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In this research, the energy potential of switchgrass (SG) was analyzed to find promising directions for producing bioenergy from this biomass. The first direction is determining the thermal energy of bioethanol extracted from SG biomass after its pretreatment, enzymatic hydrolysis (saccharification), and fermentation of the resulting glucose. It was established that after a two-stage pretreatment of 1 ton of SG with dilute solutions of nitric acid and alkali, the largest amount of bioethanol can be extracted with an energy potential of 4.9 GJ. It is also shown that by the utilization of solid and liquid waste, the production cost of bioethanol can be reduced. On the other hand, the direct combustion of 1 ton of the initial SG biomass used as a solid biofuel provides an increased amount of thermal energy of 18.3 GJ, which is 3.7 times higher than the energy potential of the resulting bioethanol extracted from 1 ton of this biomass. Thus, if the ultimate goal is to obtain the maximum energy amount, then another direction for obtaining bioenergy from biomass should be implemented, namely, direct combustion, preferably after pelletizing. Studies have shown that fuel characteristics of SG pellets such as the gross thermal energy and density of thermal energy are lower than those of wood pellets, but they can be improved if the SG biomass is densified into pellets together with binders made from polymer waste. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study on the process of the pelletization of pine sawdust with the addition of herbaceous waste from elderberry, in the working system of a pellet press with a flat matrix, in the context of producing fuel pellets. Based on the research, the impact of the addition of herbal waste in the form of elderberry waste on the granulation process of pine sawdust and the assessment of the quality of the obtained pellets were determined. The addition of herbaceous waste from elderberry to pine sawdust had a beneficial effect on the kinetic durability of the obtained fuel pellets, with an increase of up to approximately 1.3% (from 98.03 to 99.31%). Based on the obtained results, it can be concluded that the mechanical strength of all the tested pellets is higher than 97.5%, which is consistent with the ISO 17225-1:2021-11 standard. The bulk density of pellets with the addition of herbaceous waste from elderberry increased (from 649.34 to 658.50 kg∙m−3) as did their density (from 1231.38 to 1263.90 kg∙m−3). The addition of herbaceous waste from elderberry in amounts ranging from 10% to 20% did not have a significant effect on the power requirements of the pelletizer, which decreased compared to the pelletization process of pure pine sawdust. The percentage of this decrease compared to the pelleting process with pure pine sawdust was approximately 10%. The addition of herbaceous waste from elderberry to pine sawdust slightly reduces the energy value (i.e., the heat of combustion and the calorific value) of the obtained pellets. The addition of 30% elderberry waste resulted in a decrease in the heat of combustion from 20.27 to 19.96 MJ·kgd.m.−1, while the calorific value of the pellets decreased from 19.98 to 18.69 MJ·kgd.m.−1 compared to pine sawdust pellets. Hence, adding herbaceous waste from elderberry seems to be a good way of managing large amounts of waste of this kind generated in herbal processing plants. This method of waste management opens new perspectives towards more sustainable and economically effective energy production. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to evaluate the qualities of Miscanthus pellets blended with pine sawdust at various ratios (Miscanthus/pine sawdust—0:100, 25:75, 50:50, 75:25, and 100:0) and relate them to energy generation potential under typical production conditions of the widely used bioenergy production technologies according to literature. Samples of each material were milled to the required sizes and blended in the proportions mentioned above. Water was added (6%) to each mixture to achieve a uniform moisture content of 10% on wet basis. The mixtures were then subjected to pressure agglomeration in the form of mechanical compression using a single pellet press so that homogeneously sized fuel pellets were obtained. Thereafter, the pure and blended pellet samples were examined using a range of analytical techniques to reveal any alterations in characteristics important to the utilization of the pellets as a green energy source. The results showed that, although temperature variations generally caused an estimated 6% moisture loss on a wet basis during pelleting with positive influence on the features of the pellets, the quality of the pellets in terms of ash composition (2–4%), hardness (41–46 kg/pellet), and heating value (20–21 MJ/kg) was in general more desirable for the blended pellets than for pure Miscanthus pellet. Structural analysis also revealed low levels of hydrophobic groups in the blends relative to pure Miscanthus, which were consistent with the fractions of pine sawdust and were also the reason for the pellets' increased hardness. [ABSTRACT FROM AUTHOR]

