Physicochemical Properties Of Biochar Research Articles

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.

Comparative analysis of biochar production methods and their impacts on biochar physico-chemical properties and adsorption of heavy metals

Rapid industrialization, urbanization, and population growth result in vast amounts of organic waste being produced, including agricultural waste, animal waste, industrial waste, sewage sludge, and municipal solid waste. Biochar production from solid waste has become a popular waste management method. However, in rural areas of developing nations, biomass is typically used for cooking without being charred. Urban biowaste-derived biochar may enhance soil fertility and overall soil health. However, large-scale biochar production from an electronic muffle furnace could be very expensive, and there is little information on the conversion of biowastes to biochar using traditional kilns or its effects on biochar characteristics, and farmers' biochar production methods are yet underdeveloped. Hence, this study provides biochar production from biowastes using two production methods: 1) a traditional kiln (a tin kiln) intended for use by small farmers and gardeners, and 2) a laboratory muffle furnace, with the aim of evaluating biochar characteristics. Biochar produced in a muffle furnace and tin kiln has found similar physicochemical and adsorption properties at the same pyrolysis conditions. They include high pH, EC, CEC, Pava, Ca, Mg, K, and carbon content. We expect these biochars to have larger long-term effects on agricultural characteristics and soil carbon sequestration. However, the present results might be utilized to drive cleaner biochar production for agricultural use in developing nations, which may multiply local producer benefits.

Insights into microplastics (MPs) removal using aquatic plant-derived biochar from Taihu Lake at varying carbonization temperatures

Microplastics (MPs), recognized as significant emerging contaminants, are prevalent in both terrestrial and aquatic ecosystems. This study investigates the potential of biochar derived from Polygonum amphibium L. (PAL) sourced from Taihu Lake and processed through a low-temperature carbonization method, for in the removal of MPs. This approach addresses the escalating presence of MPs in aqueous environment, especially during the COVID-19 pandemic, simultaneously tackles the issue of waste biomass contributing to eutrophication. The study focused on the impact of carbonization temperatures (450℃-550℃) on physicochemical properties of biochar. Additionally, the effect of contact time, initial concentration of MPs, and environmental factors at various carbonization temperatures were also examined. The results reveal that the biochar yield and adsorption performance of biochar are significantly influenced by carbonization temperature. The adsorption capacity of biochar for MPs removal increases with the carbonization temperature up to 500 ℃, attributed to enhanced diffusion, surface adsorption, interactions, and cation-π electron interactions between the biochar and MPs. However, at a pyrolysis temperature of 550 ℃, the increase in adsorption capacity of biochar-550 is marginal due to increased competitive binging and destabilization of biochar under basic conditions. Overall, the optimum carbonization temperature is identified as 500 ℃, yielding a char rate is 32.23% and an adsorption capacity for MPs of 80.3 mg/g, thereby offering a promising solution for MP removal and water eutrophication management.

Production and Analysis of Physical, Chemical and Physico-chemical Properties of Biochar from Various Feed Stock Sources

Biochar was derived from a range of biomass materials and its physical and physicochemical characteristics were assessed. Due to the pyrolysis of various biomass products, such as grass, cotton stalks, coconut husk, coconut shell, paddy straw, rice husk, Eichhornia, sugarcane bagasse, and neem wood in the pyrolysis unit. The biochars' characteristics were extremely diverse. Prosopis is superior to other biochars in terms of pore space, pH, EC, CEC, organic C, total N, Mg, available nutrients, and carbon fractions, as evidenced by the large amount of biochar that was recovered from it.
 Prosopis wood biochar, which can function as a soil enhancer and improve the physical properties of the soil, is superior than cotton stalk biochar and drymatter biomass biochars. It can also increase nutrient availability and retention. Given its higher recovery and diffusion, Prosopis' resource can be used. As a result of the substantial differences between the various biomass, characterizing biochar made from each one is necessary before mass producing it for agricultural application.

