Recent application of biochar on the catalytic biorefinery and environmental processes

Biochar, produced and activated from thermochemical methods, was applied as catalyst for catalytic biorefinery and environmental pollutant removal. In this review, recent advanced studies of biochar catalyst were discussed.     

生物质炭的制备、改性以及在挥发性有机物吸附方面的应用

挥发性有机物（VOCs）是大气中重要的污染源之一,对环境和人类健康产生严重的危害。吸附法是工业中最常用的去除VOCs的方法,吸附剂是吸附技术的关键,生物质炭是一种由生物质基材料在高温下热解活化等工艺制得的炭材料,具有较高的比表面积、丰富的孔隙结构和化学活性表面,在环境污染控制领域具有广泛应用。基于最近的研究,本文系统地综述了常用于去除VOCs的生物质炭的制备和改性方法,以及生物质炭在吸附VOCs的应用研究。本文首要目标是评估生物质炭去除VOCs的能力,特别是经过各种改性和活化工艺后,评价生物质炭作为吸附剂去除VOCs的适用性;确定改性和活化后对VOCs吸附能力的影响;揭示生物质炭对VOCs可能存在的吸附机理。最后,文章也对生物质炭的再生提出了建议和展望。     

Revolutions in algal biochar for different applications: State-of-the-art techniques and future scenarios

Algae are potential feedstock for the production of bioenergy and valuable chemicals. After the extraction of specific value-added products, algal residues can be further converted into biogas, biofuel, and biochar through various thermochemical treatments such as conventional pyrolysis, microwave pyrolysis, hydrothermal conversion, and torrefaction. The compositions and physicochemical characteristics of algal biochar that determine the subsequent applications are comprehensively discussed. Algal biochar carbonized at high-temperature showed remarkable performance for use as supercapacitors, CO₂ adsorbents, and persulfate activation, due to its graphitic carbon structure, high electron transport, and specific surface area. The algal biochar produced by pyrolysis at moderate-temperature exhibits high performance for adsorption of pollutants due to combination of miscellaneous functional groups and porous structures, whereas coal fuel can be obtained from algae via torrefaction by pyrolysis at relatively low-temperature. The aim of this review is to study the production of algal biochar in a cost-effective and environmental-friendly method and to reduce the environmental pollution associated with bioenergy generation, achieving zero emission energy production.     

Iron-based biochar as efficient persulfate activation catalyst for emerging pollutants removal: A review

In recent years, biochar (BC) as a low-cost, easily available biomass product, is widely applied in sulfate radical-based advanced oxidation processes (SR-AOPs) for emerging pollutants remediation. Herein, a state-of-art review of iron-based biochar catalysts is currently available in SR-AOPs application. A general summary of the development of biochar and the catalytic properties of biochar is presented. Especially, the synthetic strategies of different types of iron-based biochar catalysts are discussed. Moreover, the theoretical calculation to interpret the interaction between biochar and iron species is discussed to explore the activation mechanisms. And the regeneration methods of biochar-based catalyst are presented. The unresolved challenges of the existent biochar-based SR-AOPs are pointed out, and the outlooks of future research directions are proposed.     

A Review on Current Status of Biochar Uses in Agriculture

In a time when climate change increases desertification and drought globally, novel and effective solutions are required in order to continue food production for the world’s increasing population. Synthetic fertilizers have been long used to improve the productivity of agricultural soils, part of which leaches into the environment and emits greenhouse gasses (GHG). Some fundamental challenges within agricultural practices include the improvement of water retention and microbiota in soils, as well as boosting the efficiency of fertilizers. Biochar is a nutrient rich material produced from biomass, gaining attention for soil amendment purposes, improving crop yields as well as for carbon sequestration. This study summarizes the potential benefits of biochar applications, placing emphasis on its application in the agricultural sector. It seems biochar used for soil amendment improves nutrient density of soils, water holding capacity, reduces fertilizer requirements, enhances soil microbiota, and increases crop yields. Additionally, biochar usage has many environmental benefits, economic benefits, and a potential role to play in carbon credit systems. Biochar (also known as biocarbon) may hold the answer to these fundamental requirements.     