Hydrothermal gasification of fuel pellets obtained from co-pelletized agricultural residues such as barley straw, canola hull and oat hull was performed in a batch reactor. The effects of process conditions such as temperature (300–500 °C), reaction time (20–60 min) and feed-to-water mass ratio (1:05–1:15) were investigated to optimize the gasification process for large gas yields. The maximum yield of gas was attained at the temperature, reaction time and feed-to-water mass ratio of 500 °C, 60 min and 1:10, respectively. The highest hydrogen gasification efficiency (113%), hydrogen selectivity (52%), cold gasification efficiency (41%) and heating value of gas (920 kJ/Nm3) were found for the hydrothermal gasification of canola hull pellet at the optimal conditions. The temperature was the most paramount variable followed by reaction time and feed-to-water mass ratio. Physicochemical characterization of hydrochar produced at higher gasification temperatures revealed higher carbon content, thermal stability, alkalinity and structural deformity. The liquid products obtained from hydrothermal gasification of canola hull pellets also showed the presence of partially degraded or reformed organic compounds, which can be extracted as precursors for value-added chemicals. • Gasification of biomass pellets was performed in subcritical and supercritical water. • Gasification was optimized for temperature, reaction time and feed-to-biomass ratio. • Effects of parameters on gas yields: temperature > reaction time > feed-to-biomass ratio. • High carbon content and thermal stability were found in hydrochar with temperature. • Liquid products from gasification of biomass pellets contained chemical building blocks. [ABSTRACT FROM AUTHOR]

This paper presents research findings on the pelleting process of pine sawdust using bakery waste in a pelletizer. The addition of bakery waste (white wheat–rye bread, whole-grain rye bread, and pumpkin bread) to pine sawdust had a beneficial effect on the kinetic strength of the pellets obtained, an increase of up to approximately three percentage points. The density of pellets with the addition of bakery waste also increased, while the bulk density of the pellets decreased. The addition of bakery waste also had a positive effect on the power demand of the pelletizer. It was reduced from 3.08% (at a 10% addition of white wheat–rye bread) to 22.18% (at a 20% addition of pumpkin bread), compared to the process of compacting pure pine sawdust. In addition, all the pellets containing bakery waste had a lower energy yield (EY) determined based on lower heating value and energy inputs. This index was lower by 53 Wh·kg−1 for pine sawdust pellets with a 10% addition of pumpkin bread. The greatest reduction, on the other hand, was by 173 Wh·kg−1 for pellets, with a 20% addition of white wheat–rye bread. In each case, an increase in the share of bakery additives resulted in a decrease in the energy yield from the pellets obtained. The smallest reduction in EY was found when pumpkin bread was used as an additive (from 53 to 133 Wh·kg−1). Considering all the parameters analyzed characterizing the pellets obtained, it was concluded that the addition of bakery residues to pelletized pine sawdust should not exceed 10%. Further increases in the proportion of bakery waste did not yield relative benefits, due to the deterioration of the energy characteristics of the pellets obtained. [ABSTRACT FROM AUTHOR]

The global market for fuel pellets (FPs) has been steadily growing because of a shift to coal substitutes. However, sustainability and the availability of biomass are the main issues. Various kinds of bio-wastes can be valorized through cutting-edge technologies. In the coffee industry, a valuable organic waste called spent coffee grounds (SCGs) is generated in bulk. SCG can be divided into two components, namely spent coffee ground oil and defatted spent coffee grounds (DSCG). SCG and DSCG can be used to produce FPs with excellent higher heating values. This review highlights that burning FPs composed of 100% SCG is not feasible due to the high emission of NOx. Moreover, the combustion is accompanied by a rapid temperature drop due to incomplete combustion which leads to lower boiler combustion efficiencies and increased carbon monoxide emissions. This was because of the low pellet strength and bulk density of the FP. Mixing SCG with other biomass offers improved boiler efficiency and emissions. Some of the reported optimized FPs include 75% SCG + 20% coffee silverskin, 30% SCG + 70% pine sawdust, 90% SCG + 10% crude glycerol, 32% SCG + 23% coal fines + 11% sawdust + 18% mielie husks + 10% waste paper + 6% paper pulp, and 50% SCG + 50% pine sawdust. This review noted the absence of combustion and emissions analyses of DSCG and the need for their future assessment. Valorization of DSCG offers a good pathway to improve the economics of an SCG-based biorefinery where the extracted SCGO can be valorized in other applications. The combustion and emissions of DSCG were not previously reported in detail. Therefore, future investigation of DSCG in boilers is essential to assess the potential of this industry and improve its economics. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study on the process of the pelletization of pine sawdust with the addition of herbaceous waste from elderberry, in the working system of a pellet press with a flat matrix, in the context of producing fuel pellets. Based on the research, the impact of the addition of herbal waste in the form of elderberry waste on the granulation process of pine sawdust and the assessment of the quality of the obtained pellets were determined. The addition of herbaceous waste from elderberry to pine sawdust had a beneficial effect on the kinetic durability of the obtained fuel pellets, with an increase of up to approximately 1.3% (from 98.03 to 99.31%). Based on the obtained results, it can be concluded that the mechanical strength of all the tested pellets is higher than 97.5%, which is consistent with the ISO 17225-1:2021-11 standard. The bulk density of pellets with the addition of herbaceous waste from elderberry increased (from 649.34 to 658.50 kg∙m−3) as did their density (from 1231.38 to 1263.90 kg∙m−3). The addition of herbaceous waste from elderberry in amounts ranging from 10% to 20% did not have a significant effect on the power requirements of the pelletizer, which decreased compared to the pelletization process of pure pine sawdust. The percentage of this decrease compared to the pelleting process with pure pine sawdust was approximately 10%. The addition of herbaceous waste from elderberry to pine sawdust slightly reduces the energy value (i.e., the heat of combustion and the calorific value) of the obtained pellets. The addition of 30% elderberry waste resulted in a decrease in the heat of combustion from 20.27 to 19.96 MJ·kgd.m.−1, while the calorific value of the pellets decreased from 19.98 to 18.69 MJ·kgd.m.−1 compared to pine sawdust pellets. Hence, adding herbaceous waste from elderberry seems to be a good way of managing large amounts of waste of this kind generated in herbal processing plants. This method of waste management opens new perspectives towards more sustainable and economically effective energy production.

