Pyrolyzing dairy manure solids to recover manure nutrients

PI: Rebecca Larson


Larson is an associate professor of biological systems engineering and extension specialist at UW–Madison. Her research and extension interests include all areas of biological waste including manure management, handling and treatment of agricultural waste, diffuse source pollution, agricultural sustainability, and waste-to-energy technologies including biogas production from anaerobic digestion.

Graduate student: Jane Halloran is a graduate student at UW–Madison pursuing a master’s degree in biological systems engineering and is mentored by Rebecca Larson and Joseph Sanford, assistant professor at UW–Platteville. She received a bachelor’s degree in agricultural and biological engineering from the University of Illinois at Urbana-Champaign. Her research experience includes biochar, soil chemistry, and other soil properties.

Manure nutrients are a valuable crop resource, but losses of manure nutrients are a major concern for dairy systems in Wisconsin. Manure processing to recover manure nutrients can reduce losses and increase livestock system sustainability. Pyrolysis of manure solids can densify manure nutrients as biochar, increasing economically viable transport distances and improving nutrient use efficiency. Halloran joins Larson and Sanford’s team to improve livestock system sustainability by integrating pyrolysis and biochar into manure systems to recover nutrients. In this research, separated manure solids will be dried and pyrolyzed to produce biochar, thus recovering and densifying manure nutrients in the separated solids portion of manure. Prior to biochar production, cation salts will be added to the separated manure solids and pyrolyzed to alter the surface chemistry. The biochar produced with cation salts has shown increased ability to further uptake nutrients from the separated manure liquid stream. Therefore, these biochar’s will be assessed on their nutrient recovery efficiency from separated manure liquid streams to further density nutrients and increase biochar value. The manure based biochars (both with and without cation salts) will then be assessed for nutrient availability using mineralization studies to guide improved use of manure nutrients. The outcomes will identify the potential for biochar integration into manure systems for nutrient recovery and improved manure processing. This work aims to reduce environmental losses of manure nutrients while increasing manure value.

Joseph Sanford