BioEnergy Research最新文献

Biomass gasification is an established and widely utilized renewable energy system. The research work aims to develop and construct a downdraft gasifier to investigate gasifier performance. The gasifier’s performance and cold gas efficiency were calculated for three volumetric airflow rates: 7.16 m³/h, 5.97 m³/h, and 4.78 m³/h. The efficiency was found maximum of 69.6% for an airflow rate of 7.16 m³/h. The oxidation zone and neck region of the gasifier reactor had the maximum recorded temperatures of 845 °C and 823 °C for Swietenia macrophylla (SM) and Mangifera indica (MI), respectively. A two-dimensional computational fluid dynamics (CFD) model for a downdraft gasifier was also developed using ANSYS/FLUENT software. The simulation results provided valuable insights into thermal characteristics and the gasification process taking place inside the gasifier. Taking into account the introduction of wood at a rate of 6.2 kg/h and the flow of air at a rate of 7.16 m³/h, predictions were made about the composition of syngas, and subsequently, validation of the model was conducted with experimental data. The simulation study visually represents the gasification process, illustrating the distribution of velocity and the contours of carbon monoxide, carbon dioxide, and hydrogen within the gasifier.

Two two-step transesterification processes are presented for biodiesel (BD) production from 300 t/d unused low-grade oil (LGO) with 24.5 wt% of free fatty acid (FFA). Acid-catalyzed (case 1) and enzymatic (case 2) esterifications were used for FFA reduction. The FFA in LGO was converted into fatty acid methyl esters (FAME) by H₂SO₄-catalyzed esterification (case 1) or transformed into sodium salts (soap) via a neutralization reaction with NaOH (case 2). In case 2, FFA was separated from soap and transformed into monoesters via enzymatic esterification. The two de-acidification processes decreased the FFA content of LGO to 0.5 wt%, enabling the production of 294 t-BD/d through subsequent alkali-catalyzed transesterification. Case 2, using an enzyme, was proposed to reduce the concentration of H₂SO₄, resulting in less corrosion to downstream equipment. The total production cost of case 2 ($62 million/y) was 32% higher than that of case 1 ($47 million/y) because of the greater consumption of CH₃OH, H₂SO₄, NaOH, and enzyme during FFA reduction. The total capital investment for case 2 ($41 million) exceeded that of case 1 ($31 million). Consequently, the minimum fuel selling price of case 2 (0.58 $/kg-BD) is higher than that of case 1 (0.42 $/kg-BD). The net CO₂ emissions reduction of the produced BD is 2.47 kg-CO₂/kg-BD for case 1 and 2.34 kg-CO₂/kg-BD for case 2. Given the variability in the acidity and composition of the feedstocks, future studies should include comparative economic and environmental analyses of various raw materials.

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Coffee silver skin, an organic residue from coffee production, demonstrates low solid fuel characteristics such as low bulk density and heating value, necessitating enhancements for solid fuel applications. Torrefaction in a flue gas environment (5% O₂, 15% CO₂, and a balance of N₂, v/v) is more energy-efficient than inert torrefaction, using recovered flue gas to improve fuel quality and process efficiency. Three input factors were assessed: temperature (200, 250, and 300 °C), residence time (30, 45, and 60 min), and gas media (N₂ and flue gas). Four performance metrics were evaluated: energy yield, upgrading energy index, specific energy consumption, and energy-mass co-benefit. Temperature significantly influenced most outcomes, except for energy-mass co-benefit, which was medium-dependent. Optimal torrefaction conditions achieving maximum energy yield (71.48%) and energy-mass co-benefit (5.30%) were identified at 200 °C for 30 min with flue gas. The torrefied material’s properties include moisture content, volatile matter, fixed carbon, and ash content of 3.03%, 69.24%, 27.04%, and 1.01%, respectively. Furthermore, the hydrophobicity of pelletized coffee silver skin notably increased under flue gas conditions, evident by a contact angle greater than 100°, indicating that flue gas torrefaction is a feasible approach for producing high-grade solid fuel.

