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The effects of torrefaction of the biopellets made from hardwood chip residue (HW), camellia oilseed cake (CO), and pruning remnants of the toothache tree (TA) and mulberry tree (MT) were evaluated. Torrefaction of the biopellets reduced the volatile matter content of biopellets by 18–58% and increased their heating value by 18–58% without negatively impacting durability or fines content. Torrefaction also reduced the initial ignition time of biopellets by 50–59% and prolonged their combustion duration by 15–24%. Regardless of the type of feedstock, all biopellets exhibited mass yields in the range of 60–80% and energy yields ranging from 80–95%. The novelty of this study lies in the application of torrefaction to already-formed biopellets, which enhances pellet quality without the need for binders, and the use of unused forest biomass and wood chip residue from pulp mills. The use of unused forest biomass and wood chip residue from pulp mills for biopellet production not only provides a sustainable and efficient method for waste utilization but also contributes to environmental conservation by reducing the reliance on fossil fuels. Overall, the torrefaction of biopellets represents a promising technology for producing high-quality solid biofuel from a variety of woody biomass feedstocks without compromising pelletizing efficiency. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the influence in torrefaction of the chemical structure of biomasses from nine poplar commercial SRC clones, evaluated through analytical pyrolysis. The chemical data were integrated into a dataset including LHV gain, representative of torrefaction aptitude and six chemical variables obtained through analytical pyrolysis, which were: (i) CH2Cl2 extractives; (ii) total extractives; (iii) Py-lignin; (iv) holocellulose; (v) (syringil/guaiacyl) ratio; and (vi) (pentosan/hexosan) ratio. Significant univariate and bivariate linear relations were obtained with LHV gain from torrefaction as dependent variable vs. Py-lignin, CH2Cl2 extractives and (cP/cH) ratio. Representative results were: (i) a negative correlation of −0.82 and −0.76 between LHV gain and the (pentosan/hexosan) ratio and Py-lignin, respectively, and (ii) a positive correlation of 0.79 between LHV gain and CH2Cl2 extractive amounts. Factorial and discriminant analysis allowed for clustering the tested clones in three groups, evidencing relevant influences of (S/G) ratio, Py-lignin, and, to a lesser extent, (cP/cH) ratio in the classification of these groups, clearly showing the impact of chemical variables of feedstock in torrefaction. The results contribute: (i) to the validation of use of the expedite analytical pyrolysis technique for classification of biomasses in accordance with their torrefaction aptitude and, thereby, (ii) to optimizing strategies in technological issues as diverse as poplar clone genetic breeding and modeling biomass torrefaction and pyrolysis. [ABSTRACT FROM AUTHOR]

Gluten-based foam composites containing various additives were produced to develop materials derived from mostly renewable resources. The fillers included walnut shells, torrefied walnut shells, paraffin wax, milkweed fibers, hemp fibers, and cotton fibers. The effects of the fillers on the foam composites' properties were determined using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, compression testing, and water uptake measurements. SEM results showed that most of the fillers were well dispersed in the gluten matrix except for the cotton fibers, which produced agglomerated fiber bundles. FTIR results indicated that foams had a more aggregated structure with higher β-sheet contents than gluten powder. In general, foam composites containing fibers had larger compressive modulus values than those containing particulates. The sample containing 10 wt% milkweed fibers had the highest value of 67.03 ± 12.01 MPa. Also, composites containing torrefied walnut shells had higher compressive strength values than those containing raw walnut shells, indicating better compatibility with the gluten matrix. Moreover, the water uptake values of the foam composites varied from 110 to 270%, with the samples containing milkweed fibers having the largest values. [ABSTRACT FROM AUTHOR]

Sunflower husk (SFH) contributes 45–60% of the total sunflower seed weight and is a by-product of the sunflower oil industry. Among other elements, SFH ash contains K, Na, Ca and Mg. These elements cause rapid growth of ash deposits on convective heating surfaces of the boiler, resulting in reduced efficiency. The aim of this paper is to examine the possibility of producing quality fuel from SFH by its pretreatment with the technique of torrefaction in a fluidized bed in superheated water vapor. Continuous monitoring of the innovative SFH torrefaction process allowed for the determination of optimal process durations. SFH could be converted into a biofuel, having high calorific value and suitable characteristics for co-combustion with coal. Furthermore, the torrefaction in a fluidized bed of superheated water vapor allowed for a 6-fold reduction in the required process duration in comparison with data reported from the literature for the process of torrefaction in a dense bed, along with a 3-fold reduction in the chlorine content in SFH ash. These effects are beneficial to resolve the problem of corrosion on convective heating surfaces of boilers. However, torrefaction in superheated water vapor did not significantly reduce the content of alkaline and alkaline-earth elements in SFH ash. Still, this issue may be alleviated by significantly increasing the duration of SFH pretreatment. [ABSTRACT FROM AUTHOR]

In this study, the effect of pressurized torrefaction both by gas-pressurized (GP) and mechanical pressure (MP) at 250 °C on the properties of bio-oil was investigated. GP torrefaction enhanced the deoxygenation reactions and resulted in low O/C atomic ratio of torrefied biomass. The GP torrefaction at 4 MPa (GP-4.0) could remove oxygen content by 46.0%. Acids content in bio-oil for GP-4.0 were reduced to 3.6%, while phenols content increased to 46.7%. However, the yield of bio-oil was only 30.5% for GP-4.0. In contrast, MP torrefaction promoted the cross-linking reactions. The combination of MP torrefaction at 40 MPa and pyrolysis at 250 °C for 30 min (MP-40–30) could remove the oxygen content by 28.2%. The yield of bio-oil was as high as 44.7% for MP-40–30. Acids and furans content in bio-oil decreased, while alcohols, phenols, and hydrocarbons content in bio-oil increased for MP-40–30. Moreover, the hydrocarbons content in bio-oil increased to 11.9% for MP-40–30. Results from this study provided necessary information needed for developing the pyrolysis polygeneration from pressurized torrefied biomass. [ABSTRACT FROM AUTHOR]

