Consider Composting

Publish date:
Social count:

The average horse produces seven to nine tons of manure a year. Multiply that times the number of horses at your operation, and count yourself lucky if you aren’t paying someone to cart the stuff away. Want to turn that problem into a profit? Consider composting, a process that can transform your massive manure mountain into valuable fertilizer.

“It’s pay dirt,” says Meghan Hamilton-Yallen of Sleepy Hollow Farm in North Dartmouth, Mass. Sleepy Hollow, a boarding-and-training farm that she co-owns with her husband, Michael Yallen, sells composted manure in recycled feedbags to organic farmers, gardeners, and greenhouses for $8 a bag.

Sleepy Hollow is a small operation, with eight horses on about five acres. But composting works for large stables as well. For example, the Potomac Horse Center in North Potomac, Md., composts manure and stall wastes for more than 80 horses. Instead of being trucked off site, the material is turned into a soil enhancer. Breeding farms—even Three Chimneys, the premier thoroughbred farm in Midway, Ky.—are turning to composting as a way to cut the costs of manure disposal and pasture fertilizer.


Composting enlists microbes such as bacteria and fungi to break down manure and other wastes. These hardworking microbes are aerobic (they require oxygen to live), and they don’t function in a typical manure pile because the pile shuts out air. Without them, manure can take two years to decompose, and the process produces unpleasant byproducts like methane gas. Your pile grows larger—and smellier.

Aerobic microbes kick decomposition into high gear, cutting the time it takes to about three months and shrinking the volume of your pile by half. In the process, they generate enough heat to kill worm eggs, pathogens, and even weed seeds. There are no smelly byproducts, and the end product—rich, dark, compost—is packed with nutrients that help plants grow.

To pull off this trick, you need to provide the materials and conditions—the right levels of moisture, temperature, and oxygen—that the helpful microbes need. The key to success lies in how you build and monitor your compost piles.

“The procedure can be really simple, or more technical if you want a faster process,” says Hamilton-Yallen, who grew up in a farming family and studied composting as part of a program at the University of Maine. You’ll find the basics here; for help in setting up a composting system that’s tailored to your operation and climate, contact your county cooperative extension office, local branch of the National Resources Conservation Service or a supplier of composting products and services.


Put your composting center in a spot that’s convenient to your barn, but not right next to it. Compost piles should be located away from buildings because they may spontaneously combust, says Jenifer Nadeau, an animal science professor and extension specialist at the University of Connecticut. Pick a dry place that won’t be affected by storm runoff, she advises, at least 200 feet from streams, ponds, other surface water, and private wells. Check with local officials for other requirements, such as minimum distance from property lines.

Good composting systems can be set up in several ways.

• Sleepy Hollow has a basic “turned pile” system, using three piles in rotation. One pile receives fresh stall wastes while a second is “cooking” and the third is ready to use. Fresh piles are turned once or twice a week, using the bucket loader on the farm tractor. This incorporates air and mixes the outer and inner layers. Putting the piles on a concrete pad makes it easier to scrape up and turn the material, but a pad isn’t strictly necessary, Hamilton-Yallen says.

• Large farms, obviously, need more than three small piles. Windrows—long, freestanding piles—are another option for them. In this setup, you add new manure at one end of the windrow and take finished compost from the other.

• A “passive” system does away with turning by running perforated drainage pipes horizontally under the pile, so that air can get to it. The manure will take much longer to compost, Nadeau says, but it will get there eventually. This type of system would generally not be recommended for larger horse farms with 10 or more horses.

• Aerated static pile composting uses electric blowers to move air through perforated pipes placed under the piles. An electronic timer switches the blowers on and off automatically, so oxygen levels stay relatively constant. The oxygen stimulates the microbes that help maintain the proper temperatures. This method composts faster and takes less tending than turned piles and is one of the best solutions for active horse farms.

Many farms construct three three-sided bins to contain their piles, using 2" x 6" boards and heavy-duty posts or concrete blocks. The aeration system is then installed in each. The first bin or bay is filled with raw waste and, when full, is covered with a layer of previously-composted manure and left to compost using the blowers. The second and third bays can then be filled with new manure and bedding. By the time the third one is full, the pile in the first bay, which has been composting for 30 to 60 days depending on the number of horses, will have successfully been composted and can be removed.

If you are dealing with a large number of horses (over 35) or don’t have the space for composting bays, piles can be made over an aeration system, applying the same principles as above.

The company O2Compost (, designs and sells such systems for horse farms.

If you are not using aeration, pile size matters, Nadeau says. A pile must be at least four feet square and four feet deep to reach active composting temperatures. As a rule of thumb, the base width of the pile should be twice its height.

Besides the size of the pile, three steps are keys to success.

• Control the heat. While the microbes are working their magic, you’ll need to monitor temperatures in the pile. A basic compost thermometer with a 20-inch probe costs less than $30; find one at a garden center or at online retailers. As the microbes go to work, the temperature should rise to between 120 to 160 degrees, says Hamilton-Yallen. If the pile’s too cold, microbe activity slows to a crawl, and pathogens and weed seeds won’t be killed. If it’s too hot, the microbes may die. In this case, reduce the size of the pile and turn more often.

• Control the moisture. The pile should have about as much moisture as a freshly wrung-out sponge—30 to 40 percent dry matter, Nadeau says. Test by squeezing a sample in your hand. If it’s dry and crumbly, add water with a hose. If it’s wringing wet (or if water runs out of the pile), it’s too wet for the microbes. In many parts of the United States, piles should be covered (with tarps or a roof) to keep moisture levels consistent.

• Control the mix. How much and what type of bedding goes into the pile will affect composting speed. Straw breaks down faster than sawdust or wood shavings, which have high levels of carbon. (The ideal carbon-to-nitrogen ratio for compost is between 20 to 1 and 40 to 1, Nadeau says; in wood products the ratio is 500 to 1.) If there are a lot of shavings or sawdust in your pile, the whole process slows down. Solutions to this are to use less bedding, turn piles more often, or balance the carbon by adding blood meal or other materials high in nitrogen.

After several weeks, you’ll see the temperature in your pile gradually drop, signaling that the process is finished. The compost should cure for several more weeks before it’s used, but it won’t need turning during that time. Finished compost will have a soil-like texture and smell earthy, says Nadeau.


Finished compost is useful stuff—and, unlike fresh horse manure, it can be used right away. Work a half-inch layer into garden soil at planting time, or spread a quarter inch on pastures. Use it as mulch around landscaping. Or sell it, in bulk or in bags as Sleepy Hollow does.

“The only negative is the time you put in, but that’s minimal,” says Hamilton-Yallen. Stabling horses involves moving manure around anyway, she adds, and demand for compost is growing with increased interest in organic gardening. Whether you sell it or spread it, you may find that the benefits of composting are well worth the effort.