This study presents the performance of NaOH-catalized ethanolic organosolv pretreatment on guava seed cake (waste industrially generated after oil extraction process of guava seed) aiming to extract hemicellulose and lignin. The pretreatment assessment also included cellulose conversion to glucose by enzymatic hydrolysis. The pretreatment used NaOH 10 and 60% (m/m), temperatures of 120 and 170 °C, and ethanolic aqueous solution concentrations of 30 and 70%. NaOH concentration was the most significant factor in the extraction yield of hemicelluloses, and the temperature was the most significant in the lignin extraction and cellulose conversion to glucose. At 170 °C, ethanolic aqueous solution concentration of 30%, and NaOH concentration of 60%, the highest yield of extracted hemicellulose was 97.3%. The maximum extraction of lignin (45%) was reached at 170 °C, ethanol aqueous solution concentration of 70%, and NaOH concentration of 60%. The best cellulose conversion to glucose (50.3%) was obtained with material pretreated at 170 °C, ethanol aqueous solution concentration of 30%, and NaOH concentration of 60%. The extracted hemicelluloses presented low molecular weight (14.7–59.3 kDa), and, according to qualitative chemical analysis, the extracted hemicelluloses and lignin showed great correspondence with the commercial ones.

The aviation sector plays a vital role in global transportation, economic growth, and social integration. However, its rapid expansion has led to increased emissions. Sustainable aviation fuel (SAF) provides a promising solution by offering a clean-burning, renewable alternative to conventional jet fuel. SAF can be produced through various processes and feedstocks, significantly reducing the aviation industry’s environmental footprint. Fast pyrolysis (FP) presents a cost-effective and scalable approach for SAF production due to its low-cost feedstocks, rapid reaction times, and simpler technology. However, estimating the economic viability of FP for SAF production is complex and labor-intensive, requiring detailed process models and numerous assumptions. Furthermore, determining the relationship between feedstock properties and the minimum selling price (MSP) of the fuel can be challenging. To address these challenges, this study developed a data-driven framework for the preliminary estimation of SAF's MSP from FP. Synthetic data was generated using Generative Adversarial Networks (GAN) and Variational Autoencoders (VAE), and hyperparameter optimization was performed using Grid Search to enhance model accuracy and predictions. Five surrogate models were evaluated: linear regression, gradient boost regression (GBR), random forest (RF), extreme boost regression (XGBoost), and elastic net. Among these, GBR and RF showed the most promise, based on metrics such as R², RMSE, and MAE for both original and synthetic datasets. Specifically, GBR achieved a Train R² of 0.9999 and a Test R² of 0.9277, while RF recorded Train and Test R² scores of 0.9789 and 0.9255, respectively. The use of data from the VAE further improved model accuracy. Additionally, a publicly accessible graphical user interface was developed, enabling researchers to estimate the MSP of SAF based on biomass properties, plant capacity, and location.

Lignocellulosic biomass has diverse applications in bioenergy, biochemical, and biomaterial production. Enhancing these processes through pretreatment to obtain cellulose-rich material (CRM) using low transition temperature mixtures (LTTMs) is crucial. This study explores the impact of biomass type, LTTMs type, and heating methods on biomass pretreatment. Choline derivatives combined with glycerol were used for pretreatment of corncob, giant Juncao grass, and inflorescence hemp. Microwave irradiation heating was compared to conventional heating at 90 °C and 150 °C, with residence times of 5 and 10 min. The study demonstrated efficient breakdown of lignocellulosic structures to obtain CRMs. Corncob showed high-efficiency pretreatment with a 153% increase in cellulose content and 27% lignin removal. Pretreatment with LTTMs effectively increased cellulose content and delignification. The impact of different choline derivatives (ChCl, ChOAc, ChOH) was evident, with extraction efficiency influenced by anion type in the order OH⁻ > OAc⁻ > Cl⁻. The ChOH pretreatment increased cellulose content by 157% and lignin removal by 56%. Microwave-assisted heating surpassed conventional heating in lignocellulosic fractionation, achieving higher cellulose content and effective lignin removal. Microwave heating increased cellulose content by 343% and lignin removal by 82% at 150 °C, which was three times more than conventional heating, with a reaction time of 10 min compared to 720 min. Temperature and residence time were critical in lignin removal. The process allowed for the preservation of hemicellulose at lower temperatures or its extraction at higher temperatures.

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During the anaerobic digestion (AD) of food waste, the deliberate secession of substrate rapidly increases the microbial cell population, which can reach a maximum in 2–3 d. During short-term resting (STR), an increase in free NH₃ due to an increase in pH is a key inhibitor of cell proliferation; therefore, cell growth would be further promoted if free NH₃ was reduced. To explore adopting an STR technique to increase microbial cells in the AD of organic waste, we attempted to reduce free NH₃ by controlling the pH in the reactors. Two semi-continuously treated reactors were fed with food waste at a loading rate of 3.0 g-VS/L/d for 40 days and then the feeding was stopped in both reactors until day 47. One of the reactors was maintained at pH 7.37 ± 0.03, whereas pH was not controlled in the other. During STR, the cell density in the pH-controlled condition reached a maximum of 7.48 × 10¹⁰ cells/mL, which was twice as high as that before STR, and 1.7-times higher than that in the non-pH-controlled condition. These results demonstrated that mitigating NH₃ using pH can affect cell proliferation during STR.

