Search Results (198)

Agricultural production residues are an easily accessible raw material for energy recovery in a circular economy. Therefore, the possibility of biogas production from herb processing waste, namely common thyme (Thymus vulgaris L.), peppermint (Mentha × piperita L.), curled mint (Mentha crispa L.), and currants (woody stems and leaves), was investigated. In this study, the evaluation of the natural biodegradability of plant waste under conditions typical for an agricultural biogas plant was consciously carried out without the application of pre-treatment processes (shredding, steam hydrolysis, chemical treatment) to facilitate the methane fermentation process. The average values of biogas production efficiency ranged from 75 to 320 m³/mg DM for herb species and from 152 to 209 m³/mg DM for currant varieties under normal conditions. As part of laboratory tests, the elemental composition, i.e., C, H, N, S, O, was determined. Moreover, the analysis showed the energy potential of the tested waste in thermochemical processes (combustion). Garden thyme residues have particularly high energy potential, as indicated by the high calorific value, low nitrogen and sulfur content, and low ash content. Full article

Pellets produced from raw or torrefied shredded logging residues have been investigated in the study. The research material came from pine and spruce stands in Poland, Slovakia, Czechia and Hungary. Torrefaction temperatures (T_t) of 250, 300, and 400 °C were applied. Before pressure agglomeration, 3% wheat flour was added to the torrefaction material as a binding agent. Pellets with a diameter of 8 mm were produced at constant humidity, compaction pressure (P) of 140 or 180 MPa and agglomeration temperature (T_a) of 100, 120 or 140 °C. The produced pellets were assessed for their physicomechanical parameters (density, radial compressive strength, compression ratio, modulus of elasticity), chemical parameters (extractive compounds, cellulose, lignin) and energy parameters (ash content, elemental composition, calorific value). The results were subjected to basic statistical analysis and multi-way ANOVA. The produced pellets varied in physical, mechanical, chemical and energy properties. A significant effect of torrefaction temperature, agglomeration temperature and compaction pressure on the results was observed. In terms of physicomechanical parameters, the best pellets were produced from the raw material, while in terms of energy parameters, those produced from the torrefied material were superior. Pellets of satisfactory quality produced from torrefied logging residues could be obtained at T_t = 250 °C, T_a = 120 °C and P = 180 MPa. Pellets with specific density of approximately 1.1 g·cm⁻³, radial compressive strength of 3–3.5 MPa, modulus of elasticity of 60–80 MPa and calorific value of 20.3–23.8 MJ·kg⁻¹ were produced in the process. Full article

The present study investigates the potential of poplar (Populus spp.) biomass from phytoremediation plantations as a feedstock for downdraft fixed bed gasification. The biomass was characterized in terms of moisture, ash content, elemental composition (C, H, N, O), and calorific values (HHV and LHV), confirming its suitability for thermochemical conversion. Gasification tests yielded a volumetric syngas production of 1.79 Nm³ kg⁻¹ biomass with an average composition of H₂ 14.58 vol%, CO 16.68 vol%, and CH₄ 4.74 vol%, demonstrating energy content appropriate for both thermal and chemical applications. Alkali and alkaline earth metals (AAEM), particularly Ca (273 mg kg⁻¹) and Mg (731 mg kg⁻¹), naturally present enhanced tar reforming and promoted reactive gas formation, whereas heavy metals such as Cd (0.27 mg kg⁻¹), Pb (0.02 mg kg⁻¹), and Bi (0.01 mg kg⁻¹) were detected only in trace amounts, posing minimal environmental risk. The results indicate that poplar pruning residues from phytoremediation sites can be a renewable and sustainable energy resource, transforming a waste stream into a process input. In this perspective, the integration of soil remediation with syngas production constitutes a tangible model of circular economy, based on the efficient use of resources through the synergy between environmental remediation and the valorization and sustainable management of marginal biomass—i.e., pruning residues—generating environmental, energetic, and economic benefits along the entire value chain. Full article

