Digestibility Of Corn Stover Research Articles

Synergistic enhancement of the secondary peak in methane production from anaerobic digestion of corn stover: The combined effects of polydopamine thermally modified tourmaline and magnetic field

This study explored the impact of using polydopamine thermally modified tourmaline (PTMT) in combination with various structured magnetic fields on methane production during the anaerobic digestion (AD) of corn stover. Results show that PTMT, when used with a spatial magnetic field, significantly enhances the secondary peak of methane production. Specifically, coupling PTMT at a concentration of 3.0 g/L with an 11.4 mT spatial magnetic field increased cumulative methane yield by 34.5 %, from 261 mL/g VS to 351 mL/g VS. Microbial diversity analysis indicated that the ST group (PTMT with a spatial magnetic field) was predominantly composed of Halobacterota (37.8 %), much higher than the control group's (C) Halobacterota (15.6 %). The energy conversion efficiency of corn stover in the ST group reached 31.3 %, with substrate carbon flow to CH4 at 0.156 mol, representing increases of 34.1 % and 33.3 %, respectively, compared to the C group. Economic analysis revealed that the net profit of the ST group was 13.2 % higher than that of the C group. This novel approach of combining PTMT with a spatial magnetic field offers a promising strategy for the efficient conversion of corn stover to methane.

A novel player of methylotrophic methanogensis pathway in boosting anaerobic digestion of corn stover with effluents recycling

Effluents recycling proves to be an effective method for enhancing the performance of anaerobic digestion system for lignocellulosic-like biomass. However, a limited understanding exists regarding the regulation mechanisms of methanogens. This study aims to systematically assess the dynamic interactions between process parameters, microbial communities, and methanogenic activity throughout the AD process of corn stover with effluents recycling. The results show a significant increase in the specific biogas yields of corn stover to 369 ± 115 mL/g VS with effluents recycling, an 87 % improvement compared to the control system. Effluents recycling can recover nitrogen and selectively enrich the abundances of microorganisms such as Herbinix hemicellulosilytica, Bacteroides paurosaccharolyticus and Methanosarcina mazei, etc. Correspondingly, the strategy improves the abundance of CAZymes, enhancing the efficient depolymerization of cellulose, glucuronoarabinoxylan, xyloglucan and pectin. Methanol and methylamines originating from enhanced pectin hydrolyzation and the biogenic amine pathway boost methylotrophic methanogenesis. This study addresses knowledge gaps in producing-pathways of precursors for methylotrophic methanogenesis and elucidates the mechanism to boost methanogenesis process of lignocellulosic-like biomass with effluents recycling.

Effect of alkaline deep eutectic solvents pretreatment on CH4 yield from anaerobic digestion of corn stover

Deep eutectic solvents (DES), comprising hydrogen bond donors (HBD) and acceptors (HBA), are gaining prominence in biomass pretreatment due to their excellent lignin depolymerization capabilities. This study explored the impact of alkaline DES pretreatment, specifically focusing on CH4 yield from corn stover anaerobic digestion. Batch experiments were conducted to assess the influence of ethylene glycol (EG) concentration, pretreatment time, and organic loading rate (OLR) on CH4 yield. Results indicated that these factors markedly affected the cumulative CH4 yield. Subsequent optimization using Box-Behnken design (BBD) significantly enhanced the CH4 yield by 1.16 times, achieving the optimal conditions at 0.4 v/v EG concentration, 33.8 min of pretreatment, and 22.2 w/v OLR. Notably, DMER64 and Methanobacterium emerged as the dominant bacterial and archaeal communities, constituting 40.2 % and 71.9 % respectively. Spearman correlation analysis underscored that enhanced substrate accessibility fostered a hydrogen-based, CH4-producing synergistic metabolic pathway. Alkaline DES pretreatment notably resulted in 20.5 % of the carbon flow being directed to CH4, demonstrating its efficacy in converting corn stover into a viable clean energy source and mitigating the environmental impact of agricultural waste.

