Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: The ethanol production potential of lignocellulosic feedstocks including crop residues like cotton stalks, hays and straws (wheat, sorghum, triticale etc.) and energy crops like switchgrass was investigated. Biomass was converted using the traditional three step: pretreatment, hydrolysis and fermentation approach. Chemical (acid, alkali, ozone, oxidizers) and microbial/fungal pretreatment methods, suitable for the various feedstocks, were studied to determine optimal conditions for delignification and enhanced accessibility by cellulolytic enzymes. Enzyme based hydrolysis for conversion of the polymeric sugars to fermentable sugars was performed at various enzyme activity levels. Separate (SHF) and simultaneous saccharification and fermentation (SSF) studies on pretreated switchgrass resulted in complete conversion of glucose to ethanol. Glucose did not inhibit fermentation/ethanol production during both SHF and SSF. Xylose could not be utilized effectively by Saccharomyces cerevisiae (ATCC 24859) used for fermentation of sugars derived from the various feedstocks. Results of the studies conducted on various lignocellulosic materials have been published in peer reviewed journals and books and have been presented at professional conferences. Information on the prospects of ethanol produced from lignocellulosic feedstocks has also been presented to the general public at field days. PARTICIPANTS: Post-doctoral researchers, graduate students and undergraduate students were involved in various aspects of this project. The goals were accomplished in collaboration with faculty from departments of Crop Science, NCSU and Agronomy, Montana State. Industrial collaborations with Novozymes, North American were established during the study. TARGET AUDIENCES: The primary audiences include: Researchers in the areas of biological and agricultural science and engineering Crop scientists Agricutlural economists Secondary audiences include: Agribusiness consultants Farmers Venture capitalists looking at the potential of cellulosic ethanol PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Three new experimental switchgrass germplasms (St6-1, St6-3E and St6-3F) containing 22.71 to 30.95% glucan, 13.27 to 19.37% xylan and 17.39 to 20.60% lignin (on dry matter basis) were studied. Oven- or freeze-dried switchgrass whole-plant samples were pretreated with dilute sulfuric acid at 10% solid loading in an autoclave at 121C/15 psi. The effect of three acid concentrations (0.5, 1.0 and 1.5% w/v) and residence times (30, 45 and 60 min) on switchgrass composition was investigated. Influence of plant part was also studied for freeze-dried samples that had been separated into stems and leaves prior to drying. The greatest hemicellulose removal observed was 83.58% for oven-dried and 85.87% for freeze-dried samples resulting from intense pretreatment involving greater acid concentration (1.5% w/v H2SO4) or longer residence time (60 min). Hemicellulose in leaf was easily solubilized during acid pretreatment. Delignification was not significant during acid pretreatment and was limited to 10% for all samples investigated. Cellulolytic enzymes including cellulases and cellobiases, obtained from Novozymes North America, Franklinton, NC, mixed at an activity ratio of 1:4 FPU/CBU were added during hydrolysis at cellulase activities of 0, 15 and 30 FPU/g dry biomass. The effect of xylanase supplementation at 0.25% w/w dry biomass was also tested. The greatest glucan to glucose conversion obtained was 104.70-106.65% for freeze-dried St6-3F leaf samples after being pretreated with 1.0% acid for 60 min at 121C/15 psi and hydrolyzed by cellulase at 15 FPU/g dry biomass supplemented with xylanase or by cellulase alone at 30 FPU/g dry biomass. Addition of cellulase significantly impacted (P < 0.05) hydrolysis efficiency while adding xylanase did not appreciably enhance glucose yield. Fermentation of switchgrass hydrolyzates by S. cerevisiae resulted in almost complete utilization of glucose for ethanol production. The greatest ethanol yield from the most effective acid pretreatment was 0.082 g/g initial biomass obtained with oven-dried St6-3E and freeze-dried St6-3F whole-plant samples. A 60% theoretical ethanol yield at 0.092 g/g initial biomass was achieved through a 7-day simultaneous saccharification and fermentation (SSF) of oven-dried St6-3E switchgrass pretreated with 1.5% sulfuric acid for 60 min at 121C/15 psi. Similar studies with chemical and fungal agents on determination of optimal processing conditions for cotton stalks, hays, and straws indicated that alkali pretreatments seemed to provide better delignification, enzyme digestibility and lower production of enzyme or yeast inhibitors like furfurals. Limited by the current technological challenges, the various feedstocks tested have the potential to generate approximately 66% of the theoretical ethanol yield. This implies that it may be possible to produce an equivalent of nearly 23 - 40 gallons of ethanol per ton of dry feedstock. Post-doctoral researcher and graduate/undergraduate students involved in this project gained hands on experience in experimental, analytical, and statistical techniques which were been beneficial for them in gaining employment in the energy sector.