纤维素制取乙醇技术

以纤维素为原料生产燃料乙醇由于其原料来源广泛及环保效益良好而被认为是最有前景的生产燃料乙醇的方法之一.以纤维素为原料生产乙醇主要包括水解和发酵两个转化过程.本文介绍了纤维素生产燃料乙醇的原理及工艺过程,同时讨论了各工艺过程需要解决的关键技术问题,分析了过程的经济性,最后介绍了国内外的应用现状,展望了纤维素生产燃料乙醇的产业化前景.     

纤维素制取乙醇技术

以纤维素为原料生产燃料乙醇由于其原料来源广泛及环保效益良好而被认为是最有前景的生产燃料乙醇的方法之一。以纤维素为原料生产乙醇主要包括水解和发酵两个转化过程。本文介绍了纤维素生产燃料乙醇的原理及工艺过程,同时讨论了各工艺过程需要解决的关键技术问题,分析了过程的经济性,最后介绍了国内外的应用现状,展望了纤维素生产燃料乙醇的产业化前景。     

Characterization and Artificial Neural Networks Modelling of methylene blue adsorption of biochar derived from agricultural residues: Effect of biomass type,pyrolysis temperature,particle size

Biochar has been explored as a sorbent for contaminants, soil amendment and climate change mitigation tool through carbon sequestration. Through the optimization of the pyrolysis process, biochar can be designed with qualities to suit the intended uses. Biochar samples were prepared from four particle sizes (100–2000 µm) of three different feedstocks (oak acorn shells, jift and deseeded carob pods) at different pyrolysis temperatures (300–600 °C). The effect of these combinations on the properties of the produced biochar was studied. Biochar yield decreased with increasing pyrolysis temperature for all particle sizes of the three feedstocks. Ash content, fixed carbon, thermal stability, pH, electrical conductivity (EC), specific surface area (SSA) of biochar increased with increasing pyrolysis temperature. Volatile matter and pH value at the point of zero charge (pH_pzc) of biochar decreased with increasing pyrolysis temperature. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the surface of the biochar was rich with hydroxyl, phenolic, carbonyl and aliphatic groups. Methylene blue (MB) adsorption capacity was used as an indicator of the quality of the biochar. Artificial neural networks (ANN) model was developed to predict the quality of the biochar based on operational conditions of biochar production (parent biomass type, particle size, pyrolysis temperature). The model successfully predicted the MB adsorption capacity of the biochar. The model is a very useful tool to predict the performance of biochar for water treatment purposes or assessing the general quality of a design biochar for specific application.     

固体杂多酸在生物质水解转化中的应用

随着化石资源的日益枯竭,寻求可替代清洁能源已成为全球重大课题。生物质是一种可再生的清洁能源,目前人们尝试通过利用生物质转化缓解日益增长的能源需求。杂多酸是应用在清洁工艺中的重要催化剂,结构和酸度的设计调变性及较高的热稳定性,使其广泛用于生物质的水解转化反应平台。目前固体杂多酸在水溶剂、有机溶剂及两相体系中降解生物质有着各自不同的优缺点。本文综述了杂多酸在不同反应体系中水解转化生物质制备精细化学品的研究进展,并对其在生物质水解转化利用中的应用前景进行了展望。     

Characterization and comparative study of pyrolysis kinetics of the rice husk and the elephant grass

A comparative evaluation of different biomasses allows the choice that presents the best potential as fuel for energy production. The knowledge of the thermal and kinetics parameters of the biomass in the process of thermal conversion is fundamental as their chemical and physical characterization. Various methodologies have been developed for the determination of kinetic parameters as apparent activation energy and reaction order from the thermogravimetric analysis. In this work, the apparent activation energy needed to break the bonds of hemicelluloses and cellulose of rice husk and elephant grass during the thermal conversion was evaluated according to the kinetics models of Flynn and Wall and Model Free Kinetics developed by Vyazovkin. The biomass elephant grass and rice husk were characterized for moisture, ash and volatile matter by ASTM E871, ASTM E1755, ASTM E872, respectively, and fixed carbon by difference. The percentage of carbon, hydrogen, nitrogen, and oxygen were determined by ultimate analysis. The elephant grass showed to be more suitable for production of bio-oil through pyrolysis due to the higher percentage of volatile, less ash content and less energy required to break the bonds of hemicellulose and cellulose than rice husk in the thermal conversion process.     

