I just read an article on Horse Manure Management with a portion of the article devoted to coposting the manure. The author says that composting the manure by putting it in a pile for 6-12 months will yield a fairly dry product and reduce the volume by 40-60%. Aerating the pile by either putting perforated PVC pipes in it or turning the pile can speed up the composting process. Keeping the pile moist during the composting process is also important. When composted properly the pile should not have an unpleasant smell but a sweet smell. The finalized product makes a good slow release fertilizer that can be topdressed. To read the article go to the following web site http://aurion-solutions.com and look up articles on horse manure management.