The co-pyrolysis of torrefied oiltea camellia shells (OCS) and reused polypropylene (PP) was investigated for pyrolysis oil, pyrolysis gas and carbon nanotubes (CNTs) distribution characters in a two-stage pyrolysis system. Compared with raw OCS/PP, the quality of pyrolysis oil from torrefied OCS and PP was upgraded while yield decreased gradually. In particular, torrefaction pretreatment was beneficial to the formation of aromatic hydrocarbons and the higher selectivity of phenols in pyrolysis oil. And serious N 2 torrefaction (260 N) and slight CO 2 torrefaction (200C) is more conducive to the synthesis of C6–C11 (gasoline component). In addition, torrefaction could contribute to lower volatiles, which resulted in a lower yield of CNTs. For comparison, higher graphitized CNTs was prepared from the co-pyrolysis of torrefied OCS and PP. Appropriate torrefaction temperature and atmosphere have a potential for high value conversion of pyrolysis oil, pyrolysis gas and CNTs from co-pyrolysis of biomass and plastics. [Display omitted] • Aromatic hydrocarbons and phenols were the main content obtained by torrefaction. • CO 2 torrefaction exhibited higher gas and lower bio-oil yield than N 2 torrefaction. • Production of liquid oil, CNTs and gas from torrefied biomass and plastics. • Strategies to facilitate biomass high value on products conversion were provided. [ABSTRACT FROM AUTHOR]

The characteristics of biochar vary widely depending on the type of biomass and thermochemical conversion method. In this study, four types of biomass (kenaf, rice husk, corncob, and wood chips) were subjected to hydrothermal carbonization and torrefaction at 220 °C, 260 °C, and 300 °C for 30 min. The acquired biochars showed significant differences in the type of reaction and biomass. At each temperature, the decomposition of volatiles was more severe in hydrochar (HC) than in torrefied char (TC). The mass yields of HC were 44.30–61.63 wt.% (220 °C), 20.89–37.04 wt.% (260 °C), and 12.59–29.19 wt.% (300 °C), whereas the mass yields of TC were 94.73–97.69 wt.% (220 °C), 87.19–95.04 wt.% (260 °C), and 68.22–80.78 wt.% (300 °C). The elemental and thermal characteristics of TC changed gradually as the reaction temperature increased, and the characteristics of HC were enhanced rapidly. Wood chip biochar that was reacted at 300 °C showed the highest heating values of 28.77 MJ/kg (HC) and 21.09 MJ/kg (TC). The results of chemical analyses showed that hydrothermal carbonization strongly affected the cleavage of inter- and intra-molecular carbon bonds in cellulose and hemicellulose. In contrast, torrefaction removed the thermally fragile moisture and hemicellulose content from biomass. [ABSTRACT FROM AUTHOR]

Poultry litter was converted to biochar by torrefaction and to hydrochar by hydrothermal carbonisation. Many parameters were measured for the resulting chars, to investigate the effects of the production method and production temperature. SEM showed the presence of large quantities of crystalline material on the surface of the biochars. The elemental composition of some crystals was determined as 35% K and 31% Cl. This was confirmed as sylvite (KCl) crystals, which explains the high levels of water-extractable potassium in the biochar and may also be important in germination inhibition. Biochars almost totally inhibited germination, whilst hydrochars decreased germination. Although germination occurred on hydrochar, root growth was severely inhibited. Consequently, the germination index may be better to determine total phytotoxicity as it measures both effects and could be used as a bioassay for chars used as soil amendments. Washing removed germination inhibition in a low-temperature char (350 °C), possibly by removing KCl; however, root toxicity remained. There were very low levels of heavy metals, suggesting they are not the source of toxicity. In biochars, pore mean size decreased with temperature from 350 °C to 600 °C, due to changes in pore size distribution. The mean pore size was measured directly using SEM. The merits of this method are discussed. Low-temperature biochars seem best suited for fuel as they have a high calorific value, high hydrophobicity, a low ash content and a high yield. Higher temperatures are better for soil amendment and sequestration applications with a smaller mean pore size, higher surface area, and higher pH. [ABSTRACT FROM AUTHOR]

Our goal was to explore the potential of bamboo as a solid biomass fuel through torrefaction and compare it with previous studies on unused forest biomass chips. The torrefaction process involved temperatures of 230–310 °C increased in 20 °C intervals, each lasting an hour. Significant differences in mass were evident between the 270 and 290 °C processing conditions during thermogravimetric analysis. Differential thermogravimetric analysis showed that both the initial and peak temperatures increased with higher processing temperatures. The mass yield ranged from 32.37 to 76.74%, and the calorific value varied from 19.50 MJ/kg to 28.68 MJ/kg. Compared to previous studies on the torrefaction of Liriodendron tulipifera and Pinus koraiensis, bamboo exhibited a relatively lower mass yield and calorific value; however, it was considered suitable compared to unused forest biomass wood chips. The optimal conditions for torrefaction were found to be 270 °C during processing. [ABSTRACT FROM AUTHOR]

Poultry litter was converted to biochar by torrefaction and to hydrochar by hydrothermal carbonisation. Many parameters were measured for the resulting chars, to investigate the effects of the production method and production temperature. SEM showed the presence of large quantities of crystalline material on the surface of the biochars. The elemental composition of some crystals was determined as 35% K and 31% Cl. This was confirmed as sylvite (KCl) crystals, which explains the high levels of water-extractable potassium in the biochar and may also be important in germination inhibition. Biochars almost totally inhibited germination, whilst hydrochars decreased germination. Although germination occurred on hydrochar, root growth was severely inhibited. Consequently, the germination index may be better to determine total phytotoxicity as it measures both effects and could be used as a bioassay for chars used as soil amendments. Washing removed germination inhibition in a low-temperature char (350 °C), possibly by removing KCl; however, root toxicity remained. There were very low levels of heavy metals, suggesting they are not the source of toxicity. In biochars, pore mean size decreased with temperature from 350 °C to 600 °C, due to changes in pore size distribution. The mean pore size was measured directly using SEM. The merits of this method are discussed. Low-temperature biochars seem best suited for fuel as they have a high calorific value, high hydrophobicity, a low ash content and a high yield. Higher temperatures are better for soil amendment and sequestration applications with a smaller mean pore size, higher surface area, and higher pH.