Optimization of Oxygen Parameters for Determination of Carbon and Nitrogen in Biochar Materials

Recently, there has been increased focus on biochar materials due to their ability to sequester carbon for long-term in soil. In the production of biochar or charcoal, plant biomass is heated in a low or no oxygen environment. This process results in a product with unique characteristics. But there is limited research on the standardization of methods for determining total carbon (C) and nitrogen (N) in the biochar materials whose properties vary by feedstock type and pyrolytic conditions. The objective of this study was to determine the oxygen dosing time (OT) and dose (OD) for total organic carbon (TC) and nitrogen (TN) analysis in biochar materials by dry combustion method (using Vario Max CNS analyzer). Central composite rotatable design was used to determine the effect of five levels of oxygen dosing time (OT) and dosing level (OD) on measurement of total carbon and total nitrogen in four types of plant originated biochars. OT and OD level interaction had significant impact on the measurement of TC and TN in all types of biochar materials. Optimum levels of OT and OD were determined as 103 to 110 sec and 180 to 232 ml/min, respectively.     

Efficient Conversion of Biomass to Formic Acid Coupled with Low Energy Consumption Hydrogen Production from Water Electrolysis

The development of a new electrolytic water hydrogen production coupling system is the key to realize efficient and low-cost hydrogen production and promote its practical application. Herein, a green and efficient electrocatalytic biomass to formic acid (FA) coupled hydrogen production system has been developed. In such a system, carbohydrates such as glucose are oxidized to FA using polyoxometalates (POMs) as the redox anolyte, while H₂ is evolved continuously at the cathode. Among them, the yield of glucose to FA is as high as 62.5 %, and FA is the only liquid product. Furthermore, the system requires only 1.22 V to drive a current density of 50 mA cm⁻², and the Faraday efficiency of hydrogen production is close to 100 %. Its electrical consumption is only 2.9 kWh Nm⁻³ (H₂), which is only 69 % of that of traditional electrolytic water. This work opens up a promising direction for low-cost hydrogen production coupled with efficient biomass conversion.     

Preparation of Bamboo-Based Hierarchical Porous Carbon Modulated by FeCl3 towards Efficient Copper Adsorption

Using bamboo powder biochar as raw material, high-quality meso/microporous controlled hierarchical porous carbon was prepared—through the catalysis of Fe³⁺ ions loading, in addition to a chemical activation method—and then used to adsorb copper ions in an aqueous solution. The preparation process mainly included two steps: load-alkali leaching and chemical activation. The porosity characteristics (specific surface area and mesopore ratio) were controlled by changing the K₂CO₃ impregnation ratio, activation temperature, and Fe³⁺ ions loading during the activation process. Additionally, three FBPC samples with different pore structures and characteristics were studied for copper adsorption. The results indicate that the adsorption performance of the bamboo powder biochar FBPC material was greatly affected by the meso/micropore ratio. FBPC _2.5-900-2%, impregnated at a K₂CO₃: biochar ratio of 2.5 and a Fe³⁺: biochar mass ratio of 2%, and activated at 900 °C for 2 h in N₂ atmosphere, has a very high specific surface area of 1996 m² g⁻¹ with a 58.1% mesoporous ratio. Moreover, it exhibits an excellent adsorption capacity of 256 mg g⁻¹ and rapid adsorption kinetics for copper ions. The experimental results show that it is feasible to control the hierarchical pore structure of bamboo biochar-derived carbons as a high-performance adsorbent to remove copper ions from water.     

Biochar modified Co–Al LDH for enhancing photocatalytic reduction CO2 performance and mechanism insight

This study prepared a biochar-based photocatalyst (Co–Al LDH–C) via facile ultrasonic-assisted solvent treatment. The Co–Al LDH–C photocatalyst shows better photocatalytic activity in CO₂ reduciton than the pure Co–Al LDH without biochar modification. The Co–Al LDH–C affords a CO generation rate of 29.2 µmol g^?1. The enhanced CO₂ reduction activity is attributed to the biochar in Co–Al LDH enhanced the light absorption property and separation efficiency of the charge carriers. Additionally, a mechanism insight of Co–Al LDH reduction CO₂ is also investigated by a series of characterizations and experiments results. This work offers a new insight for CO₂ reduction by waste utilization of biomass and improved the performance of Co–Al LDH, and extends the broad potential application of biochar-based photocatalyst in the photocatalytic conversion from solar to carbon resource.

