Biochar Properties Research Articles

Predicting Cd(II) adsorption capacity of biochar materials using typical machine learning models for effective remediation of aquatic environments

The screening and design of “green” biochar materials with high adsorption capacity play a pivotal role in promoting the sustainable treatment of Cd(II)-containing wastewater. In this study, six typical machine learning (ML) models, namely Linear Regression, Random Forest, Gradient Boosting Decision Tree, CatBoost, K-Nearest Neighbors, and Backpropagation Neural Network, were employed to accurately predict the adsorption capacity of Cd(II) onto biochars. A large dataset with 1051 data points was generated using 21 input variables obtained from batch adsorption experiments, including preparation conditions for biochar (2 features), physical properties of biochar (4 features), chemical composition of biochar (9 features), and adsorption experiment conditions (6 features). The rigorous evaluation and comparison of the ML models revealed that the CatBoost model exhibited the highest test R2 value (0.971) and the lowest RMSE (20.54 mg/g), significantly outperforming all other models. The feature importance analysis using Shapley Additive Explanations (SHAP) indicated that biochar chemical compositions had the greatest impact on model predictions of adsorption capacity (42.2 %), followed by adsorption conditions (37.57 %), biochar physical characteristics (12.38 %), and preparation conditions (7.85 %). The optimal experimental conditions optimized by partial dependence plots (PDP) are as follows: as high Cd(II) concentration as possible, C(%) of 33 %, N(%) of 0.3 %, adsorption time of 600 min, pyrolysis time of 50 min, biochar dosage of less than 2 g/L, O(%) of 42 %, biochar pH value of 11.2, and DBE of 1.15. This study unveils novel insights into the adsorption of Cd(II) and provides a comprehensive reference for the sustainable engineering of biochars in Cd(II) wastewater treatment.

Influence of washing parameters on biomass and biochar properties of empty fruit bunches from oil palm plantation

Influence of washing parameters on biomass and biochar properties of empty fruit bunches from oil palm plantation

Effect of different exfoliation routes on the properties of chicken feather and elephant grass hybrid biochar

AbstractLiquid‐phase exfoliation, a technique for enhancing the properties of biochar, has been recognized as effective, circumventing the limitations of other methods such as high expenses, scalability, and complexity. This study explored the synergistic effect achieved by combining chicken feathers with elephant grass to create a composite feedstock for biochar production. The biochar was subjected to liquid‐phase exfoliation using acid and acetone. Elemental analysis indicated that the co‐carbonization of the combined biomass produced an enriched hybrid biochar. The oxygen content in both exfoliation routes (acid and acetone) increased, with an increase and decrease in carbon content in acetone and acid exfoliation, respectively. Textural analysis revealed significant enhancement, with surface areas of the acid‐exfoliated biochar more than twice the size of the hybrid biochar. The pore volume of both exfoliated samples was double that of the hybrid biochar. Microscopic surface examination revealed rougher, porous structures in the exfoliated biochars in comparison with the smooth, cohesive surface in hybrid biochar. Functional group analysis showed the presence of aromatic rings, a carbocyclic group, and an alkene, suggesting potential applications in adsorption. This study provides an efficient method for using liquid‐phase exfoliation to enhance biochar properties, benefiting industries reliant on biochar production and biomass utilization by improving product quality, sustainability, and environmental impact.

Biochar production using a Flexible Counter Flow Multi-Baffle (F-COMB) reactor

Pyrogenic carbon capture and storage (PyCCS) based on biochar is considered a negative emission technology (NET) aimed at mitigating climate change, with the potential to reduce CO2 by 0.3–2 gigaton/yr at the cost of $30–120/ton-CO2. The annual biochar production needs a substantial scaling up of the current production rates (i.e., >150 million tons by 2050) to meet the above demand. However, current biochar production predominantly relies on a small-scale operation, which generally leads to high operational costs and limited control of the biochar properties. This work presents the operation of a state-of-the-art 1 ton/d pilot-scale Flexible Counter Flow Multi-Baffle (F-COMB) pyrolyzer designed for continuous biochar production, which is a prototype reactor for the scale-up. The F-COMB utilizes counter-flow and vortex mixing in a multi-baffle column structure to enable efficient contact of feedstock with hot gas. It boasts high energy efficiency and economic feasibility through a short residence time, reduced gas flow rate, and simple structure. It produces wood pellet biochar with accurate control of the reaction conditions such as temperature, retention time, hot gas flow rate, and feedstock loading. Moreover, continuous biochar production is done successfully with three flexible baffles configuration, demonstrating the significant potential for the scale-up.

