Sample Characterization
The samples were collected in October 2011 and transported to the laboratory on
ice. Once reaching the laboratory, the samples were characterized for pH, total solids
(TS), volatile solids (VS), and chemical oxygen demand (COD), according to Standard
Methods (APHA, 1998).
Specific Methanogenic Activity Test (SMA)
Specific methanogenic activity tests (SMA) were used to characterize available
inoculum sources, prior to incubation, as developed by Zeeuw (1984). In this study, the
SMA was conducted based on the methods of Sorensen (1993) and used to
determinate if the inoculum of the effluent of Kilby farm (co-digestion system) was a
better inoculum source for the laboratory testing compared to a inoculum source from a
digestion system that does not utilize food waste co-digestion. Effluent and Influent from
Kilby digester and the effluent from a dairy manure-only digester at the USDA Beltsville
Agricultural Research Center (BARC), located in Beltsville-Maryland, were analyzed.