Process design critically depends on the characterization of fuels and their kinetics under process conditions. This study steps beyond the fundamental methods of thermogravimetry to modulated (MTGA) and Hi-Res™ (high resolution) techniques to (1) add characterization detail and (2) increase the utility of thermal analysis data. Modulated TGA methods overlay sinusoidal functions on the heating rates to determine activation energy as a function of temperature with time. Under devolatilization conditions, Hi-Res™ TGA maintains a constant mass loss with time and temperature. These two methods, run independently or overlaid, offer additional analysis in which multiple samples at different heating rates are run to different final temperatures. Advanced methods allow researchers to use fewer samples by conducting fewer runs, targeting practical experimental designs, and quantifying errors easier. The parameters of the studies included here vary the heating rate at 10, 30, and 50 °C/min; vary gas-phase oxygen for pyrolysis or combustion conditions; and particle size ranges of 100–125 µm, 400–425 µm, and 600–630 µm. The two biomass fuels used in the studies are pinewood from Northern Sweden and wheat straw. The influence of torrefaction is also included at temperatures of 220, 250, and 280 °C. Apparent activation energy results align with the previous MTGA data in that combustion conditions yield higher values than pyrolysis conditions—200–250 kJ/mol and 175–225 kJ/mol for pine and wheat combustion, respectively, depending on pre-treatment. Results show the dependence of these parameters upon one another from a traditional thermal analysis approach, e.g., the Ozawa-Flynn-Wall method, as well as MTGA and Hi-Res™ thermogravimetric investigations to show future directions for thermal analysis techniques.

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The Amazon region contains numerous areas dedicated to sustainable timber extraction. This operation has low yields and generates a large amount of waste. However, this waste can be repurposed for energy generation, providing income for locals and reducing reliance on non-renewable energy sources prevalent in the region. This study aimed to assess the impact of torrefaction on various wood residues for briquette production. Wood residues from Mimosa scabrella Benth (Bracatinga), Dipteryx odorata (Aubl.) Willd. (Cumaru), and Aspidosperma populifolium A.DC. (Peroba mica) were torrefied at temperatures ranging from 180 to 220 °C for sixty minutes under a nitrogen atmosphere. Briquettes were produced using laboratory equipment with loading pressures between 7 and 14 MPa. Torrefied particle properties were evaluated based on proximate composition and calorific value tests, while briquette quality was assessed for physical and mechanical properties. The results demonstrated the briquetting potential of different wood species before and after torrefaction, with optimal outcomes achieved by torrefaction at 220 °C due to its enhancement of energy density. Briquettes showed optimal characteristics at compression pressures of 14 MPa, resulting in increased density (between 1.10 and 1.24 g·cm−3) and compression strength (between 7.20 and 21.02 MPa). The ash values were low and met the requirements. The utilization of waste for briquette production offers a significant alternative for energy generation in economically disadvantaged communities, while also enabling the replacement of non-renewable energy sources. [ABSTRACT FROM AUTHOR]

Torrefaction encourages homogeneity and enhances the energy-producing capabilities of biomass. In the current study, bean husk (BH) and sesame stalks (SS) were torrefied for 30 and 60 min at operating temperatures of 200, 225, 250 and 275, and 300 °C with nitrogen purging. Mass yield (MY), higher heating value (HHV), energy yields (EY), and torrefaction severity index (TSI) were examined. The variations of the biochar characteristics, pyrolysis kinetics by applying two models (Coats and Redfern (CR) and Direct Arrhenius (DA)), and crystallinity index (CRI) were depicted. Depending on pyrolysis kinetics, thermodynamic activation parameters were derived to elucidate biomass pyrolysis. The alterations in the torrefied materials' composition were also analyzed using Fourier transform infrared spectroscopy (FTIR). The calculations revealed that the torrefied SS and BH decreased MY by 32.74, 29.02% and decreased EY 26, 20.97%, increased high heating values by 14.1, 13.52%, increased fixed carbon by 55.1, 39.91% respectively, and had a slight reduction in bulk density (approximately 2%). Generally, 275 °C and 30 min were the optimal conditions for a balanced torrefaction of SS and BH based on the HHV that reached to 20.5, 16.2 MJ/kg and EY that reached to 86.16 and 85.56% respectively. The FTIR, XRD, and the thermogravimetric results showed that the torrefaction treatment altered samples owing to carbohydrate breakdown, a rise in lignin, and a reduction in hemicellulose as the temperature of the torrefaction process increased. The CR methodology yielded greater frequency factor (A) and activation energy (Ea) values than the DA method. The broadest peak width, lowest average Ea, and lnA were seen in sesame stalks that had been torrefied at 300 °C and 30 min that reached to 107.85 (kJ/mol) and 13.57 (min−1). Results indicated an excellent linear relationship with the index of comprehensive pyrolysis (CPI), CRI, atomic H/C ratio, severity index, and EY. [ABSTRACT FROM AUTHOR]

Within the scope of eco-friendly green technology, the interest in alternative biosorbents in heavy metal removal from water is increasing. However, chemical- or thermal- activation pretreatments are needed for biomass to have good biosorbent properties. The thermal processes such as carbonization and pyrolysis, which are frequently applied for activation, cause high energy consumption and lead to severe degradation in biomass structure and in surface functional groups. The importance of this study stems from the torrefaction of various biomass species at low temperatures for the purpose of biosorbent preparation and the testing of the biosorbents' heavy metal removal capacity. Thus, biomasses such as tea production waste, corn stalk, pine cone, brown seaweed, rhododendron, and grape seed were torrefied at temperatures of 150–300 °C and the obtained biosorbents were used to remove Pb(II), Cr(VI), and Cd(II) from aqueous solution where concentrations of each metal were 1000 ppm. Effects of the torrefaction temperature, solution temperature, and solution pH on metal uptake were studied by batch adsorption tests. It was determined that the biomasses torrefied at 150 °C has the optimum metal removal capacity. When torrefied corn stalk was used, 17.9 mg/g for Pb(II) and 16.8 mg/g Cr(VI) could be separated from solution, while the maximum Cd(II) uptake was 20.8 mg/g for torrefied tea production waste. It was concluded that the heavy metal removal capacity of biosorbents prepared by low-temperature torrefaction is at non-negligible levels. [ABSTRACT FROM AUTHOR]