Examining diverse remediation mechanisms of biochar in soil contaminated with polycyclic aromatic hydrocarbon (PAH) of various ring structures: A global meta-analysis

Biochar is a widely recognized solution for addressing polycyclic aromatic hydrocarbon (PAH) contamination. However, it is unclear how the different physicochemical properties of PAHs affect remediation mechanisms, thereby affecting the remediation efficiency of biochar. In this study, a meta-analysis of 56 studies with 2236 observations was conducted to quantify the contributions of the preparation parameters and physicochemical properties of biochar, soil properties, and application measures to remediation efficiency. The research results revealed that PAH contents in the contaminated soil were significantly reduced by an average of 24.99 % after the application of biochar. Random Forest analysis identified feedstock, biochar SSA, soil pH, and rate of biochar application to be the most critical factors among the four categories. The reduction of PAH contents in the contaminated soil first decreased from 37.61 % to 17.44 % and then increased to 40.29 % with an increase in the number of aromatic rings from 2 to 6. Our study results suggest that biochar prepared from bio-waste at low temperatures could be favorable for reducing the content of NAP in soil. Wood-derived biochar pyrolyzed at a relatively high temperature is recommended for remediation of soil contaminated with PAHs with 5 or 6 aromatic rings. Our study provides a new perspective and an optimized strategy for the remediation of PAH-contaminated soils with biochar.

Excess sludge-based biochar loaded with manganese enhances catalytic ozonation efficiency for landfill leachate treatment

This study developed an efficient and stable landfill leachate treatment process, which was based on the combination of biochar catalytic ozonation and activated sludge technology for intensive treatment of landfill leachate, aiming to achieve the standard discharge of leachate. The focus is to investigate the effect of manganese loading on the physicochemical properties of biochar and the mechanism of its catalytic ozonation. It was found that more surface functional groups (CO, Mn–O, etc.) and defects (ID/IG = 1.27) were exposed via the change of original carbon structure by loading Mn, which is conducive to the generation of lattice oxygen. Meanwhile, generating different valence states of Mn metal can improve the redox properties and electron migration rate, and encourage the production of reactive oxygen species (ROS) during the reaction process and enhance the catalytic efficiency. The synergistic action of microorganisms, especially denitrifying bacteria, was found to play a key role in the degradation of nitrogenous pollutants during the activated sludge process. The concentration of NH+4-N was reduced from the initial 1087.03 ± 9.56 mg/L to 9.05 ± 1.91 mg/L, while COD was reduced from 2290 ± 14.14 mg/L to 86.5 ± 2.12 mg/L, with corresponding removal rates of 99.17% and 99.20%, respectively. This method offers high efficiency and stability, achieving discharge standards for leachate (GB16889-2008). The synergy between Mn-loaded biochar and microorganisms in the activated sludge is key to effective treatment. This study offers a new approach to solving the challenge of waste leachate treatment.

Pb(ΙΙ), Cd(ΙΙ), and Mn(ΙΙ) adsorption onto pruning-derived biochar: physicochemical characterization, modeling and application in real landfill leachate

The aim of this study was to systemically evaluate how different pyrolysis temperatures (400, 550, and 700 °C) and particle sizes (1–2 mm and 63–75 µm) were influenced biochar evolution, made from urban pruning waste, during pyrolysis process and to establish their relationships with biochar potential for removal of lead (Pb), cadmium (Cd), and manganese (Mn) from real municipal solid waste landfill leachate. The effects of pH (2–7), contact time (30–300 min) and adsorbent dosage (0.1–5 g L−1) on heavy metals removal were also examined. The results showed that physicochemical properties of biochar were greatly influenced by pyrolysis temperature. Particle size, however, showed little influence on biochar characteristics (p > 0.05). The yield, volatile matter, hydrogen and oxygen contents, and surface functional groups decreased consistently with increasing pyrolysis temperature. An increase in the pH, electrical conductivity, ash, fixed carbon, and specific surface area values was also found. In biochar samples formed at high temperatures (i.e., 550 and 700 °C), Fourier transform infrared spectroscopy-FTIR studies confirmed the increase in aromaticity. Field emission scanning electron microscopy-FESEM images showed differences in the microporous structure and lower size pores at higher temperatures. Biochar pyrolyzed at 700 °C with a particle size of 63–75 µm (i.e., Lv700-63) showed the highest removal efficiency performance. Pb and Cd ions were completely removed (100%) by 0.2 g L−1 Lv700-63 at 7.0 pH and contact times of 120 and 90 min, respectively. The maximum percentage removal of Mn was 86.20% at optimum conditions of 0.2 g L−1 Lv700-63 dosage, 7.0 pH, and 180 min contact time. The findings suggests that the surface complexation, π-electron coordination, and cation exchange were the dominant mechanisms for the Pb, Cd, and Mn removal onto Lv700-63.

