Fossil fuels are the main source of energy. But due to the effect of CO2 on the environment and global energy challenges, the replacement of fossil fuels has become necessary.
Organic waste, as the main constituent of solid biomass, has a high potential for biochar generation.
Biomass wastes suitable for biochar production include agricultural, forestry crop residues, municipal solid waste, food and animal manures, etc.
Biomass-derived biochar is a very rich source of carbon produced from biomass by thermal combustion in an oxygen-limited environment.
The unique properties of biochar such as large specific surface area, high porosity, functional groups, high cation exchange capacity and stability make it suitable for various applications. Speed and ease of preparation, eco-friendly nature, reusability and cost-effectiveness are some of the advantages of biochar.
Biochar has attracted the attention of many researchers by establishing its effectiveness in removing various contaminants.
Process parameters are primarily responsible for determining biomass yield. Parameters include temperature, biomass types, residence time, heating rate, pressure, etc.
Temperature is the main parameter affecting the characteristics of biochar.
Commonly used thermochemical techniques for biochar production include pyrolysis, hydrothermal carbonization, gasification, flash carbonization, and torrefaction. Among all these methods, pyrolysis is the most commonly used to produce biochar.
Organic compounds found in biomass decompose at a specific temperature in an oxygen-limited environment. Factors that affect the pyrolysis product include process temperature, residence time, biomass type, and heating rate.
Although biochar is composed entirely of carbon and ash, the elemental composition and characteristics differ depending on the type of biomass, reaction conditions, and type of reactors used during the carbonization process.
Therefore, the application and effectiveness of biochar in various fields depend on the type of biomass used to produce biochar.
Characterization of biochar is very important to determine biochar elemental composition, surface functional groups, stability and structure.
Characterization of biochar can be carried out using various modern techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Brunauer Emmett Teller (BET), nuclear. Magnetic resonance (NMR), Raman spectroscopy, etc. Recent literature has focused on the characterization of biochar and its main objective is to differentiate biochar from other soil organic matter. Different properties of biochar can be identified using the above characterization techniques, for example: SEM for biochar morphology, FTIR to determine functional groups, etc. The mechanism by which biochar absorbs toxic heavy metals and other contaminants is adsorption.
The detailed literature regarding the properties of biochar and its analysis and quantification techniques will pave the way for knowledge on the efficacy of biochar in various sectors. Due to its many benefits and eco-friendly nature, biochar has been used to solve many environmental problems such as adsorption of pollutants, reduction of greenhouse gas emissions, composting, wastewater treatment, soil remediation, energy production and catalysts. The ability of biochar to adsorb organic and inorganic pollutants depends on its high surface-to-volume ratio and its affinity toward non-polar groups.
Biochar has also been used in agricultural fields to remove pollutants from the soil.
Many agricultural residues have been used to produce biochar, such as rice straw, wheat straw, wood waste, sugar beet residue, corn cobs, etc. These biomasses are composed mainly of cellulose, hemicellulose and lignin components.
During the pyrolysis process, these components are thermally decomposed at different temperatures and their mechanisms are discussed in detail.
The production of biochar using different techniques such as pyrolysis, hydrothermal gasification, roasting has been conferred. Characterization techniques such as SEM, XRD, FTIR, TGA, BET, etc. were explored. In addition to this, the stability of biochar, its use in various applications such as removal of organic and inorganic pollutants, carbon sequestration and catalyst were discussed.The adsorption efficiency of biochar is directly proportional to the physicochemical properties such as functional groups, surface area, cation exchange capacity, etc.
The physicochemical properties of biochar can be improved by treating biochar with acidic, alkaline or oxidizing agents. The surface can be modified by acid treatment.
The physicochemical properties of biochar can be improved by treating biochar with acidic, alkaline or oxidizing agents.
The surface can be modified by acid treatment. The physicochemical properties of biochar can be improved by treating biochar with acidic, alkaline or oxidizing agents. The surface can be modified by acid treatment.
Biochar Production Methods
Growing interest in using biochar for various applications has led to increased conversion of biomass into biochar. Thermochemical conversion is a common technique for biochar production. The thermochemical conversion method includes pyrolysis , hydrothermal carbonization , gasification and torrefaction . For maximum yield of biochar, the technique chosen for production should be appropriate depending on the type of biomass and the process conditions such as heating rate , temperature , residence time , etc. must also be optimal .
These conditions are crucial because they can affect the physical and chemical states of the biochar during the production process. The morphology of biochar from plant biomass varies depending on the process conditions since it involves a loss of weight of the biomass. Initially, weight loss due to water loss around 100 °C continues with degradation of cellulose, hemicellulose and lignin occurring above 220 °C. Finally, weight loss occurs due to the burning of carbon residue.
Pyrolysis _
The process of thermal decomposition of organic materials in an oxygen-free environment in a temperature range of 250 to 900 °C is called pyrolysis. This process is an alternative strategy to convert residual biomass into value-added products such as biochar, syngas and bio-oil.
During the process, lignocellulosic components like cellulose, hemicellulose and lignin undergo reaction processes such as depolymerization, fragmentation and cross-linking at specific temperatures, resulting in a different state of the products like solid, liquid and gas. Solid and liquid products include charcoal and bio-oil while gaseous products are carbon dioxide, carbon monoxide and hydrogen as well as syngas (C 1 -C 2 hydrocarbons).
Different types of reactors such as paddle kilns, bubbling fluidized beds, trolley reactors and rotary stirred sand kilns are used for biochar production.
Pyrolysis can be classified as fast and slow pyrolysis process depending on the heating rate, temperature, residence time and pressure.
The biochar yield during the pyrolysis process depends on the type and nature of the biomass used.
Temperature is the main condition of the operating process that determines the effectiveness of the product.
Generally, biochar yield decreases and syngas production increases as the temperature increases during the pyrolysis process .
Rapid pyrolysis:
Fast pyrolysis is considered a direct thermochemical procedure that can liquefy solid biomass into liquid bio-oil with high potential for energy application. The fast pyrolysis conditions are described by:
(i) rapid heating rates of biomass particles (>100 o C/min),
(ii) accompanied by short durations of biomass particles and pyrolysis fumes (0.5 to 2 s) at high temperatures and
(iii) moderate pyrolysis processing temperatures (400-600 o C).
A key distinguishing feature of fast pyrolysis innovation is the need to maintain the residence time of the fumes in the hot zone down to the base, to obtain high quality bio-oil. This can be achieved by ensuring rapid extinction or cooling of the fumes.
