Physicochemical Characteristics Of Biochar Research Articles

Investigations of thermal effects during pyrolysis of agro-forestry biomass and physicochemical characterizations of biofuel products

The development of biofuels from waste residues is critical due to higher emissions of greenhouse gases from petroleum and coal and rising energy demand. Converting agricultural and forestry biomass into biofuel products efficiently is a practical approach for simultaneously addressing renewable energy security and waste management challenges. This study examines the physicochemical characteristics of several agro-forestry residues such as camelina meal, mustard meal, flax straw, hemp straw and spruce wood to assess their suitability as feedstocks for pyrolysis to generate biochar, bio-oil and gases. An analysis was conducted to evaluate the influence of temperature (300–525 °C), heating rate (5–35 °C/min) and reaction time (30–75 min) to assess their impact on conversion efficiency and product distribution during pyrolysis. The optimal temperature, heating rate and reaction time for pyrolysis of camelina meal as a model biomass were determined to be 450 °C, 5 °C/min and 30 min, respectively. Physicochemical characteristics of biochar and bio-oil were analyzed to determine the impact of controlled thermal breakdown through slow pyrolysis. As the temperature increased, the calorific value, carbon content and thermal stability of biochar increased due to the removal of volatile matter and the development of aromatic carbon and phenolic features.

Synthesis of biochar-ZnAl-layered double hydroxide composite for effective heavy metal adsorption: Exploring mechanisms and structural transformations

Rapid industrialization has increased the extent of heavy metal contamination in water sources, demanding effective wastewater treatment methods. To mitigate this issue, adsorption techniques play a crucial role in wastewater treatment. Layered double hydroxides (LDHs) are commonly employed in such processes; however, they exhibit limitations in effectively adsorbing contaminants. Here, biochar (BC) was incorporated into LDHs using a simple hydrothermal method and subsequently used for Cd2+ and Pb2+ adsorption. Additionally, the physicochemical characteristics of BC and ZnAl-LDH-BC were assessed utilizing various instruments. The obtained ZnAl-LDH-BC400 and ZnAl-LDH-BC600 had surface areas of 52.55 and 102.56 m²/g, respectively, several times greater than those of the original BC. Adsorption performance was investigated using different kinetic and isothermal models. The Langmuir–Freundlich and pseudo-second-order kinetic models demonstrated the adsorption of single-layer chemicals. Furthermore, the highest observed adsorption capacities for Cd2+ and Pb2+ were 99.8 mg g−1 and 128.4 mg g−1, respectively, when using ZnAl-LDH–BC600. In contrast, BC600 demonstrated adsorption capacities of 42.1 mg g−1 for Cd2+ and 51.7 mg g−1 for Pb2+. Cd2+ and Pb2+ adsorption by ZnAl-LDH-BC was primarily governed by surface precipitation and cation exchange processes. These findings highlight the mechanisms underlying the removal of heavy metals using ZnAl-LDH-BC and provide valuable theoretical and applied insights into the management of agricultural waste and control of water pollution.

Evaluation of coconut biochar as a soil amendment for enhanced productivity of sweet peppers (Capsicum annuum L.) in Joanna, Black Bush Polder, Corentyne, Berbice, Guyana

