Search Results (123)

Second-, third-, and fourth-generation biofuels represent an important response to the challenges of clean energy supply and climate change. In this context, the Horizon 2020 “TO-SYN-FUEL” project aimed to produce advanced biofuels together with phosphorus from municipal wastewater sludge through a combination of technologies including a Thermo-Catalytic Reforming system, Pressure Swing Adsorption for hydrogen separation, Hydrodeoxygenation, and biochar gasification for phosphorous recovery. This article presents the environmental performance results of the demonstrator installed in Hohenberg (Germany), with a capacity of 500 kg per hour of dried sewage sludge. In addition, four alternative scenarios are assessed, differing in the source of additional thermal energy used for sludge drying: natural gas, biogas, heat pump, and a hybrid solar greenhouse. The environmental performance of these scenarios is then compared with that of conventional fuel. The comparative study of these scenarios demonstrates that the biofuel obtained through wood gasification complies with the Renewable Energy Directive, while natural gas remains the least sustainable option. Heat pumps, biogas, and greenhouse drying emerge as promising alternatives to align biofuel production with EU sustainability targets. Phosphorus recovery from sewage sludge ash proves essential for compliance, offering clear environmental benefits. Although sewage sludge is challenging due to its high water content, it represents a valuable feedstock whose sustainable management can enhance both energy recovery and nutrient recycling. Full article

This study investigates the influence of feedstock blending on the structural and thermal properties of biochar produced via downdraft gasification at 850 °C. Biochars from 100% oak, a 1:1 oak-–pine blend, and a ternary blend of 50% oak, 30% pine, and 20% RDF were analyzed using SEM, BET, TGA, XRD, Raman spectroscopy, and CHN elemental analysis. The oak biochar exhibited the highest surface area (107.7 m²/g) and fixed-carbon content (79.94%), while the RDF-based biochar showed a 99.2% decrease in surface area (0.86 m²/g) and a 19.7% reduction in fixed carbon. These findings underscore RDF’s detrimental impact on porosity and stability, despite its waste valorization potential, suggesting its limited use in applications requiring high adsorption or structural integrity. Further studies should optimize RDF preprocessing and blending ratios to balance sustainability with functional performance. Full article

This study investigates how the inclusion of refuse-derived fuel (RDF) alters the surface chemistry and electrostatic behavior of oak-based biochar. Biochars were produced using downdraft gasification at 850 °C from 100% oak (HW) and a ternary blend comprising 50% oak, 30% pine, and 20% RDF (HW/SW/RDF). Characterization using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), zeta potential, pH, and electrophoretic mobility was conducted to assess surface functionality and colloidal behavior. The RDF-containing biochar exhibited a 43.3% increase in surface nitrogen content (from 0.24% to 0.90%) and a 6.6% rise in calcium content (from 2.07% to 2.27%) alongside the introduction of chlorine (0.20%) and elevated silicon levels (0.69%) compared to RDF-free counterparts. A concurrent reduction in oxygen-containing functional groups was observed, as O1s decreased from 15.75% in HW to 13.37% in HW/SW/RDF. Electrokinetic measurements revealed a notable decrease in zeta potential magnitude from −31.5 mV in HW to −24.2 mV in HW/SW/RDF, indicating diminished surface charge and colloidal stability. Moreover, the pH declined from 10.25 to 7.76, suggesting a loss of alkalinity and buffering capacity. These compositional and electrostatic shifts demonstrate that RDF inclusion significantly modifies the surface reactivity of biochar, influencing its performance in catalysis, ion exchange, and nutrient retention. The findings underscore the need for tailored post-treatment strategies to enhance the functionality of RDF-modified biochars in environmental applications. Full article

Against the backdrop of escalating global carbon emissions, the steel industry urgently requires a transition toward green and low-carbon practices. As a conditionally carbon-neutral renewable energy source, biochar holds potential for replacing traditional fossil-based reducing agents. This study aims to investigate the mechanism and performance differences between biochar (wood char, bamboo char) and conventional reducing agents (semi-coke, coke powder, anthracite) in the direct reduction process of carbon-bearing briquettes. Through reduction experiments simulating rotary kiln conditions, combined with analysis of reducing agent gasification characteristics, carbon-to-oxygen (C/O) molar ratio control, X-ray diffraction (XRD), and microstructural examination, the high-temperature behavior of different reducing agents was systematically evaluated. Results indicate that biochar exhibits superior gasification reactivity due to its high specific surface area and developed pore structure: wood char and bamboo char show significantly enhanced reaction rates above 1073 K, approaching complete conversion at 1173 K. In contrast, anthracite and coke powder, characterized by dense structures and low specific surface areas, failed to achieve complete gasification even at 1273 K. Pellets containing bamboo char achieved the highest metallization rate (90.16%) after calcination at 1373 K. The compressive strength of the pellets first decreased and then increased with rising temperature, consistent with the trend in metallization rate. The mechanism analysis indicates that the high reactivity and porous structure of biochar promote rapid CO diffusion and synergistic gas–solid reactions, significantly accelerating the reduction of iron oxides and the formation of metallic iron. Full article

