Date of Graduation

12-2012

Document Type

Thesis

Degree Name

Master of Science in Biological Engineering (MS)

Degree Level

Graduate

Department

Biological and Agricultural Engineering

Advisor/Mentor

Danielle J. Carrier

Committee Member

Edgar C. Clausen

Second Committee Member

Thomas A. Costello

Keywords

Applied sciences, Bioenergy, Dilute acid pretreatment, Enzymatic hydrolysis, Mixed biomass, Sweetgum

Abstract

The possibility of using sweetgum from southern pine dominated forests as a biobased refinery feedstock was investigated. First, a baseline hydrolysis scheme for sweetgum wood and bark was designed. Sweetgum wood and bark were pretreated with 0.98% (v/v) sulfuric acid at 140°C for 30, 40, 50, 60 or 70 min and at 160°C for 30, 40, 50 or 60 min. The water insoluble solid (WIS) fraction was hydrolyzed with a cellulase enzyme cocktail. Results showed that maximum xylose and glucose yields from the wood were 82 and 86%, respectively. Similarly, the respective maximum yields of xylose and glucose from the bark were 93 and 24%. Concentrations of detected inhibitory compounds such as furfural, hydroxymethylfurfural (HMF), formic acid and acetic acid ranged from 0.1 to 32.3 g/ 100 g of raw dry biomass. The second part of this project investigated the effect of adding oak wood, sweetgum bark, or oak bark, to sweetgum wood on xylose and glucose yields obtained from dilute acid pretreatment and enzymatic hydrolysis. Carbohydrate recoveries for each species and mixed biomass samples were obtained by using previously established hydrolysis protocols at 160°C for 20 min. Mixed biomass samples were prepared to reflect real-life forestry harvesting scenario and consisted of 70% sweetgum wood plus 1) 30% sweetgum bark; 2) 30% oak bark; 3) 30% oak wood. 100% sweetgum was the control. Results showed that oak wood yielded 35% of its theoretical xylose content and sweetgum wood, 65%. Both woody species resulted in higher glucose and lower formic acid recoveries than their respective bark material. Analysis of data with the Dunnett Control's test in JMP 10.0 showed contamination of sweetgum wood did not have a significant effect (P > 0.05) on hydrolysis except with sweetgum bark which exhibited a significantly higher xylose concentration than the control. In conclusion, sweetgum wood was a good source of carbohydrate for a biobased refinery, but the removal of bark might be necessary to achieve desirable yields. It is important to note that all the above results were obtained with intensively washed pretreated biomass, which will not be realistic for a real-life sustainable biorefinery

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