Agriculture plays a vital role in providing food globally including Guyana, however, the increase in the human population adversely decreases farm size, which results in nutrient depletion on existing farms due to extensive farming activities on the same land season after season. Biochar is commonly used as a non-conventional farming system to enhance the soil’s quality and simultaneously to produce better yield of various staple food crops. Therefore, the purpose of this study was to evaluate the effectiveness of coconut biochar as a soil amendment and to quantify its impact on the growth performance of sweet peppers (Capsicum annuum L.) in Joanna, Black Bush Polder, Corentyne, Berbice, Guyana. A field trial was carried out using the randomized block experimental design with 15 g, 30 g, 45 g biochar; 2 g NPK; and control, each replicated on clayey loam soil. The physico-chemical characteristics of biochar were determined along with the soil-biochar mixture before and after cultivation. In addition, vegetative and reproductive parameters of the sweet peppers, nutrient content of the fruits and chlorophyll content of the leaves were examined. The results obtained from this study revealed that biochar played a minor role in enhancing the yield of the sweet peppers (31.44 g) and amending the soil characteristics when compared to the control. It was observed in this study that soil pH (8.4), organic carbon (1.9 %), carbohydrates concentration (1.25 %) of fruits and chlorophyll content (a:5.6097µM, b: 5.4833 µM, total: 11.093 µM) of the leaves increased with the application of biochar. Based on the obtained results, it can be inferred that biochar may potentially be recommended in the range of 30 g to 45 g as a soil amendment to enhance the growth performance of sweet peppers, however, further experiments with diverse crops and soils are still required to investigate the use of the exact quantity of biochar sourced from different materials.

Potassium-phosphorus-sulfur augmented biochar production from potentially toxic elements abated gypsum pond wastewater of phosphate fertilizer industry

Present study highlights scope and process for production of environmentally safe (reduced F, Cr, Cd content) and multi-nutrient (K, P, S) enriched biochar utilizing highly acidic gypsum pond wastewater (GPW; P and S rich) and banana peduncle (K rich) waste. Untreated and treated [potentially toxic elements (PTE) adsorbed on Crassostrea shells] GPW soaked biomass pyrolyzed at 400, 600, 800 °C and produced K-P-S enriched biochar (KPS-B-400/600/800 and T-KPS-B-400/600/800). Physicochemical characteristics of biochar were investigated by XRD, FTIR and surface area analyser. The K, P and S contents were 14–15.53, 1.88–2.27 and 3.75–4.77% in the untreated biochar produced at 400, 600 and 800 °C respectively, with corresponding values of 15.21–18.43, 2.05–2.91 and 0.62–1.09% in the treated biochar. At various temperatures, K, P and S formed mineral phases such as K(H2PO4), KH5(PO4)2, K2CaP2O7 and K2SO4 in untreated biochar, and K3P, K2SiP2 and K2S in treated biochar. Sulfite (SO32-) was identified as pre-dominant functional group in untreated and treated biochar. Water soluble and Toxicity Characteristic Leaching Procedure (TCLP) F contents in T-KPS-B-800 were lowered to 0.005% and 0.013% respectively and values were well below permissible limits. Toxic Cd TCLP content reduced by 5.75% in T-KPS-800 over KPS-800, whereas Cr reduction of 44% was eastimated in T-KPS-400 with respect to KPS-400 due to treatment of GPW with molluscan shells. Above findings establish an alternative way of nutrients recovery and PTE reduction from phosphate fertilizer industry GPW.

Physico-chemical characterization of walnut shell biochar from uncontrolled pyrolysis in a garden oven and surface modification by ex-situ chemical magnetization

The shells of walnuts (WS) are major refuse in the global fruits and nuts trade. This, otherwise discarded, lignin-rich material can be carbonized to biochar—a value-added product with environmental applications such as carbon sequestration, soil amelioration, and pollutant adsorption. These applications are dictated by structural and chemical characteristics of the biochar carbon. Conventional controlled pyrolysis (CPy) of biomass is cost-intensive and technically too complex for widespread adoption, especially in emerging economies. Here, walnut shell biochar (BWS0) is derived through uncontrolled pyrolysis (UCPy) in a pyrolysis oven and further hybridized as magnetic biochar through ex-situ chemical co-precipitation. The physico-chemical characteristics of biochar and its water-extractable fractions are comprehensively investigated to understand their carbon structure and environmental applicability. The sp2 amorphous carbon sequestered in BWS0 is 0.84 kgCO2/kgbiomass with a BET (N2) surface area of 292 m2/g and is comparable to biochar from CPy in terms of carbon structure. The polyaromatic hydrocarbons present are only trace amounts of naphthalene, biphenyl, and phenanthrene. The magnetization decreases porosity of BWS0 while greatly facilitating its separation from aqueous media. BWS0 is suitable for adsorption of cations (between pH 2.8 and 9.45) and hydrophobic pollutants with only 19 mg L−1 fouling from their intrinsic dissolved organic carbon. In combination with fast-release N, P fertilizers, BWS0 (C/N of 24.8) is suitable for application in hydrophilic soils at higher loading rates. The results suggest an avenue where WS biochar can also be prepared via UCPy for direct environmental applications. Future investigations into soil incubation and adsorption tests are recommended.Graphical abstract

