Pretreatment Of Cotton Stalks Research Articles

Enhancement of methane yield from cotton stalks by mechanical pre-treatment

Cotton stalks (CS) are lignocellulosic agricultural by-products, a potential source for biogas production, but pretreatment must be considered since hydrolysis is the rate-limiting stage for lignocellulosic biomass substrates. This study investigates the feasibility of mechanical pretreatment of CS to enhance methane production. Batch anaerobic digestion of CS samples with particle sizes ranging from 0.5 to 65 mm was carried out in 1 L eudiometer batch digesters for 48 days at 37°C. Results showed that methane yield was inversely proportional to particle size, and the quality of biogas was good (54.0–55.2% CH4). Significant increases in methane yield were observed with 20.3% and 26% for samples with a particle size of 3 mm and 0.5 mm, respectively, compared to untreated CS. The coefficient of anaerobic energy turnover was relatively low (20.2–25.5%). Reduction of the CS particle size to 3 mm or less is recommended to achieve effective methane conversion and decrease the retention time in an anaerobic digester from 31 to about 25 days. However, to offset the high energy demand required for grinding, further research should be conducted in combining size reduction with chemical and physicochemical pretreatment.

Preparation and properties of bio-geopolymer composites with waste cotton stalk materials

Abstract To promote the effective utilization of plant stalk resources, cotton fibers and cotton powders were obtained by crushing and screening waste cotton stalks, which were then utilized for the preparation of bio-geopolymers. This study explores the influence of the size and content of cotton stalk fibers and curing methods based on the physical and mechanical properties of a geopolymer. Pretreatment of cotton stalk was applied to improve the fiber-matrix bonding performance and enhance the mechanical properties of the proposed geopolymers. Compressive and flexural bending tests and a hydrochloric acid erosion test were carried out to measure and evaluate the bio-geopolymers containing cotton stalk powder. Scanning electron microscopy and X-ray energy spectrometer (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) techniques were applied to investigate the micro-characteristics of the geopolymerization products. The test results demonstrate that the addition of untreated cotton stalk fibers reduces the density of the geopolymers and the compressive strength, whereas the flexural strength is slightly increased. Alkali treatment has proven to be effective in fiber-matrix bonding, and the compressive and flexural strengths are improved by 4.8% and 11.5% respectively compared to the untreated ones. The cotton stalk powder can effectively improve the compressive strength of geopolymer, while the acid corrosion resistance of bio-geopolymer decreases. Through SEM-EDS, XRD, and FTIR analyses, the effects of cotton stalk powders on geopolymer are mainly filling and cementing. The sugar precipitated from cotton stalk in alkaline environment reduces the compactness of a geopolymer gel. Alkali treatment and PVA solution treatment on cotton stalk can effectively reduce the effect of the precipitated sugar on geopolymer gel.

Enhancement of methane production from Cotton Stalk using different pretreatment techniques

China produces large amount of cotton stalk (CS) residues as agricultural biomass, which are incinerated on-site, causing air pollution. The high organic content of CS could be utilized for biogas production, but the direct digestion without pretreatment always leads to a low methane yield and biodegradability, due to the complicated structure of lignocellulose. In order to search best fitting pretreatment methods in effective anaerobic digestion (AD) of CS, effects of various pretreatments including KOH, NaOH, Ca(OH)2, alkali hydrogen peroxide (AHP), H2SO4, H3PO4 and steam explosion (SE) were studied. It was seen that all treatments resulted in varying methane yields. Among all the pretreatments, acid pretreatment is not suitable for AD of CS. The results showed that the highest cumulative methane yield (CMY) of 192.4 mL·gVS−1 was obtained after 3% AHP pretreatment of CS, and the methane yield improved by 254.3% than the untreated CS. Therefore, AHP treatment was proven to be an efficient pretreatment technique. XRD and FTIR analyses had shown that pretreated CS had favorable structural changes. This research is beneficial in developing environment friendly and cost-effective pretreatment technologies to utilize CS for methane production in future application.