Excellent adsorption and catalytic oxidation of toluene facilitated by metal-free nitrogen-doped mesoporous biochar

In this study, we synthesized a series of nitrogen-doped mesoporous biochar by a salt-templating method to assess the potential of our modified biochar for advanced remediation of toluene through either adsorption or catalytic oxidation. The principal findings indicated that the incorporation of nitrogen and the mesopore-forming agent significantly influenced the toluene removal performance by altering the physicochemical properties of the biochar. Notably, the sample synthesized at 900 °C (BUPZ-900) exhibited the exceptional toluene adsorption capacity, reaching 283.85 mg/g, due to its high surface area and mesopore volume. Advanced characterizations revealed that different nitrogen functionalities played distinct roles in the adsorption performance. The presence of graphitic nitrogen in BUPZ-900 enhanced toluene adsorption through π-π dispersion interactions. Conversely, BUPZ-600, boasting a high nitrogen content (8.66 at%) and a predominance of pyridinic-N (3.92 at%), exhibited the highest catalytic activity, despite its low adsorption capacity attributed to a smaller surface area. This heightened activity was attributed to the basicity of pyridinic-N, which acted as active sites, despite the material’s lower surface area. Our study highlights the promise of nitrogen-doped mesoporous biochar as an effective adsorbent or catalyst for advanced remediation of volatile organic compounds (VOCs), even in the absence of metal catalysts. This work emphasizes the critical role of synthesis temperature and nitrogen functionalization in optimizing biochar properties for environmental applications.

Biochar Production and Its Potential Application for Biocomposite Materials: A Comprehensive Review

Biochar, an organic, porous, and carbon-rich material originating from biomass via pyrolysis, showcases compelling attributes and intrinsic performances. Its appeal as a reinforcement material for biocomposites, as well as its auspicious electrical properties, has gained more attention, and makes biochar a versatile candidate for applications ranging from energy storage to catalytic devices. This scientific review undertakes a comprehensive exploration of biochar, spanning production methodologies, physicochemical intricacies, and critical process parameters. The focus of this paper extends to optimization strategies for biochar properties tailored to specific applications, with a dedicated inquiry into diverse production methods and activation strategies. This review’s second phase delves into a meticulous analysis of key properties within biochar-based composites, emphasizing limitations and unique performance characteristics crucial for diverse applications. By synthesizing a substantial body of research, this review aims to catalyze future investigations by pinpointing areas that demand attention in upcoming experiments, ultimately emphasizing the profound potential of biochar-based materials across technical and scientific domains.

Comprehensive pyrolysis investigation of Lemongrass and Tagetes minuta residual biomass: bio-oil composition and biochar physicochemical properties

Comprehensive pyrolysis investigation of Lemongrass and Tagetes minuta residual biomass: bio-oil composition and biochar physicochemical properties

Importance of pyrolysis temperature and particle size on physicochemical and adsorptive properties of urban wood-derived biochar

Physicochemical properties of biochars made from urban wood waste at different pyrolysis temperatures (400-700 °C) and particle sizes (1-2 mm and 63-75 μm) were compared to their ability for heavy metals adsorption at various contact times (30-300 min) and adsorbent dosages (0.1-5 g L-1) in real landfill leachate. The yield, volatile matter, hydrogen and oxygen contents, and functional groups of biochars decreased with increasing pyrolysis temperature; while pH, electrical conductivity, ash, fixed carbon, and specific surface area (SSA) increased. FE-SEM images showed that the creation of pores on the surface of biochars increased significantly with increasing pyrolysis temperature. Moreover, particle size exhibited no significant effect on the properties of biochars (p>0.05), except for the SSA. The SSA of biochars with a particle size of 63-75 μm was significantly higher than that measured in 1-2 mm biochars. The adsorption efficiency of heavy metals from landfill leachate increases with increasing pyrolysis temperature, contact time and adsorbent dosage. Conversely, reducing the particle size increases the adsorption efficiency. The highest adsorption efficiency for Pb, Zn, Ni, Cd, and Mn was obtained as a result of using biochar pyrolyzed at 700 °C with a particle size of 63-75 μm (i.e., BC700/63-75) by 60.39%, 75.01, 64.36, 58.87%, and 71.15%, respectively. Pseudo second-order kinetic and the Langmuir isotherm were recognized as the most appropriate models to describe the adsorption process. The chemical adsorption was identified as the main mechanism for the adsorption of metal ions onto BC700/63-75.