The urgent need to reduce greenhouse gas emissions and shift towards renewable energy has increased attention on biochar as a viable negative emission strategy. This review assesses the potential of biochar produced from organic and waste biomass via thermochemical processes—including pyrolysis, gasification, and hydrothermal carbonization—to address climate and energy challenges. Recent advances in biochar production are critically examined, highlighting how process design controls improve key properties such as carbon stability, atomic ratios, porosity, and energy density. These factors influence biochar’s performance in carbon sequestration and its utility across industrial sectors, ranging from agriculture and construction to energy generation and carbon capture systems. Results indicate that large-scale adoption of biochar could lower carbon emissions, enhance soil fertility, and produce renewable fuels like hydrogen, while also benefiting circular economy initiatives. However, obstacles remain, including economic costs, feedstock logistics, process optimization, and potential environmental or social impacts. This review underscores that unlocking biochar’s full promise will require interdisciplinary research, robust quality standards, and supportive policies. With integrated efforts across science, industry, and policy, biochar can serve as an effective and sustainable technology for emission reduction and contribute significantly to global carbon neutrality goals. Full article

Hemp (Cannabis sativa L.) is a high-yielding crop cultivated for fiber and seed production, generating substantial lignocellulosic residues such as hurds. These byproducts can be valorized through pyro-gasification, a thermochemical process that offers a sustainable alternative to combustion and produces biochar—a promising soil amendment due to its ability to enhance soil quality and mitigate drought stress. This research explores the viability of utilizing industrial hemp hurds as a direct feedstock for biochar production within the context of agricultural exploitation. The study specifically focuses on assessing the feasibility of converting raw, unprocessed hemp hurds into biochar through pyrolysis. A comprehensive characterization of the resulting biochar is conducted to evaluate its properties and potential applications in agriculture, establishing a foundational understanding for future agronomic use. Specific analysis included proximate and ultimate analysis, thermogravimetric analysis (TGA), SEM-EDS, and phytotoxicity testing. The biochar exhibited an alkaline pH (≥9), a low H/C ratio (0.37), and suitable macro- and micronutrient levels. Microstructural analysis revealed a porous architecture favorable for nutrient retention and water absorption. Germination tests with corn (Zea mays L.) showed a germination index above 90% for substrates containing 0.5–1% biochar. These findings establish a foundation for future research aimed at thoroughly exploring the agricultural potential of this material. Full article

Gasification of municipal solid waste and other biogenic residues (e.g., biomass and biowaste) is increasingly recognized as a promising thermochemical pathway for converting non-recyclable fractions into valuable energy carriers, with applications in electricity generation, district heating, hydrogen production, and synthetic fuels. This paper provides a comprehensive analysis of major gasification technologies, including fixed bed, fluidized bed, entrained flow, plasma, supercritical water, microwave-assisted, high-temperature steam, and rotary kiln systems. Key aspects such as feedstock compatibility, operating parameters, technology readiness level, and integration within circular economy frameworks are critically evaluated. A comparative assessment of incineration and pyrolysis highlights the environmental and energetic advantages of gasification. The valorization pathways for main product (syngas) and by-products (syngas, ash, tar, and biochar) are also explored, emphasizing their reuse in environmental, agricultural, and industrial applications. Despite progress, large-scale adoption in Europe is constrained by economic, legislative, and technical barriers. Future research should prioritize scaling emerging systems, optimizing by-product recovery, and improving integration with carbon capture and circular energy infrastructures. Supported by recent European policy frameworks, gasification is positioned to play a key role in sustainable waste-to-energy strategies, biomass valorization, and the transition to a low-emission economy. Full article

