As excreted, livestock waste typically has an energy content between 1,000 and 2,000 Btu per pound.Īnother developing opportunity for digestate solids is as a renewable construction material. The maximum energy content of livestock manure is 8,500 Btu per pound however ash and moisture content reduce the energy potential. Solids can be dried and pelletized for use as fertilizer or fuel. Other value added products using digestate solidsĭigestate solids can also be used as substrate in compost, providing sources of carbon and nutrients. Bedding with digestate solids requires intensive management to ensure that a healthy environment, with low pathogen concentrations, is provided for the animals. In addition, excess solids may be sold to neighboring farms for bedding or soil amendment, creating a revenue stream and route for nutrient export. Utilizing digestate solids for bedding provides a significant cost offset to dairy and livestock farms. Gould, MSU Extension Livestock beddingīedding for livestock is another opportunity for putting digestate solids to use. Digestate solids as a fertilizer source can be used “as separated” (wet), blended with other materials and composted or dried and pelletized.ĭigestate Solids used in freestall at Crave Brothers Dairy, WI Photo: M.C. Actual nutrient content of digestate solids will vary depending on feedstocks, digester type, management, and solid-liquid separation technology. The high carbon content of digestate solids adds organic matter to the soil and improves the water holding capacity of the soil. Digestate solids contain higher concentrations of plant-available nitrogen and phosphorus compared to as-excreted manure, according to research. Mineralized nutrients are easily used by a crop. Digestate solids are high in fiber, consisting mainly of fibrous undigested organic material (lignin and cellulose), microbial biomass, animal hair, and nutrients.ĭuring the anaerobic digestion process, nutrients contained in the feedstock are mineralized. The volume and the moisture content of the separated solids will vary depending on the technology used. Common solid-liquid equipment can produce digestate solids with a moisture content of 18 to 30%. Solids can be extracted from the digestate using solid-liquid separation technologies such as slope screens, rotary drum thickeners and screw-press separators. Organic fertilizer, livestock bedding, compost, fuel pellets, and construction material (medium density fiberboard and fiber/plastic composite materials) are a few examples of value-added byproducts that could be created from digestate solids. Undigested biomass (referred to as digestate solids, fiber or biofiber) contained in the effluent (digestate) of anaerobic digesters provides opportunities for value-added byproducts.
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