The saw-milling residues are biowaste generated during the sawing of logs into lumber, and they may be lucrative when turned into biowaste pellets. Using biowaste as a renewable fuel helps address the limited availability of fossil fuels, reduces pollution, and additionally decreases the need for landfill. This study investigated the thermal reaction kinetics and physical properties of oxidative torrefied sawdust (TSD) and waste medical plastic pyrolysis oil (WMPPO) blended pellets, TSD25 and TSD50, referring to 25% and 50% of WMPPO with TSD, respectively, using thermogravimetric analysis (TGA), whereas the pellets are prepared using a small-scale pellet processing system. The reported additional physicochemical properties like density, pellet durability index (PDI), moisture adsorption, and impact resistance (IR) were as per the American Society of Agricultural and Biological Engineers (ASABE) recommended tests for densified fuel pellets, proximate Fourier transform infrared spectroscopy (FTIR) were used for identifying the blend's chemical composition active constituents. Ultimate analysis was carried out for the elemental analysis, and the morphological study was conducted using scanning electron microscopy. The samples have a moisture content of less than 10%, a volatile matter content that seems to be 75 to 82%, and an ash content that seems to be 1.05 to 6.65%. Oxidative torrefied sawdust scanning electron micrographs reveal micro, macro, and meso pores and improved the Brunauer-Emmett-Teller (BET) surface area. FTIR and TGA validate the addition of 50% WMPPO with TSD-controlled combustion zone temperature with the activation energy of 27.63 kJ/mol for an effective thermal conversion process. The physicochemical properties of density, pellet durability index (PDI), moisture adsorption, and impact resistance (IR) for sawdust (SD), TSD, and TSD blends with WMPPO are also reported. Both low-temperature torrefaction and waste medical plastic pyrolysis oil blending reduce volatile loss and improve fuel pellet physicochemical and thermochemical characteristics. [ABSTRACT FROM AUTHOR]

Bioenergy with carbon capture and storage (BECCS) or utilization (BECCU) allows net zero or negative carbon emissions and can be a breakthrough technology for climate change mitigation. This work consists of an energetic, exergetic, and economic analysis of an integrated process based on chemical looping combustion of solar-torrefied agro-industrial residues, followed by methanation of the concentrated CO2 stream with green H2. Four agro-industrial residues and four Italian site locations are considered. Depending on the considered biomass, the integrated plant processes about 18–93 kg h−1 of raw biomass and produces 55–70 t y−1 of synthetic methane. Global exergetic efficiencies ranged within 45–60% and 67–77% when neglecting and considering, respectively, the valorization of torgas. Sugar beet pulp and grape marc required a non-negligible input exergy flow for the torrefaction, due to the high moisture content of the raw biomasses. However, for these biomasses, the water released during drying/torrefaction and CO2 methanation could be recycled to the electrolyzer to eliminate external water consumption, thus allowing for a more sustainable use of water resources. For olive stones and hemp hurd, this water recycling brings, instead, a reduction of approximately 65% in water needs. A round-trip electric efficiency of 28% was estimated assuming an electric conversion efficiency of 40%. According to the economic analysis, the total plant costs ranged within 3–5 M€ depending on the biomass and site location considered. The levelized cost of methane (LCOM) ranged within 4.3–8.9 € kgCH4−1 but, if implementing strategies to avoid the use of a large temporary H2 storage vessel, can be decreased to 2.6–5.3 € kgCH4−1. Lower values are obtained when considering hemp hurd and grape marc as raw biomasses, and when locating the PV field in the south of Italy. Even in the best scenario, values of LCOM are out of the market if compared to current natural gas prices, but they might become competitive with the introduction of a carbon tax or through government incentives for the purchase of the PV field and/or electrolyzer. [ABSTRACT FROM AUTHOR]

This study compared kenaf-based solid fuel characteristics using three processes: hydrothermal carbonization (HTC), torrefaction (TOR), and low-ash TOR, (LA_TOR). Solid fuels were produced by conducting the ash removal process at 50 °C for 60 min in an autoclave, followed by HTC or TOR at various temperatures (160, 200, 240, 280, and 320 °C) for 60 min. The resulting products' chemical compositions and fuel properties were then compared. The study found that under HTC at 320 °C, the product had the highest carbon content compared with the products from TOR and LA_TOR at 320 °C. Thus, HTC produced the highest-quality solid fuel of the three methods. However, this process showed a low energy yield and significant energy loss. In contrast, LA_TOR exhibited a high energy yield, low energy loss, and effectively reduced the ash content of the product. This demonstrates its suitability for industrial-scale applications that demand fuel with low ash content and energy loss. [ABSTRACT FROM AUTHOR]

This study investigates a comprehensive process for the production of methanol and electricity from bagasse. A total of four main scenarios (S1–S4) were considered in this study, they are bagasse gasification for methanol and electricity co-production with torrefaction (S1), and bagasse gasification for the production of electricity only with torrefaction (S2) while the other two (S3 and S4) are without torrefaction process respectively. The gasification process was modelled in Aspen Plus using a kinetic-free equilibrium model using steam and pure oxygen as the gasification agent. For the syngas cleaning, the Rectisol process was employed while for the methanol synthesis, hydrogenation reactions of CO2 and CO coupled with the water gas shift reaction were employed. From the result obtained, the process involving torrefaction has more syngas yield; hence, more methanol was synthesized (0.48kgMeOH/kgBagasse) when compared to the process without torrefaction (0.41kgMeOH/kgBagasse). The syngas from the torrefaction processes also has higher lower heating values (LHV) of 9.25 MJ/Nm3 and 8.71 MJ/Nm3 for S1 and S2, when compared to that without torrefaction (S3 and S4) with LHV of 9.00 MJ/Nm3 and 8.49 MJ/Nm3 respectively. In addition, the economics involved in the production process of the four scenarios were investigated in terms of the key economic parameters which include the net present value (NPV), the rate of return on investment (ROROI), and the discounted payback period (DPBP). The result showed that S1 is the most economically viable production route. The sensitivity analysis also shows that revenue from the sales of the main products (methanol and electricity), as well as the cost of raw material materials, was the most sensitive. These two will incur the highest risk on the total investments from the four scenarios. [ABSTRACT FROM AUTHOR]