Publications
- R. A. Silverstein, Y. Chen, Y., R. R. Sharma-Shivappa, M. D. Boyette, J. A. Osborne. 2007. Comparison of Chemical Pretreatment Methods for Converting Cotton Stalks to Ethanol. Bioresource Technology. 98: 3000-3011.
- J. Shi, M.S. Chinn, R. Sharma-Shivappa. 2008. Microbial pretreatment of cotton stalks by solid state cultivation of Phanerochaete chrysosporium for bioethanol production. Bioresource Technology. 99:6556-6564.
- J. Shi, R. Sharma-Shivappa, M.S. Chinn. 2008. Microbial pretreatment of cotton stalks by submerged cultivation of Phanerochaete chrysosporium for bioethanol production. Bioresource Technology. Accepted.
- J. Shi, R. Sharma-Shivappa, M.S. Chinn, R.A. Dean, R.B. Shivappa. 2007. Challenges in quantification of ligninolytic enzymes from Phanerochaete chrysosporium cultivation for pretreatment of cotton stalks. Transactions of ASAE. 50(6): 2347-2354.
- Y. Chen, R. Sharma-Shivappa, D. Keshwani, C. Chen. 2007. Potential of Agricultural Residues and Hay for Bioethanol Production. Applied Biochemistry and Biotechnology. 142(3): 276-290.
- Y. Chen, R. Sharma-Shivappa, C. Chen. 2007. Ensiling agricultural residues for bioethanol production. Applied Biochemistry and Biotechnology. 143(1): 80-92.
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Progress 05/01/03 to 09/30/08
Outputs
OUTPUTS: The ethanol production potential of lignocellulosic feedstocks including crop residues like cotton stalks, hays and straws (wheat, sorghum, triticale etc.) and energy crops like switchgrass was investigated. Biomass was converted using the traditional three step: pretreatment, hydrolysis and fermentation approach. Chemical (acid, alkali, ozone, oxidizers) and microbial/fungal pretreatment methods, suitable for the various feedstocks, were studied to determine optimal conditions for delignification and enhanced accessibility by cellulolytic enzymes. Enzyme based hydrolysis for conversion of the polymeric sugars to fermentable sugars was performed at various enzyme activity levels. Separate (SHF) and simultaneous saccharification and fermentation (SSF) studies on pretreated switchgrass resulted in complete conversion of glucose to ethanol. Glucose did not inhibit fermentation/ethanol production during both SHF and SSF. Xylose could not be utilized effectively by Saccharomyces cerevisiae (ATCC 24859) used for fermentation of sugars derived from the various feedstocks. Results of the studies conducted on various lignocellulosic materials have been published in peer reviewed journals and books and have been presented at professional conferences. Information on the prospects of ethanol produced from lignocellulosic feedstocks has also been presented to the general public at field days. PARTICIPANTS: Post-doctoral researchers, graduate students and undergraduate students were involved in various aspects of this project. The goals were accomplished in collaboration with faculty from departments of Crop Science, NCSU and Agronomy, Montana State. Industrial collaborations with Novozymes, North American were established during the study. TARGET AUDIENCES: The primary audiences include: Researchers in the areas of biological and agricultural science and engineering Crop scientists Agricutlural economists Secondary audiences include: Agribusiness consultants Farmers Venture capitalists looking at the potential of cellulosic ethanol. