Date of Award

1-2011

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Dr. John B. Miller

Abstract

Trap grease offers a promising and less expensive alternative to food grade vegetable oils for biodiesel production, but its commercial marketability could be affected by its intense and offensive odor. Identification, quantitation and eventual elimination of the odorant compounds are vital challenges that need to be addressed before commercialization can be achieved. A rapid method using HS-SPME and GC/MS was developed in this study to identify and quantify the major volatile odorant compounds present in trap grease. The main odorant compounds were identified as short chain free fatty acids (SC-FFA) from C4 - C10.

Sensory evaluations by human subjects were performed with a positive and expansive correlation between the concentration of short chain free fatty acids in trap grease and the perceive odor intensity observed when applying Stevens' Power Law. In addition, odor descriptors identified by the sensory odor panel in trap grease including rancid, fatty, waxy and oily can be match with descriptors associated with SC-FFA from C4, C6, C8 and C10 respectively. Trap grease biodiesel was not found to have significantly stronger odor than soybean biodiesel and petrodiesel. When trap grease biodiesel was mixed into a 20% mixture with petrodiesel (B20) it did not have a significantly higher odor when compared to petrodiesel or commercial B20 mixtures.

Identification and quantitation of monosaccharide sugars is important to establishing the ethanol production potential of benthic algae. In this study, the geographic and seasonal variations in the carbohydrate content of benthic algae grown with a Algal Turf Scrubber (ATS) operation were examined using a method modified from an ASTM method involving hydrolyzing oligosaccharides to liberate the monosaccharides, then conversion to a sugar alcohol followed derivatization (acetylation) to enable analysis with GC.

Differences in the total monosaccharide composition and differences in the individual monosaccharide breakdown were seen at the 13 different ATS sites examined with locations from western Michigan to central Florida and along the US east coast in Chesapeake Bay. The total monosaccharide content varied from less than 5 % of the ash free dry mass to as much as 36 %.

Fermentation studies were conducted and the ethanol production results were compared to the monosaccharide content and pretreatment schemes. The growth rate and ethanol production potential of benthic algae is compared to other biomass energy crops including corn and switchgrass. Although additional research and development remain, the methods developed in this work should eliminate many of the analytical challenges associated with developing these complex feedstocks into sustainable commercial biofuels.

Access Setting

Dissertation-Open Access

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