Biochar from phytoremediation plant residues: a review of its characteristics and potential applications.

Phytoremediation is a cost-effective and eco-friendly plant-based approach promising technique to repair heavy metal-contaminated soils. However, a significant quantity of plant residues needs to be properly treated and utilized. Pyrolysis is an effective technology for converting residues to biochar, which can solve the problem and avoid secondary contamination. This paper reviews the generation, and physicochemical properties of biochar from phytoremediation residues, and its application in soil improvement, environmental remediation, and carbon sequestration. In spite of this, it is important to be aware of the potential toxicity of heavy metals in biochar and the environmental risks of biochar before applying it to practical applications. Future challenges in the production and application of residue-derived biochar include the rational selection of pyrolysis parameters and proper handling of potentially hazardous components in the biochar.

Effect of pyrolytic temperatures on the 2,4-dichlorophenol adsorption performance of biochar derived from Populus nigra.

To investigate the correlation between the physicochemical properties of biochar and its adsorption performance for 2,4-dichlorophenol (2,4-DCP), Populus nigra was subjected to oxygen-limited pyrolysis at temperatures ranging from 300 to 600 ℃. The experimental results showed that as the pyrolysis temperature increased, the specific surface area and degree of graphitization of the resultant biochar increased, but the amount of oxygen-containing functional groups decreased. Populus nigra biochar produced at 450 ℃ exhibits the best adsorption performance for 2,4-DCP due to its excellent physicochemical properties and greater electron exchange capability. The removal of 2,4-DCP is a multi-step adsorption process dominated by chemisorption, which involved oxygen-containing functional groups-mediated hydrogen bonding, as well as π-π electron donor-acceptor (EDA) interaction between the aromatic rings and Cl atoms. The study highlights the potential of Populus nigra residues for producing biochar as an affordable and effective adsorbent for 2,4-DCP removal.

The Importance of the Targeted Design of Biochar Physicochemical Properties in Microbial Inoculation for Improved Agricultural Productivity—A Review

Biochar has great potential as a soil conditioner and as a carrier of beneficial microorganisms that support the removal of pollutants, influence the circulation of nutrients, and support plant growth. This review summarizes and discusses factors shaping the physicochemical properties of biochar, including feedstock, pyrolysis conditions, and accompanying processes used as post-pyrolysis modification to improve the functionality of biochar. Key physical and chemical properties such as high porosity and specific surface area, nutrient content, pH, and biochar functional groups are discussed in detail to show biochar’s potential as a carrier for microorganisms. This review also discusses and summarizes biological indicators that allow for assessing the quality and efficiency of the microbiological modifiers. Finally, this paper presents the benefits and limitations of biochar application to agriculture and provides recommendations for future research to improve the quality and expand the applicability of biochar-based inoculants.