Taking Advantage of Disposal Bamboo Chopsticks to Produce Biochar for Greenhouse Crop Cultivation

Biochar is a value-added product that can be used for many purposes, particularly for environmental and agricultural purposes. In this study, pyrolysis at 450–500 °C was used to upgrade urban waste such as disposable bamboo chopsticks (DBCs) into biochar. The properties of DBC biochar were analyzed, and the biochar was subsequently used to cultivate Romaine lettuce to assess its potential as a soil amendment. Its properties, including specific surface area (SSA), pore size, pore volume, pH, cation exchange capacity (CEC), contents of carbon (C), hydrogen (H), nitrogen (N), oxygen (O), macronutrient content, and the atomic ratio of H/C, O/C, (O+N)/C, and C/N, were analyzed. The experimental pots consisted of four treatments, each with ten replicates: unamended soil (TC), soil amended with 10% (w/w) vermicompost (TV), soil amended with 10% vermicompost mixed with 1.5% biochar (TVB1.5), and soil amended with 10% vermicompost mixed with 2.5% biochar (TVB2.5). Fundamental physicochemical soil properties and plant yield (plant height, leaf width, number of leaves, and fresh weight) were investigated. The results indicated that the DBC biochar was neutral (pH 6.80) and had a high CEC (10.86 cmol/kg), 66.80% C, 3.76% H, 25.93% O, and 0.61% N. It had mesopores (39.077 Å), a large SSA (0.542 m2/g), and a pore volume of 0.005 cc/g. The biochar exhibited high aromaticity and hydrophobicity. Based on these results, the DBC biochar has the potential to be used as a soil amendment: it significantly enhances soil quality and increases plant yields. The application of 2.5% biochar resulted in the highest yield. Doi: 10.28991/ESJ-2024-08-03-07 Full Text: PDF

Co-pyrolysis of waste wood and plastic to produce quasi graphitic carbon: enhanced biochar properties for metal coatings through safe sequestration and green technology

Use of waste polystyrene as an additive in the preparation of biowaste derived char can provide significant new properties that enhance the performance of the epoxy coating on steel surface. This work establishes a cost-effective Quasi-graphitic carbon (QGC) derived from the co-pyrolysis of Eucalyptus wood chips and polystyrene as a mix in epoxy (EP) matrix for enhanced the coating properties. The QGC material was characterized by FTIR, XRD, Raman, SEM-EDX, TGA, etc. Results show the incorporation of 0.1 wt.% QGC to the EP matrix enhances corrosion resistance by 98.6 % and boosts mechanical properties with a 245.45 % increase in hardness and a 57.31 % rise in elastic modulus compared to pure EP coatings. Microscopic analysis reveals a smoother, more compact surface with fewer structural defects comapred to pure EP coating. Adhesion tests score the category of 4B, 5B, and water contact angle improve to 102.8°, compared to 61.6° for pure EP coatings. These eco-friendly materials, created through environmentally conscious processes can be a safe alternative to the conventional toxic chemicals used to protect against corrosion,particularly in marine environments.

Thermo-chemical processes for the sustainable utilization of oil-bearing biomass: A case study on apricot seed valorization

This study investigated the thermochemical processing of defatted residue to achieve zero-waste utilization of oil-bearing biomass using apricot seed as the model compound. Defatted apricot seeds (DAS) obtained after oil extraction from apricot seed were valorized through pyrolysis platform, focusing on enhancing sustainability using CO2 as the reaction medium. The results showed that CO2 plays a crucial role in the pyrolysis process, leading to an enhanced CO formation through homogeneous reaction between CO2 and volatile matters stemming from DAS. Specifically, CO2 oxidized volatile matters while simultaneously reducing to CO and influenced the morphological properties of DAS biochars (DASBs), leading the development of pores with sizes of less than 16 nm and exceeding 50 nm. The larger pore size of DASBs fabricated under N2 and CO2, compared to 2 nm (the molecular size of triglycerides), makes them suitable as porous materials for thermally induced transesterification. The presence of alkaline metals in DASBs expedited thermally induced transesterification. At ≤ 330 °C, DASB fabricated under CO2 condition exhibited faster reaction kinetics than under N2 condition. This suggests that the use of CO2 in the fabrication of DASB results in favorable surface properties conducive to the thermally induced transesterification of apricot oil.

