Search Results (305)

The water–energy–carbon (WEC) nexus provides a systems framework for minimizing trade-offs among water security, energy reliability, and carbon mitigation. Within this framework, waste-derived biochar catalysts offer a circular pathway that simultaneously valorizes residues, reduces process energy demand, and supports carbon management through stable carbon storage and catalytic co-benefits. This review consolidates recent advances in biochar-based catalysts engineered from agricultural, industrial, municipal, and sludge-derived wastes, highlighting how feedstock selection and thermochemical processing, namely pyrolysis, hydrothermal carbonization (HTC), and torrefaction, as well as activation and post-modification (heteroatom doping and metal/metal-oxide incorporation) govern structure–property–performance relationships. The synthesized catalysts have been widely applied in water and wastewater treatment, including adsorption–advanced oxidation process (AOP) hybrids, Fenton-like systems, peroxydisulfate/persulfate (PS) and peroxymonosulfate (PMS) activation, photocatalysis, and the removal of emerging contaminants. They have also demonstrated strong potential in energy conversion processes such as the hydrogen evolution reaction (HER), oxygen reduction and evolution reactions (ORR/OER), biomass reforming, and carbon dioxide (CO₂) conversion. In addition, these materials contribute to carbon management through sequestration pathways, avoided emissions, and life cycle assessment (LCA)-based sustainability evaluations. Finally, we propose a WEC-aligned design roadmap integrating techno-economic analysis (TEA), LCA, and scale-up considerations to guide next-generation biochar catalysts toward robust performance in real matrices and deployment-ready systems. Full article

This study investigates the conversion of textile wastewater sludge (TWS) and textile cotton waste (TCW) into solid biofuels through pelletization and torrefaction, addressing the growing need for sustainable waste management and alternative fuels in the textile sector. Blended feedstocks were conditioned to ~10% moisture, pelletized into 8 mm cylinders, and thermally upgraded at 200–240 °C for 30–90 min. Proximate and ultimate analyses, calorific value measurements, compressive strength testing, bulk and true density assessment, and TGA–DTG were used to evaluate fuel properties, while response surface methodology (RSM) optimized torrefaction parameters. The TCW-rich 20:80 (TWS:TCW) blend with 5% starch exhibited the most favorable overall performance, achieving a calorific value of 3377 kcal kg⁻¹, ash of 10.3%, bulk density of 554 kg m⁻³, and maximum compressive strength of 14.9 N mm⁻². Torrefaction at 200 °C for 60 min increased the GCV to 4083 kcal kg⁻¹ with a high mass yield of 92%, indicating mild thermal decomposition and good energy retention. Further Torrefaction at 220–240 °C increased GCV to 4362–4565 kcal kg⁻¹, accompanied by expected mass-yield reductions due to increased devolatilization. TGA–DTG confirmed faster and cleaner decomposition for TCW-rich pellets and higher residues for sludge-rich blends. RSM indicated temperature as the dominant factor governing mass and energy yields. These findings demonstrate that optimized co-pelletization and mild-to-moderate torrefaction can effectively transform textile residues into energy-dense, mechanically stable biofuels suitable for industrial heat applications. Full article

To compete with fossil fuels, biofuels produced from renewable waste biomass must be cost-effective, adaptable to existing heat and power infrastructure, and possess desirable fuel properties and performance metrics matching those of fossil fuels, while having a much lower carbon footprint. However, handling and processing biowastes in thermochemical biorefineries is challenging owing to their high moisture content, low bulk density, poor grindability, low calorific value, and heterogeneous physicochemical properties. Torrefaction has emerged as an effective thermochemical technology for upgrading biowastes into torrefied biomass, which exhibits improved, homogeneous physicochemical properties, including higher calorific value, higher bulk density, better grindability, and hydrophobicity. This review synthesizes the current state of research on torrefaction, with particular emphasis on process parameters, reactor designs, commercial-scale implementations, and an analysis of its strengths, weaknesses, opportunities, and threats. The comparative advantages and limitations of different torrefaction reactors are highlighted, emphasizing how each reactor’s characteristics determine its suitability for specific circumstances and operating conditions. This article also considers the technical and economic challenges associated with scaling up torrefaction. The discussion on specific case studies on techno-economic analysis of torrefaction outlines the key barriers and provides incentives for researchers to consider when upscaling the technology. The strengths, weaknesses, opportunities, and threat analysis offers strategic insights for policymakers and industry stakeholders into possible actions to support torrefaction and its upscaling. Full article

