Search Results (126)

Biomass pellets and briquettes are commonly treated as compacted solid biofuels, but their potential extends beyond direct combustion and heat generation. This review aims to synthesise current knowledge on pellets and briquettes as both energy carriers and functional materials for agro-environmental, biological, sorption, and material applications. A structured narrative review was conducted using Web of Science, Scopus, and OpenAlex, complemented by targeted searches of standards, life-cycle assessment studies, and recent experimental literature. This review discusses key physicochemical, mechanical, and environmental properties, including density, moisture content, durability, ash content, higher heating value, elemental composition, storage stability, and biodegradability. It also compares major energy pathways, including combustion, combined heat and power, torrefaction, hydrothermal carbonisation, pyrolysis, and gasification, with non-combustion uses such as fertiliser and microbial carriers, sorbents, bedding materials, mushroom substrates, biocomposites, and lightweight building components. Published studies indicate that the environmental performance of densified biomass depends strongly on feedstock origin, drying energy, transport, end-use technology, and system boundaries. The review proposes a quality-to-function framework in which pellet and briquette quality is interpreted in relation to the intended application rather than through a single universal fuel-quality criterion. This approach supports more precise biomass valorisation within circular bioeconomy systems. Full article

When a fuel briquette is pressed using solar electricity in summer and burned for heating in winter, the briquette functions as a seasonal energy store—without batteries, self-discharge, or capital investment in storage infrastructure. This paper quantifies such “indirect energy storage” at an operating briquette production facility in Sumy, Ukraine, using 2024 operational data from a 34 kW hybrid solar power plant integrated into the production process without battery storage under continental climate conditions (50°55′ N) and full-scale military conflict. The objective was to determine the contribution of the solar power plant (SPP) to energy supply, analyse the structure of electricity consumption, and quantify the mechanism of indirect accumulation of renewable energy through transformation into solid biofuels. The study tested two hypotheses: (H1) that integration of a solar power plant into industrial daytime operation (6:00–22:00) achieves a self-consumption rate close to 100%, displacing grid electricity without curtailment or storage losses; and (H2) that the solar fraction embedded in produced briquettes constitutes a quantifiable mechanism of indirect seasonal energy storage despite a temporal mismatch between solar peaks (summer) and product demand (winter). Methods included statistical analysis of monthly and intraday operational data; Pearson correlation analysis between solar generation and production cycles; energy audit of production processes; decomposition of specific consumption into pressing and packaging components; and a simple economic assessment (NPV, IRR, LCOE, payback) with sensitivity analysis. Annual production reached 1222.975 t of briquettes. Total specific electricity consumption (including two short packaging campaigns in June and July only) was 141.3 ± 12.6 kWh/t (CV = 8.9%). After deducting 4962 kWh of dedicated packaging electricity (2.9% of annual consumption), the specific consumption for briquette pressing alone was 136.7 ± 5.0 kWh/t (CV = 3.7%)—within the European benchmark range of 80–150 kWh/t for wood densification, with tight monthly variation indicating a stable, well-tuned pressing operation throughout the year. The SPP supplied 18.3% of total annual electricity, peaking at 33.06% in May and averaging 29.95% from March to August. Intraday analysis of 530 five-minute intervals confirmed a 100% self-consumption rate across all seasons (H1 supported). A total of 223.4 t of briquettes containing accumulated solar energy were produced during the spring–summer period. A weak negative correlation (r = −0.28) between monthly SPP generation and briquette production was observed but did not reach statistical significance (p = 0.385); this descriptive—rather than causal—relationship is consistent with the expected temporal shift between summer surpluses and winter demand, and is itself a signature of indirect rather than direct energy coupling (H2 supported in a descriptive sense). The compound efficiency along the solar-to-stored-fuel chain was estimated at approximately 68%, providing a quantitative indicator for the indirect-storage concept. Economic analysis yielded a simple payback period of about 3 years, NPV (20 yr, 12%) ≈ 1.15 million UAH, IRR ≈ 33%, and LCOE ≈ 3.28 UAH/kWh—61% below the prevailing industrial tariff of 8.45 UAH/kWh—with sensitivity analysis showing positive NPV across ±20% variation in electricity price and ±15% in CAPEX. To the best of the authors’ knowledge, this is the first empirical quantification of biomass-solar integration as a seasonal energy buffer operating without battery storage. The solar energy accumulated in briquettes is sufficient to heat 56–74 households for a full winter season. Regional scaling of the present configuration—under explicit assumptions of comparable facility sizes and operating regimes—could in principle provide fuel for 15,000–20,000 households (8–12% of regional heating needs during energy crises). These findings are directly relevant to post-conflict energy recovery and to regions where attacks on energy infrastructure have left solid biofuels as the primary available heating source. Full article