Biomass pellets are one of the most crucial feedstocks for bioenergy production on a global scale due to their numerous advantages over raw biomass resources. Pellets provide improved energy density, bulk density, moisture content, and homogeneity thereby reducing storage, handling, and transportation costs. To produce high-quality solid fuel, it is necessary to comprehend the properties of wood fuel. This study explored the potential of Khaya senegalensis (khaya) as a dedicated energy crop (DEC) for the production of green energy. It thrives in less-than-ideal conditions and grows rapidly. The low durability of energy pellets raises the risk of dust and fire during handling and storage. In addition, the potential for fines and dust formation is strongly correlated with the mechanical strength of materials. Due to this necessity, the current study examines the effects of pelletization factors, including temperature and pressure, on pellet properties, particularly on its mechanical properties. The durability and compressive strength of pellets were determined using a sieve shaker and a universal testing machine, respectively. The highest mechanical durability was observed at 3 tons of pressure and 75 degrees Celsius, each with a value of 99.6%. The maximum axial compressive strength was measured at 57.53 MPa under 5 tons of pressure. When pelletized at 125 °C, the axial compressive strength increased by 13.8037% to 66.06 MPa compared to the strength obtained at 5 tons of pressure. Pelletizing Khaya feedstocks at 4 tons of pressure, on the other hand, produced a slightly lower diametral compressive strength of 7.08 MPa compared to 7.59 MPa at 125 °C. The experimental results revealed that the aforementioned factors significantly affect the mechanical properties of pellets. The elucidation of wood biomass, solid fuel qualities and pelletization parameters of this potential energy crop may facilitate the production of high-quality pellets from Khaya senegalensis wood to meet the increasing local and worldwide energy demands. [ABSTRACT FROM AUTHOR]

This paper presents research findings on the pelleting process of pine sawdust using bakery waste in a pelletizer. The addition of bakery waste (white wheat–rye bread, whole-grain rye bread, and pumpkin bread) to pine sawdust had a beneficial effect on the kinetic strength of the pellets obtained, an increase of up to approximately three percentage points. The density of pellets with the addition of bakery waste also increased, while the bulk density of the pellets decreased. The addition of bakery waste also had a positive effect on the power demand of the pelletizer. It was reduced from 3.08% (at a 10% addition of white wheat–rye bread) to 22.18% (at a 20% addition of pumpkin bread), compared to the process of compacting pure pine sawdust. In addition, all the pellets containing bakery waste had a lower energy yield (EY) determined based on lower heating value and energy inputs. This index was lower by 53 Wh·kg−1 for pine sawdust pellets with a 10% addition of pumpkin bread. The greatest reduction, on the other hand, was by 173 Wh·kg−1 for pellets, with a 20% addition of white wheat–rye bread. In each case, an increase in the share of bakery additives resulted in a decrease in the energy yield from the pellets obtained. The smallest reduction in EY was found when pumpkin bread was used as an additive (from 53 to 133 Wh·kg−1). Considering all the parameters analyzed characterizing the pellets obtained, it was concluded that the addition of bakery residues to pelletized pine sawdust should not exceed 10%. Further increases in the proportion of bakery waste did not yield relative benefits, due to the deterioration of the energy characteristics of the pellets obtained.