Slow pyrolysis: In slow pyrolysis, the heating rate is much lower, around 5 to 7 o C/min and has a longer residence time, greater than 1 hour.
The slow pyrolysis innovation offers better carbon yield compared to different pyrolysis and carbonization strategies. Biochar could be used as a dirt enhancer to improve soil quality.
The majority of biomass is composed of cellulose, hemicellulose and lignin. These components are converted into biochar using different reaction conditions and mechanisms.
Breakdown of cellulose
The mechanism of cellulose decomposition is identified by reducing the degree of polymerization constituting two reactions:
1) By slow pyrolysis, including decomposition of cellulose with a longer residence time and a lower heating rate
2) By rapid pyrolysis, occurring at a high heating rate by rapid volatilization resulting in the development of levoglucosan. In addition to solid biochar, levoglucosan also undergoes a dehydration process to produce hydroxymethylfurfural which can decompose to produce liquid and gaseous products like bio-oil and syngas, respectively. In addition, hydroxymethylfurfural can also undergo several reactions such as aromatization, condensation, and polymerization to produce solid biochar again.
Decomposition of Hemicellulose The decomposition mechanism of hemicellulose is similar to that of cellulose. Hemicellulose undergoes depolymerization to form oligosaccharides. This can go through a series of reactions including decarboxylation, intramolecular rearrangement, depolymerization and aromatization to produce either biochar or the compound decomposes into syngas and bio-oil.
Decomposition of lignin Unlike the decomposition mechanism of cellulose and hemicellulose, the decomposition mechanism of lignin is complex.
The lignin β-O-4 bond breaks, leading to the production of free radicals. These free radicals capture protons from other species, resulting in the formation of broken down compounds. Free radicals travel to other molecules leading to chain propagation.
Hydrothermal carbonization
Hydrothermal carbonization is considered a cost-effective method for biochar production because the process can be carried out at low temperatures, around 180 to 250 °C.
The product using the hydrothermal process is called hydrochar to differentiate the product from dry processes such as pyrolysis and gasification. During the process, the biomass is mixed with water and placed in a closed reactor.
The temperature increases slowly to maintain stability. At different temperatures, products are produced as follows: biochar at a temperature below 250°C called hydrothermal carbonization, bio-oil between 250 and 400°C called hydrothermal liquefaction, and synthetic gas products such as CO, CO2 , H 2 and CH4 produced at a temperature above 400 o C called hydrothermal gasification. The hydrolyzed product undergoes a series of reactions such as dehydration, fragmentation and isomerization to form the intermediate product 5-hydroxymethylfurfural and its derivatives. Additionally, the reaction proceeds through condensation, polymerization, and intramolecular dehydration to produce the hydrochar. The high molecular weight and complex nature of lignin complicates the mechanism. The decomposition of lignin begins with a dealkylation and hydrolysis reaction producing phenolic products like phenols, catechols, syringols, etc. Finally, coal is produced by repolymerization and cross-linking of intermediates. Components of lignin that are not dissolved in the liquid phase are transformed into a hydrocarbon similar to a pyrolysis reaction.
Gasification _ _
Gasification is a thermochemical method of decomposition of carbonaceous material into gaseous products, that is to say the synthesis gas comprising CO, CO 2 , CH 4 , H 2 and traces of hydrocarbons in the presence of decomposing agents. gasification such as oxygen, air, steam, etc. and at high temperature. . It should be noted that the reaction temperature is the most important factor in determining the production of syngas. It was found that as temperature increased, carbon monoxide production increased while other contents such as methane, carbon dioxide and hydrocarbons decreased. The main product of this process is syngas and the coals are considered the least efficient by-product.
The gasification mechanism can be subdivided into several stages as follows:
Drying
During this process, the moisture in the biomass is completely evaporated without energy recovery. Moisture content varies among different biomass materials. Drying is used as a separate process during the gasification process when the biomass contains a high moisture content.
Oxidation/Combustion
The oxidation and combustion reactions of gasification agents are the main energy sources of the gasification process. These gasification agents react with the combustible species present in the gasifier to produce CO 2 , CO and water.
Roasting and flash carbonization
Roasting is an emerging technique for biochar production. It uses a low heating rate, called mild pyrolysis.
Oxygen, moisture and carbon dioxide present in the biomass are removed using inert atmospheric air in the absence of oxygen at a temperature of 300 o C using various decomposition processes.
The torrefaction process changes the properties of biomass such as particle size, moisture content, surface area, heating rate, energy density, etc. The roasting process can be carried out
(a) Steam roasting: In this process, the biomass is treated with steam with a temperature not exceeding 260°C and a residence time of about 10 minutes.
(b) Wet roasting: also called hydrothermal carbonization, it takes place with the contact of the biomass with water at a temperature of 180 to 260 °C and a residence time of 5 to 240 min.
(c) Oxidative roasting: This process is carried out by treating the biomass with oxidizing agents such as gases which are used for the combustion process to generate thermal energy. This thermal energy is used to produce the required temperature.
The mechanism of the torrefaction process is an incomplete pyrolysis process and the process takes place under the following reaction conditions: temperature – 200-300 o C, residence time – less than 30 min, heating rate – less than 50 o C /min and in the absence of oxygen. .
The dry roasting process can be classified into different phases such as heating, drying, roasting and cooling. Again, drying can be classified into pre-drying and post-drying processes.
Heating
During this process, the biomass is heated until the desired drying temperature is maintained and the moisture content of the biomass evaporates.
Preheating
This process occurs at a temperature of 100 o C until the moisture content present in the biomass completely evaporates.
Post-drying
The temperature rises to 200°C and the water contained completely evaporates. Mass content is lost due to increasing temperature.
Roasting
This process is the main step in the entire roasting process. It is carried out at 200°C and a stable temperature is obtained during the process.
Cooling
After the product is formed, the temperature is allowed to cool before it comes into contact with air and room temperature is obtained. The flash fire is ignited on the biomass-packed bed at high pressure and the biomass is converted into solid phase and gas phase products. The entire process is carried out at a temperature of 300 to 600 °C and a reaction time of less than 30 min. About 40% of the biomass is converted into solid products and the process decreases with increasing pressure. The flash carbonization process is very limited to the literature and is not commonly used.
Factors Affecting Biochar Properties
The reaction conditions during the pyrolysis process are mainly responsible for the production of biochar. Factors such as raw materials, temperature, particle size, heating speed, etc. mainly influence the properties of biochar.