Synergistic effects of low temperature and alkali on the anaerobic digestion of corn stover

Combined with the climatic conditions in cold areas, the effect of the NaOH-pretreatment at low temperature on the methane yield of corn stover was studied by anaerobic digestion at batch mode. For the alkali/freezing pretreatment, the sample reached a maximum specific methane yield of 280.48 ± 21.75 mL/g VS at the conditions of freezing time of 15 days and 2.0 % NaOH. Lower temperature-alkali pretreatment had an obvious effect on the structure of samples, with significant changes in the contents of elemental C, N, cellulose, and lignin, as well as an increase in crystallinity. In addition, a higher energy conversion efficiency (77.9 %) was obtained for the sample pretreated by alkaline/freezing. The results showed that the methane yield after pretreatment followed by alkali/freezing treatment > water/freezing treatment > freezing treatment. Therefore, alkali/freezing pretreatment is an effective method to improve the performance of the anaerobic digestion of corn stover. This study could provide a pathway for developing a low-temperature pretreatment by combining with the climate characteristics of cold areas.

Anaerobic Digestion of Corn Stover Pretreated with Sulfuric Acid in Different Soaking Durations

<p>The biogas production of pretreated corn stover has been determined in different soaking durations. Batch anaerobic digestion applies three different soaking durations in sulfuric acid pretreatment under room temperature. The study aimed to probe the effect of soaking durations during sulfuric acid pretreatment. The experiment was conducted in 600 mL digesters at room temperature. Biogas volume was measured using the water displacement method every three days. The observed cumulative biogas yields varied between 48.74 mL/g VS and 99.95 mL/g VS. The highest biogas yield was obtained when corn stover was soaked in sulfuric acid for 6 hours. The 24 h-pretreated corn stover got the lowest biogas yield. The statistical result proved a significant effect of soaking durations on biogas production (p < 0.05). The logistic model provided a better fit than the first-order model, with R2 values ranging from 0.9923 to 0.9987 and divergence between experimental and predicted values varying between 0.12% and 1.48%.</p>

NaOH-urea pretreatment enhanced H2 and CH4 yields via optimizing mixed alkali ratio, pretreatment time, and organic loading rate during anaerobic digestion of corn stover

This work studied the impact of NaOH-urea pretreatment on corn stover for H2 and CH4 production through two-stage anaerobic digestion. Results showed that the NaOH-urea pretreatment process improved CH4 production more significantly compared to H2. Optimized by Box-Behnken design (BBD) experiments, the CH4 cumulative yield was increased by 34.2 % at NaOH: urea = 3.2: 26.8, time = 15.7 min, and organic loading rate (OLR) = 23.4 w/v. Microbial community diversity analysis showed that the hydrogen and methane production stages formed communities dominated by Bacteroidales and Methanobacteriales, respectively. In addition, NaOH-urea pretreatment enhanced the metabolite energy recovery efficiency by 28.5–40.9 %. Finally, the return on investment (ROI) of the NaOH-urea pretreatment process reached 26.1 % with significant economic benefits. This research proposed a chemical pretreatment process for anaerobic digestion of corn stover by optimizing the pretreatment conditions of NaOH- urea.

Evaluation and modelling of biogas production from batch anaerobic digestion of corn stover with oxalic acid

Evaluation and modelling of biogas production from batch anaerobic digestion of corn stover with oxalic acid

Effect of pelleting on the enzymatic digestibility of corn stover

Pelleting of lignocellulosic biomass to improve its transportation, storage and handling impacts subsequent processing and conversion. This work reports the role of high moisture pelleting in the enzymatic digestibility of corn stover prior to pretreatment, together with associated substrate characteristics. Pelleting increases the digestibility of unpretreated corn stover, from 8.2 to 15.5% glucan conversion, at 5% solid loading using 1 FPU Cellic® CTec2 per g solids. Compositional analysis indicates that loose and pelleted corn stover have similar non-dissolvable compositions, although their extractives are different. Enzymatic hydrolysis of corn stover after size reduction to normalize particle sizes and removal of extractives confirms that pelleting improves corn stover digestibility. Such differences may be explained by the decreased particle size, improved substrate accessibility, and hydrolysis of cross-linking structures induced by pelleting. These findings are useful for the development of processing schemes for sustainable and efficient use of lignocellulose.