The current study employs a tri-culture system, involving Trichoderma reesei and Penicillium janthinellum for cellulase production followed by the utilization of Saccharomyces cerevisiae for bioethanol production using pretreated rice straw as substrate. The fungal co-culture resulted in the production of maximum cellulase enzyme with the following activities: FPase, 1.09 IU/mL; CMCase, 24.47 IU/mL; beta-glucosidase, 4.74 IU/mL; and xylanase, 36.74 IU/mL respectively. Furthermore, the current work also represents a lesser studied aspect, concomitant biodetoxification, and cellulase production. Both T. reesei and P. janthinellum were able to metabolize the acid pretreatment by-products such as formic acid, acetic acid, HMF, and furfural. By implementing a cyclic shifting of temperature strategy, a maximum bioethanol titer of 17.05 g/L with a productivity of 0.405 g/(L × h) was achieved using the tri-culture system. This represents a 3.7-fold improvement compared to the SSF process conducted at the mutual optimum incubation temperature of 37 °C. This study presents a scope for a one-step process for fungal cellulase production and biodetoxification of the lignocellulose pretreated hydrolysate to avail an inhibitor-free medium for subsequent yeast co-culture for bioethanol production.

In this work, biochar was synthesized by carbonizing spent coffee grounds by conducting oxygen-limited pyrolysis in a muffle furnace. Six varieties of biochar have been synthesized at 550 ℃ and 750 ℃ with a ramp rate of 10 ℃/min and carbonization time of 120 min. Acid- and alkali-activated biochars were produced by carbonizing the activated biomass at 550 ℃ and 750 ℃. ZnCl₂ and KOH were used as activating agents for acid and alkali activation, respectively. All the synthesized biochar yield was recorded as 40–60 wt% of the biomass weight. BET surface area increased significantly after activation and the values varied between 1.01 and 720.52 m²/g. The process of chemical activation has resulted in increased BET surface area in comparison with the pristine biochar. Other characterizations include FESEM analysis, elemental analysis through EDX, FTIR, UV–visible spectroscopy, XRD analysis, TGA, and Raman spectroscopy. Raman spectra and UV–visible spectra of activated samples revealed a higher graphitic quality and absorbance, respectively, whereas XRD analysis demonstrated the changes in structural phases. Activated carbon based on spent coffee grounds has displayed higher thermal stability and better surface chemistry than pristine biochar, enabling its application in various domains that foster circular economy.

As carbon dioxide (CO₂) emissions rapidly increase, alternative strategies are needed to capture and mitigate carbon dioxide using microorganisms. To enhance CO₂ fixation and biomass production in microalgae, achieving the optimum concentration of dissolved carbon in the culture medium is essential. This study focuses on enhancing biomass production and CO₂ biofixation efficiency in Chlorella sp. BRE5 by increasing dissolved inorganic carbon (DIC) through the strategic use of sodium hydroxide (NaOH) and CO₂. Under shake flask study, the highest specific growth rate of 0.195 day⁻¹, biomass productivity of 123.2 mg/L/day, and CO₂ biofixation rate of 231.6 mg/L/day were found at NaOH dose of 0.25 g/L with CO₂ (1%, v/v) supplementation. Further, optimized NaOH with different supply strategies of 1% CO₂ was conducted in a photobioreactor (PBR) study. The best result was observed in PBR, where 1% CO₂ strategically sparged (3-day intervals) with optimum NaOH dose. Under this condition, biomass yield, CO₂ consumption rate, lipid productivity, and lipid content were found to be 2.25, 2.25, 4.19, and 1.87 times higher than the control. The outdoor cultivation of microalgae using a DIY bottle bioreactor (DIY BBR) was performed, resulting in less biomass and lipid productivity than that of the PBR study due to uncontrolled environmental conditions. The fatty acid methyl ester (FAME) profile comprised C16-C18 (84.86–90.69%), indicating the suitability for biodiesel production. This strategic supply of combined NaOH and CO₂ enhances DIC in the medium, facilitating both the CO₂ biofixation rate and biomass production.

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