These factors have a direct effect on the yield of biochar rather than its quality. Detailed knowledge of biochar property analysis is important to determine the application of biochar. Various biomasses from different sources such as plant materials, agricultural residues, biomass from wood, solid waste, etc. have been used to produce biochar.
Pyrolysis is a commonly used method for biochar production, which is typically carried out between 400 and 1000 °C. Solid waste and animal waste produce more biochar compared to other biomass materials such as woody biomass, agricultural residues, etc.
Raw materials
Biomass is considered a complex solid material, composed of biological, organic or inorganic materials derived from living or living organisms. Biomass is characterized into two types (i) woody biomass and (ii) non-woody biomass. Woody biomass essentially includes tree residues and forest residues. The attributes of woody biomass are low moisture, low debris, fewer voids, high density and calorific value. Non-woody biomass includes animal waste, industrial and agricultural solid waste. The attributes of non-woody biomass are high debris content, high moisture, high voids, low density and calorific value. Among the different attributes of biomass raw material, moisture content has a significant impact on biomass formation.
Biomass moisture can exist in different forms such as liquid water, water vapor and be adsorbed in the pores of biomass. Higher moisture content in biomass primarily inhibits char formation and increases the amount of energy required to reach the pyrolysis temperature. Low moisture content in biomass is preferable for biochar formation due to the impressive decrease in thermal energy and reduction in time required for the pyrolysis process, making biochar formation economically feasible compared to biomass with a high moisture content.
Carbonization temperature
Pyrolysis is the best-known method for exchanging biomasses into biochar through a thermochemical disintegration process in an oxygen-deprived, elevated temperature environment. Depending on the conditions, pyrolysis cycles can be grouped into three basic classifications: (i) slow pyrolysis (temperatures <300 °C), (ii) moderate pyrolysis (temperatures 300 to 500 °C), and (iii) fast pyrolysis (temperatures higher than 500 oC). The pyrolysis temperature influences the physicochemical properties and structure of the biochar, e.g. elementary components, pore structure, surface area and functional groups. The impact of pyrolysis temperature on these properties can be attributed to the influx of volatile substances at high temperatures.
Residence time The extension of the residence time at low pyrolysis temperature (300 o C) led to a slow decrease in biochar yield and a reformative expansion of the pH and iodine adsorption number of biochars. Nevertheless, increasing the residence time at high pyrolysis temperature (600 °C) had little impact on the yield or pH of the biochar, while decreasing the iodine adsorption number of the biochars.
Created by the thermochemical discussion of natural build-ups in an oxygen- restricted condition.The document's source is:
Biotechnology Reports 28 (2020) e00570
Biomass pretreatment
Pretreatment of biomass before pyrolysis influences the characteristics of the biochar.
Common pretreatment methods available involve immersing the raw materials in a solution and reducing the size of the biomass particles.
Reducing the particle size of biomass results in high biochar yield. For example, pine wood biomass was pretreated by immersing it in a dilute acid solution. Pretreatment methods such as nitrogen and metal doping can influence biochar production and solution pretreatment such as soaking or steaming can influence the elemental composition and properties of biochar while cooking method can increase the carbon content and reduce the oxygen and moisture content of biochar. biochar. Potential biomass for biochar generation, used independently or in the form of mixtures. Depending on the innovation used, practical implementation is most often limited by humidity or the mineral substance of the biomass. For example, the presence of chlorine and soluble base metals can lead to consumption. Due to different production technologies and biomass, the properties of the produced biochar can vary greatly. While components, e.g. hydrogen (H), O, nitrogen (N) and sulfur (S) are volatilized during pyrolysis, minerals, e.g. phosphorus (P), K, calcium (Ca), magnesium (Mg), and silicon (Si) remain and their concentrations increase in the resulting biochar. The presence of harmful compounds or components in biochar may be the result of polluted biomass during pyrolysis/gasification.
Characterization of biochar
Biochar characterization is performed to determine the ability to remove pollutants or other applications. Structural and elemental analysis also makes it possible to predict the impact of biochar on the environment. In addition, metals interact with biochar which is a function of pH as
1) the function of biochar differs depending on pH
2) the speciation of metal contaminant ions varies depending on pH. These characteristics of biochar have shown its ability to act as a very effective adsorbent to remove most pollutants from the soil. Biochar characterization techniques are based on structure, surface functional groups, and elemental analysis. Currently, many modern characterization techniques have been reported to characterize biochar, such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric (TGA), nuclear magnetic resonance (NMR) spectroscopy. , Brunauer-Emmett-Teller (BET), proximate and ultimate analysis, Raman spectroscopy, etc.
Functional groups
Essential functional groups present on the surface of biochar that increase its sorption properties include carboxylic (-COOH), hydroxyl (-OH), amine, amide, and lactonic groups. The main factors that influence the surface functional groups of biochar are biomass and temperature [82]. Furthermore, when other properties such as pH, specific surface area and porosity increase, there is a risk of reduction of the functional groups of the biochar. The surface functional groups are characterized by Fourier transform infrared spectroscopy (FTIR). Biochar produced at different temperatures showed a significant difference in their surface functional groups. Besides FTIR, NMR (nuclear magnetic resonance) can also be used to determine the surface functional groups present in biochar.
Surface area and porosity
Usually, biochar with increased surface area and high porosity will possess high sorption property. The porous surface of biochar forms during the pyrolysis process when there is an increase in water loss during the dehydration process. According to the International Union of Pure and Applied Chemistry, pores present in biochar can be micro (<2 nm), meso (2-50 nm), and macro (>50 nm).
Biochar with smaller pores cannot adsorb pesticide molecules despite their polarity or charges.
The pore size of biochar can be characterized by SEM (scanning electron microscopy). Surface area is the key to determining the sorption capacity of biochar while temperature plays a major role in biochar formation. Surface area may vary between treated and untreated raw materials. Commercially, activated carbon has a larger surface area.
Biochar produced without an activation process has a low specific surface area and is less porous. Thus, during biochar production, an activation process is involved to increase the porosity and surface area of the biochar. Both physical and chemical activation process can be involved in the activation process.