Carbon content determines the aggregation of biochar colloids from various feedstocks

The aggregation kinetics of biochar colloids (BCs) play a crucial role in the fate and transport of contaminants, as well as the carbon (C) cycle in the environment. However, the colloidal stability of BCs from various feedstocks is very limited. In this study, the critical coagulation concentration (CCC) of twelve standard biochars pyrolyzed from various feedstocks (municipal source, agricultural waste, herbaceous residue, and woody feedstock) at 550 °C and 700 °C were investigated, and the relationship between the physicochemical characteristics of biochar and the colloidal stability of BCs was further analyzed. The CCC of BCs in the NaCl solution followed the trend of municipal source < agricultural waste < herbaceous residue < woody feedstock, which was similar to the order of C content in biochar. The CCC of BCs showed a strong positive correlation with the C content of various biochars, especially pyrolyzed at a higher temperature of 700 °C. The BCs derived from lignin-rich feedstock (e.g., woody feedstock) had the highest colloidal stability, followed by cellulose-rich feedstock (e.g., agricultural waste and herbaceous residue). The BCs derived from organic matter-rich feedstock (municipal source) were easy to aggregate in the aqueous environment. This study quantitatively provides new insights into the relationship between BCs stability and biochar characteristics from various feedstocks, which is critical to assess biochar environmental behavior in aqueous environments.

Development of a Dual-Chamber Pyrolizer for Biochar Production from Agricultural Waste in Sri Lanka

This study investigates the design and development of a pyrolysis reactor for batch-type biochar production from rice husks. The main objective is to develop an appropriate technology to regulate pyrolysis temperature and biomass residence time that can be easily operated under field and household conditions with minimal operational and technical requirements. The designed novel dual-chamber reactor comprises two concentrical metal cylinders and a syngas circulation system. The outer cylinder is for energy generation and the inner one is for pyrolysis. Temperature profiles, energy exchanges, syngas production, and the physicochemical characteristics of biochar were obtained to determine the performance of the reactor. Different trials were carried out to obtain different pyrolysis temperatures under constant amounts of feedstock and fuel. The temperature was monitored continuously at three predetermined reactor heights, the temperature profile varied from 380 °C to 1000 °C. The biochar yield was 49% with an average production rate of 1.8 ± 0.2 kg h−1. The reactor consumed 11 ± 0.1 kg of rice husk as feedstock and 6 ± 1 kg h−1 of wood as fuel. The gaseous products from the pyrolysis were CH4, CO2, H2, CO, and CnHm, which contributed 23.3 ± 2.3 MJ m−3 of energy as fuel for the pyrolysis process. The specific surface area of the biochar was 182 m2 g−1. The achieved operational capacity and thermal efficiency of the reactor show biochar production is a suitable option to convert discarded biomass into a value-added product that can potentially be used in several environmental applications.

The impact of pyrolysis conditions on orange peel biochar physicochemical properties for sandy soil.