For the first time, Eriolobus trilobatus bark from Turkey has been characterized in terms of its chemical, extractive, fuel, and ash characteristics using SEM–EDS, wet chemical analysis, phenolic analysis, FT-IR, TGA, XRF, XRD, BET surface area measurement, proximate analysis, and ash fusion temperature (AFT) determination. The results showed that the bark contains 13% ash, dominated by calcium oxalate, and 15% extractives, largely composed of polar phenolic compounds with moderate radical-scavenging potential. Thermal decomposition of bark proceeds in four distinct stages, associated with the sequential degradation of extractives/hemicelluloses, cellulose, lignin/suberin, and inorganic fractions. The higher calorific value of 14.9 MJ/kg indicates moderate fuel quality compared with conventional woody biomass. Ash is mesoporous with a CaO-rich structure highly suitable for catalytic applications in biodiesel production and biomass gasification. Ash fusion analysis revealed a high flow temperature (1452 °C), indicating a very low slagging risk during thermochemical conversion. Overall, E. trilobatus bark is a promising material for value-added biorefinery pathways, enabling processes for the production of biochars, CaO-based catalysts, phenolic extracts, and sustainable energy. The valorization of E. trilobatus bark not only enhances the economic potential of forestry residues but also provides environmental co-benefits through carbon soil amendment and landscape applications. Full article

In order to expand the raw material base of lignocellulosic briquettes, and due to the shortage of wood materials, the use of lignocellulosic residues from the agricultural sector (such as hemp waste) became the main objective of this research. In order to state the significant differences between these briquettes, the lignocellulosic briquettes were obtained from hemp core waste and oak sawdust on the same hydraulic briquetting installation. The main properties of the two categories of briquettes were determined; we obtained a bulk density of about 450 kg/m³ for hemp core waste and 530 kg/m³ for oak sawdust. Also, the calorific values of the two categories of materials were about 18.2 MJ/kg and 17.5 MJ/kg, high calorific values (HCV) for hemp core waste/oak sawdust, and the calcined ash content was 5.8% for hemp and 0.8% for oak sawdust briquettes. As a general conclusion, through their physical–mechanical, calorific and chemical properties, it can be stated that the remains of the core obtained when obtaining hemp fibers can be used successfully to make fuel briquettes. Full article

The growing amount of waste worldwide requires new solutions for its management. Agricultural by-products account for almost 10% of the waste generated. One of them is sheep wool, a natural fibre with beneficial physicochemical properties. Currently, sheep wool production amounts to approximately 1–2 million tonnes per year, of which 60% is used in the manufacture of clothing. Nevertheless, it poses a considerable challenge in terms of disposal due to its keratin-rich composition and slow biodegradability. This review analyses the chemical and physical properties of sheep wool and assesses its potential as biomass based on its carbon content and other elemental components. This allows us to provide a critical comparative analysis of the main technological pathways for the use of waste sheep wool as biomass, including anaerobic digestion, pyrolysis, direct combustion and gasification. The review highlights both the opportunities and limitations of these processes, comparing sheep wool in terms of energy potential and carbon footprint with other biomass. The review shows that the calorific value of sheep wool (19.5 MJ/kg) is competitive with traditional plant-based biofuels and the use of waste sheep wool as biomass source can contribute to reduction in CO₂ emissions of 2.1 million tonnes per year. The use of sheep wool as biomass can not only contribute to waste reduction but also supports the goals of sustainable agriculture and climate neutrality. The selected methods may offer a new and effective way of reducing waste and allow all sheep wool produced to be introduced into the circular economy. Full article

