The solids may be further processed by composting them and using them for bedding, with the surplus applied to cropland or sold to plant nurseries and other markets. Composting, with temperatures up to 140 degrees F, reduces the level of organisms. Without this treatment, use of the solids as bedding will increase the incidence of mastitis in milking cows. Composting will produce a drier product than most newly separated solids. The optimum moisture content for composting is 50 percent to 60 percent.
Higher moisture requires aeration by forced air or turning.
A wide variety of commercial separators are used. Some of the more commonly used types are static inclined screen, vibrating screen, rotary screen, belt press, perforated roll press, screw press and centrifuge. Each of these separator types has one or more disadvantages, such as high initial cost, high operating cost, high maintenance cost or inadequate degree of separation. In general, these devices produce a solid with about 70 percent to 80 percent moisture. Solids with less than 15 percent dry matter weep moisture that must be collected and handled.