Manure processing is generally incorporated into livestock systems to change the characteristics of manure in order to gain a higher value end product, reduce operational burdens, or reduce risks associated with the land application of manure. Some common manure processing systems include composting, sand separation (SS), solid liquid separation (SLS), and anaerobic digestion (AD). For many processing systems, the processed manure or at least a fraction of the processed manure is still land applied, therefore understanding the impacts to the manure characteristics is critical for increasing nutrient use efficiency following land application. Processing technologies aside from composting are rarely found at facilities with less than 1,000 animal units, or the number of animals requiring a Wisconsin Pollutant Discharge Elimination System (WPDES) permit. For those permitted facilities SS is the most common processing technology reported from those that were surveyed with AD and SLS also being incorporated by many farms.
Soil Science Extension
University of Wisconsin Madison