Process design critically depends on the characterization of fuels and their kinetics under process conditions. This study steps beyond the fundamental methods of thermogravimetry to modulated (MTGA) and Hi-Res™ (high resolution) techniques to (1) add characterization detail and (2) increase the utility of thermal analysis data. Modulated TGA methods overlay sinusoidal functions on the heating rates to determine activation energy as a function of temperature with time. Under devolatilization conditions, Hi-Res™ TGA maintains a constant mass loss with time and temperature. These two methods, run independently or overlaid, offer additional analysis in which multiple samples at different heating rates are run to different final temperatures. Advanced methods allow researchers to use fewer samples by conducting fewer runs, targeting practical experimental designs, and quantifying errors easier. The parameters of the studies included here vary the heating rate at 10, 30, and 50 °C/min; vary gas-phase oxygen for pyrolysis or combustion conditions; and particle size ranges of 100–125 µm, 400–425 µm, and 600–630 µm. The two biomass fuels used in the studies are pinewood from Northern Sweden and wheat straw. The influence of torrefaction is also included at temperatures of 220, 250, and 280 °C. Apparent activation energy results align with the previous MTGA data in that combustion conditions yield higher values than pyrolysis conditions—200–250 kJ/mol and 175–225 kJ/mol for pine and wheat combustion, respectively, depending on pre-treatment. Results show the dependence of these parameters upon one another from a traditional thermal analysis approach, e.g., the Ozawa-Flynn-Wall method, as well as MTGA and Hi-Res™ thermogravimetric investigations to show future directions for thermal analysis techniques. [ABSTRACT FROM AUTHOR]

Relevance. The widespread distribution and availability of biomass in the regions of Russian Federation make it possible to consider it as a renewable energy source with a lower negative impact on the environment compared to fossil fuels, since biomass is recognized as a carbon-neutral fuel. The use of biomass as a fuel in the form of pellets is increasing, which provides increased density and heat value. At the same time, pellets as a fuel or as a technological raw material have a significant disadvantage – low hydrophobicity. This problem is solved by torrefaction – low-temperature pyrolysis at a temperature of 200–300°C to produce bio-carbon. The study of the wood pellets torrefaction in order to improve it is an urgent task. Aim. To identify the impact of the parameters of the torrefaction of wood pellets on the thermal characteristics of the product (the highest heat value of bio-coal) and the regime parameters of the process (mass and energy yields), as well as to determine the parameters of the chemical kinetics of low-temperature pyrolysis as the basis for mathematical modeling and development of efficient torrefaction reactors. Object. Torrefied coniferous wood pellets of domestic production (Moscow region). Methods. Experimental study of the low-temperature pyrolysis thermal characteristics; synchronous thermal analysis in an inert atmosphere. Results. It was found that during the torrefaction of wood pellets in an inert atmosphere, a change in the holding time in the range of 30–60 minutes does not significantly affect the higher heat value, mass and energy yield of bio-coal, while an increase in temperature from 250 to 300°C reduces mass and energy yield, and the higher heat value increases by 26%. The dynamics of mass loss and thermal effects when heated to 600°C at a rate of 10 K/min are determined by means of the synchronous thermal analysis. It is established that the chemical kinetics of the process is described by a generalized reaction of the order n=1.507, in the Arrhenius equation the activation energy E=71.25 kJ/mol, the pre-exponential factor A=4772 s–1.

This study investigated the torrefaction of durian peel using air and nitrogen as carrier gases. A multilevel factorial design coupled with response surface methodology (RSM) and ANOVA analysis was employed to analyze the impact of torrefaction parameters on chemical properties and energy yield. Durian peel, an agricultural waste product, was torrefied at temperatures ranging from 200 to 320 °C for residence times between 0 and 30 min. Results showed that air torrefaction significantly enhanced thermal decomposition, reducing mass yield from 94.65 % to 30.63 % as the temperature increased from 200 °C to 300 °C with a 30-min holding time. Air torrefaction also increased the higher heating value (HHV) from 19.02 MJ/kg to 35.26 MJ/kg at 300 °C, compared to nitrogen, which achieved a maximum HHV of 32.49 MJ/kg. ANOVA analysis revealed that torrefaction temperature and carrier gas significantly affect energy yield and chemical properties. Air torrefaction positively affected HHV while reducing mass yield compared to nitrogen. Low-temperature air torrefaction showed enhanced energy yield improvement. These findings provided insights for optimizing torrefaction processes enhancing utilization wasted durian peel as a sustainable bioenergy resource.

Excessive use of fossil energy has negative impacts, which can cause climate change and environmental degradation. Thus, there is a need to find alternative, more sustainable energy sources. Biomass derived from Empty Fruit Bunch (EFB) waste is a newfound renewable energy source. However, its utilization is not optimal due to its low heating value and high chlorine (Cl) and potassium (K) content, which can interfere with combustion. EFB is washed with peat water to reduce potassium and chlorine content, and the torefaction process is used for combustion. This research aims to develop bio-coal production from empty fruit bunches using the torefaction method using fixed beds and continuous tubular reactors. The production process development also aims to obtain a larger production capacity than previous studies. This study uses varying weights of EFB produced into bio-coal, namely 250, 500 and 1000 grams, with a torefaction process temperature of 200°C for 30 minutes. As a result, the peat water flow rate decreased K, Cl and K2O content to the lowest content reduction value, which amounted to 8.31%, 0.42% and 3.96%, respectively. The heating value of bio-coal produced in a fixed bed reactor is 26,166 kJ/kg, while in a continuous tubular reactor, it is 21,720 kJ/kg. Based on these results, the fixed bed reactor shows a higher heating value than the continuous tubular reactor. The heating value obtained from these two types of reactors is comparable to sub-bituminous coal, which is usually used in steam power plants.