Unlocking biosolid pyrolysis: Towards tailored biochar with different surface properties

To develop a thorough understanding of the thermal decomposition process of biosolids and the qualities of biosolid-derived biochar, this study performs a thermogravimetric analysis (TGA) of biosolids and examines the properties of biosolid-derived biochar produced from varying temperatures of pyrolysis. The pyrolysis of biosolid is conducted under varying heating rates (10, 15, 20 and 25 °C/min) until reaching the maximum temperature of 900 °C. The kinetic triplet (kinetic model, activation energy, and frequency factor) at the corresponding conversion point is determined by analysing the TGA results of the biosolids. The thermal degradation of hydrated compounds shows activation energies ranging from 80 to 100 kJ/mol, whereas the thermal decomposition of organic matter in biosolids exhibits activation energies ranging from 120 to 497 kJ/mol. As the temperature increases, the thermal reactions transition from simple surface reactions with frequency factors below 109 s−1 to more complex reactions with frequency factors above 109 s−1. The distributed activation energy model (DAEM) is established using the approximated temperature function and the activation energy distribution functions. The DAEM shows the mean activation energies of 93–128 kJ/mol, 279–287 kJ/mol and 359–377 kJ/mol for activation energy distribution peaks. The standard deviations of the mean activation energies are 30–64 kJ/mol, 23–30 kJ/mol and 23–41 kJ/mol, respectively. As the pyrolysis temperature is raised from 700 °C to 900 °C, both the specific surface area and micropore volume of biosolid-derived biochar increase, from 48.25 m2/g to 65.74 m2/g and 0.0313 cm3/g to 0.0369 cm3/g, respectively. The findings of this study demonstrate biosolid pyrolysis kinetics, which is essential for establishing a pyrolysis facility for biosolid management and producing biosolid-derived biochar with varying qualities.

Deep learning prediction and experimental investigation of specific capacitance of nitrogen-doped porous biochar

N-doped porous biochar is a promising carbon material for supercapacitor electrodes due to its developed pore structure and high chemical activity which greatly affect the capacitive performance. Predicting the capacitance and exploring the most influential factors are of great significance because it can not only avoid the trial-and-error experiments but also provide guidance for the synthesis of biochar with the aim of capacitance enhancement. In this study, a CNN model with ReLU activation function was established using DenseNet architecture for specific capacitance prediction. The importance and impacts of the physiochemical properties of N-doped porous biochar to the capacitance were revealed. With the guidance of the model, N-doped porous biochar samples with high capacitance were synthesized, the data of which were further used for model validation. This study provides not only a deep learning model which can be used in practice for capacitance prediction but also directions for the synthesis of N-doped porous biochar with high capacitive performance.

Assessment of Pistachio Shell-Based Biochar Application in the Sustainable Amendment of Soil and Its Performance in Enhancing Bell Pepper (Capsicum annuum L.) Growth

This study aimed to (a) analyze the influence of pyrolysis temperature on pistachio shell-based biochar (PSB) properties and (b) assess the PSB effect on green bell pepper (Capsicum annuum L.) growth. Pyrolysis experiments were conducted at different temperatures, determining 450 °C as optimal for soil amendment. The effect of PSB addition at different mass ratios was analyzed considering the physicochemical properties of the mixtures and the agronomic parameters of green bell pepper plants and fruits under greenhouse conditions. Results demonstrated enhancements in soil properties upon biochar incorporation, including a decrease in pH by 1%, a decrease in electrical conductivity (EC) by 4–14%, and increases in cation exchange capacity (CEC) by 4–8%, organic matter (OM) and organic carbon (OC) by 100–200%, and total nitrogen (TN) by 35%, relative to unamended soil. Agronomic variables revealed improvements, particularly during the reproductive and maturity stages, with plants treated with 1% biochar (SB1) exhibiting enhanced growth and chlorophyll content, alongside increased flower and fruit yields. Notably, the 2% biochar treatment (SB2) yielded superior fruit weight and length results, suggesting the potential for biochar to enhance both the quality and quantity of green bell pepper fruits, thereby contributing to sustainable agricultural practices.