Biochar modification methods and mechanisms for salt‐affected soil and saline‐alkali soil improvement: A review

AbstractThe continuous growth of the world's population has led to an increased demand for food. Biochar (BC) contains valuable functional groups and nutrients, which have been demonstrated to enhance soil properties and boost crop yield. Nonetheless, unmodified BC exhibits significant alkalinity and a large salt concentration; thus, its efficacy in improving saline‐alkali soil remains a matter of contention. Therefore, scholars aim to address the aforementioned limitations by adapting BC. In this paper, a summary is given of the methods used to modify BC and the effects of modified BC on salt‐affected soil and saline‐alkali soil properties, including pH, nutrients and microbial activity. The effects and principles of different modifiers and modification methods on BC's physicochemical properties (porosity and functional group content and type, etc.) were revealed. Furthermore, the principle of soil improvement by modified BC varies depending on the modification method. Although modified BC can effectively enhance salt‐affected soil, its excessive application and improper selection of modifiers can aggravate Na+ toxicity or introduce other pollutants into salt‐affected soil. Therefore, using modified BC with care is imperative according to the actual situation. In this review, we provide a detailed introduction to the methods and principles of BC modification for saline‐alkali soil. Furthermore, we identify the shortcomings and future research directions in this field. These insights are valuable when choosing proper BC modification methods for salt‐affected soil.

Biochar derived from agricultural waste and its application as energy source in blast furnace

Is biochar obtained from agricultural residues an alternative to the coal used in blast furnaces - BF? This work provided a comparison between biomass and PCI coal, and evaluated the influence of pyrolysis temperature on the combustion indexes and physicochemical properties of biochars. Coconut-shell, corncob, and eucalyptus bark biomasses were pyrolyzed at different temperatures (300 °C–500 °C) to produce biochar. Samples of biomasses and biochars were characterized using proximate analysis, HHV, FTIR, XRD and SEM coupled with EDXA. Pyrolysis led to increased fixed carbon content and HHV in the biochar. However, the higher the temperature, the lower the mass yield. The combustion indexes results revealed that the raw biomasses do not meet the reference values. Coconut-shell and corncob biochars produced at 300 °C and 350 °C demonstrated combustion indexes similar to those of reference PCI coal. The results suggested that both the choice of biomass and the pyrolysis temperature had influence on the properties of biochar produced. Coconut-shell and corncob biochars, produced at relatively low temperatures, exhibited suitable combustion properties and could serve as partial substitutes of PCI coal in a BF. Eucalyptus bark biochar, due to its higher ash content, may be less suitable for these applications.

Preparation and physicochemical properties of biochar from the pyrolysis of pruning waste of typical fruit tree in north China

Routine maintenance of fruit trees generates a substantial quantity of pruning waste each year. This waste is potential feedstock for producing energy, materials, and other products. The feasibility of making biochar from the waste via pyrolysis was evaluated. The effects of seven tree species, different pruning sites, and temperature on the pyrolysis process, and the physicochemical properties of the biochar were studied. Pyrolysis of different tree species at 500 °C yielded 27.5 to 33.3% biochar, with a high calorific value (approximately 30 MJ/kg), low ash content (approximately 4%), and capturing up to 60% of the carbon element present. Simultaneously, when the temperature was increased from 400 to 700 °C, the yield of biochar decreased from 35.8% to 24.3%, but the properties improved with the higher heating value rising from 29.2 to 31.3 MJ/kg and the iodine value from 234 to 252 mg/g. The biochar has a good pore structure with a specific surface area of 237 m2/g, total pore volume of 0.175 cm3/g, and average pore size of 2.96 nm. In general, biochar from the pyrolysis of fruitwood pruning waste generated here could be an ideal feedstock to produce high-value-added products, such as solid fuels, activated carbon, and electrode materials.

Screening the optimal modified biochar for nitrogen retention in black soil.

Reducing the environmental problems caused by nitrogen loss and nitrogen pollution is of great significance. The addition of biochar to soil is a new method for increasing nitrogen interception due to the special structural and physicochemical properties of biochar. The optimal modified biochar was screened out after acid-base modification and batch adsorption test in this paper. And then the effects of different soil and biochar mixing methods on soil physicochemical properties and nitrogen adsorption and retention were explored through soil column leaching test. The results showed that the biochar with a pyrolysis temperature of 700°C had the best adsorption effect on nitrogen after being modified by 0.1mol/L HCI, and the adsorption capacity of nitrate nitrogen reached 121.46 mg/g. The adsorption process of ammonia nitrogen and nitrate nitrogen conformed to the Langmuir model and was mainly homogeneous monolayer. After mixing the selected modified biochar with black soil, the pH increased by 4.77%, the content of ammonia nitrogen increased by 4.89%, and the nitrate content increased by 16.62%. In this study, the adsorption effect of biochar on nitrogen in black soil was discussed, so as to explore the optimal use of biochar in soil, which provided some reference basis for the relevant research.