The prickly pear (Opuntia ficus-indica L., Cactaceae) seeds can be used as an alternative food product by the torrefaction process. Torrefaction is a pre-treatment process of biomass into solid fuel within a temperature range of 60–200 °C. This study aimed to investigate the effect of torrefaction parameters on the antioxidant potential of prickly pear seeds, which is considered a food by-product, by using the Central Composite Design approach (CCD).The best torrefaction parameters found to have the optimal phytochemical contents were: 200 °C and 50 min with 104.86 ± 1.94 GAE/g extract for Total Phenolic Content (TPC), 200 °C and 50 min with 81.23 ± 0.90 mg QE/g extract for Total Flavonoid Content (TFC), 200 °C and 50 min with IC50 = 90.66 ± 2.09 μg/ml for free radical scavenging activity (DPPH assay), 200 °C and 50 min with IC50 = 124.9 ± 4 μg/ml for radical cation total antioxidant capacity (ABTS assay). Our results demonstrated an increase of antioxidant activities with the increase of torrefaction parameters. Therefore, torrefaction has proven to be a value-added process to exploit prickly pear seed biomass and use it as a source of antioxidant food additives.

Improving energy content and hydrophobic nature of woody biomass can be pursued through torrefaction. This gives torrefied biomass with a low bulk density, potentially increasing storage and transport costs. To overcome this issue, densifying the torrefied biomass is necessary. However, poor binding of particles makes densification challenging without using a binder. Therefore, the aim of this study was to investigate the physicochemical characteristics and techno-economic aspects of torrefied rubberwood biomass (TRWB) when pelletized using various cassava-based binders at different blending ratios. The selected binders included cassava starch (CS), cassava pulp (CP), and cassava chip (CC). Each binder at 5%, 10%, or 15% (wt.) was mixed with TRWB and water before pelletizing using a flat die machine. The results revealed that pelletizing TRWB with different cassava-based binders at various blending ratios influenced the physicochemical characteristics of the TRWB pellets, particularly dimensions, bulk density, fuel and atomic ratios, and energy content. The TRWB pellets demonstrated energy densities in the range of 7.95–11.39 GJ/m3, and their mechanical durability and fine content fell within acceptable ranges. The TRWB pellets maintained their shape during 120 min of water soaking, with water absorption levels varying by binder dose. The pelletizing ability, material, and energy costs of TRWB pellets depend on binder type and dose. CP can be applied as a binder for pelletizing torrefied rubberwood biomass. However, the mechanical durability of the product needs to be above the user requirement or standard. [ABSTRACT FROM AUTHOR]

Energy production from coal combustion is responsible for nearly 40% of global CO2 emissions including SOx and NOx. This study aims to produce solid biomass fuels from oil-palm residues by torrefaction, having a high heating value (HHV) equivalent to fossil coals. The experiments were designed using Design Expert version 13 software to optimize the conditions affecting the fuel characteristics of the torrefied products. The statistical analysis suggested that the optimal conditions to achieve a high HHV and fixed carbon content while retaining the mass yield of biomass mainly depended on the temperature and torrefying time, while the size played a less important role in affecting the properties. The optimal conditions were observed to be at 283 °C (120 min) for EFBs, 301 °C (111 min) for PF, and 285 °C (120 min) for PKSs. The maximum HHV of 5229, 5969, and 5265 kcal/kg were achieved for the torrefied EFBs, PF, and PKSs, respectively. The energy efficiency of torrefied biomass was increased to 1.25–1.35. Ecoefficiency analysis suggested that torrefaction should be carried out at high temperatures with a short torrefying time. This low-cost bio-circular torrefied biomass showed promising fuel characteristics that could be potentially used as an alternative to coals. [ABSTRACT FROM AUTHOR]

The reaction mechanism and kinetics of the torrefaction process were reviewed, the effects of torrefaction temperature, residence time, heating rate, and torrefaction atmosphere on the physical and chemical properties of products were analyzed, and the effects of torrefaction on the subsequent pyrolysis, combustion, and gasification were discussed・ Torrefaction is usually performed under an inert atmosphere, in which the commonly used gas is nitrogen・ In addition, other atmospheres such as 02, C02, flue gas and NH3 have also been applied・ Different atmospheres can change the distribution of torrefaction products・ The study of torrefaction kinetics is helpful to reveal the thermal degradation behavior of torrefaction biomass and to provide reference for the design of torrefaction reactors・ Combining torrefaction with pyrolysis, gasification, combustion, and other processes can obtain high-quality bio-oil and hydrogen-rich synthesis gas and improve the utilization efficiency of biomass energy・ Finally, the development of lignocellulosic biomass torrefaction pretreatment technology was prospected regarding atmosphere, integrated optimization and production. [ABSTRACT FROM AUTHOR]

This study examines the considerable volume of food waste generated annually in Slovenia, which amounted to over 143,000 tons in 2020. The analysis shows that 40% of food waste consists of edible parts, highlighting the potential for reduction through increased consumer awareness and attitudes towards food consumption. The study shows that the consumption phase contributes the most to waste food (46%), followed by primary production (25%) and processing/manufacture (24%). The study addresses various thermodynamic processes, in particular, thermal conversion methods, such as torrefaction pyrolysis and hydrothermal carbonization, which optimize energy potential by reducing the atomic ratio (H/C) and (O/C), thereby increasing calorific value and facilitating the production of solid fuels. The main results show the effectiveness of torrefaction, pyrolysis and hydrothermal carbonization (HTC) in increasing the energy potential of food waste. [ABSTRACT FROM AUTHOR]