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Three new experimental switchgrass germplasms (St6-1, St6-3E and St6-3F) containing 22.71 to 30.95% glucan, 13.27 to 19.37% xylan and 17.39 to 20.60% lignin (on dry matter basis) were studied. Oven- or freeze-dried switchgrass whole-plant samples were pretreated with dilute sulfuric acid at 10% solid loading in an autoclave at 121C/15 psi. The effect of three acid concentrations (0.5, 1.0 and 1.5% w/v) and residence times (30, 45 and 60 min) on switchgrass composition was investigated. Influence of plant part was also studied for freeze-dried samples that had been separated into stems and leaves prior to drying. The greatest hemicellulose removal observed was 83.58% for oven-dried and 85.87% for freeze-dried samples resulting from intense pretreatment involving greater acid concentration (1.5% w/v H2SO4) or longer residence time (60 min). Hemicellulose in leaf was easily solubilized during acid pretreatment. Delignification was not significant during acid pretreatment and was limited to 10% for all samples investigated. Cellulolytic enzymes including cellulases and cellobiases, obtained from Novozymes North America, Franklinton, NC, mixed at an activity ratio of 1:4 FPU/CBU were added during hydrolysis at cellulase activities of 0, 15 and 30 FPU/g dry biomass. The effect of xylanase supplementation at 0.25% w/w dry biomass was also tested. The greatest glucan to glucose conversion obtained was 104.70-106.65% for freeze-dried St6-3F leaf samples after being pretreated with 1.0% acid for 60 min at 121C/15 psi and hydrolyzed by cellulase at 15 FPU/g dry biomass supplemented with xylanase or by cellulase alone at 30 FPU/g dry biomass. Addition of cellulase significantly impacted (P < 0.05) hydrolysis efficiency while adding xylanase did not appreciably enhance glucose yield. Fermentation of switchgrass hydrolyzates by S. cerevisiae resulted in almost complete utilization of glucose for ethanol production. The greatest ethanol yield from the most effective acid pretreatment was 0.082 g/g initial biomass obtained with oven-dried St6-3E and freeze-dried St6-3F whole-plant samples. A 60% theoretical ethanol yield at 0.092 g/g initial biomass was achieved through a 7-day simultaneous saccharification and fermentation (SSF) of oven-dried St6-3E switchgrass pretreated with 1.5% sulfuric acid for 60 min at 121C/15 psi. Similar studies with chemical and fungal agents on determination of optimal processing conditions for cotton stalks, hays, and straws indicated that alkali pretreatments seemed to provide better delignification, enzyme digestibility and lower production of enzyme or yeast inhibitors like furfurals. Limited by the current technological challenges, the various feedstocks tested have the potential to generate approximately 66% of the theoretical ethanol yield. This implies that it may be possible to produce an equivalent of nearly 23 - 40 gallons of ethanol per ton of dry feedstock. Post-doctoral researcher and graduate/undergraduate students involved in this project gained hands on experience in experimental, analytical, and statistical techniques which were been beneficial for them in gaining employment in the energy sector.
Publications
- . Shi, M.S. Chinn, R. Sharma-Shivappa. 2008. Microbial pretreatment of cotton stalks by solid state cultivation of Phanerochaete chrysosporium for bioethanol production. Bioresource Technology. 99:6556-6564.
- J. Shi, R. Sharma-Shivappa, M.S. Chinn. 2008. Microbial pretreatment of cotton stalks by submerged cultivation of Phanerochaete chrysosporium for bioethanol production. Bioresource Technology. Accepted.
- J. Shi, R. Sharma-Shivappa, M.S. Chinn, R.A. Dean, R.B. Shivappa. 2007. Challenges in quantification of ligninolytic enzymes from Phanerochaete chrysosporium cultivation for pretreatment of cotton stalks. Transactions of ASAE. 50(6): 2347-2354.
- Y. Chen, R. Sharma-Shivappa, D. Keshwani, C. Chen. 2007. Potential of Agricultural Residues and Hay for Bioethanol Production. Applied Biochemistry and Biotechnology. 142(3): 276-290.