A study of irradiation-induced creep and re-sintering of large grain sized fuel of the VVER type was carried out using the developed procedures and experimental facilities under irradiation with fission rates of 1.0 × 1013 and 1.2 × 1013 1/(cm3 s). Strain diagrams generated during creep studies within the strain range of 10−40 MPa were obtained at effective sample temperatures of 943, 1020, 1200 and 1301 K. It was demonstrated that strain is controlled by irradiation-induced creep within the temperature range of up to 1123 K. This was confirmed by its linear dependency on stress. At higher temperatures, the effect of radiation-thermal creep grows, and its contribution to the total strain increases with the growth of stress. Creep rate values obtained at temperatures of 1200 and 1301 K are higher than those of uranium dioxide with standard grain size. Strain diagram produced during the studies of re-sintering of an 88.32 mm high fuel column was obtained at the effective sample temperature of 960 K. In terms of height, re-sintering amounted to 0.070−0.095%. It was demonstrated that irradiation-induced re-sintering did not affect the irradiation-induced creep rate within the experimental accuracy range. [ABSTRACT FROM AUTHOR]

In this study, the possibility of sintering industrial pressed uranium dioxide pellets using microwave radiation for the production of nuclear fuel is shown. As a result, the conditions for sintering pellets in an experimental microwave oven (power 2.9 kW, frequency 2.45 GHz) were chosen to ensure that the characteristics of the resulting fuel pellets meet the regulatory requirements for ceramic nuclear fuel, including the following: a density of about 10.44 g/cm3; a volume fraction of open pores of tablets of about 0.1%; an oxygen coefficient of no more than 2.002; hydrogen content of about 0.30 ppm; and the change in density after re-sintering on average no more than 1.16%. [ABSTRACT FROM AUTHOR]

The present study addresses valorisation of abundantly available, low-cost pine needle (PN) waste into cellulolytic enzymes and high calorific value (CV) fuel pellets (FP). Initial studies in flasks involving hot water steam pre-treatment (HWSP) using Aspergillus niger MTCC 9652 for 5 days resulted in an increase in Cellulase, Endoglucanase and Xylanase activities compared to the untreated pine needles (UPN). Fermentation experiments were scaled-up in a 6-L Solid State fermentation (SSF) packed bed reactor (PBR) at different bed heights (BH) using UPN. The maximum cellulase and xylanase yields were achieved as 9.97 ± 0.27 FPU g-ds−1 and 8276 ± 254 IU g-ds−1, respectively, at 72 h using UPN in the PBR. The fermented residue showed 53.5% consumption of holocellulose, a decrease in crystallinity index to 29.5% from 46%, with an increase in total lignin content of 45.9%. The fermented residue was processed for pellet production, resulting in a higher CV (19.13 ± 0.69 MJ kg-1) than the pellet made from unfermented PN (17.63 ± 0.66 MJ kg−1), along with enhanced compressive strength. Sulphur content (0.14%) was below the permissible limit of SO x emission for fuels with ash content less than 5%. Therefore, the present study represents a novel and sustainable biorefinery approach for PN valorisation. [Display omitted] • Holo-cellulosic contents of the waste PN were converted into cellulolytic enzymes. • Maximum cellulase (9.97 FPU/g-ds) and xylanase (8267 IU/g-ds) were produced in PBR. • Better enzyme productivity was achieved in the SSF PBR compared to flask. • FP made from the fermented PN residue have higher CV (19.13 MJ kg -1) than the untreated PN. • Waste PN can be a potential low-cost substrate for producing cellulolytic enzymes and FP. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-hydrothermal carbonization process and pelletizing technology were integrated to produce fuel pellets. • Co-hydrothermal carbonization of pomelo peel and gasifier coke exhibited feedstock complementarity and synergistic effects. • Optimized synergistic effect was observed in 5:5 blending ratio of two feedstocks with an energy yield of 84.16%. • Co-hydrothermal carbonization reduced ash and sulfur content of gasifier coke to 4.99% and 0.35%, respectively. • Co-hydrothermal carbonization enhanced compressive strength and drop resistance of the pellets to 11.89 MPa and 99.8 %. The production of nitrogen fertilizer in China generates a substantial quantity of gasifier coke (GFC) as an industrial by-product, posing challenges for its effective recycling. In this study, a combination of co-hydrothermal carbonization (co-HTC) and pelleting technology was employed to convert pomelo peel (PP) and GFC into fuel pellets. Notably, these two feedstocks, characterized by significantly distinct physicochemical properties, exhibited beneficial complementarity, mitigating the limitations of using a single feedstock for fuel preparation. The severe caking and non-uniformity of PP hydrochar resulted in significant flaws in the pellets prepared through direct blending with GFC. The co-HTC technology significantly alleviated the poor processability of PP hydrochar and the low energy density of PP hydrochar pellet while greatly improving the flammability of GFC and the mechanical strength of GFC pellet. The results demonstrated a significant enhancement in uniformity of hydrochar after co-HTC, leading to a reduction in compression energy consumption to 6.16–7.62 J/g and an increase in pellet energy density to 30.60–35.08 GJ/m3. The ignition temperature and the activation energy of GFC were significantly reduced. The co-HTC technology effectively addressed the challenge of GFC pelletizing by achieving fuel pellets with a compressive strength of 11.89 MPa and a drop resistance of 99.8 %. Interestingly, the co-HTC process showed significant synergistic effects, increasing the energy yield of PP hydrochar to 73.38–92.9 % and effectively reducing the ash and sulfur content in GFC to 4.99–11.92 % and 0.35–0.55 %, respectively. The most pronounced synergistic effects were observed when blending PP and GFC in a 5:5 ratio. The complementarity of feedstocks and the synergistic effects of co-HTC converge to facilitate the conversion of biomass and industrial waste into high-performance fuel pellets. [ABSTRACT FROM AUTHOR]