This research addresses the effects of moisture content, particle size, and compression pressure on the quality of fuel briquettes produced from groundnut shells. The objective is to optimize the briquetting process for quality attributes. Experiments were performed using a prototype briquetting machine with a 3 × 3 × 2 factorial design. The experiments considered moisture (6.48%, 9.63%, and 12.17%), particle sizes (3 mm, 5 mm, and 7 mm), and compression pressure (70 MPa, 140 MPa). Quality attributes measured included density, breaking index, rolling index, water resistance, moisture resistance, and compressive strength. Findings showed optimal processing variables for quality with lower particle sizes (3 mm) and higher levels of pressure (140 MPa). The lowest level of moisture (6.48%) showed optimal mechanical properties, represented by maximum density of 1301.81 kg m⁻³ with maximum mechanical strength of 97.01% fracture resistance and 91.12% rolling resistance. Maximum water resistance of 13.25% was obtained with intermediate values of moisture (9.63%). The data obtained showed that increasing particle size and moisture content negatively affected briquette quality. Groundnut shells possess promise for the production of superior-quality fuel briquettes. This research validates the criticality of optimizing processing variables. This research poses critical challenges regarding scale and environmental effects. Full article

Indonesia, particularly Central Java, generates substantial amounts of agricultural biomass residues, including melinjo shells, tobacco stalks, and cacao shells, which remain underutilized for energy applications. This study addresses the limited scientific evidence on the fuel properties and environmental performance of these residues by systematically evaluating their suitability as briquette feedstocks. A factorial experimental design was applied using three biomass types and two binders (tapioca starch and clay). The produced briquettes were characterized for moisture content, ash content, volatile matter, and higher heating value according to the Indonesian National Standard (SNI 01-6235-2000), and their environmental performance was assessed using a Life Cycle Assessment (LCA) approach to estimate associated environmental costs. The results indicate that briquettes made from melinjo shells with tapioca starch binder exhibited the most favorable performance, achieving a moisture content of 7.01%, ash content of 13.58%, volatile matter of 47.15%, and a calorific value of 5453.43 cal g⁻¹. However, the ash and volatile matter contents exceeded the recommended limits for solid biofuels. These findings demonstrate that melinjo shells are a promising feedstock for briquette production due to their relatively high energy content, while further improvements in carbonization conditions and reductions in binder proportion are required to enhance fuel quality and environmental performance. Full article

The energy utilization of residual woody biomass is a relevant strategy for the decentralized energy transition and local waste management in rural areas. The objective of this study was to characterize (physically, chemically, and energetically) five types of residual biomass: pine branches, huinumo (this material refers to the long, thin pine needles that, after drying and falling, form a layer on the forest floor), cherry branches and leaves, and grass waste generated in the community of San Francisco Pichátaro, Michoacán, Mexico, in order to evaluate its viability for the production of densified solid biofuels. A comprehensive analysis was conducted, including moisture content, higher heating value, proximate characterization, structural chemical analysis (using the Van Soest method), elemental CHONS analysis, ash microanalysis (by ICP-OES), and a multicriteria analysis with normalized energy and compositional indicators. The results showed that huinumo and cherry leaves were the most outstanding biomasses, presenting the highest heating values (20.7 MJ/kg) and low moisture and ash contents. Pine branches obtained the most balanced results, characterized by their equilibrium in fixed carbon and lignin, as well as their low potassium content. The multicriteria analysis showed that there is no absolute optimal biomass; however, it indicates that pine branches and huinumo are the most robust feedstocks for the production of briquettes or pellets. The results confirm the significant technical and environmental potential of local lignocellulosic residues for the production of solid biofuels and for contributing to sustainable energy solutions at the local scale. Full article

