poop can also contain a hardy toxoplasmosis parasite. Pet poop compost is only suitable for decorative plants and there are a few other precautions you need to take, which I'll explain later.

Why Compost Pet Poop?

Even though the finished is potentially toxic, there’s several reasons to compost dog and cat poop.

1. People keep a lot of pets. There are an estimated 70-80 million dogs and 74-96 million cats in the United States, according to the American Pet Products Association. Every single one of them poops daily. An average 50-pound dog, like Kimbo, makes about 200 pounds of poop every year.
2. Pet poop goes to landfill. An estimated 5 percent of all landfill material is made up of pet poop, according to Doody Calls. We’re running out of space for trash. More importantly, organic matter in landfills make harmful methane while trapping nutrients that should be recycled.
3. Pet poop pathogens wash into waterways. When people don’t pick up dog poop, it washes into gutters, streams, and recreational areas, according to the City of Austin’s Watershed Protection Department. It can cause algae blooms, decrease oxygen for fish, and contaminate swimming and fishing areas. 
4. Compost rebuilds soil. Pesticides, compaction, and erosion wear away at soil health. Adding compost increases the soil’s ability to absorb water, boosts plant health, and adds a spongy structure that resists compaction.

Simply put, it's better for pet poop to stay out of the landfill and out of our waterways so we can keep the natural cycle of life going as nature intended.

How to Compost Pet Poop

All kinds of critters are drawn to decomposing
poop. Ox beetle larva turn into North America's
largest beetle.

There are several ways to compost pet poop. While hot composting with chickens is my favorite way to compost kitchen scraps, I decided to use an underground microbial method. It's basically a miniature septic tank for dog poop.

If you've ever seen a pile of dog crap when you're walking in a park, you'll know that it doesn't take long for beetles, sow bugs (rollie pollies), and other critters to start munching on the brown. With the proper moisture, nature will reduce the pile into crumbles in a matter of days. However, in full sun, many of the organisms that would ordinarily eat doo doo dry up. That's what's happened when you see the white skeletal remains of poop -- it dried out before fully decomposing.

One big advantage of hot composting, whether it's kitchen scraps or pet poop, is that the heat generated kills most pathogens (and seeds, which is important to gardeners who add discarded fruit and spent plants from the garden). The downside is that it's very hands on -- you must physically mix the pile up at least once a week during the breakdown process. This helps break the material up evenly and introduces oxygen into the core of the pile, which microbes and bugs need to turn the organic waste into lovely compost. I've got a strong stomach and I don't mind getting elbow deep in kitchen scraps, but the thought of churning up a big steaming pile of dog crap is repulsive. Imagining the stench makes me not want to breathe for fear of somehow inhaling the toxic fumes from my imagination.

I'd rather let microbes and invertebrates do the dirty work.

In short, composting pet poop in a hands-off way needs microorganisms, moisture, and a way to contain the stink.

A note about composting cat poop

When composting cat poop, you must use biodegradable kitty litter -- standard clay litter will not decompose, it will clog your composter, and make a mess of your garden. It took about 2 weeks for me to transition my cats from clay to pine pellets. Every day, I mixed in more and more until it was all pellets. One big downside is that the pellets didn't hide the stink like clay litter does. Another downside is that the pellets expand quite a bit, taking up a lot of space in the bin. My composter quickly filled with expanded pine pellets and there wasn't enough room to compost everything in a single bin. I later added a second bin, but it still wouldn't have been enough for the cats. I stopped composting my cat's poop because it would have meant adding one bin per cat (plus the stink in the litter boxes was awful) and I didn't have the space for 4 bins -- 2 dogs (my step son's dog lived with us for nearly 2 years), and 3 cats (who now live with new families).

How to Build an Underground Pet Poop Composter

We added two pet poop composters near a lantana shrub. Later
That season, the shrub grew to about 6 feet tall. Nutrition overload!