The citrus industry is considered one of the main contributors to agricultural waste. Peels are commonly used in the food industry or as feedstock in biorefining. In this study, the potential of waste orange peel biochar for agricultural applications in sandy soil was investigated. This will not only increase the percentage of agricultural waste recycling, but also lead to more sustainable agriculture with environmental benefits such as carbon sequestration. Biochar was produced through slow pyrolysis in the temperature range 300-600°C and at two holding durations (10 min and 60 min). Both factors had a significant impact on the physicochemical characteristics of biochar in the heating region 300-450°C. However, varying the holding time for pyrolysis temperatures beyond 450°C had a diminishing effect on biochar properties compared with the impact of increasing pyrolysis temperature. The study also looked at certain properties that are specific to agricultural application not previously reported for orange peel. Very high cation exchange capacities of 70 cmol kg-1 were achieved at 300°C, whereas water holding capacity was not strongly influenced by pyrolysis conditions. Preliminary planting tests indicate potential for improving agricultural sustainability in sandy soils. The technoeconomic analysis of biochar showed that the pyrolysis process can be profitable with sufficient plant capacity.

Physicochemical characteristics of biochars can be beneficially manipulated using post-pyrolyzed particle size modification

This work aimed to study the changes in the physicochemical properties of biochars induced by post-pyrolyzed particle size processing. Twelve distinct physicochemical attributes of four different particle sized biochars, derived from three different feedstocks, including rice husk, tea wastes and woodchips; were investigated. Amongst all of the investigated characteristics water repellency (η2 = 0.99) and mean pore diameter (η2 = 0.95) were the characteristics most affected by feedstock type and particle size, respectively. The interaction effect between biochar type and particle size was extremely significant (P < 0.001) for surface area and mean pore diameter. While feedstock mainly controlled biochar characteristics, most characteristics were also particle size dependent, where size dependency was more influential on physical than chemical properties. For most properties a significant interaction effect between biochar type and particle size was also detected.

Characterization and adsorption performance of biochars derived from three key biomass constituents

The effects of biomass constituents on biochar adsorption performance are still unclear. In this work, three main biomass constituents, lignin, cellulose and xylan (hemicellulose), were converted into biochar. These biochars showed obvious differences, which were observed by physicochemical characteristics analysis. Based on the acid-base titration, the contents of functional groups on different biochars decreased as lignin > hemicellulose > cellulose. The findings from elemental analyses showed that the degree of lignin pyrolysis was lower than cellulose and hemicellulose; however, lignin biochar had the highest yield and ash content. The scanning electron micrographs demonstrated that both lignin and xylan biochars were similarly spherical, while cellulose biochar was fibrous. Furthermore, the sulfadimidine (SMT) adsorption experiments revealed that physicochemical characteristics of biochars obviously affected the adsorption behavior. Cellulose and xylan biochars indicated similar pH-dependent sorption patterns, but the latter exhibited higher adsorption capacity. In contrast, lignin biochar had no adsorption capacity due to the high ash content. The adsorption was dominated by the electrostatic repulsion, EDA interactions, hydrogen bonds and negative charge-assisted hydrogen-bond. Overall, these observations are of significant importance for guiding in the selection of feedstock used for biochar preparation and predicting the sorption behavior of SMT on biochars.

Field-aged biochar stimulated N2O production from greenhouse vegetable production soils by nitrification and denitrification

Evidence suggests that biochar is among ideal strategies for climate change mitigation and sustainable agriculture. However, the effects of soil aging on the physicochemical characteristics of biochar and nitrous oxide (N2O) production remain elusive. We set up a microcosm experiment with two greenhouse vegetable production (GVP) (alkaline and acid) soils by using the 15N tracing technique and quantitative polymerase chain reaction (qPCR) to investigate the mechanisms of N2O production as affected by fresh (FB) and aged biochar (AB) amendment. The results showed that AB increased the specific surface area, organic C, ammonium sorption capacity and cation exchange capacity, whereas decreased the pore size and pH relative to the FB. Results also demonstrated that FB effectively decreased N2O emissions from both soils while it enhanced the abundance of nirK and nosZI genes in alkaline soil and reduced the abundance of ammonia-oxidizing bacteria (AOB) amoA and increased nirK and nosZII genes in acid soil. In contrast, AB significantly stimulated nitrification and denitrification in both soils and thus significantly increased the N2O emissions by 43–78%. Furthermore, AB induced increases in ammonia-oxidizing archaeal (AOA) amoA and nirK gene abundances in alkaline soil and fungal nirK gene abundances in acid soil. These results suggest that AB may not be suitable for the mitigation of soil N2O emissions in GVP soils thus improving our understanding of the potential mechanism of biochar in N2O emissions.