The valorization of agro-industrial residues for solid biofuel production represents a sustainable strategy to meet energy demand, reduce open-field burning, and mitigate environmental impacts. This study aimed to assess the feasibility of producing high-quality briquettes from agro-industrial residues such as oregano stems, pecan shells, and peanut shells sourced from a semi-arid region of northern Mexico. Raw materials were obtained from local industries, processed, and characterized through proximate analysis and determination of higher heating value (HHV). Briquettes were manufactured under various compaction pressures and temperatures without the use of binders, and their physical and energy properties were evaluated according to international standards. Results indicated that all briquette types met Class A quality standards, with moisture contents between 6 and 9%, ash contents below 6%, and HHVs ranging from 18.9 to 21.0 MJ kg⁻¹. Pecan shell briquettes exhibited the highest particle density (1.18 g cm⁻³), while peanut shell briquettes demonstrated superior mechanical performance and the highest Impact Resistance Index (97% and 200, respectively). Oregano stem briquettes showed lower densities but maintained satisfactory energy properties (19.5 MJ kg⁻¹). Beyond its energy potential, this valorization approach contributes to local economic development, reduces environmental pollution, and decreases dependence on firewood in rural communities. Full article

The lack of centralized waste management infrastructure in certain regions makes plastic waste an escalating environmental and economic problem. This research investigates how modular portable pyrolysis systems function as sustainable decentralized solutions. A standard shipping container houses a custom-designed pyrolysis unit which demonstrates flexibility and adaptability. The system contains a batch rotary kiln reactor with a processing capacity of 750 kg per batch which is fed with urban plastic waste, to produce pyrolytic oil, syngas and char. The produced pyrolytic oil exhibits an energy content comparable to that of conventional diesel fuel. Additionally, the integration of biomass briquettes and recycled pyrolytic gas can reduce to a big extent the external energy requirements, improving the system’s overall energy autonomy. Therefore, the system becomes economically reliable due to its low operational expenses and the short cycle of approximately 7-h operation. The unit’s mobility enables on-site treatment operations which reduces both transportation emissions and expenses. The analysis includes technical design elements together with performance metrics for different plastics. This conceptual study demonstrates the feasibility of containerized pyrolysis as a practical method to enhance plastic waste chemical recycling rates while presenting a scalable framework for industrial symbiosis and local waste-to-energy conversion. Full article

Biomass briquettes are an environmentally friendly fuel and have extensive utilization prospects. Compaction pressure is a crucial factor during the production of biomass briquettes, affecting its densification and subsequent potassium release behavior. The release of alkali metals during combustion is typically studied using offline analytical techniques. However, these methods fail to provide real-time measurement of alkali metals release during the combustion process. Therefore, FES, through its equipment simplicity, low operational cost, real-time measurement, and robust adaptability to industrial environments, is commonly employed. In this study, the effect of compaction pressure (80, 130, and 180 MPa) of camphor wood briquettes on potassium release in a premixed flame was investigated by means of Flame Emission Spectroscopy. A spectrometer was used to obtain flame spontaneous emission spectra at three heights above the burner. Based on the proposed spectral analysis method and a calibration procedure, time-resolved flame temperature and concentration of gas-phase potassium in camphor wood briquette combustion were simultaneously measured. The experimental results at the three measurement heights showed that both peak concentration and the amount of gas-phase potassium released from biomass briquettes decreased with the increase in compaction pressure. Furthermore, the amount of potassium released from biomass briquettes at a compaction pressure of 180 MPa was the lowest at all three measurement heights, at 28.0, 14.5, and 21.8 ppm·s. Moreover, the potassium release rate from 0 to 63 s was rapid, and there was an exponential increase in the release ratio curve. The release ratio of potassium reached 50% before entering the ash stage under a compaction pressure of 80 and 130 MPa; in comparison, it only reached 35% under 180 MPa. The potassium release ratio at HAB = 4 cm under compaction pressures of 80, 130, and 180 MPa was 54%, 50%, and 35%, respectively. The findings of this study directly link compaction pressure to K release and demonstrate the applicability of FES for real-time alkali metal detecting, offering both theoretical and practical pathways toward cleaner biomass combustion. Full article