The pretreatment for torrefaction impacts the performance of biomass fuels and operational costs. Given their diversity, it is crucial to determine the optimal torrefaction conditions for different types of biomass. In this study, three typical solid biofuels, corn stover (CS), agaric fungus bran (AFB), and spent coffee grounds (SCGs), were prepared using fluidized bed torrefaction. The thermal stability of different fuels was extensively discussed and a novel comprehensive fuel index, "displacement level", was analyzed. The functional groups, pore structures, and microstructural differences between the three raw materials and the optimally torrefied biochar were thoroughly characterized. Finally, the biomass fuel consumption for household heating and water supply was calculated. The results showed that the optimal torrefaction temperatures for CS, AFB, and SCGs were 240, 280, and 280 °C, respectively, with comprehensive quality rankings of the optimal torrefied biochar of AFB (260) > SCG (252) > CS (248). Additionally, the economic costs of the optimally torrefied biochar were reduced by 7.03–19.32%. The results indicated that the displacement level is an index universally applicable to the preparation of solid fuels through biomass torrefaction. AFB is the most suitable solid fuel to be upgraded through torrefaction and has the potential to replace coal. [ABSTRACT FROM AUTHOR]

Torrefaction and combustion have been applied to naturally decomposed red oak logging residues. The results indicated that four-year natural decomposition would lower the energy density of red oak from 20.14 to 18.85 MJ/kg. Torrefaction reduced the O/C and H/C ratios but improved the energy yield values. Two combustion stages were observed for all samples, and no hemicellulose derivative thermogravimetric peak appeared for torrefied samples. The differential scanning calorimetry exothermic heat flow increased after torrefaction. In addition, the Kissinger–Akahira–Sunose average activation energy of untorrefied samples decreased in the first stage (from 157.77 to 149.52 KJ/mol), while it increased in the second stage (from 131.32 to 181.83 KJ/mol). The ∆H, ∆G, and ∆S values of all samples decreased in the first stage, while they increased when the conversion rate was greater than 0.5 for torrefied samples. These findings can aid in a better understanding of the fuel performance of torrefied and untorrefied naturally decomposed red oak logging residues. [ABSTRACT FROM AUTHOR]

Biomass energy for heating is going to be part of the spectrum of renewable energy sources. However, biomass combustion produces emissions of various pollutants with negative effects at both local and global scales. To reduce some of the locally important pollutant load, thermally treated biomass fuels may offer a partial solution. In this study, two biomass feedstocks, i.e., spruce chips and rapeseed straw, were thermally treated at 300 °C to produce biochars. Subsequently, both original materials and biochars were burned in a 25 kW retort combustion device. In both cases, the biochar showed lower emissions of carbon monoxide and nitrogen oxides, usually almost across the whole range of tested combustion conditions. In total, for the emission production per unit of net calorific value, the spruce biochar showed reductions in CO and NOx productions of 10.8% and 14.5%, respectively. More importantly, in rapeseed straw biochar, the difference was more pronounced. The total production was reduced by 28% and 42%, again in CO and NOx emissions, respectively. [ABSTRACT FROM AUTHOR]

This work explores the effects of the temperature (250, 280, 310°C), time (20, 40, 60 min), sewage sludge mixing ratio (25, 50, 75%) on the solid fuel quality and yield of the biochar produced from sewage sludge blended with pine sawdust. The optimal conditions for the torrefaction of sewage sludge and pine sawdust were investigated by the response surface methodology. Mathematical models were developed on the weight yield, high heating value and ash content and experimental data were examined through analysis of variance. The results depicted that the effects of temperature and mixing ratio were more considerable than residence time for the three response variables. The optimum point for weight yield, HHV, ash were predicted to be 60.82%, 21.58 MJ kg-1 and 18.78% at 310°C, 20 min and sewage sludge mixing ratio of 25%, respectively. The experimental results show that the average values of the experiments were 56.4%, 22.9 MJ kg-1, and 21% for weight yield, HHV and ash content, respectively. [ABSTRACT FROM AUTHOR]

Torrefaction techniques are often used to improve the properties of biomass fuels. This study developed a new detailed lumped model to investigate the reaction mechanism of rice husk (RH) and rice straw (RS) degradation during the torrefaction process. The validity of this model was confirmed by comparing it with the experimental result. The van Krevelen diagram and CHO index are obtained by the simulation. A new parameter (loss of O/loss of energy) was also defined to account for the energy efficiency of the torrefaction system. The calculation of the Chemkin model showed that 260 °C is relatively an optimum torrefaction temperature for rice husks, while for straw is 270 °C. Compared to rice husk, rice straw has a higher energy yield and more loss of oxygen after torrefaction. The simulation can provide information on the whole range of temperature, which makes up the experimental defects such as time consumption and high cost. Combining the van Krevelen diagram, CHO index and the new parameter (loss of O/loss of energy) could provide useful information that deepens the understanding of the biomass torrefaction process and the inherent connection between the different indexes. It is believed that the research result can provide some valuable insights and guidance for understanding and optimizing the torrefaction process. [ABSTRACT FROM AUTHOR]

In this study, an experimental strategy to obtain biochar and activated carbon from torrefied palm kernel shell as an efficient material for CO2 removal was evaluated. Biochar was obtained by slow pyrolysis of palm kernel shell at different temperatures (350 °C, 550 °C, and 700 °C) and previously torrefied palm kernel shell at different temperatures (220 °C, 250 °C, and 280 °C). Subsequently, activated carbons were prepared by physical activation with CO2 from previously obtained biochar samples. The CO2 adsorption capacity was measured using TGA. The experimental results showed that there is a correlation between the change in the O/C and H/C ratios and the functional groups –OH and C=O observed via FTIR in the obtained char, indicating that both dehydration and deoxygenation reactions occur during torrefaction; this favors the deoxygenation reactions and makes them faster through CO2 liberation during the pyrolysis process. The microporous surface area shows a significant increase with higher pyrolysis temperatures, as a product of the continuous carbonization reactions, allowing more active sites for CO2 removal. Pyrolysis temperature is a key factor in CO2 adsorption capacity, leading to a CO2 adsorption capacity of up to 75 mg/gCO2 for biochar obtained at 700 °C from non-torrefied palm kernel shell (Char700). Activated carbon obtained from torrefied palm kernel shell at 280 °C (T280-CHAR700-AC) exhibited the highest CO2 adsorption capacity (101.9 mg/gCO2). Oxygen-containing functional groups have a direct impact on CO2 adsorption performance due to electron interactions between CO2 and these functional groups. These findings could provide a new experimental approach for obtaining optimal adsorbent materials exclusively derived from thermochemical conversion processes. [ABSTRACT FROM AUTHOR]