Pretreatment of cotton stalks by synergistic interaction of Daedalea flavida and Phlebia radiata in co-culture for improvement in delignification and saccharification

Selective lignin degrading white rot fungi Daedalea flavida MTCC 145 (DF-2) and Phlebia radiata MTCC 2791 (PR) interacted synergistically in co-culture to enhance the lignolytic enzymes production during pretreatment of cotton stalks in solid state fermentation. The peak activity of laccase increased to 14.19 ± 0.85 IU g−1 solid on fifteenth day of pretreatment by co-culture, higher than three folds and eight folds to the pretreatment by monoculture of DF-2 and PR respectively. Increase in peak activity of MnP was observed in co-culture compared to its activity in monoculture of PR, whereas additive effect of LiP activity was observed in co-culture. Due to increase in lignolytic activities, lignin degradation increased during pretreatment in co-culture. Lignin degradation was 35.13 ± 1.66% (w/w) after 20 days pretreatment with co-culture. Lignin degradation was 36.29 ± 1.21% (w/w) and 31.02 ± 1.27% (w/w) with DF-2 and PR respectively after 40 days pretreatment, which showed significant reduction of pretreatment time to half in co-culture. The glucose released after enzymatic hydrolysis of 20 days co-culture pretreated cotton stalks 142.88 ± 5.39 mg g−1, was higher than glucose released 117.09 ± 2.26 and 79.21 ± 1.86 mg g−1 from DF-2 and PR pretreated stalks, respectively. Cotton stalks were characterized by FT-IR, SEM, XRD and TGA-DTG to confirm the results.

Bioconversion of alkali delignified cotton stalk using two-stage dilute acid hydrolysis and fermentation of detoxified hydrolysate into ethanol

Green biotechnology offers a promising approach to convert most of the solid agricultural wastes particularly lignocellulosic biomass into liquid biofuels. In this study, pretreatment of cotton stalk with sodium hydroxide (3% w/v; room temperature for 24h) removed lignin (52.48±1.17%) with minimum sugar loss (3.50±0.09%). Subsequent two-stage dilute acid hydrolysis of alkali delignified cotton stalk released 29.40±0.85g/L sugars with 63.50±1.06% holocellulose hydrolysis along with furfurals (1.32±0.10g/L) and phenolics (2.18±0.15g/L) in the hydrolysate. Detoxification of hydrolysate with overliming and adsorption with activated charcoal caused 59.12% and 78.44% reduction in total furfurals and phenolics, respectively. Batch fermentation of detoxified acid hydrolysate with monoculture and cocultures of Saccharomyces cerevisiae VS3 and Pichia stipitis NCIM3498 showed ethanol production of 6.28±0.08g/L, (yield, 0.39g/g); 10.14±0.19g/L (yield, 0.45g/g) and 11.64±0.32g/L (yield, 0.47g/g), respectively.

Cellulose Degrading Microbial Community Degradation Diluted Acid Pretreatment Cotton Stalks and Optimization of Fermentation Techniques

Cotton stalk is rich and low cost renewable cellulosic resources in Xinjiang autonomous region, but two-thirds of these stalks are not used to their fullest extent. Nowadays, more research has been reported concerning the pretreatment of cotton stalks, saccharification, ethanol production and other aspects. The experiment screened cellulose degrading microbial community, and optimized conditions of saccharification. In oder to degrading lignin and cellulose of cotton straw and improving the efficiency of hydrolysis of cellulose, to decompose diluted acid pretreatment cotton stalk by cellulose degrading microbial community. We studied the microbial fermentation period, fermentation technical parameters, and curves of cellulase activity. We designed single factors , and orthogonal experiment to optimize the fermentation technical parameters. The results showed that the fermentation period was 5-day, single factor experiment, the optimum of fermentation temperature was 32°C (P < 0.01), orignal pH was 4.8 (P < 0.01), inoculation size was 5%(P < 0.01) and nitrogen source was urea(P < 0.01), and orthogonal experiment, the optimized conditions were nitrogen source, (NH4)2SO4, temperature, 42°C, original pH 6.8, inoculation quantity 1.0%. Under optimized conditions, CMC, FPU, b-G, glycosylated ratio and lose weight reached respectively 47.12 U/mL, 24.35 U/mL, 13.05U/mL, 37.21% and 26.38%.

