Working with separated manure solids – Evaluating composting as a beneficial management practice
Download PDF Newsletter here March / April 2013
Phosphorus based manure management regulations come into full effect for all types of livestock operations in Manitoba as of November 2013. Pork producers in some areas of the province are challenged in having access to an adequate land base to remain in compliance once manure management fully shifts from N- to P-based, and need options for handling manure. At NCLE’s Agricultural Byproducts Processing Research and Demonstration Facility, researchers are looking at innovative means of processing manure to find suitable options for managing manure phosphorus and to improve the value of the processed material while ensuring environmental sustainability.
The Prairie Agricultural Machinery Institute, in collaboration with Maple Leaf (formerly the Puratone Corporation), MLMMI and NCLE, recently completed a comprehensive evaluation of the suitability of centrifugation for concentrating phosphorus in the solid fraction of separated hog manure to improve the economics of hauling. However, the best way to store and handle these separated solids in our climate to limit odours, buildup of harmful gases and loss of nitrogen is unclear. Jolene Rutter, MSc candidate with Mario Tenuta is evaluating composting of separated solids as a beneficial management practice (BMP) for controlling odour and conserving nutrients to capture both environmental and soil health benefits. “Composting the solids stabilizes the nitrogen instead of losing it to the atmosphere through volatilization. Stabilization of the nutrients also makes it is easier to store until it is needed and can be applied to maintain long term soil fertility,” explains Rutter. Applying composted manure to agricultural land improves soil fertility, and increases microbial diversity, moisture-holding capacity and soil organic matter levels.
Key requirements for proper composting are having a suitable carbon to nitrogen, or C:N, ratio, and suitable air space, or porosity, in the windrow.
Separated solids are characterized by both low carbon and low porosity, requiring the addition of a carbon source such as straw or wood shavings to create the ideal “recipe” for composting. In the first year of her study Rutter used straw as the carbon source in building compost windrows, but found the straw was not completely broken down. Rutter attributed the presence of straw particles in the end product to a few possible factors, such as freezing temperatures impeding completion of the composting process, and poor contact between the straw and the solids limiting moisture retention. In the fall of last year Jolene looked at wood shavings to see if the smaller particle size improved moisture retention and insulation capacity of the window compared to using straw. However, wetter and cooler weather conditions in this second trial resulted in increased methane and nitrous oxide emissions from the wood shaving-amended windrow compared to wheat straw because the high moisture combined with the smaller pore space meant the windrows were initially anaerobic. The wood shavings did result in excellent retention of ammonia. The second trial is continuing to see if the composting process resumes as the weather warms.
Jolene has shared this research at multiple industry events including Manitoba Hog and Poultry days, the MAFRI-led annual Soil and Manure Management Field Clinic, and most recently, the Waste to Worth conference hosted by the Livestock and Poultry Environmental Learning Center in Denver, Colorado (read the presentation summary here).
To learn more about this research, contact Jolene Rutter (Jolene_Rutter@hotmail.com) or Mario Tenuta (Mario.Tenuta@ad.umanitoba.ca).
Acknowledgements
Western Economic Diversification Canada, Manitoba Pork Council, Manitoba Horticultural Productivity Enhancement Centre, Manitoba Rural Adaptaion Council, NSERC, Prairie Agricultural Machinery Institute, Compo-stages, Puratone