- Y. Chen, R. Sharma-Shivappa, C. Chen. 2007. Ensiling agricultural residues for bioethanol production. Applied Biochemistry and Biotechnology. 143(1): 80-92.
- R. A. Silverstein, Y. Chen, Y., R. R. Sharma-Shivappa, M. D. Boyette, J. A. Osborne. 2007. Comparison of Chemical Pretreatment Methods for Converting Cotton Stalks to Ethanol. Bioresource Technology. 98: 3000-3011.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: The potential of microbial pretreatment of cotton stalks by Phanerochaete chrysosporium to degrade lignin and facilitate fuel ethanol conversion was investigated under two different conditions: submerged cultivation (SmC) and solid state (SSC) cultivation. Although microbial pretreatments showed significant lignin degradation (19.38 and 35.53% for SmC and SSC, respectively), a study on hydrolysis and fermentation of the microbial pretreated cotton stalks showed no increase in cellulose conversion (10.98% and 3.04% for SmC and SSC pretreated samples, respectively) compared to untreated cotton stalks (17.93%). Lignin degradation products produced during the course of pretreatment or hydrolysis are the most plausible compounds that can be inhibitory to cellulolytic enzyme activities thus decreasing cellulose conversion. Washing of pretreated cotton stalks caused no significant increase in cellulose conversion. However, heating and washing treatment remarkably improved (P<0.05)
cellulose conversion to 14.94% and 17.81% for SmC and SSC 14 day pretreatment, respectively. Ethanol yields were low for all untreated and pretreated samples mainly due to the low cellulose conversion. Although, potentials and some critical aspects of fungal pretreatment using P. chrysosporium have been explored in this study, further investigation is still required especially to improve the selectivity for preferential lignin degradation and to optimize the hydrolysis efficiency. Switchgrass is a competitive feedstock and three new experimental germplasms of switchgrass are currently being investigated for bioethanol production. Either freeze or oven dried samples were pretreated with dilute sulfuric acid solutions at 10% solids loading in an autoclave at 121 C and 15 psi. Three acid concentrations (0.5, 1.0 and 1.5%) and three residence times (30, 45 and 60 min) were investigated. Results of the composition analysis of biomass feedstock (mainly cellulose, hemicellulose and lignin)
determined before and after each pretreatment were compared for the selection of optimal pretreatment processing conditions. The pretreated samples from optimal pretreatments will be hydrolyzed and fermented to determine bioethanol yields. An optimum hydrolysis condition will be determined for performing a simultaneous saccharification and fermentation (SSF) run. Current results suggest that milder pretreatment (lower acid concentration and shorter residence time) generally gives higher solid recovery. In addition, they also show that pretreatment can effectively promote hemicellulose degradation although, compared to alkali pretreatment, significant reduction in the amount of lignin does not occur.
PARTICIPANTS: Dr.Mari Chinn (Asst. Prof, Biological and Agricultural Engineering(BAE)) Dr. Ralph Dean (Prof, Plant Pathology) Dr. Joe Burns (Prof, Crop Sci) Dr.Jay Cheng (Assoc. Prof, Biological and Agricultural Engineering) Jian Shi (doctoral student) Deepak Keshwani(doctoral student) Jiele Xu (doctoral student) Ying Yang (MS student)
TARGET AUDIENCES: Engineers, scientists, farmers, agri business investors
Impacts
Biomass such as agricultural and aquatic crops and residue, herbaceous and woody energy crops, animal and human waste, and forestry residue offers a tremendous opportunity to use domestic and sustainable resources to meet fuel, power, and chemical needs. Biofuels including ethanol made from starch and biodiesel made from vegetable oil clean our air, support rural economies, and improve energy independence and balance of trade. Converting all the corn (a starchy feedstock) produced in the US is expected to meet less than 10% of the nation's fuel requirements. Besides, the technology for conversion of corn to ethanol is well established with a little scope for improvement. Alternative feedstocks and better conversion techniques therefore need to be exploited. Efficient conversion of lignocellulosic biomass such as cotton stalks left in the field and energy crops like switchgrass that require low inputs has potential to reduce dependence on fossil fuels and support rural
economies. This project is therefore investigating pretreatment, hydrolysis and fermentation methods for increased bioethanol yields from North Carolina based lignocellulosic feedstocks.