Stability of biochar
The stability or resistance of biochar to biotic and abiotic soil degradation was used to determine the carbon sequestration capacity of biochar. Many studies have been investigated to evaluate the stability of biochar. The temperature used in the pyrolysis process is considered an indication of the stability of the biochar. This prediction is inaccurate and simple. Immediate examination has long been used to study the nature of coal, moisture, charcoal, ash and fixed carbon. Immediate examination requires high temperatures (900 o C to ensure the presence of volatile materials and 750 o C for ash determination) for an extended period; this has disadvantages and can lead to an exaggerated estimate of carbon by underestimating the ash content.
Methods for assessing biochar stability can be divided into three classes:
(a) direct or indirect qualification or quantification of biochar C structures such as aromaticity;
(b) quantification or qualification of stable C by thermal, chemical or thermochemical methods such as chemical oxidation, thermal degradation, etc. And
(c) incubation of biochar in soil and modeling of C mineralization.
The last method Incubation and modeling is a biochemical technique for measuring the stability of biochar and forms the basis of the first two methods. The results obtained from the first two methods resemble indirect stability results which correlate with the results obtained from the incubation and modeling method. A well-defined property of biochar is the presence of a C structure comprising a crystalline phase and an amorphous phase. Assessment of biochar stability can be done by evaluating the C present in the biochar or stable C structures. Therefore, the C structure is the determining element to evaluate the stability of biochar. The main indicators of biochar C structures are aromatic condensation and aromaticity. Biochar with a high degree of aromatic condensation and aromaticity resists thermochemical and biological degradation and thus exhibits high stability. The elemental composition of biochar represents CC bonds or aromaticity.
Biochar properties such as pore structure, pH, minerals, sorption mechanism, surface area and particle size also contribute to biochar stability. Biochar stability assessment by incubation and modeling is considered a major class due to the direct and precise results obtained. This method gives longevity values that remain under incubation conditions. These values are based on data modeling. The ideal stability of biochar can be acquired by incubating the biochar in soil until complete degradation and calculating the degradation time. It takes hundreds of years for complete degradation of biochar, so calculating the longevity value is impossible.
However, this incubation and modeling process is expensive and time-consuming. The use of radioactive 14C isotopes is another new approach to analyze the stability of biochar. 14C-labeled C complex substrates were used to determine the impact of biochar and straw on SOC microbial turnover. Evaluation of thermochemical stability to oxidation allows for biotic and abiotic degradation. However, biochar can be used as a tool for various applications. Current techniques available for determining biochar stability do not provide accurate results. Therefore, the development of new methods for assessing the stability of biochar will improve the application of biochar for climate change mitigation.
Biochar and environment
Although biochar is used for various purposes, its influence on the environment must be properly analyzed to avoid its negative impacts. The main factor to focus on when pre-applying is stability.
Biochar constitutes the carbon structure. Therefore, the stability of biochar is related to the stability of the carbon structure. Aromaticity and aromatic condensation are the main measures of the carbon structures of biochar.
The dissolved organic matter released by the biochar retains a high degree of aromaticity, strength and stability. When biochar is used to treat wastewater, the carbon content of the water increases due to the release of carbon from the biochar. Biochar produced from sludge containing heavy metals may leach during the treatment process, causing heavy metal contamination.
Similarly, when biochar acts as a catalyst, the stability gradually decreases by reusing the biochar several times. Biochar instability can also be due to structural damage. The stability of biochar therefore plays an important role in environmental concerns. Additionally, the toxicity of biochar to soil microbes should also be studied before its application. Since the physicochemical properties of biochar vary with biomass, it is important to study the toxic effect(s) of biochar on the environment in detail. A different toxicity test can be performed with bacteria, algae, fish, etc.
To combat global environmental change, biochar, a crucial innovation, has been widely added to agricultural soils. Originates from the thermochemical discussion of natural accumulations in a low-oxygen environment.
Biochar expansion has been shown to alter soil porosity, moisture content, pH, and the size of labile C and N pools, which would have a notable impact on soil CO2 emissions. Biochar alterations in agricultural soils may be a potential instrument to mitigate environmental changes, with lower CO2 emissions and higher dry waste production.
Applications du biochar
Le fait qu’il soit écologique, peu coûteux et facile à préparer à partir de diverses biomasses à l’aide de techniques thermochimiques pour répondre à de vastes applications environnementales fait du biochar un domaine d’intérêt intense parmi les chercheurs.
Le biochar joue un rôle important dans l’élimination des contaminants et des polluants du sol et de l’environnement aqueux, qui peuvent être déterminés à l’aide du type de biomasse et de la température de pyrolyse.
Le biocharbon riche en carbone produit par pyrolyse à haute température a une plus grande efficacité d’élimination des polluants organiques en raison de ses propriétés enrichies telles que la porosité, la surface, le pH, la moindre teneur en carbone dissous et la nature hydrophobe.
De même, le biochar produit à basse température possède des groupes fonctionnels contenant de l’oxygène, haute teneur en carbone organique dissous et moins poreux, ces types de biochar sont donc plus adaptés à l’élimination des polluants inorganiques. D’autres facteurs comme le pH et le temps de séjour contribuent également à la capacité d’élimination du biochar.
Le biochar peut également être utilisé pour d’autres applications telles que les catalyseurs, le traitement des eaux usées, le compostage, le stockage d’énergie, la séquestration du carbone et l’amendement des sols.
Assainissement des polluants
Polluants organiques
Les applications récentes du biochar se concentrent sur l’utilisation du biochar pour éliminer les polluants organiques du sol et de l’eau. Le biochar, lorsqu’il est appliqué sur le sol, adsorbe les polluants organiques présents dans le sol.
Peu de contaminants organiques comprennent des produits chimiques agricoles tels que les insecticides, les herbicides, les pesticides, les fongicides comme l’atrazine, la simazine, le carbofuran, etc., des produits chimiques industriels tels que les HAP (hydrocarbures aromatiques polycycliques) dont le phénanthrène, le catéchol, le pyrène, le naphtalène, l’anthracène, etc., les antibiotiques. et des médicaments comme l’acétaminophène, la tétracycline, l’ibuprofène, la sulfaméthazine, la tylosine, etc., des colorants cationiques tels que le bleu de méthylène, la rhodamine, le violet de méthylène, etc., et des composés organiques volatils tels que le butanol, le benzène, le furane, le trichloréthylène, etc.
L’adsorption des polluants organiques dans le sol a été augmentée en augmentant la concentration de biochar.
La teneur en pesticides tels que le carbofuran a été minimisée en raison de l’adsorption ou de la dégradation du biochar lorsque sa concentration augmente dans le sol.