This quick-start guide will help you pick a good pet poop composting site, go over how to make the bin, and help you avoid a few pitfalls. It is suitable for composting dog and cat poop (see note above about composting cat poop), but compost made from cat and dog poop must never be applied to edible gardens. There are pathogens in the poop that can make you sick and won't breakdown using this composting method. Read the article above for details. You will need a place to dig down into at least 3 feet of well-draining soil for this method to work. If you have shallow soil, soil that pools, or don't want to dig, it's game over.

This composting method relies on microorganisms, like poop-eating bacteria, and invertebrates, like worms and beetles, to break down pet poop. The resulting compost is only suitable for decorative plants; never add pet poop compost to plants you plan to eat you or could get sick.

What you'll need:

• Sturdy outdoor plastic trash can with tight fitting lid (30 gallons)
• You'll need one can per 50 pounds of dog
• You'll need one can per cat (biodegradable kitty litter takes up a LOT of space)
• Drill with 1/4-inch drill bit or knife
• Jig saw or serrated knife
• Shovel
• Place to dig down 3 feet into well-draining soil 
• Large rocks for drainage

Where to place pet poop compost bin:

Since dog and cat poop has a high risk of containing pathogens, you'll need to make sure you keep it away from your garden and places where children play.

• Avoid flooding -- Check how your yard drains during a heavy rain and place the bin away from the drainage path. You don't want to flood your bin because too much water can kill the organisms that break down poop, plus it will spill the load into the waterway.
• Keep away from food gardens -- Place the bin as far away from your food garden as possible to avoid contamination. Plan your food garden beds on higher ground and the pet poop composter is downstream so there is no risk of heavy rains washing poopy water into your food.
• Keep out of direct sunlight -- For this composting method to work, you'll want the bin to stay relatively cool and very moist, but not drenched. Direct sunlight will dry the bin out and temperatures above 75°F or so makes it difficult for the organisms to establish. Planting a shrub nearby can help shade the bin.
• Place away from house -- The bin will smell like poop during much of the decomposing cycle, so keep it away from your house. It'll also attract all kinds of beetles, worms, roaches, and predators, like spiders and birds, that prey on them. You probably don't want those critters in your house.

Making the pet poop compost bin:

This is the easiest step in the process -- you basically drill a bunch of drainage holes and cut a large opening in the bottom.

I later cut the bottom out of the can to increase drainage.

• Drill the holes -- Using a 1/4-inch drill bit or larger, drill a row of holes about 2 or 3 inches apart starting from the bottom and reaching up to about 12 inches from the top. Continue drilling holes in a row every 4 to 6 inches all the way around the outside of the trash can.
• Cut the bottom out -- Using a jigsaw or serrated knife, cut a large hole into the bottom of the trashcan. I recommend leaving a 2- to 3-inch lip around the outside of the bottom to help keep the walls of the can from caving in over time. 
• Drill holes into the bottom rim -- To prevent pooling at the bottom, drill more holes around the perimeter of what's left of the bottom of the trashcan.

Installing the pet poop compost bin:

Being underground helps attract bugs to the pet poop composter.

Now for the hard part -- dig a hole deep and wide enough for the trashcan to fit so that the lid is maybe an inch or so above ground level. This will help keep the bin cool, allow water to drain deep into the soil, and attract a huge variety of microorganisms and invertebrates to feast on the decomposing poop.

• Avoid utilities -- Check with utility companies before digging to make sure you don't sever cable, water, or power lines. In Texas, call 811 to request a free utility survey. A crew will come out and place marking flags or spray paint the various underground infrastructure.
• Dig -- There's no getting around it, digging is exhausting work, but you'll only have to do it once. Make sure the hole is a few inches wider than the trashcan. When you drop it in, the earth should not be pressing up against the can, causing it to buckle or you'll have trouble later.



Add rocks to the base to help the pet poop composter drain.