Pretreatment of cotton stalk with ionic liquids including 2-hydroxy ethyl ammonium formate to enhance biomass digestibility

Cotton stalk was subjected to ionic liquid pretreatment via several ionic liquids; 2-hydroxy ethyl ammonium formate (HEAF), 1-allyl-3-methyl imidazolium chloride (AMIMCl), 1-butyl-3-methyl imidazolium chloride (BMIMCl), 1-ethyl-3-methyl imidazolium chloride (EMIMCl) and 1-ethyl-3-methyl imidazolium acetate (EMIMAc). Ionic liquids readily provided conversion of cotton stalk into fermentable sugars upon enzymatic hydrolysis through reshaping the organized and rigid structure into a less organized and less durable form. The impact of ionic liquid pretreatment was mostly recognized for EMIMAc pretreated cotton stalk, which exhibited a highly deconstructed structure whereas modest changes were detected for those pretreated via other ionic liquids. Biomass digestibility was 65% for EMIMAc pretreated cotton stalk after 72h of enzymatic hydrolysis, which was 9-fold higher compared to untreated cotton stalk. Despite being incapable of dissolving cellulose, HEAF pretreatment resulted in an enzymatic digestibility of 26%, which was similar to the digestibilities attained by AMIMCl and EMIMCl pretreatments. EMIMAc recycling was also feasible with respect to enzymatic digestibility and structural features including the deconstructed structure and reduced crystallinity for the pretreated samples as analyzed by characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR).

Different ionic liquids favor different lignocellulosic biomass particle sizes during pretreatment to function efficiently

Cotton stalks at four different particles sizes (<0.15 mm, 0.15–0.5 mm, 0.5–1.0 mm and 1.0–2.0 mm) were subjected to ionic liquid pretreatment via 1-ethyl-3-methylimidazolium acetate (EMIMAc) and 1-ethyl-3-methylimidazolium chloride (EMIMCl) followed by the enzymatic hydrolysis of pretreated biomass. The changes in crystalline structure, lignin content and digestibility of the pretreated samples were investigated in addition to the glucose yield obtained from cotton stalks. For EMIMAc pretreatment, the lowest glucose yield (57%) was obtained upon the pretreatment of cotton stalks having the smallest particle size prior to pretreatment (<0.15 mm) while cotton stalks with larger particle sizes gave higher glucose yields of which were at least 71%. On the contrary, EMIMCl pretreatment functioned more efficiently with cotton stalks having smaller particle sizes (<0.15 mm and 0.15–0.5 mm) where increasing the biomass particle size further caused a decrease in the glucose yield from approximately 49% to 33%, unlike the EMIMAc pretreatment. These differences in the glucose yields obtained for different ionic liquids suggest that the ideal particle size of biomass prior to pretreatment may change from one ionic liquid to another.

Microbial pretreatment of cotton stalks by submerged cultivation of Phanerochaete chrysosporium

This study used the fungus, Phanerochaete chrysosporium, to pretreat cotton stalks with two methods, shallow stationary and agitated cultivation, at three supplemental salt concentrations. Pretreatment efficiencies were compared by evaluating lignin degradation, solid recovery and carbohydrate availability over a 14-day period. Shallow stationary cultivation with no salts gave 20.7% lignin degradation along with 76.3% solid recovery and 29.0% carbohydrate availability. The highest lignin degradation of 33.9% at a corresponding solid recovery and carbohydrate availability of 67.8% and 18.4%, respectively, was obtained through agitated cultivation with Modified NREL salts. Cultivation beyond 10 days did not significantly increase lignin degradation during 14 days of pretreatment. Manganese addition during shallow stationary and agitated cultivation resulted in higher solid recoveries of over 80% but lower lignin degradation. Although agitated cultivation resulted in better delignification, results indicate that pretreatment under submerged shallow stationary conditions provides a better balance between lignin degradation and carbohydrate availability.