Simultaneous pretreatment with ultraviolet light and alkaline H2O2 to promote enzymatic hydrolysis of corn stover

Pretreatment processes are essential for the preparation of biofuels from lignocellulosic feedstocks. Based on alkaline H2O2 pretreatment, photocatalytic alkaline H2O2 pretreatment (U-AHP) was investigated to examine the effects of reaction time, alkali concentration, and H2O2 concentration on the enzymatic digestion of corn stover. The optimum process conditions were determined by orthogonal tests: 1% NaOH, 2% H2O2, and reaction time of 8 h. Under these conditions, the lignin removal efficiency of UH-AHP was 90.2% and the saccharification yield was 94.7%. Furthermore, FT-IR, XRD, and SEM analyses showed that U-AHP pretreatment caused structural damage to the maize straw and increased the crystallinity of the cellulose, and it was speculated that the U-AHP pretreatment reaction was a complex mechanism, which might be a multiple synergistic reaction. This study shows that U-AHP pretreatment is a simple, green and effective method to promote lignin removal.

Enhanced anaerobic digestion of corn stover using magnetized cellulase combined with Ni-graphite coating

The effects of combining magnetized cellulase (MC) with Ni-graphite (NG) coated materials on the anaerobic digestion of corn stover were investigated. In pretreatment of the corn stover, cellulase showed higher glycosylation efficiency in a 30 mT magnetic field environment than in other magnetic fields, and the reducing sugar content reached 0.182 mg/L. Treatment with the combination of magnetized cellulase and Ni-graphite coated material resulted in a 74.35% increase in cumulative CH4 yield. Analysis of the composition of the microbial community showed that the addition of Ni-graphite coating significantly influenced the composition of the microbial community. The electrically active microorganisms Bacteroidota (46.98%) and Methanomicrobiales (6.08%) became the dominant bacteria and archaea when the corn stover was treated with the NG+MC combination. Carbon balance calculations showed that the combination treatment resulted in carbon flow distributions that differed from other treatments, and the energy conversion efficiency (ECE) reached 57.1%.

Densification pretreatment triggers efficient methanogenic performance and robust microbial community during anaerobic digestion of corn stover

The recalcitrant characteristics of lignocellulosic waste and difficulties in biomass transportation and storage severely limit bioenergy production through anaerobic digestion (AD). In this study, Densifying Lignocellulosic biomass with Chemicals (DLC) pretreatment was developed to address these issues. The results showed that DLC treated corn stover (CS) reached a cumulative methane yield of as high as 224.30 mL/g VS (Volatile Solids), which was 59.27 % higher than that of un-treated. The reduced scum formation in the reactor, increased components consumption of solid phase, and higher organic biodegradability of liquid phase in AD of DLC treated CS enhanced methane yield. Microbial analysis indicated that DLC pretreatment affected the bacterial and methanogenic community structure, and a co-network with Comamonas and Methanobacterium, etc. as hub microbes was constructed. This study proposed a promising technology that could be potentially applied to industrial AD of lignocellulosic biomass.

Anaerobic Digestion of Corn Stover for Improved Biomethane Yield: Effect of Organic Nitrogen Sources (Soybean Curd Residue and Fish Waste)