• Check drainage -- Once you're a 12 to 18 inches down, it's a good idea to see how well that spot drains. Flood it until the hole is full of water (water can also make it easier to dig into the subsoil). The water should drain at a noticeable rate. If it takes several hours or longer to drain, you will likely have drainage problems during heavy rains. In this case, dig the hole about 6 inches deeper than needed, and add a deep layer of sand or light gravel to encourage drainage. 
• Place the can -- The can should sit in the hole as level as possible with only a few inches exposed at the top. When you place the lid on the can, it should be just above ground and easy to close and remove.
• Add rocks for drainage

  

  I keep a hand trowl nearby for when I scoop the poop.

  -- Add a layer of large stones or bricks to the bottom of the bin making sure to leave large spaces in between; don't pack them in or the bin won't drain as well. The rocks will also hold the bin in place.
• Back fill the hole -- Lightly fill the spaces between the ground and the outside of the bin with some of the soil you removed. Water the soil in, but don't pack it by stomping or you'll increase the risk of collapsing the plastic walls of the bin. Avoid stepping too close to the edges as you tend the bin. 

Feeding the pet poop compost bin:

Add a few dried leaves every time you add poop to the composter.

Now you're ready to start adding poop, but you'll also need additional material. Compost requires two main ingredients:

• "Green" or nitrogen-rich material, in this case the poop
• "Brown," or carbon-rich material, like dried leaves. 

Too much of one or the other will send the compost bin off balance and slow decomposition.

• Add poop -- Every time you add poop, you'll want to add a handful of leaves, dried grass, or coarse sawdust, like pine shavings used in animal bedding.
• Add microbes -- Once the poop is about 6 inches deep, add a treatment of Rid-X, a septic tank treatment that adds poop-eating bacteria to your composter. The bacteria will breakdown the poop. Worms and grubs from the surrounding soil will also find the poop and further breakdown the material.
• Flood the composter -- This will break up some of the poop and activate the bacteria in the septic starter, distributing it throughout the pile. It also adds a lot of moisture the microbes and bugs need to live. 
• Keep it moist -- Check the moisture level each time  you add poop. Often, there will be moisture condensed on the sides and inside of the lid. This is a good sign

My 50-pound dog takes about 6 months to fill the composter. I chose to install two composters so that while one is breaking down, I can fill up the other one. This means I harvest twice a year and never have to swap poop.

Harvesting finished pet poop compost:

If you only have one pet poop composter, you'll eventually have to swap the poop. As you fill up the composter with poop, the bacteria and invertebrates are breaking it down from the bottom up. By the time you fill up the composter, the bottom will be ready to harvest, but you'll have a layer of fresh poop on top.

• Remove poop --

  

  When I swap the poop, the chickens enjoy pecking out the bugs.

  Dig out the top layer until you get to the decomposed layer, and set aside the poopy layer for later. 
• Harvest compost -- Shovel the finished compost into a wheelbarrow or bucket so you can use it in your decorative garden. You'll often dig up the rocks you placed at the bottom for drainage, so replace them once you're done. 
• Flush the bin -- Give the whole composter a good flush. This helps make sure drainage is still working and tidies up the bin.
• Add the poop -- Return the poopy layer you set aside earlier and dump in a dose of Rid-X, then soak it in. You're ready to keep composting poop. 

Using two pet poop composters:

Having two or more pet poop composters keeps the operation as hands off as possible. While one bin is full and breaking down, the next one is accepting fresh poop.

• If you have two or more composters,

  

  Composter on left is ready to harvest, the one at right will sit.

  when the first bin is full, simply add a thin layer of leaves, mulch, or whatever brown material you're using to keep moisture and odors in while the poop breaks down. 
• Add another dose of Rid-X to the full bin and water it in. 
• Add poop to the second composter, following the stops above, while the first one breaks down. 
• After about four to six months, you'll be ready to dig up the compost and  use it on your decorative plants. 

The end result looks and smells just like compost -- rich and earthy. Make sure to wash hands thoroughly after handling pet poop compost.