Manure treatment and utilization in production systems

Manure is a valuable fertilizer but a potential source for pathogen transmission, and emission of air, water or soil pollutants. This chapter introduces current technologies and management methods that can help an animal feeding operation maximize the value of manure while minimizing its risks. Processing manure involves a chain of management processes including capturing, handling, storing, treating, and utilizing manure. Manure can be a liquid, slurry or solid. It is essential to select the manure processing methods according to the physical form of manure and the utilization demand. Treatment for slurry or liquid manure often begins with solid-liquid separation, whereby particles of different sizes and different types of nutrients in the manure can be divided into separate streams for more effective treatment. The separation efficiency can be improved by precipitation, coagulation, or flocculation. Composting, the most widely adopted method to treat solid manure, reduces the volume of manure and transform it into a low pathogen and odor product. Methods to utilize manure include land-application, pelletizing, biofuel production, nutrient extraction, and feed-stock for various value-added products. Manure from different streams of processing has distinct nutrient characteristics. Land-application of manure must consider nutrient availability, nutrient balance and its leaching and runoff, and risks for transmission of pathogens. Pelletizing manure reduces the handling and transportation cost, allowing it to be exported to nutrient deficient regions. Solid manure can be used for energy production by pyrolysis, and liquid and slurry manure can produce biogas in an anaerobic digestion system before land-application. Besides these conventional strategies, nutrient extraction and feed-stock for various value-added products are emerging pathways to increase manure value.