The increasing demand for sustainable materials has driven interest in biocomposites that incorporate low-value agricultural residues to offset the use of virgin plastics. The study investigated the production of blend pellets from raw and torrefied almond shells and post-consumer plastic waste as a potential feedstock for biocomposite and biofuels applications. Almond shells were torrefied in a lab-scale fixed-bed reactor at 300 °C for 30 min prior to the pelleting tests. High-density polyethylene (HDPE) and polypropylene (PP) wastes were size-reduced in a Crumbler (rotary shear grinder) fitted with a 2 mm head and a 2 mm screen to remove the fines. A portion of the crumbled HDPE, and torrefied almond shells were further ground in a Wiley mill fitted with 2 and 1 mm screens for flat die pelleting tests. The flat die pellet mill used for testing had a 6 mm die and a length-to-diameter (L/D) ratio of 2.0. The blend ratio consisted of 30% torrefied almond shells and 70% HDPE, with a 10% starch binder. The measured pellet properties include unit, bulk and tap densities, durability, and expansion ratio. The bulk density of the blend pellets ranged from 360 to 410 kg/m³, and durability ranged from 80% to 88%. The blend pellet unit density ranged from 830 to 880 kg/m³. The blend pellets produced using crumbled HDPE, PP and raw and torrefied almond shells in a ring die pilot-scale pellet mill with an L/D ratio of 6 and steam conditioning exhibit similar densities to those of HDPE pellets produced using a flat die pellet mill, albeit with lower durability. The study indicated that a smaller grind size and preheating the blend before pelleting produce blend pellets with higher density and greater durability. Full article

This paper examines the study of an advanced design for a continuously operating fluidized bed reactor applied to sunflower husk torrefaction in a superheated steam environment, which is simulated in a cold model of the reactor. The simulated reactor has a diameter of 0.3 m and contains six vertical baffles installed along the reactor walls, providing loop-like movement of crushed husk particles from the reactor loading point to the reactor biomass unloading point. The residence time of crushed sunflower husk biomass particles in the reactor was studied by introducing colored biomass particles into the bed; these particles had the same mass and size as the undyed material. According to modeling results, replacing superheated steam with room-temperature air in the “cold” model may not lead to significant changes in the hydrodynamics of the fluidized bed or their effect on particle mixing. Experiments were conducted at an air velocity of 0.6 m/s relative to the cross-section of the empty apparatus, which is 3.5-fold greater than the minimum fluidization velocity. Samples were collected at the reactor outlet and dissolved in distilled water. The transparency of the resulting solution was measured using a KFK-3 photometer, and the amount of colored substance in each sample was determined accordingly. The most probable average residence time of biomass particles in the cold model amounted to 6–8 min at a Peclet number of 47. To ensure full operation of the torrefaction reactor under ideal plug-flow conditions, the reactor must be equipped with 24 baffles. The residence time of biomass particles required for optimal operation of the reactor was estimated to 24–32 min, which may be sufficient to produce biochar with a high calorific value, suitable for co-firing with coal. Full article

Cachaça, a traditional Brazilian spirit, undergoes significant sensory refinement through barrel aging. In this study, we investigated how heat treatment of Brazilian woods (Balsam, Jaqueira, Jequitibá, Amburana, and Ipê) affects the sensory profile of cachaça, using Oak as a benchmark. Physicochemical characterization, toasting assessments, sensory analysis, and artificial intelligence (AI) were integrated to develop a predictive model for optimizing wood selection and heat-treatment conditions to achieve targeted sensory profiles. Applying this model, we produced a five-wood cachaça, a novel spirit distinguished by its complexity and customized sensory attributes. This approach reveals that each wood species develops distinct characteristics depending on toasting parameters such as time and temperature, challenging the current Brazilian practice where a single toasting condition is applied to all woods without prior physicochemical analysis. Linking wood composition with sensory outcomes through AI, this work introduces an unprecedented product innovation and demonstrates the potential of multi-criteria analysis to guide spirit maturation, enhance product design, and reshape the beverage industry. Full article

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

Biochar has gained significant attention as a multifunctional material linking biomass energy technologies with sustainable agriculture, providing combined benefits in soil improvement, waste valorization, and climate mitigation. This review examines biochar within the context of thermochemical conversion processes—pyrolysis, gasification, and torrefaction—and summarizes the operational parameters that influence both energy yields and biochar quality. It synthesizes agronomic, environmental, and engineering research to explain the mechanisms through which biochar enhances soil structure, nutrient retention, water availability, microbial activity, and carbon stability. The review also assesses its role as a long-term carbon sink and its potential integration into negative-emission systems such as bioenergy with carbon capture and storage (BECCS). However, the way that biomass conversion factors concurrently influence energy performance, biochar physicochemical quality, and its agronomic and climate-mitigation consequences across many environmental contexts is rarely integrated into a unified analytical framework in current evaluations. To close that gap, this review identifies cross-cutting patterns, trade-offs, and uncertainties while methodically integrating the information on the co-behavior of various aspects. Circular economy initiatives, carbon markets, and rural development are mentioned as key potential. On the other hand, economic variability, variable performance across soil types, lack of regulatory harmonization, rivalry for biomass, and logistical limits are big hurdles. Standardized production techniques, long-term field research, life cycle and techno-economic evaluations, and integrated system design are among the top research priorities. Overall, the evidence suggests that biochar is a promising tool for creating resilient and low-carbon agriculture and energy systems, provided that scientific, technological, and governance advancements are coordinated. Full article

