Master of Science in Biological and Agricultural Engineering (MSBAE)
Biological and Agricultural Engineering
High demand for energy and increasingly expensive petroleum prices led to development of new alternative fuels for transportation, such as bio-ethanol and bio-diesel. Even though a cost reduction in the production of cellulolytic enzymes is occurring, the conversion of plant cellulose into sugars still remains an expensive and slow process. Pretreatment of lignocellulose materials to remove lignin and alter physical/chemical structures significantly improves hydrolysis of cellulose to give high yield of sugars. In this study, ultrasonic pretreatment of energy cane bagasse was used in the presence of ammonia (NH4OH) to enhance the saccharification process by separating lignin, cellulose and hemicellulose from each other in biomass. The process performance was investigated as a function of low ultrasonic frequency (20, 20.5, 21 kHz) at a power level of 100 W for the reaction time of 30 min at 80 to 90°C reaction temperature. The pretreatment was performed for four different combination mixtures:(1) energy cane bagasse with 28% NH4OH and water at a ratio of 1:0.5:8 (w:w:w) and processed immediately, (2) energy cane with water at a ratio of 1:8.5 (no ammonia) and processed immediately, (3) energy cane soaked with 28% NH4OH and water with the same ratio for 3 hours, then drained and pretreated ultrasonically and (4) energy cane soaked with water with the same ratio for 3 hours (no ammonia), then drained and pretreated ultrasonically. Composition analyses were performed after pretreatment to quantify glucose yield and lignin removal rates. Enzymatic hydrolysis tests were also performed to quantify the sugar yield. Results for composition analysis for different pretreatment combinations were obtained against the control. The objective was to find the best frequency for which high glucan % and cellulose digestibility % for degrading them to simple sugars were obtained. The pretreatment process was performed again for all the four combination mixtures mentioned as a function of pretreatment reaction time (30, 45, 60 min) with constant frequency at 20 kHz, power level of 200 W and increase in reaction temperature of above 120 ° C. All the energy cane combination mixtures were pretreated along with their respective controls (without ultrasonic frequency). The cellulose digestibilities among various combination mixture samples based on a particular frequency were not statistically significant but varied significantly compared to the untreated energy cane bagasse. The energy cane bagasse with 28% NH4OH and water for 60 min reaction time obtained the highest cellulose digestibility of almost 44% for both non-soaked and soaked samples compared to 20.44% for the untreated energy cane bagasse (control). Energy cane bagasse with water for 60 min reaction time obtained cellulose digestibility of 34.14%, whereas the water soaked and drained sample for 60 min reaction time obtained cellulose digestibility of 38.12%. The maximum theoretical glucose yield was 24.29 g / 100 g of dry biomass for the combination mixture of energy cane bagasse with 28% NH4OH and water for 60 min reaction time. Theoretical glucose yield for energy cane bagasse with 28% NH4OH and water soaked and drained sample for 60 min reaction time was 23.99 g / 100 g of dry biomass, whereas the theoretical glucose yield for water (no ammonia) for 60 min reaction time was 10.07 g / 100 g of dry biomass. Theoretical glucose yield for water soaked and drained sample for 60 min reaction time was 10.91 g / 100 g of dry biomass. The results also indicated that pretreatment time and various combination mixtures were statistically significant at the 95% confidence interval for % glucose yield of pretreated energy cane bagasse. The pretreatment efficiency was also observed via increased porosity and fiber swelling of the treated energy cane fibers through Scanning Electron Microscopy (SEM). These results demonstrated that ultrasonic pretreatment along with NH4OH can be used as a potential pretreatment method for lignocellulosic biomass to produce biofuels.
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Methrath Liyakathali, Niyaz Ahamed, "Ultrasonic pretreatment of energy cane bagasse for biofuel production" (2014). LSU Master's Theses. 3733.