Publications
- J. Shi, R. Sharma-Shivappa, M.S. Chinn, R.A. Dean, R.B. Shivappa. 2007. Challenges in quantification of ligninolytic enzymes from Phanerochaete chrysosporium cultivation for pretreatment of cotton stalks. Transactions of ASAE. Accepted.
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Progress 10/01/05 to 09/30/06
Outputs
Lignocellulosic biomass is a great potential resource for bioethanol production. The sugars released from feedstocks such as corn stover, cotton stalks and wheat straw can be fermented into ethanol. However, in order for the sugars to be available, the biomass must be pretreated to reduce lignin and cellulose fiber crystallinity. This project investigated the use of subcritical water to pretreat cotton stalks for ethanol production. The impact of temperature, treatment time and stalk particle size was studied. Subcritical water was tested at temperatures of 230, 275 and 320C, holding times of 2, 6 and 10 minutes and ground particles sizes of 1/8, 3/16 and 1/4 inches using a response surface model experimental design. Whole and smashed cotton stalks were also pretreated with subcritical water for each time-temperature combination. Enzymatic hydrolysis was performed on the three ground sample combinations showing the highest lignin degradation and the three with the
highest percent total sugars. Lignin analysis was done on all pretreated samples and sugars were analyzed using DNS assay for the subcritical water pretreatments and HPLC for the chemical pretreatments. The highest percent total sugar of 46.3% was found for 230C, 10 minutes and 3/16 inches and the highest percent lignin reduction of 36.7% was found for 320C, 2 minutes and 3/16 inch particle size. This suggests that lower temperatures produce more total sugars and higher temperatures produce higher lignin degradation. Response surface models were developed for percent total sugars and percent lignin reduction as a function of time, temperature and ground particle size with R-squared values of .6048 and .5112, respectively. The maximum percent total sugar for the whole cotton stalks was 44.8% for the 230C, 10 minutes combination and for the smashed stalks it was 22.6% for the 320C, 2 minutes combination. Except in one case, smashing the stalks did not increase the percent total sugars
and did not increase the lignin reduction in any cases when compared to the whole stalks. Also, the ground stalks did not show any significant increase in lignin degradation when compared to whole and smashed but there was an increase in the percent total sugars for two of the whole sample sets and four of the smashed sample set. Pure lignin and cellulose samples were pretreated with subcritical water revealing that interaction between the components of lignocellulosic biomass affects the effectiveness of subcritical water pretreatment.
Impacts
North Carolina is one of the major cotton producing states in the United States with yields averaging 900 lbs per acre at a value of $253 million. High cotton production is accompanied by generation of nearly 2.1 tons/acre of cotton stalk waste each year. This results in problems with boll weevil infestation due to excessive accumulation of cotton stalk that are allowed to mulch on the fields to enrich the soil and prevent erosion. This project is developing efficient and environmentally friendly biomass conversion processes for the utilization of these and other crop/residues like switchgrass and barley. Successful conversion processes offer tremendous potential in the area of renewable energy generation and can help reduce dependence on fossil fuels to advance not only North Carolina's economy but the nation as well.
Publications
- R. A. Silverstein, Y. Chen, Y., R. R. Sharma-Shivappa*, M. D. Boyette, J. A. Osborne. 2006. A Comparison of Chemical Pretreatment Methods for Saccharification of Cotton Stalks. Bioresource Technology. In Print.
- J. Shi, R. Sharma-Shivappa*, M.S. Chinn. 2006. Microbial pretreatment of cotton stalks by submerged cultivation of Phanerochaete chrysosporium for bioethanol production. Applied Microbiology and Biotechnology. Submitted.