La dégradation du carbofurane dense à la surface du biochar lors de la pyrolyse entraîne une expansion de la porosité et l’adsorption de certains pesticides.
Le pesticide peut être adsorbé à la surface du biochar, en raison de la qualité des groupes fonctionnels carboxyliques et phénoliques.
L’absorption de pesticides par les plantes cultivées dans le sol a également diminué.
Par conséquent, la quantité de biochar doit être optimisée en fonction d’un domaine d’application spécifique afin de faciliter une meilleure adsorption des polluants.
Le mécanisme d’élimination est directement lié à l’interaction entre le biocharbon et les polluants. Le mécanisme se produit par physisorption (attraction/répulsion électrostatique, diffusion des pores, (liaison H et hydrophobe) et de chimisorption (interaction électrophile) en présence de divers groupes fonctionnels tels que OH, COOH, etc.
D’autres mécanismes d’élimination comprennent la transformation chimique, la séparation et la biodégradation. Les principaux facteurs qui affectent les interactions biocharbon-polluant organique sont la température, le pH, le type de biomasse et le rapport entre le polluant et le biocharbon appliqué.
Il a également été constaté que l’application de biochar diminuait la biodisponibilité des polluants organiques du sol et leur absorption par les plantes et les microbes.
Par exemple, il a été constaté que le biocharbon dérivé de bois dur à haute température de pyrolyse diminue la biodisponibilité des pesticides dans le sol en raison de la surface du biocharbon et de sa porosité pour adsorber les polluants organiques par rapport au biocharbon produit à basse température.
La diffusion, la séparation et l’attraction électrostatique étaient les principaux mécanismes d’adsorption contribuant à cette élimination. L’efficacité d’élimination a été comparée entre le sol amendé avec du biochar et un sol non entravé.
Il a été constaté que le sol amendé au biochar réduisait la disponibilité de polluants dans le sol pour l’absorption par les plantes, tandis que les plantes cultivées dans un sol non amendé augmentaient l’absorption des pesticides.
L’élimination des polluants augmente avec l’augmentation de la concentration de biochar. Les propriétés du biochar influencent la sorption des polluants organiques.
Le biochar possédant une petite taille de particules possède une grande surface et présente de meilleurs résultats d’élimination. Le temps d’élimination requis s’est également révélé inférieur.
Outre les propriétés du biocharbon, les conditions du sol contribuent également à l’adsorption ou à la dégradation des polluants.
Par exemple, la sorption des pesticides se produit uniquement à faible pH. L’adsorption s’est avérée être un mécanisme important pour l’élimination des polluants organiques lorsqu’elle est combinée à la dégradation et à l’immobilisation du contenu organique. Semblables aux pesticides, les colorants cationiques comme le bleu de méthylène,
Polluants inorganiques
Les polluants inorganiques tels que les métaux sont toxiques et non biodégradables lorsqu’ils sont présents à des concentrations plus élevées et constituent donc une menace sérieuse pour la vie humaine et l’environnement. Les métaux lourds comme le cuivre, le zinc, le cadmium, le plomb, le nickel et le mercure sont les plus cancérigènes et toxiques. Ces polluants inorganiques sont rejetés dans l’environnement soit par les effluents industriels, soit par les eaux usées municipales.
Contrairement aux polluants organiques, le biocharbon produit à basse température convient à l’absorption des contaminants inorganiques.
Le biochar produit à basse température possède de nombreux groupes fonctionnels, une teneur élevée en carbone organique et est poreux. L’échange d’ions est le mécanisme dominant pour éliminer les polluants inorganiques, en particulier les métaux lourds.
Les caractéristiques physicochimiques du biochar influencent l’adsorption de la structure poreuse et améliorent la réduction des métaux lourds. Le biochar possède également des propriétés d’immobilisation qui permettront d’évaluer la modification chimique des métaux lourds, notamment les groupes fonctionnels de surface, le pH et la capacité d’échange de cations. Les techniques de caractérisation du biochar telles que les analyses SEM, FTIR, TEM et XRD ont montré que le biochar possède une forte efficacité d’adsorption pour les métaux lourds. Le potentiel zêta et la capacité d’échange cationique du biochar diminuent avec l’augmentation du pH du sol. Le sol amendé au biochar possède plus de puissance pour l’immobilisation des métaux lourds. Par exemple, la concentration de métaux lourds tels que le plomb, le cadmium et le cuivre était potentiellement réduite dans les sols amendés au biochar.
La biomasse utilisée pour produire du biochar pour éliminer les polluants inorganiques est constituée de produits agricoles tels que l’épi de maïs, la betterave sucrière, la paille de soja, le panic raide, etc., les déchets animaux et les boues d’épuration. Parmi les métaux lourds, le cuivre possède une forte affinité pour les groupes OH et COOH et son élimination dépend principalement du type de biomasse et du pH. Un autre facteur, le pH, contribue également à l’efficacité de l’élimination, mais le processus dépend du métal.
À un pH de 6,0 à 7,0, l’élimination s’est faite par échange d’ions, tandis qu’à un pH plus élevé de 7,0 à 9,0, le mécanisme d’élimination s’est fait par complexation de surface et par attraction électrostatique.
Par exemple, l’élimination du Cr s’est avérée maximale à pH 2,0, tandis que l’élimination du Pb était élevée à pH 2,0 et 5,0. À un pH plus élevé, la solubilité du métal diminue, ce qui entrave la mobilité du métal dans le sol. Le dosage du biochar contribue également à l’élimination des métaux lourds.
Une efficacité d’élimination plus élevée peut être obtenue avec une dose accrue de biocharbon, ce qui augmente également la surface et le pH. Outre l’utilisation du biochar comme matériau absorbant pour éliminer les polluants organiques du sol, il peut également être utilisé pour éliminer les polluants inorganiques d’un environnement aqueux.
Le biochar possède le pouvoir d’éliminer les polluants dissous présents dans les eaux souterraines.
L’uranium peut être efficacement éliminé des eaux souterraines à l’aide de biocharbon.
De nombreux facteurs contribuent à l’efficacité de l’élimination. Le dosage du biochar est le facteur clé. De nombreuses études documentaires soutiennent qu’une dose accrue de biocharbon améliore l’élimination des métaux lourds.