Agricultural residues such as maize byproducts and discarded cocopeat substrates are abundant but underutilised biomass resources. Improving their fuel quality requires densification, such as pelletisation, combined with thermochemical upgrading. In this study, pellets were prepared by blending cocopeat and maize residues at weight ratios of 9:1, 7:3, and 5:5, followed by torrefaction at 220, 250, and 280 °C. Their fuel characteristics were evaluated through mass yield, elemental and proximate analyses, chemical composition, calorific value, combustion indices, and grindability. Results showed that increasing maize residue content reduced ash and fuel ratio but increased volatile matter, while cocopeat-rich pellets provided higher fixed carbon and lignin contents, improving thermal stability. Torrefaction significantly enhanced calorific value (up to 21.83 MJ/kg) and grindability, while increasing aromaticity. However, higher torrefaction severity decreased the combustibility index but improved volatile ignitability, indicating a trade-off between ignition behaviour and stable combustion. An optimal balance was observed at 250 °C, where energy yield and combustion performance were maximised. This study demonstrates the feasibility of valorising discarded cocopeat substrates, blended with maize residues, into renewable solid fuels, and provides practical guidance for optimising blending ratios and torrefaction conditions in waste-to-energy applications. Full article

High-temperature corrosion is a frequently observed phenomenon in waste incineration facilities. Municipal solid waste presents substantial corrosion potential attributed to elevated chlorine content and significant inhomogeneity in calorific value and chemical composition, rendering stable plant operation and corrosion control challenging. Conventional countermeasures, such as cladding or reduced steam parameters, lack temporal resolution and incur substantial costs or reduced efficiency. For this study, a waste incineration plant was equipped with an online corrosion monitoring system featuring ten sensors distributed across three vertical boiler passes. The system employs an electrochemical measurement principle to enable the detection of corrosion with temporal resolution. The recorded data reveals decreasing corrosion attack and increasingly stable deposits along the flue gas path. Combined with the temperature measurements, the sensor data proves the effectiveness of the shower cleaning in the third pass and confirms successful removal of the deposits. Statistical analysis shows a correlation between CO content and sensor data, while other parameters (e.g., steam flow, flue gas temperatures) exhibit no conclusive correlations, emphasizing the system’s added value. Chemical analysis of the electrodes and deposits reveal significant indications of chlorine and sulfur, suggesting chlorine-catalyzed active oxidation as the predominant corrosion mechanism. Full article

The paper presents an analysis of methods for utilizing digestate for energy purposes from two different biogas plants using different technologies. Biogas plant A used only cattle manure and corn silage as substrates, while biogas plant B used technology based on the utilization of food production waste. The analysis showed differences in the chemical, elemental, and thermogravimetric composition of both types of digestate. An analysis of the energy inputs required to produce fuel from digestate was also performed, along with energy balance calculations. The research and analysis led to the conclusion that both types of digestate are suitable for energy recovery. The possibilities of optimizing the process using excess heat from the biogas plant were also analyzed. In the case of digestate A, the combustion heat of digestate B was 17.20 MJ·kg⁻¹, while for digestate A, it was 14.80 MJ·kg⁻¹. The calorific value of digestate A at 8.79% moisture content was 13.40 MJ·kg⁻¹, while for digestate B at 6.03% moisture content, it was 15.80 MJ·kg⁻¹, respectively. Full article

In the current study, lavender plant (Lavandula angustifolia Mill.) waste, as obtained after the essential oils steam distillation process as well as lignocellulose biomass of two of the most common pine species (Pinus nigra L., Pinus brutia L.), was characterized in terms of chemical composition, moisture, ash content, and calorific value, in order of its potential to be used as feedstock material in pellets production to be assessed, studying different materials ratios. The lavender material was introduced at low percentages (0, 5, 10 and 15% w/w) in the feedstock of pellets, in order to maintain the total ash content of the mixed feedstock as adequately low-lying, ensuring the classification of pellets in qualitative categories of A1, A2 and B (residential uses, ENplus). The resultant lavender–pine mixed syntheses were densified in a multi-mold pelletizing machine and the pellets were characterized with regard to physical, morphological, mechanical, hygroscopic, and thermal characteristics, based on the limits set by the respective ENplus standards as benchmarks. The results demonstrated that although lavender waste has a high content of ash and extractives compared to wood, it can be used in a mixture (<15% lavender percentage) with pure wood material to produce pellets of adequate quality for residential use. The lavender waste presence favored pellets’ mechanical strength, dimensions, hydrophobicity, dimensional stability, bulk density (marginally) and resultant quality of the pellets. Lavender slightly decreased the calorific value of pellets, though without recording a significant adverse impact. The lavender material mixed with black pinewood (at 15%) revealed the best pellets’ feedstock performance. The findings exhibited that lavender lignocellulosic residues are suitable for producing high-performance residential pellets, provided that the lavender content does not exceed 15% of the feedstock. Full article