- J. Shi, M.S. Chinn*, R. Sharma-Shivappa. 2006. Microbial pretreatment of cotton stalks by solid state cultivation of Phanerochaete chrysosporium for bioethanol production. Applied Microbiology and Biotechnology. Submitted.
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Progress 10/01/04 to 09/30/05
Outputs
Cotton stalks left in the field after harvest lead to disposal issues and difficulty in cultivation apart from being a potential source of cotton diseases and pests. However, the lignocellulosic characteristic of cotton stalks make it a promising resource for production of fuel ethanol thereby providing a solution to these problems and benefiting both the environment and economy. This study aimed at utilizing a fungal microorganism to pretreat cotton stalks for facilitating the conversion of this renewable feedstock into ethanol. Two submerged microbial pretreatment strategies, shallow stationary cultivation and shaking cultivation utilizing Phanerochaete chrysosporium, were investigated. Shallow stationary and shaking cultures, each at three salt combinations, were compared by evaluating lignin degradation, solids recovery and fermentable sugar availability over a 16 days culture period. For shallow stationary cultivation, the group with no additional salts (ST)
resulted in 21.1% lignin degradation along with 74.7% solids recovery. The fermentable sugars available were 31.8% . For shaking cultivation, pretreatment with Modified NREL salt addition (SHS) resulted in a lignin degradation of 30.8% accompanied with 67.3% and 24.3% solids recovery and fermentable sugar availability, respectively. These results indicated that pretreatment with P. chrysosporium can degrade lignin in cotton stalks and has the potential to be an energy-saving, low cost, simple, and environmental friendly approach if optimized conditions are developed. Microbial pretreatment can significantly reduce the severity of chemical pretreatment methods while adding value to biomass. Another approach being investigated (in collaboration with Dr.Mari Chinn) for microbial pretreatment of the cotton stalks involves solid substrate cultivation (SSC) of the fungus P. chrysosporium on cotton stalks. Studies using SSC methods at 65, 75 and 80% moisture content are being conducted at
salt concentrations comparable to submerged cultivation. Preliminary results from SSC studies at 75% moisture content resulted in 32% reduction of lignin while maintaining 44% of the fermentable sugars. Other evaluation criteria such as enzymatic hydrolysibility and ligninase activities will be investigated in future research in order to dedicatedly balance the reduction of lignin, preservation of fermentable sugars and maximize solids recovery.
Impacts
Cotton is one of the major crops of the Southeastern United States, and plant breeding along with improved no till cultivation practices have helped increase production. Of the nearly 14 million acres of cotton planted in the US in 2002, an estimated 940,000 acres was planted in North Carolina with a yield of 412 lb/acre. However, cotton farmers are faced with the problem of boll weevil infestation due to excessive accumulation of cotton stalk that are allowed to mulch on the fields to enrich the soil and prevent erosion. Development of efficient and environmentally friendly biomass conversion processes for the utilization of these and other probable crop residues offers tremendous potential in the area of renewable energy generation and can help reduce dependence on fossil fuels to advance not only North Carolina's economy but the nation as well.