This study presents a comprehensive characterization of oak biochar produced via downdraft gasification at 850 °C. The research employs a wide range of advanced analytical techniques to examine the biochar’s physical, chemical, and structural properties. Scanning electron microscopy (SEM) revealed a mesoporous structure, while Brunauer–Emmett–Teller (BET) analysis showed a surface area of 88.97 m²/g. Thermogravimetric analysis (TGA) demonstrated high thermal stability and carbon content (78.7%). X-ray photoelectron spectroscopy (XPS) and ultimate analysis confirmed the high degree of carbonization, with low O/C (0.178) and H/C (0.368) ratios indicating high aromaticity. Fourier transform infrared spectroscopy (FTIR) identified functional groups suggesting potential for CO₂ adsorption. The biochar exhibited a negative zeta potential (−31.5 mV), indicating colloidal stability and potential for soil amendment applications. X-ray diffraction (XRD) and Raman spectroscopy provided insights into the biochar’s crystalline structure and graphitization degree. These findings highlight the oak biochar’s suitability for diverse applications, including soil improvement, carbon sequestration, and environmental remediation. By filling knowledge gaps in oak-specific biochar research, this study underscores the benefits of optimized downdraft gasification and sets a foundation for future advancements in sustainable biochar applications. Full article

Waste biomass gasification can contribute to the production of alternative and environmentally sustainable green fuels. Research at the CREC–UWO (Chemical Reactor Engineering Center–University of Western Ontario) considers an integrated gasification process where both electrical power, biochar, and tar-free syngas suitable for alcohol synthesis are produced. In particular, the present review addresses the issues concerning tar removal from the syngas produced in a waste biomass gasifier via a catalytic post-gasification (CPG) downer unit. Various questions concerning CPG, such as reaction conditions, thermodynamics, a Tar Conversion Catalyst (TCC), and tar surrogate chemical species that can be employed for catalyst performance evaluations are reported. Catalyst performance-reported results were obtained in a fluidizable CREC Riser Simulator invented at CREC–UWO. The present review shows the suitability of the developed fluidizable Ni–Ceria γ-alumina catalyst, given the high level of tar removal it provides, the minimum coke that is formed with its use, and the adequate reforming of the syngas exiting the biomass waste gasifier, suitable for alcohol synthesis. Full article

Sewage sludge, as a by-product of wastewater treatment, poses severe environmental challenges due to its high moisture, ash, and heavy metal content. Thermochemical conversion technologies, including pyrolysis and gasification, offer promising pathways for transforming sludge into valuable products such as bio-oil, biochar, and syngas. This paper systematically reviews recent advancements in pyrolysis and gasification, focusing on process optimization and catalyst development to enhance product quality and energy recovery. In pyrolysis, factors such as temperature, residence time, and heating rate significantly influence product yields and properties, while catalytic and co-pyrolysis approaches further improve product structure and reduce environmental risks. In gasification, parameters like the equivalence ratio, steam-to-sludge ratio, and catalyst application are key to enhancing syngas yield and quality, with biomass co-gasification offering additional benefits. Despite substantial progress, commercialization remains challenged by high operational costs, catalyst durability, and environmental impacts. Future research should emphasize improving sludge pretreatment, optimizing thermochemical processes, developing efficient and cost-effective catalysts, and addressing critical issues such as bio-oil quality, tar management, and syngas purification to promote the industrial application of these technologies. Full article

Agricultural waste poses significant environmental, economic, and social challenges globally, with estimates indicating that 10–50% of agricultural products are discarded annually as waste. This review explores strategies for managing agricultural waste to mitigate its adverse impacts and promote sustainable development. Agricultural residues, such as those from sugarcane, rice, and wheat, contribute to pollution when improperly disposed of through burning or burying, contaminating soil, water, and air. However, these residues also represent untapped resources for bioenergy production, composting, mulching, and the creation of value-added products like biochar, bioplastics, single-cell protein and biobased building blocks. The paper highlights various solutions, including integrating agricultural waste into livestock feed formulations to reduce competition for human food crops, producing biofuels like ethanol and biodiesel from lignocellulosic materials, and adopting circular economy practices to upcycle waste into high-value products. Technologies such as anaerobic digestion for biogas production and gasification for synthesis gas offer renewable energy alternatives and ample feedstocks for gas fermentation while addressing waste management issues. Composting and vermicomposting enhance soil fertility, while mulching improves moisture retention and reduces erosion. Moreover, the review emphasizes the importance of policy frameworks, public-private partnerships, and farmer education in promoting effective waste management practices. By implementing these strategies, agricultural waste can be transformed into a resource, contributing to food security, environmental conservation, and economic growth. Full article

In response to significant environmental challenges, biochar has garnered attention for its applications across diverse fields. Characterized by high carbon content resulting from the thermal degradation of biomass, biochar offers a sustainable strategy for waste valorization and environmental remediation. This paper offers a comprehensive overview of biochar production from residual biomass, emphasizing feedstock selection, conversion pathways, material properties, and application potential. Key production techniques, including pyrolysis, gasification, and hydrothermal carbonization, are critically evaluated based on operational conditions, energy efficiency, product yield, and environmental implications. The functional performance of biochar is further discussed in the context of soil enhancement, wastewater treatment, renewable energy generation, and catalytic processes, such as biohydrogen production. By transforming waste into value-added products, biochar technology supports circular economy principles and promotes resource recovery. Ongoing research aimed at optimizing production processes and understanding application-specific mechanisms is crucial to fully realizing the environmental potential of biochar. Full article