Faced with the depletion of fossil resources and the need to promote a circular economy, lignocellulosic biomass represents a solution for energy transition and bioeconomy. However, wood sawdust, which contains bioactive compounds (secondary metabolites), is often burned in the open by many sawmills. This study aims to valorize Framiré wood sawdust by extracting its secondary metabolites through maceration and infusion, then converting the depleted residue into combustible briquettes. The yellowness index of the extracts ranged from 73.490 ± 0.021 (maceration) to 81.720 ± 0.014 (infusion). The total phenolic content varied from 0.097 ± 0.001 to 0.63 ± 0.049 gGAE/100 g dry matter for maceration and infusion, respectively. The extraction of bioactive compounds did not significantly affect the energy or mechanical properties of the fuels. Their higher heating value ranged from 26,153 ± 92 to 26,201 ± 90 kJ/kg for fuels with and without secondary metabolites, respectively. The Shock Resistance Index ranged from 139.33 ± 7.51% (without metabolites) to 153.00 ± 5.20% (with metabolites). A significant difference was observed in the specific consumption of the fuels, decreasing from 1.400 ± 0.100 to 0.861 ± 0.001 kg/L for fuels without and with secondary metabolites, respectively. These results open promising prospects, particularly for the use of Framiré extracts to develop flame-retardant products for wood and its derivatives. Full article

In the Republic of Moldova, orchard biomass represents an important resource for the production of densified solid biofuels, with peach having the highest sustainable energy potential (33.5 ± 6.54 GJ·ha⁻¹). However, the quality of solid biofuels derived from orchard biomass is often constrained by heterogeneity in moisture content, uneven particle size distribution, and inadequate drying or blending practices along the supply chain. Optimizing the solid biofuel supply chain is therefore essential to minimize feedstock variability, ensure consistent densification quality, and reduce production costs. The aim of this study was to improve the process of producing densified solid biofuels from orchard biomass. Specifically, the study investigated how raw material moisture and particle size influence briquette density and durability, and how ternary mixtures of peach biomass, wheat straw, and sunflower residues can be optimized for enhanced energy performance. All experimental determinations were performed using validated methods and calibrated equipment. The results showed that optimal performance is achieved by shredding the biomass with 4–8 mm sieves and maintaining the moisture content between 6 and 14%, resulting in briquettes with the density of 1.00–1.05 g·cm⁻³, ash content below 3–5%, and an energy yield of 18.4–19.2 MJ·kg⁻¹. Ternary diagrams confirmed the decisive role of peach lignocellulosic residues in achieving high density, low ash content, and increased energy yield, while wheat straw and sunflower residues can be used in controlled proportions to diversify resources and reduce costs. These findings provide quantitative insights into how mixture formulation and process parameters influence the briquette quality, contributing to the optimization of solid biofuel supply chains for orchard and agricultural residues. Overall, this study demonstrates that competitive solid biofuels can be produced through careful balancing of mixture composition and optimization of technological parameters, offering practical guidelines for sustainable bioenergy development in regions with abundant orchard residues. Full article

In this study, fallen leaves of Azadirachta indica and Prunus dulcis were treated as waste materials for the production of energy-intensive bio-coal briquettes. The physical composition revealed that the moisture content ranged from 6.8% to 8.8%, fixed carbon from 10.7% to 14.0%, volatile matter from 71.2% to 77.1%, and ash content from 4.1% to 7.6%. The chemical structure of the biomass fuel, which included carbon, hydrogen, nitrogen, sulfur, and oxygen, was noted to be 44.56–50.69%, 7.12–7.33%, 0.14–0.25%, 0.47–0.79%, and 41.08–47.46%, respectively. The higher heating value ranged from 16.8 to 18.3 MJ/kg. With increasing pressure from 5 to 20 MPa, briquette density increased from 654 to 995 kg/m³, shatter index from 81% to 94%, durability from 67% to 92%, and resistance to water penetration from 57% to 77%. A low-pressure briquette (5 MPa) burned at a higher rate of 8.0 g/min, whereas a high-pressure briquette (20 MPa) burned at a lower rate of 2.5 g/min. All leaf types tested were able to boil 1000 mL of water with 100 g of briquettes in just 7 min. Full article

This study extends the application and validation of the Gibbs Free Energy Gradient Method (GMM) for modelling gasification processes, focusing on scaling up from pilot to commercial operations. The model simulates syngas production using poplar wood and olive pomace briquettes under various gasification conditions. Experimental data from a downdraft gasifier were employed to refine the model parameters, achieving accurate predictions of syngas composition with an average error below 8%. Sensitivity analyses highlight the impact of operating conditions, particularly temperature and air flow rates, on the syngas calorific value, hydrogen yield, and energy efficiency. These results emphasize the potential of biomass residues, such as olive pomace, for sustainable energy production in a circular economy context. The findings demonstrate the robustness of the GMM for predicting gasification performance and offer practical guidance for scaling up biomass-to-energy systems while optimizing efficiency and reducing waste. Full article