This study aimed to assess the physical, chemical, and combustion properties of pellets made from corncob and rice husk residues sourced in Sucre, Colombia, and to evaluate the performance of different blending ratios. Before pelletization, the residues were ground and processed using a small-scale flat die pellet mill equipped with a 6 mm die. Physical properties were evaluated according to ISO standards for particle density, bulk density, and impact resistance assessment. Proximate and ultimate analyses, as well as heating values, were determined and compared against the ISO 17225-6:2021 classification for herbaceous biomass. The 70:30 corncob-to-rice husk blend (CC70:RH30) showed good quality, with 7.23% ash, 9.18% moisture, and an LHV of 15.19 MJ/kg, meeting the criteria for Class B pellets. Combustion performance was assessed using a custom-designed macro-TGA, revealing that co-pelletized blends exhibited improved ignition temperatures and comprehensive combustion indices compared to the individual feedstocks. Additionally, calorific values were proportional to the blending ratios. In summary, controlling the blending ratio of corncob and rice husk residues during pellet production allows modulation of both the total ash content and the lower heating value of the resulting solid biofuels, making them more suitable for thermochemical conversion routes such as combustion and/or gasification. Full article

The modern world has brought extensive socioeconomic and ecological changes. Urbanization in developing nations has significantly increased municipal solid waste, necessitating in-depth understanding of waste composition particularly in developing nations for sustainable management practices. This study aimed to classify and characterize waste while evaluating potential waste management methods. Mixed methods were used to examine landfilled waste from Soshanguve and Hatherley sites in Tshwane Metropolitan, South Africa, using techniques such as Fourier transform infrared spectroscopy, X-ray fluorescence, proximate, and ultimate analysis. Seasonal variations in waste components were analysed over two seasons. The study identified that both sites are predominantly composed of organic waste, accounting for over 42 wt.%, with moisture content of ~50 wt.%, and minimal recyclables (<5 wt.%). Seasonal variations in MSW were significant for glass (<4% increase), organic waste (<5% increase), while plastic decreased by ~7% during spring. The biodegradable waste showed high carbon (>50%) and oxygen (>40%) levels, low ash content (<18%), and calorific values of 15–19 MJ/kg. Biodegradables mainly contained oxides of calcium, silicon, iron (III), and potassium with chemical composition indicating functional groups that emphasize composting and energy recovery benefits. The research provides insights into sustainable waste management, revealing waste composition at Tshwane landfills, aiding informed decision-making for resource usage and environmental conservation. Full article

The growing interest in alternative fuels stems from the need to reduce greenhouse gas emissions and promote sustainable development. Despite the dominance of fossil fuels in aviation, pulsejet engines offer a promising platform for testing new fuels due to their simple design and fuel versatility. This study presents a multi-criteria analysis of alternative fuels for use in pulsejet engines, emphasizing environmental impacts. Both gaseous (biogas, ethyne, LPG, and natural gas) and liquid fuels (methanol, ethanol, biodiesel, Jet A-1, and SAF) were examined. Exhaust emissions (CO₂, H₂O, CO) were simulated in Ansys 2025 based on literature data and chemical calculations. Additional factors analyzed included calorific value, production cost, thermal expansion, density, life cycle emissions (LCA), CO₂ emissions per fuel mass, and renewable energy content. Using the zero-unitization method, results were normalized into a single aggregate variable for each fuel. The highest values were recorded for biogas and methanol, respectively, indicating their potential as alternative fuels. The findings support further development of sustainable fuels for pulsejet engines. Future research should address combustion optimization and noise reduction, enhancing viability in aviation and other transport sectors. Integration with the current fuel infrastructure is also recommended to facilitate broader implementation. Full article