This paper presents the results of an investigation into the effect of the physicochemical properties of carbon chars (biochars) on the performance of direct carbon solid oxide fuel cells (DC-SOFCs). Biochars were obtained from walnut, coconut, pistachio, hazelnut and peanut shells by pyrolysis at a temperature of 850 °C. The results of structural studies conducted using X-ray diffraction and Raman spectroscopy reflected a low degree of graphitisation of carbon particles. Biochar derived from walnut shells is characterised by a relatively uniform content of alkali elements, such as sodium, potassium, calcium, magnesium and iron, which are natural components of the mineral residue and act as catalysts for the Boudouard reaction. This study of gasification of biochar samples in a CO₂ atmosphere recorded that the highest conversion rate from solid phase to gaseous phase was for the biochar sample produced from walnut shells. The superior properties of this sample are directly connected to structural features, as well as to the random distribution of alkali elements. DC-SOFCs involving 10 mol% of Sc₂O₃, 1 mol% of CeO₂, 89 mol% of ZrO₂ (10S1CeZ) or 8 mol% of Y₂O₃ in ZrO₂ (8YSZ) were used as both solid oxide electrolytes and components of the anode electrode. It was found that the highest electrochemical power output (P_max) was achieved for DC-SOFCs fuelled by biochar from walnut shells, with around 103 mW/cm² obtained for such DC-SOFCs involving 10S1CeZ electrolytes. Full article

This study presents the development of a kinetic model for the gasification of biochar with carbon dioxide and compares the results obtained using a thermogravimetric analyzer (TGA) and a fluidized bed reactor (FBR). The kinetic experiments investigated the effects of the CO₂ partial pressure (0.33–1 atm), temperature (800–1000 °C), and CO₂/C ratio (3.5–10.5). Three structural models, the shrinking core model (SCM), volumetric model (VM), and power-law model (PLM), were evaluated for their ability to predict experimental results. The results demonstrated that increasing the temperature, CO₂ partial pressure, and CO₂/C ratio enhanced the gasification rate, reducing the time required for complete biochar conversion. The apparent activation energy for both reactors was similar (156–159 MJ/kmol), with reaction orders of 0.4–0.49. However, the kinetic models varied significantly between setups. In the TGA, the PLM provided the best fit to experimental data, with standard deviations of 2.6–9%, while in the FBR, the SCM was most accurate, yielding an average deviation of 1.5%. The SCM effectively described the layer-by-layer char consumption, where gasification slowed at high conversion levels. Conversely, the PLM for the TGA revealed a unique mathematical function not aligned with traditional models, indicating localized reaction behaviors. This study highlights the inability to directly extrapolate TGA-derived kinetic models to FBR systems, underscoring the distinct mechanisms governing char consumption in each reactor type. These findings provide critical insights for optimizing biochar gasification across diverse reactor configurations. Full article

The environmental impact of livestock by-products presents significant challenges, particularly in regions with intensive farming and high pollution levels, such as the Po Valley. This study evaluated the effectiveness of biochar and wood vinegar in reducing gaseous emissions during the laboratory-scale storage of livestock slurry, digestate, and liquid fractions. Various types and applications of biochar, both with and without wood vinegar, were tested across three independent incubation periods of varying durations. The results showed that ammonia (NH₃) emissions were lower from slurry compared to raw digestate and the liquid fraction, while methane (CH₄) emissions exhibited the opposite trend. Pyrolysis biochar effectively reduced NH₃ emissions by 47% on average when applied as a 5 cm surface layer. However, its effectiveness was inconsistent when mixed into the material or when produced via gasification. Biochar activated with wood vinegar significantly reduced NH₃ emissions from both slurry and digestate by 61%, but it also led to increased emissions of CH₄ and CO₂. Nitrous oxide (N₂O) emissions were detected only after at least one month of incubation and were higher when biochar was used as a cover alone or when activated with wood vinegar. Overall, applying biochar as a cover and activating it with wood vinegar proved effective in reducing NH₃ emissions during the storage of livestock by-products. However, the effectiveness varied significantly depending on the type of biochar and its method of application, particularly with respect to CH₄ emissions, highlighting the need for careful consideration when using wood vinegar-activated biochar. Full article