The present study investigated the effect of organic nitrogen sources, soybean curd residue (SCR), and fish meal (FW) on the anaerobic digestion of corn stover for biomethane production. The bioreactors were seeded with the corn stover (corn cob and corn sheath), soybean curd residue (SCR), and fish waste (FW) at different combinations: (CC/SCR), (CC/FW), (CS/SCR) and (CS/FW), including CC and CS alone. The fermentation was for 31 days under mesophilic conditions. Characteristics of the substrates indicate that CC and CS are good carbon and energy sources, but low in nitrogen content. Conversely, SCR and FW are rich nitrogen sources, with low organic carbon content. There was a remarkable increase in biogas production in all treatments, except CC/SCR 75:25 and CC/SCR 85:15 in which inhibitory effect was observed. The highest percentage increase (138%) in biogas was recorded in CS/SCR 85:15 (2.86 dm3), and the least was CC/FW 75:25 with 1.49 dm3 (24.18% increase). Significant difference (P ≤ 0.05) in biogas yield was in the following: CC/SCR 50:50, CC/FW 50:50, CS/SCR 85:15, CS/FW 50:50, and CS/FW 75:25. The composition of the biogas revealed that the treatment improved biogas production as well as biomethane content, the highest being 69.44% in CS/SCR 85:15. Regression analysis of cumulative biogas yield as a function of time (t) in the different treatments that had a significant difference in biogas yield showed a good correlation between biogas yield (GY) and time (t). Improving the biodegradability of lignocellulosic wastes could lead to a boost in the development of anaerobic digestion and biogas production technology. To improve their biodegradability during anaerobic digestion, both pre-treatments and supplementation have vital roles to play.

Comparison of Operating Methods in Cartridge Anaerobic Digestion of Corn Stover.

Anaerobic digestion of lignocellulosic biomass faces changes such as biomass floating and effluent discharge. To overcome these challenges, a unique removable cartridge anaerobic digester was built and tested using corn stover as the feedstock. Three operating methods differing in the number of cartridges and days of rotation were tested. The first method used three cartridges, with each cartridge being rotated every 7 days. The second and third methods employed four cartridges, with cartridges being rotated every 7 and 9–10 days, respectively. The retention time for methods 1, 2, and 3 was 21, 28, and 38 days, respectively. After observation spanning 1 year, it was found that the cartridge digester was capable of generating a stable amount of biogas for energy without biomass floating or effluent discharging issues. The average daily methane yield from each method was 7.57, 7.11, and 6.82 L/day/kg-VS, and the cumulative methane yield was 158.95, 199.04, and 259.00 L/kg-VS, respectively. Ammonium nitrogen and pH values were in normal ranges throughout the experiment. This study provided new knowledge in operating and optimizing this cartridge digester, which may be broadly used for the anaerobic digestion of lignocellulosic biomass in the near future.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12155-021-10252-w.

Features correlated to improved enzymatic digestibility of corn stover subjected to alkaline hydrogen peroxide pretreatment

As one of the leading pretreatment approaches, alkaline hydrogen peroxide (AHP) pretreatment can enhance the enzymatic digestibility of lignocellulose significantly. In this study, the glucan conversion of AHP pretreated corn stover (CS) without and with water-wash were 28.4% and 50.0% higher than that of raw material, respectively. In order to systematically understand its mechanism, analyses of the features of AHP pretreated and raw CS, such as specific surface area, crystallinity, zeta potential, water holding capacity and swelling capacity and others were performed. The weight-average molecular weight (Mw) of the sugars in the hydrolysate and the particle size distribution of the hydrolysis residue were also analyzed. These results explained why AHP-CS was more conducive to enzymatic hydrolysis. The deeper reason was that the removal of lignin and the destruction of hydrogen bonds within cellulose and hemicellulose increased the accessibility of cellulose and reduced the non-productive adsorption of cellulase, which significantly improved the enzymatic digestibility.

Study of two-phase anaerobic digestion of corn stover: Focusing on the conversion of volatile fatty acids and microbial characteristics in UASB reactor

Methanogenic performance and microbial communities including both bacteria and archaea in UASB reactor treating acidogenic metabolites from acidification of ensiled corn stover (ECS) were investigated. Gradient organic loading rates (OLRs) were adopted to study the conversion of volatile fatty acids (VFAs) characterized by high concentration of acetic acid and propionic acid. The removal rate of chemical oxygen demand (COD) reached above 80.0 % at OLR of 8 g/L·d and volumetric methane production rate improved significantly as the OLR increased. When OLR was 10 g COD/L·d, acetic and propionic acids in effluent were accumulated and failure of methane production occurred. Compared with the control, the methanogenic inhibition was caused by the presence of high concentration of propionic acid. The profile of conversion of individual VFAs in UASB reactors was investigated at different OLRs. Furthermore, microbial communities in anaerobic sludge at OLR of 8 g COD/L·d were compared with those in inoculum and the shift of bacteria and archaea were analyzed. The abundances of some representative acetogenic bacteria such as Proteobacteria (14.18 %) and Bacteroidetes (11.16 %) increased obviously, which contributed to the oxidation and decomposition of organic acids. Acetotrophic methanogen (Methanosaeta) and hydrogenotrophic methanogen (Methanobacterium) played synergistic roles with acetogens to efficiently complete the VFAs conversion. This study will be of great importance to guide the application of two-phase AD of agricultural waste in full-scale plant.