Torrefaction, a mild thermochemical pretreatment process, generates the fuel-torrefied biomass along with non-condensable and condensable gases. The latter can be condensed to yield a dark, viscous liquid called torrefaction condensate (TC). In this study, we investigated the effect of TC on growth and exopolysaccharide (EPS) production by the green microalgae Chlamydomonas reinhardtii, a well-known model organism. Aspen wood pellets were torrefied at different temperatures, and the condensate formed at each temperature was analyzed. Based on the GC-MS analysis, 225 °C TC was selected and used for the cultivation of C. reinhardtii. Results show that at 2 mL/L and 2.5 mL/L concentrations, TC negatively impacts growth, EPS production, as well as the composition of amino acids, lipids, and fatty acids n of C. reinhardtii. However, C. reinhardtii gradually adapted to TC and attained the growth patterns comparable to the control, showing the resilience of the culture. The biochemical and antioxidant properties of the EPS showed significant differences to that of the control. Therefore, cultivating these microalgae in TC suggests a new microalgal biorefinery approach through the utilization of low-value TC for the production of value-added products, such as EPS. Full article

This study investigates the torrefaction of polyvinyl chloride (PVC) and cellulose, two major constituents of agricultural waste, with the aim of improving chlorine removal and enhancing the energy quality of the resulting solid products. Thermodynamic simulations using HSC Chemistry 9.0 were first conducted to predict equilibrium compositions, particularly chlorine-containing species. Thermogravimetric analysis (TGA) and coupled TGA-FTIR were employed to monitor mass loss and identify gaseous chlorine compounds. Based on these preliminary results, torrefaction experiments were carried out at temperatures of 250–300 °C and durations of 30–90 min. The results demonstrate a significant synergistic effect between cellulose and PVC during co-torrefaction, achieving 97% chlorine removal under optimal conditions (9:1 cellulose-to-PVC ratio, 250 °C, 30 min). This effective dechlorination helps mitigate Cl-induced corrosion and reduces the risk of dioxin formation in industrial applications, enabling the sustainable upcycling of PVC-contaminated biomass into clean solid fuels. Torrefaction temperature exerted a stronger influence than time on mass loss, yielding approximately 40% solid residue at 300 °C. While both solid and energy yields decreased with increasing temperature and time, the O/C and H/C atomic ratios decreased by 56% and 48%, respectively, indicating a substantial improvement in fuel properties. The observed synergy is attributed to cellulose-derived hydroxyl radicals promoting PVC dehydrochlorination. This process offers a scalable and economically viable pretreatment route for PVC-containing biomass, potentially reducing boiler corrosion and hazardous emissions. Full article

The global transition to renewable energy has intensified the focus on anaerobic digestion (AD) as a sustainable solution for organic waste management and biogas production. This study presents a comprehensive techno-economic analysis (TEA) of AD systems integrated with carbon capture and digestate treatment technologies, evaluated across four distinct operational scenarios. The research leverages an innovative AI-agent framework to streamline TEA, enabling stakeholders to conduct sophisticated analyses without specialized expertise. Key findings reveal that feedstock composition significantly impacts biogas yields, with maize and rye blends (mix2) outperforming maize-dominated mixes (mix1), achieving higher biogas production (26,029 m³/y vs. 23,182 m³/y). Membrane-based CO₂ separation and liquefaction technologies demonstrated superior economic viability compared to cryogenic methods, yielding lower energy consumption (2400 MWh/y vs. 3000 MWh/y) and higher net revenues (GBP 4.0 million/y vs. GBP 3.5 million/y). Financial metrics further underscored the advantages of membrane-based systems, with the mix2 configuration achieving a net present value (NPV) of GBP 19 million and an internal rate of return (IRR) of 36%, alongside a shorter payback period (3 years). Sensitivity analysis highlighted natural gas prices and tax rates as critical determinants of economic performance, while water costs had negligible impact. The study also evaluated digestate treatment methods, finding that base-case separation outperformed torrefaction in financial returns. Full article