Systemic review for the use of biochar to mitigate soil degradation

AbstractBiochar, a black carbon material produced by high‐temperature, low‐oxygen pyrolysis of organic solids, can improve soil properties and realize carbon neutrality. However, how to effectively produce and apply biochar in the face of the complex soil environment and intractable widespread land degradation is still uncertain. This review is based on 1073 sets of data in 316 publications to address this issue. Firstly, the impact of different process parameters, namely feedstocks, pyrolysis temperature and activation on physicochemical properties of biochar are systematically summarized. Secondly, the effect of biochar on different soil degradation problems are reviewed from the perspective of the interaction between the physicochemical properties of biochar and soil characteristics. The “matching” of biochar properties, level of degradation and environmental factors can be used to design the desired biochar. Finally, future research should focus on biochar aging and costs and benefits of using biochar. The concept of “artificial intelligence designed biochar” is discussed to improve the degree of automation in biochar production and the predictability and suitability of its application for specific cases.

The Effects of Feedstock, Pyrolysis Temperature, and Residence Time on the Properties and Uses of Biochar from Broom and Gorse Wastes

Biochar (BC), which can be produced from several feedstocks, has been widely studied. However, the BC derived from highly pyrolytic shrubs, such as broom and gorse, has been less frequently used and only partially characterized. These wastes, when used for the preparation of biochar, can fix carbon and contribute to environmental conservation, helping to achieve sustainable development objectives. Eight biochars from broom and gorse were produced and fully analyzed, providing a more complete and novel description, with new insights for assessing their utilization. The aims of this study were to elucidate the effects of feedstock, pyrolysis temperature, and residence time on biochar properties and to assess the adequacy of these biochars as fuel. Elemental and proximate analyses and estimations of the lower and higher heating values were performed, and physical and chemical properties, as well as several other related energy indices, were determined. The experimental results showed that the temperature was a key factor in the properties of the biochars, while residence time was less important. The BCs obtained from the two feedstocks did not show important effects on the properties, which is consistent with the fact that they are woody legumes. These biochars had a high carbon content and were thermally stable. The BCs also had a high calorific value and suitable energetic properties. Additionally, their PAH contents were low, indicating that the use of these biochars would be safe. In conclusion, broom- and gorse-derived biochars can be considered as renewable fuels for green energy production.

Pretreatment of wastepaper with an aqueous solution of amino acid-derived ionic liquid for biochar production as adsorbent

The carbonization of lignocellulosic biomass with ionic liquids (ILs) are considered as an advantageous approach for the preparation of carbonaceous materials. The commonly used imidazolium and pyridinium based ILs have drawbacks such as toxicity, resistance to biodegradation, high cost and viscosity. These issues can be mitigated by diluting ILs with water, although excessive water content above 1 wt% can reduce the solubility of biomass. This research aims to investigate the potential of pretreating wastepaper with a “fully green” ILs, amino acid-based IL with high water content, followed by pyrolysis without IL, in enhancing the properties of biochar. For this purpose, the paper was treated with an aqueous solution of IL cysteine nitrate ([Cys][NO3]), and the IL was not involved in the pyrolysis process to prevent the formation of secondary gaseous pollutants. The findings revealed that the hemicellulose and mineral filler in the paper were eliminated during pretreatment, leading to higher carbon content but lower oxygen content. As a result, the biochar exhibited micropores of 0.42 cm3g-1 and a specific surface area of 1011.21 m2 g−1. The biochar demonstrated high adsorption capacities for Cd2+, enrofloxacin, bisphenol A, ciprofloxacin, and tetracycline, with values of 45.20 mg g−1, 49.82 mg g−1, 49.90 mg g−1, 49.88 mg g−1, and 49.65 mg g−1, respectively. The proposed mechanism for the adsorption of enrofloxacin by the biochar primarily involves physical adsorption such as pore filling and electrostatic interactions, along with chemical adsorption facilitated by graphitic nitrogen.