Biomass briquettes are increasingly used as renewable solid fuels, yet their durability under humid storage remains a key limitation. This study evaluated the mechanical performance and water resistance of briquettes made from fine (0–1 mm) and coarse (0–3 mm) charcoal fractions using molasses as a primary binder, polyvinyl alcohol (PVA, 3–7%) as a synthetic binder, and liquid soap (1–9%) as a surfactant additive. Compressive strength was measured in the dry state, after four days of water immersion, and after re-drying, while water absorption was monitored over immersion times from 15 min to 4 days. Fine-fraction briquettes showed higher strength and lower water uptake than coarse fractions, with optimal PVA contents of 6–7% providing maximum dry and post-drying strength. Moderate soap addition (2–3%) improved binder dispersion and early wet strength, whereas higher levels (>5%) reduced durability. Water absorption kinetics indicated that particle size controlled early swelling, while binder composition influenced the rate but not the final saturation. The best performance in humid storage was achieved by 0–1 mm + 4% PVA and 0–1 mm + 5% PVA + 3% soap formulations. These results support the formulation of eco-friendly binder systems that balance strength, moisture resistance, and cost for large-scale biomass briquette production. Full article

The presence of Giant Hogweed (Heracleum mantegazzianum) in agricultural landscapes raises concerns due to its impacts on agroecology. Physically removed biomass can serve as a feedstock for solid biofuel, representing a viable strategy reducing reliance on herbicides. Giant Hogweed’s bioenergy potential is currently underexplored, particularly regarding its seasonal variations in properties and the environmental impacts resulting from its use as a biofuel. This study assessed the processability of Giant Hogweed biomass into briquettes, to determine their mechanical durability and to evaluate their basic emission characteristics during combustion in a device commonly used at the household level. Biomass was sampled at two specific stages of plant development for a comparative study of briquette properties. For both summer- and autumn-harvested biomass, a high mechanical durability of the produced briquettes, approximately 97%, was achieved. Only carbon monoxide emissions from summer-harvested biomass exceeded the limits; nitrogen oxides concentrations were within the limits for both. Thermogravimetric analysis and differential scanning calorimetry revealed decomposition patterns. Autumn-harvested biomass showed better potential for briquetting, highlighting the advantages of later collection. The findings demonstrate the potential of plant and applied processing technology for valorisation as a solid biofuel, while certain aspects still need consideration. Full article

Biomass is gaining increasing importance as a renewable energy source in the global energy mix, offering a viable alternative to fossil fuels and contributing to the decarbonization of the energy sector. Among various types of biomass, agricultural residues such as bean stalks represent a promising feedstock for the production of solid biofuels. This study analyzes the impact of particle size and selected briquetting parameters (pressure and temperature) on the physical quality of briquettes made from bean stalks. The experimental procedure included milling the raw material using #8, #12, and #16 mesh screens, followed by compaction under pressures of 27, 37, and 47 MPa. Additionally, the briquetting die was heated to 90 °C to improve the mechanical durability of the briquettes. The results showed that both particle size and die temperature significantly influenced the quality of the produced briquettes. Briquettes made from the 16 mm fraction, compacted at 60 °C and 27 MPa, exhibited a durability of 55.76%, which increased to 82.02% when the die temperature was raised to 90 °C. Further improvements were achieved by removing particles smaller than 1 mm. However, these measures did not enable achieving a net calorific value above 14.5 MJ·kg⁻¹. Therefore, additional work was undertaken, involving the addition of biomass with higher calorific value to the bean stalk feedstock. In the study, maize straw and miscanthus straw were used as supplementary substrates. The results allowed for determining their minimum proportions required to exceed the 14.5 MJ·kg⁻¹ threshold. In conclusion, bean stalks can serve as a viable feedstock for the production of solid biofuels, especially when combined with other biomass types possessing more favorable energy parameters. Their utilization aligns with the concept of managing local agricultural residues within decentralized energy systems and supports the development of sustainable bioenergy solutions. Full article