BioEnergy Research最新文献

The energy crisis, climate change, and insufficient waste management practices are compelling factors driving research into sustainable waste-to-resource technologies. Anaerobic digestion, aiming to recover energy and nutrients from organic waste, aligns with the circular economy's principles. This paper provides a comprehensive overview of utilizing biodiesel byproducts for biogas production, exploring techniques for enhancing biogas yield and addressing associated challenges. Assessing the potential of biodiesel byproducts highlights their environmental sustainability and economic viability for biogas production. Non-edible seed cake, rich in nutrients, shows promise for significant biogas yield. Additionally, crude glycerol, easily biodegradable, is identified as a promising co-digester, aiding in digesting recalcitrant substrates. Empirical data reveals remarkable methane yield boosts, ranging from 14 to 226% when co-digesting with crude glycerol. Moreover, the resulting digestate enhances soil fertility, promoting healthier plant growth and productivity. Challenges in anaerobic digestion, such as substrate C/N ratio imbalance and recalcitrance, necessitate strategies like substrate pretreatment and co-digestion with compatible materials to optimize biogas yield. Furthermore, advancements in anaerobic digestion technologies are crucial for effectively converting biodiesel wastes into biogas. Additionally, interdisciplinary investigations, including techno-economic analysis, lifecycle assessment, and sensitivity analysis, are vital to enhance and validate the feasibility of anaerobic digestion for biodiesel byproducts. This review serves as a valuable resource for future utilization of biodiesel byproducts for biogas production.

The study aimed to examine the effects of adding biomass ash on the biochemical processes involved in fermentable sugar production. Corn stover was pretreated using several methods—hot water, dilute acid, alkaline, γ-valerolactone, and ionic liquid methods, each examined with ash loadings of 7.18% and 21.07%. The findings demonstrated that increased ash content adversely affected both pretreatment and enzymatic hydrolysis. Specifically, the total sugar yield was 3 to 16% lower at the higher ash content across all pretreatment methods, and up to 4.01% lower during enzymatic hydrolysis. For acidic pretreatment, the sugar yield decreased as ash content increased. In contrast, ash content had a lesser impact on alkaline pretreatment compared to acidic pretreatment. For example, using corn stover with an ash content as high as 22.65% resulted in only a 2.90% decrease in total sugar yield compared to corn stover without added ash. The primary reasons for the reduced sugar yield in higher ash biomass during acidic pretreatments were likely the neutralizing effect of the ash and decreased acid access to the substrates. During enzymatic hydrolysis, ash reduced the sugar yield by limiting enzyme access to cellulose.

This study investigates the structural and functional transformation of biochar derived from eucalyptus wood powder, rice bran, and bagasse under pyrolysis temperatures of 500 °C, 700 °C, and 900 °C. Using BET, XRD, Raman, FTIR, and particle size analysis, we quantified changes in porosity, crystallinity, and surface chemistry. BET analysis revealed that the highest specific surface area was observed at 500 °C, with eucalyptus biochar achieving 243.2 m²/g. However, at 900 °C, mesopore and macropore formation dominated, with a notable decrease in surface area. XRD and Raman data showed increased graphitization at higher temperatures, with eucalyptus biochar exhibiting the greatest graphitic structure at 900 °C. FTIR results indicated a significant reduction in functional groups at elevated temperatures, enhancing the biochar’s aromatic stability. Resistivity measurements showed a decrease in resistivity, with the resistivity of eucalyptus biochar after 900 °C pyrolysis and ball milling being as low as 0.0196 Ω/cm under 27.3 MPa pressure test, indicating its strong potential in conductive applications. These findings provide quantitative insights into optimizing biochar properties for environmental and energy applications.

This study compared the pyrolysis behaviors of corn stalk (CS) and its torrefied biomass after inert torrefaction (IT), oxidative torrefaction (OT), and wet torrefaction (WT), focused on the kinetic parameters and reaction mechanisms. Inert and oxidative torrefaction reduced volatile matter while increasing ash content and fixed carbon. Wet torrefaction reduced both volatile matter and ash content while increasing fixed carbon. Three pretreatment methods decreased oxygen content, increased carbon content, and had a higher heating value. The materials were pyrolyzed in a thermogravimetric analyzer. For CS, the average activation energy (E) values calculated by the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunosen methods were 62.5 and 60.07 kJ/mol. IT and WT showed increased trend, with values of 81.58, 81.48 kJ/mol and 69.75, 67.58 kJ/mol respectively. Conversely, OT decreased with the E values of 57.39 and 56.2 kJ/mol. Pyrolysis was divided into two stages based on various conversion rates (α) using Malek and Coats–Redfern methods. When α was below 0.5, a one-dimensional diffusion mathematical model described the pyrolysis process. When α was beyond 0.5, the pyrolysis of CS conformed to the cylindrical symmetric three-dimensional diffusion mathematical model, while IT, OT, and WT better fit the spherical symmetric three-dimensional diffusion mathematical model. However, the torrefaction atmosphere’s impact on the pyrolysis kinetic mechanism was limited, exhibiting no alterations in the diffusion model. Different torrefaction samples demonstrated a degree of homogeneity, considering the lower pretreatment temperatures and the economic feasibility of torrefaction atmospheres in oxidative torrefaction, coupled with the lowest activation energy of oxidative torrefaction products indicating more efficient pyrolysis, oxidative torrefaction was recommended as the torrefaction pretreatment process before pyrolysis engineering.

Residual biomass from agriculture is a highly promising resource for sustainable energy production. Its abundant generation and accurate estimation are essential for the development and implementation of efficient utilization strategies. However, the calculations proposed in the existing literature are often contradictory or exhibit impractically wide range. This study compiles residual biomass indices for cereal, oil, industrial, and arboreal crops. By evaluating and processing these indices, a refined set of modified indices is presented to enhance existing methodologies for calculating agricultural residues. The methodology establishes lower, average and upper bound scenarios for the residual biomass of selected crops and is applied to Greece to estimate its energy production potential. The findings suggest that Greece generates approximately 5.5 million tons of agricultural residues annually, ranging from 4.5 million tons (lower-bound) to 6.6 million tons (upper-bound). This biomass has the potential to produce 70,730 TJ of energy, corresponding to 8.4% of the country’s energy demands, with energy potential ranging between 55,644 and 82,635 TJ. The most noteworthy crops include olive trees, cotton, maize, vineyards and wheat since they account for 82% of the total estimated energy. Spatial analysis conducted at NUTS-2 and NUTS-3 levels highlights the Regions of Central Macedonia and Thessaly as having substantial potential for residual biomass to support energy conversion strategies.

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.

Graphical Abstract

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.