La porosité du biochar affecte également la sorption des métaux. Les groupes fonctionnels responsables de l’élimination du Pb et du Cr sont l’hydroxyle et le carboxylate. La compétition pour la liaison des métaux entre différents métaux existe puisque les groupes fonctionnels pour l’adsorption des métaux sont chimiquement les mêmes. L’effet de l’immobilisation du biochar sur les métaux lourds et les contaminants inorganiques dans les sols pollués doit encore être analysé. Il montre l’adsorption des contaminants organiques et inorganiques et leur pourcentage d’élimination en utilisant différentes biomasses.
Catalyseur
Le biochar peut agir comme un catalyseur qui trouve de vastes applications dans divers domaines tels que l’agriculture, l’environnement, l’énergie, etc.
Les propriétés du biocharbon en font un catalyseur puissant et prometteur. La grande surface est importante pour l’activité catalytique du biochar puisque davantage de groupes fonctionnels sont présents à la surface.
Par exemple, le groupe fonctionnel O–H est responsable de l’adsorption de la norfloxacine et les groupes C¼O et OH– conviennent à l’adsorption de l’ammonium.
En tant que catalyseur, le biochar trouve de nombreuses applications telles que la production de biodiesel, la production d’énergie, l’élimination du goudron, la gestion des déchets, la production de gaz de synthèse et d’électrodes dans les piles à combustible microbiennes, la production de produits chimiques et l’élimination des contaminants environnementaux.
Production d’énergie
Au cours du processus de gazéification de la biomasse, la formation de goudron est désagréable car la condensation du goudron entraîne une contamination et un colmatage des opérations en aval ainsi qu’une réduction de l’efficacité énergétique.
La transformation catalytique du goudron possède la capacité de convertir le goudron en hydrogène et en monoxyde de carbone.
Ces H 2 et CO sont considérés comme des composants importants du gaz de synthèse.
L’omble produit à partir de différentes biomasses telles que l’omble de paille de maïs et l’omble de paille de riz influence l’élimination du goudron.
Ainsi, l’efficacité de l’élimination du goudron est affectée par les types de char.
L’efficacité de l’élimination des goudrons diminue avec l’augmentation de la taille des particules de charbon.
Cela est dû au fait que la surface et le site actif affectent l’efficacité de l’élimination. Au cours du processus de gazéification/pyrolyse, la production d’hydrogène est renforcée par le biochar.
Production de biocarburants
Le biocarburant est un substitut parfait aux produits pétroliers car il est biodégradable, non toxique, renouvelable et présente des propriétés comparables à celles des combustibles fossiles.
Les biocarburants peuvent être créés à partir de la transestérification d’huiles végétales ou de l’estérification de graisses insaturées libres (FFA) avec des alcools.
Les catalyseurs de biochar sont utilisés pour produire des biocarburants par des réactions de transestérification et d’estérification.
Les catalyseurs à base de biocharbon peuvent être classés en deux types : (i) Catalyseurs acides solides et (ii) Catalyseurs alcalins solides
Les catalyseurs de biocharbon fonctionnalisé par un acide sont généralement disposés en sulfonant le biocharbon avec du SO 3 vaporeux ou du H 2 SO 4 liquide.
Les huiles de mauvaise qualité ou usagées contiennent pour la plupart beaucoup de FFA, ce qui va probablement réduire la vitesse de réaction et le rendement du biodiesel. De cette manière, l’amélioration des catalyseurs aptes à catalyser simultanément l’estérification et la transestérification est séduisante.
Les catalyseurs solides ont été obtenus à partir de la biomasse selon deux procédés principaux, à savoir la sulfonation et la carbonisation. La production de biocarburants est une technologie émergente et est considérée comme une stratégie alternative aux pétrocarburants.
Le biodiesel est considéré comme une source alternative au diesel pétrolier en raison de ses avantages tels que le caractère renouvelable et la facilité de stockage. Le biodiesel est composé d’esters alkyliques d’acides gras produits par transestérification ou estérification de graisses animales, d’huiles végétales et d’huiles de microalgues.
Un autre type de catalyseurs à base de biocharbon pour la production de biocarburants sont les catalyseurs alcalins supportés par le biocharbon ou les catalyseurs alcalins solides déterminés par la biomasse. Le biocharbon CaO/, le biocharbon fonctionnalisé K2CO ou KOH ont également été utilisés comme catalyseurs pour la production de biocarburant. Ces catalyseurs faciles ont montré un rendement élevé en biocarburant et une réutilisabilité décente, ce qui en fait une option attrayante contrairement aux cadres de catalyseurs de transestérification existants.
L’oxyde de calcium est un catalyseur couramment utilisé en raison de sa grande disponibilité et de son faible coût. Mais ses inconvénients comme la perte d’activité et la moindre surface le rendent inadapté. Par conséquent, le catalyseur à base de biocharbon est utilisé de préférence pour la production de biocarburants en raison de son efficacité élevée, de sa porosité et de son coût moindre. Des études ont été rapportées sur l’utilisation d’un catalyseur magnétique à base de biocharbon pour la production de biodiesel en raison de sa recyclabilité et de sa facilité de récupération. Lors de la réutilisation de ces catalyseurs, le biocharbon a montré une vitesse de réaction élevée, ce qui signifie sa capacité à agir comme catalyseur acide pour la production de biodiesel.
La gestion des déchets
De nombreux composés chimiques produits artificiellement possèdent une forte résistance à la dégradation biologique et sont biorécalcitrants.
Ces produits chimiques synthétiques sont cancérigènes pour les humains, les microbes, les plantes et d’autres espèces présentes dans l’environnement.
La dégradation des composés biorécalcitrants peut être réalisée à l’aide d’une technique prometteuse appelée procédé d’ozonation catalytique (COP).
Le biochar dérivé de la biomasse contenant une structure poreuse et des groupes fonctionnels tels que phénoliques et hydroxyles a été utilisé comme catalyseur à faible coût pour dégrader un composé organique résistant, à savoir le colorant réactif rouge 198, dans le processus d’ozonation catalytique.
Contrôle des polluants atmosphériques
L’utilisation du biocharbon comme catalyseurs de réduction catalytique sélective à basse température a été rapportée dans la littérature.
Des études ont été rapportées sur la biomasse comme les boues d’épuration et la paille de riz pour produire du biocharbon et être utilisées comme catalyseurs à basse température où l’ammoniac est utilisé comme agent réducteur.
Les charbons ont été modifiés physiquement ou chimiquement et leur efficacité d’élimination a été déterminée.