Potato peels are a waste product accounting for 15–40% of the mass of raw potatoes, depending on the processing method employed. The production of solid biofuel from potato peel was investigated in a superheated-steam fluidized bed filled with olivine sand. The co-fluidization of dried, crushed potato peels together with olivine sand was also investigated. Stable co-fluidization of olivine sand and crushed potato peels can be achieved when the mass fraction of potato peels in the fluidized bed does not exceed 3% (w/w). In a fluidized bed containing 3% % (w/w) potato peel, increasing the operational temperature of torrefaction from 200 to 300 °C with a processing duration of 30 min resulted in a 1.35-fold increase in HHV from 20.68 MJ/kg up to 27.93 MJ/kg based on ash-free dry mass. The effects of torrefaction temperature and duration on 5-hydroxymethylfurfural and furfural contents in condensable gaseous torrefaction products were studied, along with changes in the chemical composition of potato peel ash as a result of torrefaction. Furthermore, we analyzed the bed agglomeration index (BAI) predicting the possibility of agglomerate formation during combustion of torrefied potato peel in a fluidized bed and found that the probability of agglomeration may decrease along with increasing temperature and duration of the torrefaction process. Nevertheless, only the most severe torrefaction conditions of 300 °C for 30 min may completely prevent the risk of agglomerate formation during the subsequent combustion of torrefied potato peels as a solid biofuel. The proposed potato peel processing technology may be used in future frozen and fried potato factories in order to solve waste disposal issues while also reducing the costs of heat and electricity generation, as well as allowing for the recovery of high-value biochemicals from the torrefaction condensate. Full article

There is a need to address the limitations of wheat straw (WS) as a raw biomass fuel, promote its valorisation into a high-quality renewable solid fuel, and enable this fuel to replace fossil fuels in applications such as power plants and industrial boilers. This study focused on optimizing microwave torrefaction parameters to enhance key fuel properties. Optimal conditions were determined via the Box–Behnken design (BBD) within Response Surface Methodology (RSM) as 422.32 W of microwave power, 14.95 min of irradiation time, and a 15 g microwave absorber, resulting in a 69.12% mass yield, an 18.44 MJ/kg higher heating value (HHV) surpassing lignite at 16.76 MJ/kg, and a 25.50% Energy-Mass Co-efficiency Index (EMCI). Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis/derivative thermogravimetric analysis (TG/DTG) were conducted to gain insights about chemical composition and thermal stability variations due to torrefaction. LCA showed that electricity produced from 1 ton of torrefied WS reduces CO₂ emissions by 259.26 kg CO₂eq compared to electricity generated from bituminous coal. From an economic perspective, the usage of torrefied WS for power generation lead to a net profit of CNY 435.19/ton. This scalable technology, by valorising agricultural waste for fuel production, delivers dual environmental and economic benefits, laying the groundwork for industrial deployment. Full article

Raw biomass presents challenges for energy use due to its high moisture content, low bulk density, and susceptibility to biological degradation, which hinder storage, transport, and utilization. An experimental setup was developed to investigate exothermic behavior during torrefaction of agricultural and food industry wastes. Exothermic reactions were observed between 190 °C and 450 °C, with more prominent effects in corn waste, sugarcane bagasse, and straw compared to sunflower husks, palm residues, and coffee skin. A series of tests performed on a torrefaction reactor with a core-type wall heating system showed that the heat generated by exothermic reactions makes it possible to reduce the torrefaction time by a factor of 1.5 (from 120 to 80 min) to obtain biochar of the required quality, with only a slight process temperature increase (15%, from 200 to 230 °C). These findings offer practical pathways for transforming waste into valuable biochar, fostering environmental resilience and socio-economic benefits in communities reliant on biomass resources. Full article

The inefficient disposal of corn stover (CS) and the accumulation of magnesite tailings (MMTs) pose dual environmental threats. Although biomass gasification can utilize CS, its inherent drawbacks result in syngas with low heating value and high tar content. Torrefaction pretreatment can effectively improve biomass properties, and the use of steam as a reaction medium can further optimize the product’s pore structure. This study proposes a steam-assisted torrefaction pretreatment to address the inefficient utilization of CS and the disposal challenges of MMTs. The experimental results demonstrated that torrefaction at 300 °C with 30% water content for 60 min significantly improved the raw material’s properties. The optimized CSBC exhibited a well-developed pore structure and achieved a phenol removal rate of 63.4%. The addition of MMTs further enhanced the pretreatment effect, increasing the removal rate to 75.5% and confirming the superiority of the CSBC–magnesite composite system. The steam atmosphere improved phenol adsorption by regulating pore structures and surface functional groups, offering a feasible approach for utilizing solid waste resources and developing a new in situ tar control strategy. Full article