Knowledge graph and development hotspots of biochar as an emerging aquatic antibiotic remediator: A scientometric exploration based on VOSviewer and CiteSpace

As an emerging material in the field of environmental remediation, biochar produced by carbonisation of organic solid waste has been widely used in the remediation of antibiotic wastewater due to its environmental friendliness and excellent adsorption properties. This study analyses the current literature in the field in a comprehensive and scientific manner using CiteSpace and VOSviewer technologies. Between 2011 and 2023, a total of 1162 papers were published in this domain, spanning three distinct stages: applied methods, mechanism investigation, and enhanced improvement. The results of keyword clustering indicate that the remediation of antibiotics complexed with multiple pollutants by biochar is the main research topic, followed by the remediation of antibiotics by biochar in combination with other technologies. Furthermore, drawing from current research hotspots in antibiotic remediation using biochar, this study identified the pivotal mechanisms involved: (1) The primary mechanisms by which raw biochar remediates antibiotics include π-π electron donor-acceptor interactions, hydrophobic interactions, electrostatic interactions, hydrogen-bonding, and pore filling. (2) Steam activation, acid/base, metal salt/metal oxide, and clay mineral modification can improve the physical/chemical properties of biochar, enhancing its adsorptive removal of antibiotics. (3) Biochar activated persulfate and degraded antibiotics via free radical pathways (SO4−•, •OH and O2−•) as well as non-free radical pathways (1O2 and electron transfer). In addition, the challenge and prospect of biochar engineering applications for antibiotic remediation lies in improving the main mechanism of antibiotic remediation by biochar. The prospective utilization of biochar in enhancing the remediation of antibiotic-related pollutants holds tremendous value for the future.

Atlas of Microscopic Images of Biochar

Derived through the thermochemical conversion of biomass, biochar is a carbon-rich substance recognized for its significance in environmental applications and sustainable agriculture. As interest in its utilization continues to rise, it becomes crucial to comprehend how the source material and pyrolysis parameters influence the properties of biochar and, consequently, to research the suitability of various analytical methods for characterizing it. Despite the current utilization of numerous physical and chemical methods, the untapped potential of reflected light microscopy warrants further exploration. While a few recent studies suggest a correlation between certain microscopic characteristics and selected physical and chemical properties of biochar, the data are limited and difficult to compare. This is primarily due to variations in the types of original biomass used and lack of information about pyrolysis conditions. Moreover, because only a limited number of photographs taken under a reflected light microscope are publicly available to-date, it is difficult to evaluate morphological differences between various biochars and other organic materials such as inertinites from coal, charcoal, etc. To address limited availability of publicly available data, this “Atlas of Microscopic Images of Biochar” presents a collection of more than 300 images contributed by researchers from Poland, the United States, Canada, Australia, Brazil, and Denmark. These photomicrographs capture optical characteristics of a diverse array of biochar, demonstrating its unique morphological and structural features. This visual documentation can serve as a valuable resource for researchers, industry professionals, educators, and enthusiasts interested in investigating the complexities of biochar forms.

Production of sludge biochar by steam pyrolysis and acid treatment: Study of the activation mechanism and its impact on physicochemical properties

This study addresses the preparation of sludge biochar through a procedure that combines steam pyrolysis in a wide range of temperature (500–900 ºC) and acid treatment with HCl (performed before or after the pyrolysis). The acid washing after the pyrolysis maximizes BET surface area due to pore unblocking, thus making visible the pore structure generated. The drawback of the acid washing is the lower yield obtained (compared to the acid pretreatment), as well as the loss of the magnetic properties of sludge biochar. The acid pretreatment requires temperatures above 700 ºC to have a beneficial effect, due to the occurrence of additional reactions of the incorporated HCl with sludge constituents. The pretreatment results in materials with a high degree of microporosity. Among the reactions favoured, of interest is the development of magnetite in the whole temperature range. The activation protocol used in this study (especially the procedure that includes the acid pretreatment) is effective to generate biochar with magnetic properties through the transformation of the Fe introduced during the water treatment process, without adding a source of Fe. The presence of magnetite is an advantage for the reuse of sludge biochars in wastewater treatment.