Characterization of Biochar Derived from Pineapple Peel Waste and Its Application for Sorption of Oxytetracycline from Aqueous Solution

Physicochemical characteristics of biochar and its sorption potential for oxytetracycline (OTC) were investigated. Biochars from pineapple peel waste were produced via pyrolysis under oxygen-depleted conditions at 350 °C (BL350), 500 °C (BL500), and 650 °C (BL650), as well as the characteristics and polycyclic aromatic hydrocarbons contents of the samples were compared. The sorption kinetics of OTC onto the biochars was completed in three stages, i.e., a fast stage, a slow stage, and an equilibrium stage after 24 h. The kinetics data were perfectly fitted by the pseudo-second-order model with high correlation coefficients (R2 > 0.999). All of the sorption isotherms were nonlinear and well described by the Langmuir model. The Langmuir maximum sorption capacity (qmax) increased in the order of BL650 > BL500 > BL350. The thermodynamic parameters revealed that the sorption of OTC onto the biochars was spontaneous and endothermic. Fourier transform infrared spectroscopy (FTIR) of the biochars before and after sorption of OTC confirmed that the H-bonding interaction was the dominant sorption mechanism. The results demonstrated that biochars obtained from inexpensive and renewable materials could be utilized as a highly effective and environmentally friendly adsorbent for removing organic contaminants from wastewater.

Biochar applications and modern techniques for characterization

Biochar simply is the material produced when biomass undergoes any chemical processes under the conditions of pyrolysis. The variety of biomasses, including wood waste, agricultural crop leftover, organic waste, animal manure, and forestry residues, have been considered as raw material to produce biochar. Biochar is widely used for generation of heat and power and an addition to soils, in which it serves as a fertilizer and carbon sequestration agent. Also in the form of being activated, it finds significant role for various adsorption applications. The most beneficial use of a given char depends on its physical and chemical characteristics, even though the relationship of char properties to these applications is not well defined. Various widely used modern analytical techniques, which are applicable and crucial for biochar characterization, have been reviewed in the present work, such as solid state nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-rays photoelectron spectroscopy, X-rays diffraction, thermogravimetric analysis, near edge X-rays absorption fine structure spectroscopy, and gas chromatography-mass spectroscopy. Utilization of these modern techniques provides the quantitative as well as qualitative information, i.e., determining the sizes, shapes, and physicochemical characteristics of biochar, which is reliable to track changes in the carbon arrangement over reaction time and temperature, and will be useful for efficient production of biochar and application. It provides the useful information for the researchers in this area and is beneficial not only for the effective biochar production, but also for potential utilization/application, and not only for environment but also for agriculture.

Impact of pyrolysis temperature and manure source on physicochemical characteristics of biochar

While pyrolysis of livestock manures generates nutrient-rich biochars with potential agronomic uses, studies are needed to clarify biochar properties across manure varieties under similar controlled conditions. This paper reports selected physicochemical results for five manure-based biochars pyrolyzed at 350 and 700°C: swine separated-solids; paved-feedlot manure; dairy manure; poultry litter; and turkey litter. Elemental and FTIR analyses of these alkaline biochars demonstrated variations and similarities in physicochemical characteristics. The FTIR spectra were similar for (1) turkey and poultry and (2) feedlot and dairy, but were distinct for swine biochars. Dairy biochars contained the greatest volatile matter, C, and energy content and lowest ash, N, and S contents. Swine biochars had the greatest P, N, and S contents alongside the lowest pH and EC values. Poultry litter biochars exhibited the greatest EC values. With the greatest ash contents, turkey litter biochars had the greatest biochar mass recoveries, whereas feedlot biochars demonstrated the lowest.