Interaction between biochar of different particle sizes and clay minerals in changing biochar physicochemical properties and cadmium sorption capacity

Biochar exhibits substantial potential for interaction with clay minerals upon its introduction into the environment. However, the precise impact of this interaction on the surface properties of biochar and its capacity for metal sorption, particularly in relation to varying biochar particle sizes, remains unclear. Therefore, this study focused on biochar particles derived from pig bone, varying in size, and subjected them to treatment with two common clay minerals (kaolinite and montmorillonite). The objective was to scrutinize their influence on the physicochemical properties of biochar and its binding affinity for Cadmium (Cd). The results revealed that post-interaction with kaolinite and montmorillonite, the Cd sorption capacity of large biochar particles (250–425 μm) saw respective increments of 11.6% and 26.6%, whereas the Cd removal capacity of small biochar particles (25–75 μm) experienced reductions of 8.8% and 18.5%, respectively. Additionally, the surface area of the large biochar particles increased by 19.5% and 32.9%, while that of the small biochar particles decreased by 31.3% and 17.7% after interactions with kaolinite and montmorillonite, respectively. Through the analysis of 2D-FTIR-COS, it was determined that regardless of particle size, COO- on the initial pig bone biochar exhibited the highest sensitivity for Cd adsorption. However, after interaction with kaolinite and montmorillonite, Al–O and Si–O–Al groups were identified as the most responsive for the small biochar particles, while -OH and O–P–O groups exhibited heightened sensitivity for the large biochar particles in adsorbing Cd. The results of this study offer valuable insights into how typical clay minerals can impact the surface properties and metal sorption capacity of biochar of varying particle sizes, which is advantageous for optimizing the production and environmental applications of biochar.

Ruminal content biochar supplementation for enhanced biomethanation of rice straw: Focusing on biochar characterization and dose optimization

Anaerobic digestion (AD) of agricultural wastes is a promising approach for energy recovery and crop residue management. However, its recalcitrant chemical structure hinders microbial hydrolysis and reduces biomethane production under AD. Biochar supplementation has been proven to promote the digestibility and biomethanation of lignocellulosic substrates. Therefore, this study investigated the influence of different pyrolysis temperatures (450 °C, 550 °C, and 650 °C) on the physicochemical properties of biochar. Furthermore, the impact of ruminal content biochar supplementation (1 %, 2 %, and 3 %) on the AD of rice straw with rumen fluid as inoculum has been investigated. The ruminal content biochar (RUCB) supplemented reactors showed an increment in biomethane yield and the highest cumulative biomethane yield 243.11 mL/g volatile solids (VS)) was recorded at 2 % RUCB supplementation, followed by 227.12 mL/g VS at 1 % RUCB supplementation and 162.86 mL/g VS at 3 % RUCB supplementation (P > 0.05). Compared to the control reactors (128.68 mL/g VS), RUCB supplemented reactors exhibited 1.88-fold, 1.76-fold, and 1.26-fold increments in biomethane yield due to pH stabilization and facilitation of microbial biofilm formation on the biochar. The correlation analysis showed that biomethane production is positively correlated with VS reduction (R2 = 0.9852). This study proposed a potential strategy to utilize ruminal content waste as a feedstock for biochar production and its application in AD for accelerating the biomethanation of rice straw.