Biofuel is one of the world’s major alternative sources of energy derived from biomass which includes almost all organic substances. In this regard, the state and prospects of development of the world bioenergy have been considered. The positive and negative sides of increasing energy production from biomass have been revealed. The analysis of the countries with the greatest biological resources for the production of liquid and gaseous biofuels has been carried out. The leading countries in the production of various types of biofuels have been determined and the measures of state support, contributing to the development of this direction, have been analyzed. The state and prospects of bioenergy development in Russia have been considered. The export potential of the country in the field of biofuel production and its use in industry has been revealed. It has been established, that despite some successes in the use of biofuel, the development of bioenergy projects in Russia still leaves much to be desired. The reasons, hindering the development of bioenergy in Russia, and measures to stimulate the development of biofuel production have been identified. In this regard, a flexible policy of the state in terms of innovation and energy is necessary, while today the state is focused on traditional energy sources.

In this study, the possibility of sintering industrial pressed uranium dioxide pellets using microwave radiation for the production of nuclear fuel is shown. As a result, the conditions for sintering pellets in an experimental microwave oven (power 2.9 kW, frequency 2.45 GHz) were chosen to ensure that the characteristics of the resulting fuel pellets meet the regulatory requirements for ceramic nuclear fuel, including the following: a density of about 10.44 g/cm3; a volume fraction of open pores of tablets of about 0.1%; an oxygen coefficient of no more than 2.002; hydrogen content of about 0.30 ppm; and the change in density after re-sintering on average no more than 1.16%.

The purpose of this study was to obtain high-energy pellets from natural biomass sources with improved fuel properties and durability. Two biomass types, namely residues of mixed coniferous wood and olive pomace, were selected as feedstock for this purpose. It was found that olive pomace is a promising natural source for the production of fuel pellets. The chosen biomasses were used for pelletization along with auxiliary materials, such as starch, synthetic rubber (SBR), polyethylene waste (PEW), etc. The milled biomass samples and their mixtures with binders were compacted under increased pressure and temperature and then cooled. Besides, part of the pellets was coated with a melt of high-energy agents, such as PEW, etc. The pellets were studied by methods of calorimetry, water vapor sorption, and durability testing. The results have shown that fuel characteristics of the pellets containing hydrophilic starch binder were lesser than those of coals; moreover, both fuel properties and durability of these pellets were reduced after sorption of water vapor. The use of hydrophobic binder (e.g. SBR) improves the durability of the pellets, whereas the additional coating with a layer of high-energy combustible agent (e.g. PEW) allows obtaining the especial high-quality pellets with high fuel properties and high durability both in a dry and wet state. As a result, the energetic features of these special solid biofuels become comparable with those of fossil coals. [ABSTRACT FROM AUTHOR]