L’activation chimique a montré une efficacité d’élimination supérieure à l’activation physique. Cela indique que les propriétés chimiques telles que les groupes fonctionnels et les sites d’adsorption sont les principaux facteurs permettant une élimination plus élevée.
Le sulfate et les radicaux libres ont été délivrés sous la catalyse du biochar.
La surface du biocharbon explicite l’oxygène, y compris les complexes d’activité catalytique avec différentes réponses. Grâce au biocharbon, le complexe a amélioré l’activité catalytique du catalyseur.
Stockage d’énergie et supercondensateurs
Le stockage d’énergie dans les produits électriques est important pour l’utilisation par les consommateurs d’appareils électriques et électroniques.
Les supercondensateurs sont des dispositifs de stockage d’énergie qui attirent l’attention en raison de leur capacité de charge et de décharge rapide, de leur densité de puissance élevée et de leur stabilité à long cycle, tandis que les batteries rechargeables possèdent une densité d’énergie élevée et un taux de charge/décharge inférieur.
Les batteries lithium-ion sont également utilisées comme dispositifs de stockage d’énergie.
Les matériaux des électrodes prédisent les performances du dispositif de stockage d’énergie. Ces matériaux d’électrode sont constitués d’une surface spécifique élevée et d’une structure poreuse qui fournissent les sites actifs requis pour le processus d’oxydation.
Les matériaux d’électrode couramment utilisés sont les nanotubes de carbone, le charbon actif, le graphène, etc.
Le coût de ces matériaux carbonés est élevé et leur utilisation est donc limitée. En raison de cet inconvénient, l’application du biochar comme électrode gagne en intérêt.
Semblable au matériau carboné, le biochar possède également une surface plus élevée, plus poreuse et moins coûteuse. Le biochar peut agir comme électrode pour les piles à combustible microbiennes et les supercondensateurs
Conditioning of the soil
A faulty agricultural field management system has led to the emission of increased amounts of CO 2 and increased the degradation of soil organic compounds. Much research has been conducted to increase soil organic carbon content by incorporating biomass into crops and animal waste. Application of biochar in soil not only helped isolate soil carbon, but also improved soil quality by neutralizing soil pH, increasing soil cation exchange capacity, and enhancing microbial growth in the ground. Functional groups such as carboxylic, hydroxyl, and phenolic groups present in biochar interact with the hydrogen ions in the soil and reduce the concentration of hydrogen ions, thereby increasing the pH of the soil. The carbonates, bicarbonates and silicates in biochar react with H + ions and neutralize the soil pH.
Therefore, there is increased interest in the application of biochar in soil remediation in agricultural fields due to its surface properties and elemental composition. Biochar can be applied in agricultural field as follows:
a) improve soil fertility and structure;
b) increase the cation exchange capacity of the soil and minimize aluminum toxicity;
c) Support carbon sequestration and reduce the effect of greenhouse gases;
d) improve productivity by maintaining water retention;
e) improve microbial activity by mitigating nutrient leaching.
Furthermore, the use of biochar has been considered as a promising method to remediate soils contaminated with toxic pollutants, including heavy metals, pesticides, hydrocarbons, etc.
The biomass used to produce biochar is made up of base cations. These cations are transferred into the soil when biochar is applied to the soil. This activity improves the cation exchange capacity of the soil by increasing the surface area of the soil to adsorb more cations. Additionally, increasing pH also increases the CEC of the soil.
The presence of high concentration of Ca, K, N and P in biochar adds nutrients to the soil or can be used as a nutrient source for the soil microbial community.
The porous fraction of soil increases when biochar is used as a soil amendment.
Microbial growth occurs in the porous fraction, increasing the residence time of moisture, air and nutrients, thereby improving the growth, survival and activity of microbes, which also contributes to the growth of plants. Biochar produced at high temperatures is difficult to degrade and therefore present in the soil longer than biochar produced at low temperatures. Studies have also been reported on the negative effects of biochar in soil. For example, hydrochar applied in soil limited plant growth, which showed that before application, optimization of biochar is important to avoid its negative effects on plants. Applying biochar as a soil amendment reduces greenhouse gas emissions. Direct combustion of biomass releases carbon in the form of CO 2 into the environment. This carbon can be converted into biochar through a gasification or pyrolysis process which can be returned to the soil.
Carbon sequestration
Climate change is causing growing concern about minimizing CO 2 emissions into the atmosphere. Soil plays a crucial role in the carbon cycle which directly influences climate change. Carbon sequestration is a promising method for reducing CO 2 emissions in soils.
Biochar is barely resistant to degradation by microbes due to the presence of an aromatic structure. Biochar therefore shows a positive result on carbon sequestration in the soil. Many publications have been reported on carbon sequestration by biochar. However, no ideal results were observed since both positive and negative effects were obtained. Both increased and decreased carbon emissions were observed. Mineralization of organic matter present in the soil was found to be higher in low fertility soils than in high fertility soils and also in soils containing high carbon content, carbon mineralization was higher than in soils with high fertility. low carbon soils. ground.
The carbon content of biochar can be classified into two types, namely responsible carbon and recalcitrant carbon .
The responsible carbon is readily utilized by microbes during biochar application, resulting in increased carbon mineralization at the initial stage itself. Thus, biochar application restored carbon mineralization.
In revenge,
Recalcitrant carbon is present longer in the soil.
Therefore, carbon fixation due to biochar application is greater than the carbon released due to responsible carbon mineralization.
The influence of biochar on carbon sequestration is still unclear.
The effect differs depending on the type of biomass and pyrolytic conditions. Since pyrolysis conditions have a major effect on the physicochemical properties of biochar, it is mandatory to determine the association between reaction conditions and the influence of biochar on carbon sequestration.
Wastewater treatment Biochar is a solid material with a high specific surface area and high porosity, properties that make it an attractive alternative in wastewater treatment.
Biochar is considered an effective media for capturing wastewater supplements and can be incorporated into soil as an amendment.
Biochar is believed to promote the expulsion of toxins in wastewater due to its high porosity and high adsorption properties that allow poisons to aggregate on its surfaces, producing a clean effluent and supplementing a rich biochar.
There is a growing trend to use carbonized materials and raw biowastes in wastewater treatment. Many researchers have conducted a meta-study to consider the ecological and financial use of biochar and activated carbon in the removal of toxic contaminants. The review revealed that the execution of biochar disposal was that of activated carbon. It is thus demonstrated that although the immense territory of activated carbon promotes the adsorption of toxins by filling the pores, there are different elements, including surface functional groups, which clarify the execution of biochar removal . The creation of activated carbon includes a high natural effect, confirmed by the reduction of greenhouse gas emissions from biochar. Likewise, the production of activated carbon (97 MJ/kg) requires a surprisingly higher vitality demand than that of biochar (6.1 MJ/kg).