Corn Stover as Substrate for Biogas Generation and Precursor for Biosilica Production via Anaerobic Digestion

Production of fuels and chemicals from renewable biomass is crucial to sustainability of bio-based economy. In this study, anaerobic digestion of corn stover (CS) was carried out to produce biogas under mesophilic conditions. The study also investigated the potential of corn stover digestate ash as a potential source for biosilica production. A cumulative volume of 930 mL of biogas was produced with methane content of 85.87%. Higher and lower calorific values of biogas were calculated to be 36.30 MJ/m3 and 32.70 MJ/m3, respectively. Calcination of raw CS (RCS) and the digestate (CSD) was carried out at 600 °C for 3 hours. The samples generated, raw corn stover ash (RCSA) and corn stover digestate ash (CSDA) were characterized using X‐ray fluorescence (XRF), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and X‐ray diffractometer (XRD). The XRF results revealed that CSDA biosilica content was 60.49%, which was 34.84% higher than RCSA. There was reduction in most of the metallic impurities in CSDA compared to RCSA. Potassium oxide was drastically reduced from 12.34% to 1.60%, while Al2O3 was reduced from 7.17% to 6.95%. SEM images showed the changes in the surface morphology of RCSA and CSDA, while FTIR spectra identified the changes in the key functional groups present in the samples. The study showed that CS and its digestate could serve as profitable renewable feedstocks for bioenergy production and bio-based chemicals like silica.
 Keywords: Anaerobic Digestion; Biogas; Biosilica; Corn Stover; Digestate; Calorific Value

Glycerol-assisted one-step instant catapult steam explosion enhances enzymatic digestibility of corn stover

Glycerol-assisted one-step instant catapult steam explosion (ICSE) was studied for corn stover pretreatment. Glycerol addition reduced lignin content from ∼32 % to ∼24 % in pretreated solid residues with a stover/glycerol ratio from 1:0.0 to 1:2.0. Glycerol addition might help to reduce the formation of pseudo-lignin with the reduction of the total lignin recovered in pretreated solid residue from 114 % (possibly because of pseudo-lignin contribution) to 81 %. Furthermore, atomic forced microscopy analysis showed that glycerol addition improved surface roughness of pretreated corn stover. Moreover, it was proposed that glycerol-assisted ICSE likely led to the reactions of glycerol with lignin and lignin-derivatives through α-etherification and γ-esterification, preserving lignin internal β-O-4 linkages and preventing lignin condensation. Finally, enzymatic hydrolysis of corn stover pretreated by glycerol-assisted ICSE at a stover/glycerol ratio of 1:1 led to a glucan digestibility in solid residues of 98.4 % and a glucose yield of 79.3 %, which were 27.9 % and 44.7 % higher than those without glycerol addition, respectively.

Solid-state fermentation with Pleurotus ostreatus improves the nutritive value of corn stover-kudzu biomass.

