Variation in the Chemical Composition of Crude Glycerin
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Animal Sciences Honors Theses; 2009
The lack of knowledge about the component concentrations of crude glycerol is lmiting its use as a feedstuff. The goal of this project was to determine the concentrations of various compounds and their variation within crude glycerin. Sixteen samples of crude glycerin from biodiesel producers primarily from the Midwest were collected. The samples were procured from nine different vendors between January 2007 and February 2009 with the majority, nine of 16, being collected during October 2008. The glycerin in these samples resulted from biodiesel produced from soybean oil, canola oil, tallow, and restaurant waste. Color and viscosity of the samples varied. The pH of the samples was as follows: average = 8.25, range = 5.55 to 12.36, standard deviation (SD) = 2.06 and coefficient of variation (CV) = 24.93%. The ash concentration of the samples was: average = 4.79%, range = 1.28 to 8.98%, SD = 2.32 and CV = 48.35%. The ash was very variable due to the catalyst used in production of biodiesel and the different steps used in purifying the glycerin. Ethyl alcohol concentration was low in all of the samples (< 10 ppm). The concentration of methanol was very variable among the samples, reflective of the methanol added during the biodeisel production for formation of fatty acid esters without separation of the alcohol from the glycerin. Moisture was the next most variable in the samples (average = 6.12%, CV = 72.7%). Concentrations of fatty acids in the samples were negligible. Glycerol concentration in the samples was not very variable (average = 30.5%, CV = 1.7%). This was unexpected, especially in relationship with the variation in the other variables described; higher glycerol was expected in samples with less moisture and methanol. These data reveal that the composition of crude glycerin is quite variable, the high concentrations of methanol will limit the use of glycerin as animal feed from some sources, and the high concentrations of components other than glycerol will reduce the energy concentration of crude glycerin.
OARDC Undergraduate Research Grant
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