Enhanced adsorption of roxarsone on iron–nitrogen co-doped biochar from peanut shell: Synthesis, performance and mechanism

Efficient removal of organic arsenic (roxarsone, ROX) from wastewater is highly demanded on the purpose of human health and environmental protection. This work aims to prepare Fe-N co-doped biochar (Fe-N-BC) via one-pot hydrothermal method using waste peanut shell, FeCl3·6H2O and urea, followed by pyrolysis. The effect of Fe-N co-doping on biochar's physicochemical properties, and adsorption performance for ROX were systematically investigated. At the pyrolysis temperature of 650 °C, Fe-N-BC-650 shows a significantly increased specific surface area of 358.53 m2/g with well-developed micro-mesoporous structure. Its adsorption capacity for ROX reaches as high as 197.32 mg/g at 25 °C, with > 90 % regeneration efficiency after multiple adsorption–desorption cycles. Correlation and spectral analysis revealed that the pore filling, π-π interactions, as well as hydrogen bonding play the dominant role in ROX adsorption. These results suggest that the Fe-N co-doped biochar shows great potential in the ROX removal from wastewater with high efficiency.

Enhanced adsorption of phenol from aqueous solution by KOH combined Fe-Zn bimetallic oxide co-pyrolysis biochar: Fabrication, performance, and mechanism

In this study, impregnation combined with KOH activation with different mixing methods was used to prepare magnetic biochar. The effects of synthetic method on biochar physicochemical properties and adsorption performance were explored. The results showed that treatment of a Fe-Zn oxide with KOH activation provided excellent adsorption properties with adsorption capacity of 458.90 mg/g due to well-developed microporous structure and rich-in O-containing functional groups as well as exposed oxidizing functional groups (Fe2O3 and FeOOH). Langmuir-Freundlich and pseudo-second-order models accurately fit phenol adsorption. Neutral conditions (pH = 6) and lower ionic strengths were beneficial to phenol removal. Additionally, the predominant adsorption processes were physisorption and chemisorption. Correlation analyses and characterization data confirmed that pore filling, π-π interactions and surface complexation were the dominant driving forces for phenol adsorption. This research provides an environmentally friendly method for utilizing agricultural wastes for the removal of a variety of pollutions from aquatic environment.

Review on Characterization of Biochar Derived from Biomass Pyrolysis via Reactive Molecular Dynamics Simulations

Biochar is a carbon-rich solid produced during the thermochemical processes of various biomass feedstocks. As a low-cost and environmentally friendly material, biochar has multiple significant advantages and potentials, and it can replace more expensive synthetic carbon materials for many applications in nanocomposites, energy storage, sensors, and biosensors. Due to biomass feedstock species, reactor types, operating conditions, and the interaction between different factors, the compositions, structure and function, and physicochemical properties of the biochar may vary greatly, traditional trial-and-error experimental approaches are time consuming, expensive, and sometimes impossible. Computer simulations, such as molecular dynamics (MD) simulations, are an alternative and powerful method for characterizing materials. Biomass pyrolysis is one of the most common processes to produce biochar. Since pyrolysis of decomposing biomass into biochar is based on the bond-order chemical reactions (the breakage and formation of bonds during carbonization reactions), an advanced reactive force field (ReaxFF)-based MD method is especially effective in simulating and/or analyzing the biomass pyrolysis process. This paper reviewed the fundamentals of the ReaxFF method and previous research on the characterization of biochar physicochemical properties and the biomass pyrolysis process via MD simulations based on ReaxFF. ReaxFF implicitly describes chemical bonds without requiring quantum mechanics calculations to disclose the complex reaction mechanisms at the nano/micro scale, thereby gaining insight into the carbonization reactions during the biomass pyrolysis process. The biomass pyrolysis and its carbonization reactions, including the reactivity of the major components of biomass, such as cellulose, lignin, and hemicellulose, were discussed. Potential applications of ReaxFF MD were also briefly discussed. MD simulations based on ReaxFF can be an effective method to understand the mechanisms of chemical reactions and to predict and/or improve the structure, functionality, and physicochemical properties of the products.

Pyrolysis temperature had effects on the physicochemical properties of biochar

Pyrolysis temperature had effects on the physicochemical properties of biochar