A batch culture technique was used to evaluate dry matter (DM) digestibility of corn stover (Zea mays L.) and kudzu, Pueraria montana (Lour.) Merr. after solid-state fermentation (SSF) with a white-rot fungus, Pleurotus ostreatus (Jacq. ex Fr.) P. Kumm. Five dietary treatments consisting of mixtures of corn stover (C) and kudzu (K) in varying ratios, (1) 100C:0K, (2) 75C:25K, (3) 50C:50K, (4) 25C:75K, and (5) 0C:100K, were inoculated with P. ostreatus (MBFBL 400) and subjected to SSF for 0, 35, and 77days. The study was arranged as a 5 × 3 factorial design with 3 replicates. Grass hay was included in the study as a control. Interactions (P < 0.05) between treatments and fermentation time were noted for the fermentation kinetics. Asymptotic gas was the highest (P < 0.05) for 0C:100K and 100C:0K on day 77. Treatment effect (P < 0.001) and treatment × fermentation time interaction (P < 0.001) were noted for in vitro dry matter digestibility (IVDMD). On day 77, treatment 4 had the highest (P < 0.001) IVDMD value, while treatment 1 had the lowest (P < 0.001) IVDMD. There was no difference (P > 0.05) between treatments 3, 5, and control. Numerically, the ranking of their IVDMD values from the highest to the lowest is 4 > 2 > 5 > control >3 > 1. The results show that the treated corn stover and kudzu mixes were comparable with the control, which is good quality hay. This is the first report that demonstrates the potential use of a combined mixture of corn stover and kudzu in ruminant animal feed development.

Innovative hydrolysis of corn stover biowaste by modified magnetite laccase immobilized nanoparticles

Intensive studies have been performed on the improvement of bioethanol production by transformation of lignocellulose biomass. In this study, the digestibility of corn stover was dramatically improved by using laccase immobilized on Cu2+ modified recyclable magnetite nanoparticles, Fe3O4–NH2. After digestion, the laccase was efficiently separated from slurry. The degradation rate of lignin reached 40.76%, and the subsequent cellulose conversion rate 38.37% for 72 h at 35 °C with cellulase at 50 U g−1 of corn stover. Compared to those of free and inactivated mode, the immobilized laccase pre-treatment increased subsequent cellulose conversion rates by 23.98% and 23.34%, respectively. Moreover, the reusability of immobilized laccase activity remained 50% after 6 cycles. The storage and thermal stability of the fixed laccase enhanced by 70% and 24.1% compared to those of free laccase at 65 °C, pH 4.5, respectively. At pH 10.5, it exhibited 16.3% more activities than its free mode at 35 °C. Our study provides a new avenue for improving the production of bioethanol with immobilized laccase for delignification using corn stover as the starting material.

Steam Refining with Subsequent Alkaline Lignin Extraction as an Alternative Pretreatment Method to Enhance the Enzymatic Digestibility of Corn Stover

Agricultural residues are promising and abundant feedstocks for the production of monomeric carbohydrates, which can be gained after pretreatment and enzymatic hydrolysis. These monomeric carbohydrates can be fermented to platform chemicals, like ethanol or succinic acid. Due to its high availability, corn stover is a feedstock of special interest in such considerations. The natural recalcitrance of lignocellulosic material against degradation necessitates a pretreatment before the enzymatic hydrolysis. In the present study, a novel combination of steam refining and alkaline lignin extraction was tested as a pretreatment process for corn stover. This combination combines the enhancement of the enzymatic hydrolysis and steam refining lignin can be gained for further utilization. Afterward, the obtained yields after enzymatic hydrolysis were compared with those after steam refining without alkaline extraction. After steam refining at temperatures between 160 °C and 210 °C and subsequent enzymatic hydrolysis with Cellic® CTec2, it was possible to enhance the digestibility of corn stover and to achieve 65.4% of the available carbohydrates at the lowest up to 89% at the highest conditions as monomers after enzymatic hydrolysis. Furthermore, the enzymatic degradation could be optimized with a subsequent alkaline lignin extraction, especially at low severities under three. After this combined pretreatment, it was possible to enhance the enzymatic digestibility and to achieve up to 106.4% of the available carbohydrates at the lowest conditions and up to 102.2% at the highest temperature as monomers after following enzymatic hydrolysis, compared to analytical acid hydrolysis. Regarding the utilization of the arising lignin after extraction, the lignin was characterized with regard to the molar mass and carbohydrate impurities. In this context, it was found that higher amounts and higher purities of lignin can be attained after pretreatment at severities higher than four.