White mulberry (Morus alba L.) is a tree growing up to 15 m in height. It is a plant whose cultivation is historically associated with silk production. Mulberry leaves are the only food source of the mulberry silkworm caterpillars (Bombyx mori L.). The cultivation of this tree has recently gained renewed importance. Due to the content of numerous bioactive substances, mulberry is a valuable raw material for the food, pharmaceutical and herbal industries. This article presents the results of tests on pellets from 1-, 3- and 5-year-old branches, which are waste biomass remaining after pruning mulberry shrubs cultivated to obtain leaves to feed silkworms. Additionally, analyses of pellets from mulberry leaves were also carried out. For the specified mulberry biomass yield, analyses of chemical composition of mulberry biomass (branches and leaves) were carried out, and energy properties (heat of combustion and calorific value) and energy potential were calculated. The heat of combustion of pellet from mulberry branches was, on average, 19,266 MJ∙Mg⁻¹, and the calorific value was 17,726 MJ∙Mg⁻¹. The energy potential, on the other hand, was, on average, 159 GJ∙ha⁻¹ and 44 MWh∙ha⁻¹. The obtained results indicate the possibility of the effective use of mulberry branches after the annual pruning of bushes in plantations for energy purposes. Full article

Traditional coal quality assessment methods rely exclusively on the laboratory testing of physical samples, which impedes detailed stratigraphic evaluation and limits the integration of intelligent precision mining technologies. To resolve this challenge, this study investigates geophysical logging as an innovative method for coal quality prediction. By integrating scanning electron microscopy (SEM), X-ray analysis, and optical microscopy with interdisciplinary methodologies spanning mathematics, mineralogy, and applied geophysics, this research analyzes the coal quality and mineral composition of the Shanxi Formation coal seams in northern Jiangsu, China. A predictive model linking geophysical logging responses to coal quality parameters was established to delineate relationships between subsurface geophysical data and material properties. The results demonstrate that the Shanxi Formation coals are gas coal (a medium-metamorphic bituminous subclass) characterized by low sulfur content, low ash yield, low fixed carbon, high volatile matter, and high calorific value. Mineralogical analysis identifies calcite, pyrite, and clay minerals as the dominant constituents. Pyrite occurs in diverse microscopic forms, including euhedral and semi-euhedral fine grains, fissure-filling aggregates, irregular blocky structures, framboidal clusters, and disseminated particles. Systematic relationships were observed between logging parameters and coal quality: moisture, ash content, and volatile matter exhibit an initial decrease, followed by an increase with rising apparent resistivity (LLD) and bulk density (DEN). Conversely, fixed carbon and calorific value display an inverse trend, peaking at intermediate LLD/DEN values before declining. Total sulfur increases with density up to a threshold before decreasing, while showing a concave upward relationship with resistivity. Negative correlations exist between moisture, fixed carbon, calorific value lateral resistivity (LLS), natural gamma (GR), short-spaced gamma-gamma (SSGG), and acoustic transit time (AC). In contrast, ash yield, volatile matter, and total sulfur correlate positively with these logging parameters. These trends are governed by coalification processes, lithotype composition, reservoir physical properties, and the types and mass fractions of minerals. Validation through independent two-sample t-tests confirms the feasibility of the neural network model for predicting coal quality parameters from geophysical logging data. The predictive model provides technical and theoretical support for advancing intelligent coal mining practices and optimizing efficiency in coal chemical industries, enabling real-time subsurface characterization to facilitate precision resource extraction. Full article