Sizing Compost Bins
Concrete manure management pit for sustainable horse keeping practices.

Making the chore of manure management efficient is a huge undertaking. At our place, Sweet Pepper Ranch in southwestern Idaho, we have around a dozen horses—our horses, Matt’s client horses, and horses being boarded. And in the summer, we also have our horse motel customers.

As many of you already know, one horse produces about 50 pounds of manure per day. Manure management for us means dealing with about 600 pounds of manure daily; it is important for us to reduce mud and dust, parasites and pathogens, as well as odors as best we can. In addition, it just looks nicer for our business to have manure picked up and our place clean.

The compost from our manure is a wonderful soil amendment that we apply to our pastures to keep them healthy and productive. We have always composted but now it is time to upgrade from composting in piles (or heaps, as my mom used to call them) to a more organized, neater system; hence we are building cement compost bins.

A compost system should be convenient, so it’s easy-in for the manure and stall waste, and easy-out for finished compost. We chose a location for our new bins that is along the driveway, but central to our confinement areas, as well as to the pasture where we use the finished compost. If we ever want to give away finished compost, the bins will be easy for customers to access as well.

Next, we had to determine how big to make our bins. For that, I contacted one of my favorite conservation district farm planners, Jay Mirro, Senior Resource Planner with the King Conservation District in Renton, Washington. If you have not yet made acquaintance with your local conservation district, they are wonderful, non-regulatory, non-enforcement resources. Their job is to provide landowners with education and technical assistance on a whole array of natural resource issues. There is a conservation district in every county in the United States; the Puget Sound area CDs are particularly geared towards working with horse owners.

I exchanged emails with Jay to ask his advice on how big our proposed cement bins should be and he offered me these guidelines:

  • One horse generates about 10 yards of manure/year (that’s with bedding, waste hay, and removing all manure in confinement areas—but not from pastures).
  • At Sweet Pepper Ranch we estimated 7.5 yards of stall waste per horse/year (we use no bedding and only half the horses get out on pasture in the summer).
  • 12 horses x 7.5 yards = 90 total yards of manure.
  • One 12’ x 12’ x 4’ high bin will hold 21 yards of manure.
  • Three 12’ x 12’ x 4’ high bins will hold 63 yards of manure, roughly six months worth of manure.

In addition, Jay asked us:

  • Is six months storage large enough?
  • Will you or can you spread at least twice a year?
  • Do you use more bedding / less bedding?
  • Do you give away any finished compost?
  • Do you have overflow storage for finished compost if you need it?

Jay concluded that for our 12 horses, with little or no bedding use, and all manure in confinement areas picked up daily with some horses on pasture in the summer (no manure pick-up there), that three, 12′ x 12′ x 4′ high bins should be enough for nine months of manure storage. That is perfect for us as we spread the finished compost on our six acres of pasture at least twice yearly (Jay notes that horse manure production can vary greatly from horse to horse).

Jay also shared his six tips of locating a compost bin:

  • Make it convenient to where you pick it up.
  • Make it convenient to where you use it.
  • Think about fences, gates, or other obstacles to get the material into the bin or out of the bin and to the field.
  • Consider locating bins near existing farm roads or areas you already access.
  • Locate the bin in a high, dry location, and think about any wet spots that you would need to travel through to get to it.
  • Consider the visuals/esthetics of the bin in relationship to your home and neighbors.

I hope that these suggestions can be a resource for you, too, as you make adjustments to your manure management system!

Alayne

Bonus Tip

For more information on creating great compost, check out our How to Compost and Use Horse Manure tip sheet.

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