This research aimed to demonstrate the thermal pathway (torrefaction technology) to convert organic waste to be biochar/biocoal. Organic waste (cabbage) from Nonthaburi fresh market, Thailand was used as raw material. Torrefaction technology was processed in horizontal cylindrical batch reactor with Nitrogen gas purging during doing experiment. Temperature profile was preliminary checked to find out lag time. Amount of loaded weight and particle size of material were preliminary tested. Experimental conditions such as time and temperature were tested at 30 and 60 minutes, and range temperature of 220 to 300°C. Important property of product; calorific value of product in form of high heating value (HHV) and mass yield percentage were measured. The optimal conditions were evaluated with two parameters; increase of HHV compared to reference condition and % mass yield. Increase temperature was significant effect to increase HHV value of biochar. The optimal time and temperature for getting the highest heating value were 60 minutes and 280°C. [ABSTRACT FROM AUTHOR]

The results of studies of the carbohydrate components of birch and pine wood samples torrefied in the temperature range of 200–300°C are presented. An analysis of the monosaccharide composition of carbohydrates hydrolyzed by trifluoroacetic acid has been performed. Resulting from torrefaction, the level of all the monosaccharides except for glucose exhibits a decrease. Already at 200°C, the amount of xylose extracted with the use of trifluoroacetic acid decreases by approximately two times as to compare to the reference sample. Increasing the torrefaction temperature to 250°C results in a decrease in the level of extractable xylose to 1% of the dry weight of initial material. The difference between changes in the monosaccharide composition of pine and birch cell walls is represented by the dynamics of the level of extracted glucose. Owing to torrefaction, a decrease in the amount of carbohydrate components occurs and, consequently, a decrease in the biodegradability of wood is observed, which should be taken into account in the course of composite materials development. [ABSTRACT FROM AUTHOR]

Torrefied biomass is a vital green energy source with applications in circular economies, addressing agricultural residue and rising energy demands. In this study, ML models were used to predict durability (%) and mass loss (%). Firstly, data was collected and preprocessed, and its distribution and correlation were analyzed. Gaussian Process Regression (GPR) and Ensemble Learning Trees (ELT) were then trained and tested on 80 % and 20 % of the data, respectively. Both machine learning models underwent optimization through Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) for feature selection and hyperparameter tuning. GPR-PSO demonstrates excellent accuracy in predicting durability (%), achieving a training R2 score of 0.9469 and an RMSE value of 0.0785. GPR-GA exhibits exceptional performance in predicting mass loss (%), achieving a training R2 value of 1 and an RMSE value of 9.7373e-05. The temperature and duration during torrefaction are crucial variables that are in line with the conclusions drawn from previous studies. GPR and ELT models effectively predict and optimize torrefied biomass quality, leading to enhanced energy density, mechanical properties, grindability, and storage stability. Additionally, they contribute to sustainable agriculture by reducing carbon emissions, improving cost-effectiveness, and aiding in the design and development of pelletizers. This optimization not only increases energy density and grindability but also enhances nutrient delivery efficiency, water retention, and reduces the carbon footprint. Consequently, these outcomes support biodiversity and promote sustainable agricultural, ecosystem, and environmental practices.

Torrefaction treatment improves biomass grindability by transforming the fibrous herbaceous to a more brittle and lighter coal-like material. Microwave-assisted torrefaction is a promising technology for biomass conversion into energy, fuels, and chemicals. The study applied microwave absorbers in the torrefaction process to improve the thermochemical characteristics and grindability of switchgrass. Switchgrass in two particle sizes was torrefied in a microwave reactor with biochar added as a microwave absorber under inert conditions. After torrefaction, the geometric mean particle and size distribution and selected physical characteristics were evaluated, and the grindability of the torrefied ground and chopped with and without biochar were compared with those of untreated switchgrass. The geometric diameter results decreased, and the specific energy required for grinding torrefied switchgrass with biochar was significantly reduced with extended residence times and at a torrefaction temperature of 300 °C. After grinding, the lowest grinding energy of 32.82 kJ at 300 °C/20 min was recorded with torrefied ground switchgrass/biochar. The 10% biochar added/250 °C resulted in deep cell wall disarrangement, whereas at a torrefaction temperature of 300 °C, large surface deformation and carbonized weight fractions were observed.

This study aimed to improve the physical and mechanical properties of pellets produced from torrefied sugarcane leaves blended with hydrochar as a binder. The hydrochar was obtained through hydrothermal carbonization of sugarcane leaves. Pellets were produced from blends of torrefied biomass with hydrochar in different ratios. The results showed that adding 10– 50% of the binder significantly increased density and compressive strength of the torrefied pellets. Single pellet density ranged from 1,059.2 kg/m3 to 1,135.5 kg/m3 , while compressive strength increased by 58–160%. The addition of hydrochar also decreased ash content (3.4–25.2%) and reduced sulfur and nitrogen contents (6–28% and 3–16%, respectively). Optimal conditions for pelletizing were determined at 70/30 proportions of torrefied biomass and binder. The resulting pellets had 10.8% ash content, 9.20% moisture content, 1,111.2 kg/m3 single pellet density, 6.66 MPa compressive strength, and 18.37 MJ/kg lower heating value. These findings demonstrate the potential of incorporating hydrochar as a binder to improve the properties of torrefied biomass pellets.