Publications
- No publications reported this period
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Progress 10/01/03 to 09/30/04
Outputs
Cotton, which is one of the most abundant crops in the southern United States, and North Carolina in particular, is an important source of lignocellulosic biomass. In 2003, nearly 14 million acres of cotton were planted in the United States with almost 1 million acres planted in North Carolina and 1.1 million bales of cotton harvested. This increase in cotton planting and production over the years is highly beneficial for North Carolina's economy, but it also raises concerns about the disposal of the cotton stalks (agricultural residue) left in the field after the cotton is picked. Removal of the stalks from the field is necessary to destroy feeding and fruiting sites that may cause boll weevil infestation. There is a great opportunity to investigate the possibility of using efficiently pretreated cotton stalks as a feedstock for bioethanol production. Turning this agricultural waste into a value-added product would provide a method of disposal for the stalks and
present farmers with the opportunity to earn profit from waste substrates. Therefore a study was conducted to investigate the effectiveness of sulfuric acid, sodium hydroxide, hydrogen peroxide, and ozone pretreatments for conversion of cotton stalks to ethanol. Sulfuric acid, sodium hydroxide, and hydrogen peroxide at concentrations of 0.5, 1, and 2% (w/v) were used to pretreat ground cotton stalk samples at a solid loading of 10% (w/v). Treatment temperatures of 120 C at 15 psi and 90 C were investigated for residence times up to 90 minutes. Ozone pretreatment was conducted at 4 C with constant sparging. Lignin, carbohydrate, and moisture content analyses were performed on the untreated and pretreated solids. The solids from sulfuric acid, sodium hydroxide, and hydrogen peroxide pretreatments (2%, 60 min, 121 C/15psi) showing significant lignin degradation and/or high sugar availability were enzymatically hydrolyzed at 50 C. Statistical analysis showed that time, temperature and
concentration were significant (p<0.05) factors in delignification for NaOH and xylan release for H2SO4. Sulfuric acid pretreatment resulted in the highest xylan reduction (84.00% at 2% acid, 90 min, 121 C/15psi) and the lowest cellulose conversion (23.85% during hydrolysis). Sodium hydroxide pretreatment resulted in the highest level of delignification (65.63% at 2% NaOH, 90 min, 121 C/15psi) and the highest cellulose conversion (60.8%). Significantly low (p<0.05) delignification (29.51% at 2%, 30 min, 121 C/15psi ) and cellulose conversion (49.8%) was obtained with hydrogen peroxide pretreatment compared to NaOH pretreatment. However the conversion (p<0.05) was higher than H2SO4 pretreatment. Ozone pretreatment showed no significant changes in lignin, xylan, or glucan contents with increasing time. Quadratic models using time, temperature, and concentration as numeric variables were developed to predict xylan reduction for H2SO4 pretreatment and lignin reduction for NaOH
pretreatment. In addition, linear models relating a modified severity parameter (log Mo) combining the pretreatment parameters with xylan or lignin reduction were developed and resulted in R2 values of 0.88 and 0.78, respectively.
Impacts
Cotton is one of the major crops of the Southeastern United States, and plant breeding along with improved no till cultivation practices have helped increase production. Of the nearly 14 million acres of cotton planted in the US in 2002, an estimated 940,000 acres was planted in North Carolina with a yield of 412 lb/acre. However, cotton farmers are faced with the problem of boll weevil infestation due to excessive accumulation of cotton stalk that are allowed to mulch on the fields to enrich the soil and prevent erosion. Development of efficient and environmentally friendly biomass conversion processes for the utilization of these and other probable crop residues offers tremendous potential in the area of renewable energy generation and can help reduce dependence on fossil fuels to advance not only North Carolina's economy but the nation as well.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
This project aims at exploiting various agricultural (and animal) biomass resources and developing a technology platform for their conversion to bioethanol. In this regard, research is being done, with the help of a graduate student, on comparing pretreatment technologies including acid, alkali, and ozone pretreatment for delignification of cotton stalks. This is a collaborative effort with Dr. Michael Boyette and a local cotton grower. Preliminary laboratory analyses suggest that cotton stalk which contains approximately 10% moisture, 25% lignin, and 60% carbohydrates, is a good candidate for bioethanol production through proper pretreatment, hydrolysis, and fermentation. Further research is however required to optimize the various treatments and make them commericially viable.
Impacts
Cotton is one of the major crops of the Southeastern United States, and plant breeding along with improved no till cultivation practices have helped increase production. Of the nearly 14 million acres of cotton planted in the US in 2002, an estimated 940,000 acres was planted in North Carolina with a yield of 412 lb/acre. However, cotton farmers are faced with the problem of boll weevil infestation due to excessive accumulation of cotton stalk that are allowed to mulch on the fields to enrich the soil and prevent erosion. Development of efficient and environmentally friendly biomass conversion processes for the utilization of these and other probable crop residues offers tremendous potential in the area of renewable energy generation and can help reduce dependence on fossil fuels to advance not only North Carolina's economy but the nation as well.
Publications
- No publications reported this period
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