|Institution:||Louisiana State University|
|Department:||Biological & Agricultural Engineering|
|Keywords:||Microwave; Ammonia; Bio-Ethanol; Pretreatment; Sorghum Bagasse|
|Full text PDF:||http://etd.lsu.edu/docs/available/etd-07052011-143318/|
The majority of the worlds energy needs are currently met through the use of fossil fuels. The possible depletion of fossil fuel resources and environmental concerns has prompted the search for alternative renewable and environmentally friendly energy resources. The goal of this research was to develop a microwave-assisted dilute ammonia pretreatment technology for the conversion of sweet sorghum into ethanol. Conversion of biomass into ethanol requires a pretreatment step to open up the structure and decouple the cellulose, and hemicellulose and lignin in the biomass. In the first study, sorghum bagasse was pretreated with 28% ammonium hydroxide, and water at a ratio of 1:0.5:8 at different temperatures for 1h using microwave. Biomass treated at 160 oC for 1h with dilute ammonia removed 46% of the lignin while retaining 90% cellulose and 73% hemicelluloses. Evaluation of microwave pretreatment of sorghum biomass based on enzymatic hydrolysis and fermentation results was carried out also. The best ethanol yields among all different pretreatment conditions were 22±1.1g/100 g dry biomass using the 1-2mm particle size under 130 oC for 1h. The raw bagasse averaged 10±0.9g ethanol/100 g dry biomass. The concentrations of glycerol, organic acids, and furfurals were below the inhibitory level. A third study used Tween 80 in the pretreatment stage, which was supposed to enhance the performance of the pretreatment. Sorghum bagasse was pretreated with a combination of ammonium hydroxide and Tween 80 for 45min at 130oC. For 3% Tween 80 concentration, the glucose obtained from the hydrolysis was 38.1 g per 100 g dry biomass, compared to 33.2 g per 100 g dry biomass for control. The ethanol yield was 19 g per 100 g dry biomass, a nearly 19% improvement over the control. The final study was designed to test the hypothesis that by using microwave for pretreatment, the water requirements be dramatically reduced by single soaking and draining of the biomass prior to the pretreatment. The pretreatment was performed by mixing sorghum fibers and 28% ammonia hydroxide solution at a ratio of 1:0.5 and heating the mixture to 130oC for 1 h. Ethanol yields were 17 g/100 g dry biomass.