Date of Award


Degree Type


Degree Name

Master of Science (MS)


Agricultural and Biological Engineering

Committee Chair

Jiqin Ni

Committee Member 1

Albert Heber

Committee Member 2

Nathan Mosier


Volatile fatty acids (VFA) are among the most abundant organic compounds found in animal manure and act as important intermediates in the production of methane under anaerobic digestion (AD). However, VFA also contribute to odor emissions from manure. Anaerobic digestion and separation of solids may help to reduce odor pollution during manure storage and subsequent land application by reducing VFA concentrations.

Little information about the characteristics and concentrations of VFA in dairy manure related to AD is available. This thesis presents the results of VFA production during two three-month storage studies of dairy manure collected from four different sources on a dairy: a dairy barn (raw manure), the inlet of an anaerobic digester (AD influent), the digester outlet (AD effluent), and the effluent following solids separation (SS effluent). Significant temporal and spatial variations in VFA concentrations were observed in both studies. Results showed AD significantly reduced the formation of VFA in the effluent, and additional reductions occurred from separation of solids. This study revealed that the complexity of VFA characteristics made it difficult to reliably model and predict the concentrations and compositions of VFA in dairy manure.