Therefore, biochar could be more effective than activated carbon in removing toxic contaminants from wastewater while taking into account GHG releases, energy demand and therefore production cost.
Biochar – an ideal approach to improve the circular economy
This review focuses on the idea of a circular bioeconomy through the use of biochar to provide a feasible answer for its compelling administration. Larger particles of organic matter begin to break down to produce smaller atoms, which are exhausted from the procedure stream as gases, condensable fumes (oils) and burn hotly during the pyrolysis process. The extent of each end result depends on temperature, time, heating rate and weight, precursor types, and reactor design and layout. Thermochemical methods used to produce biochar, especially in rural areas, enhance the development of that specific region as well as small and medium-sized enterprises producing sufficient energy, thereby increasing the income of farmers, thereby providing management solutions for biochar. waste in the agricultural sector. Through this,
Similar interactions between different biochar production and waste reuse methodologies are necessary to develop new opportunities. By using waste from one food industry to illuminate the problems of toxic pollutants in another and the by-products intended for spreading on the ground, a circular bioeconomy has been established, new products and procedures have been developed and potential for new business creation was created. Due to their high moisture content, the important elements become fluids and if there is a low degree of water there is a high risk that the procedure will produce a higher amount of residue than oil. Regardless, at a higher temperature, above 800°C, when the heating rate is high, a greater division of debris and wispy objects is created. Bio-oil can be delivered by applying an average road temperature using moderately high heating rates. At the start of the procedure, at a temperature between 250 and 300°C, unstable materials are evacuated almost several times faster than the subsequent advance. Methodologies balanced between ease of use, energy conservation and limited releases could be integrated into the local network for feasible production of biochar, taking into account both specialized and financial points of view, further recovering the biochar and the heat produced.
The following environmental benefits can be achieved:
- Less greenhouse gas emissions;
- Economic benefit by reducing cost compared to waste
This application in the circular economy reduces waste through various processes and techniques thereby increasing their value. It opens the door to the advancement of a circular economy (CE) using an inventive combination of methodologies and beneficial strategic approaches to address the use of agricultural waste, co-products and by-products. The proposed framework could be a manageable rural energy base, in provincial cultivation networks, consistent with circular economy guidelines. The framework of anaerobic digestion and gasification, with farms providing yield and slurry and industry providing food waste, can produce energy and manure, which could then be used by the neighboring community, by focusing instead on the social benefits of moving from a linear to a linear system. The circular economy would imply. Life cycle assessment (LCA) is a widely used and standardized ecological assessment approach for measuring the environmental performance of products. The results showed that the environmental performance of pyrolysis can vary depending on many elements, including
(a) biomass feedstock,
(b) pyrolysis process,
(c) the yield of co-products, and
(d) identification of peripheral innovations.
The different phases of the life cycle of bio-oil creation by pyrolysis and bio-oil production have further been divided into five unit measures:
(i) raw material preparation and drying, (ii) pyrolysis reactor, (iii) condenser quenching, (iv) coal recovery and (v) heating cycle.
The basis of this methodology was that a multi-unit model would be generally useful in breaking down approaches to improve productivity, modernize operations, and reasonably distribute environmental burdens to improve ecological improvements.
Knowledge gaps and future prospects
Biochar is considered a renewable resource making it possible to solve many environmental problems such as the remediation of contaminants from soil, aqueous and gaseous environments. Biochar activation is another specific area to expand the application of biochar to remove particular pollutants.
Further research is needed to identify new activation methods as well as mechanisms for adsorption and desorption of various pollutants.
The study of the microbial population and their interaction with the biochar present in the soil remains to be studied in detail.
The growth and development of microbes in the presence of biochar as well as the influence of biochar properties on the microbial community need to be examined in detail.
Biochar, when amended with soil, not only helps remediate and maintain soil fertility but also helps provide micro and macro nutrients whenever needed.
Further research is needed on the analysis of microbial activity during the mineralization process and soil remediation. The interaction of biochar with soil and their binding mechanisms need to be studied in detail. The mechanism of contaminant removal during wastewater treatment is still unclear. Current studies have observed the possibility of electrochemical conversion of solid carbonaceous material into electricity in a direct carbon fuel cell. The problem consists of examining the mechanism of reaction kinetics and oxidation at the anode/electrode interface. The interaction of solid carbon and the electrolyte/electrolyte interface is very limited, so this area requires more attention. Although biochar offers vast benefits, few problems remain.
Toxic compounds such as dioxitins, chlorinated hydrocarbons, and polycyclic aromatic hydrocarbons may be present in biochar depending on the biomass used for production.
The performance of biochar used as supercapacitors requires even more attention. To assess the economic benefits and environmental impacts, a life cycle analysis of biochar should be carried out.
Biochar characterization methods have progressed thanks to the development of new techniques. Optimizing biochar properties and activation is important to achieve maximum efficiency. The use of new techniques is affected by economic viability and accessibility. Since biochar has become an alternative source, standard characterization procedures must be implemented for a better understanding of biochar properties.
Conclusions
Biochar production reveals a wide variety of biomass that has been used as feedstock and pyrolyzed by various procedures to combat water pollution. The properties of the resulting biochar are significantly influenced by the pyrolysis temperature, feedstock and pyrolysis technology. Biochar can be used as a major source for the removal of toxic pollutants. The removal of pollutants by biochar occurs mainly due to the presence of functional groups such as hydroxyl and carboxyl groups on the surface of biochar. Although the effectiveness of biochar depends on the biomass type and pyrolysis conditions, future biochar development focuses on refining the properties of biochar.
Thus, biochar appears to be a very promising option for eliminating pollutants.
Economic impacts and recyclability must be considered when developing recoverable biochar for broad environmental applications.
The relationships between the different waste management and energy production solutions differ on the parameters and multiple production techniques as well as on economic, social and ecological constraints.
Without considering how the proposed method could be used in usual practice, the closed framework establishes differentiations between the direct model and the circular model of waste organization.
In this idea of circular economy, higher energy recovery could be achieved. This review paper summarized cutting-edge information that would be useful in finding new opportunities for scientific innovation in biochar research.
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