The average horse produces 50 pounds of manure daily. That adds up to a lot of manure very rapidly, especially if you don't have a lot of acreage and must pick up most of it. In suburban areas, the worry of environmental implications from the runoff of livestock operations has caused some states to require manure management plans for small farms.
One of the easiest ways to manage manure is composting. Composting allows the breakdown of manure into fertilizer that can help amend soils. Done properly, composting produces little odor and does not attract unwanted pests.
This link from Rutgers University gives an explanation of basic composting:
Many of the state agricultural extension websites have composting box design. The website below gives ideas on different designs applicable to horse farms:
My original composting system consisted of wooden pallets that I hand turned periodically. It was inexpensive and worked when I had only two horses and younger muscles! The wooden pallets rotted after a while and hand turning is too labor intensive to be practical. I have since gone with the cinderblock system and use a tractor with a front end loader to turn the compost. We did not use cement on our cinderblocks, instead we drove t-posts through the holes in the cinderblocks. The best method would be to drive a t-post through alternate holes in the cinderblocks to give the compost box stability, especially if it is accidently hit with the front end loader. Don't ask me how I know this! Our compost boxes are approximately 12 ft by 12 ft each. The first box is slightly larger because the manure pile will shrink as it composts. The last box is also a little larger to allow for storage in the winter months when the demand for compost is at a low.
Our compost box set-up
This photo only shows three of the four boxes. The fresh manure goes into the box on the farthest right. Once that box is full, all the compost from each box is transferred to the compost box to the left. So the compost in the far right box goes into the middle box, the contents of the middle box goes into the far left box and so on. By the time the compost has reached the fourth box, it has been turned and aerated at least three times. If you can aerate more often, that helps speed the process. I also keep tarps over the boxes that have the older compost to help keep it from getting too wet and to help retain the heat and moisture. This also aids in speeding the composting process. I have found a heavy 2 X 12 piece of wood that runs the width of the compost box placed over the tarp seems to work the best for keeping the tarp from flapping too much in heavy winds.
Once the compost has gone through the aging and aerating process, I put an ad on Craigslist. I load the compost into pickup trucks or landscape trailers and charge a nominal fee for my time and equipment. I go by appointment only so I know when people are coming to the farm. Most people use the compost for their gardens and many are repeat customers. Although the process does take a little time and effort, it does make a product that is sought after by gardeners.