     

Physicochemical properties evolution of chars from palm kernel shell pyrolysis

To clarify the effect of the pyrolysis operating conditions of the biomass on the physicochemical properties of the char and its combustion reactivity, palm kernel shell was pyrolyzed at different temperatures (400–700 °C). Analyses such as proximate and ultimate analysis, XRD, FTIR, N₂ adsorption, and SEM were used to investigate the physicochemical properties of biochar samples. The results show that an increase in pyrolysis temperature led to a development of pore structure and specific surface area of the produced biochar, which was beneficial for improving the biochar combustion reactivity. Besides, with increase in pyrolysis temperature, the carbon content exhibits a raise trend, but the oxygen and hydrogen contents exhibit the opposite behavior, and the aromaticity and graphitization degree of biochar produced at high temperature also increase. The combustion reactivity of biochar was found to be highly dependent on the pyrolysis temperature, and the aromatic structure and graphitization degree have greater effects on biochar combustion reactivity than those of the specific surface area and pore structure.     

Biofuels from microalgae biomass: A review of conversion processes and procedures

Achieving the EU 2030 vision of a 15% minimum amount of biofuels utilized in the road transportation require more research on biofuel production from biomass feedstock. To this end, this review study examines the use of green, deep eutectic solvents and direct transesterification approaches for biomass conversion to biofuels. Next, biogas production from anaerobic co-digestion of microalgae biomass is presented. Lastly, the effect of operating conditions, as well as advantages and limitations of several biomass conversion techniques are outlined. Of note, this study presents promising microalgae conversion processes which could be progressed are the use of bio-based solvents and supercritical fluids for biodiesel production, hydrothermal liquefaction for biogas production, microwave-induced pyrolysis for syngas production, and ultrasound/microwave enhanced extraction for bio-oil production. These are based on the possibility of high yield and process economics. We have also enumerated knowledge gaps needed to propel future studies.     

Energy potential and thermogravimetric study of pyrolysis kinetics of biomass wastes

The use of agricultural wastes for energy conversion has been widely studied as renewable and carbon neutral energy sources. This paper aims to evaluate the energetic potential of six agricultural wastes—sugarcane bagasse, bean pods, corn stover, pineapple crown leaves, white cotton and natural coloured cotton stalks, through their characterization and pyrolysis kinetic study. The energetic potential of biomasses was evaluated by ultimate and proximate analysis, higher heating value (HHV), apparent density, and kinetic parameters of conversion and apparent activation energy (E_a) determined by Model-Free kinetics though thermogravimetric analysis data. The results indicate energetic density for dry basis biomasses, such as moisture content less than 7%, volatiles higher than 77% and moderate ash content. The HHVs were higher for the biomass with low O:C ratio. The E_a values increased with increasing O:C ratio and were also influenced by the biomass ash content. Among the studied biomasses, PCL are less explored for energy application, although the results confirm its potential for application in thermochemical processes such as pyrolysis or combustion.

     

Thermal self-sustainability of biochar production by pyrolysis

The pyrolysis of several agricultural and biofuel production residues (grape residues, sugarcane residues, dried distiller's grain, palm oil residues, apple pomace and forestry residue) has been carried out in a pilot bubbling fluidized bed pyrolyzer operating under a range of temperature from 300 to 600 °C and two vapor residence times (2 and 5 s), with the aim of determining their pyrolysis behavior including products yields and heat balance. The composition of the product gases was determined, from which their heating value was calculated. The liquid bio-oil was recovered with cyclonic condensers. The thermal sustainability of the pyrolysis process was estimated by considering the energy contribution of the product gases and of the liquid bio-oil in relation to the pyrolysis heat requirements. The most promising biomass feedstocks for the sustainable production of biochar were indentified. Furthermore, this study presented the char yield in relation to the excess heat that could be obtained by combusting the gas and bio-oil coproducts of biochar production, as functions of pyrolysis temperature and vapor residence time.     

Biomass gasification technology: The state of the art overview

In the last decades the interest in the biomass gasification process has increased due to the growing attention to the use of sustainable energy. Biomass is a renewable energy source and represents a valid alternative to fossil fuels. Gasification is the thermochemical conversion of an organic material into a valuable gaseous product, called syngas, and a solid product, called char. The biomass gasification represents an efficient process for the production of power and heat and the production of hydrogen and second-generation biofuels.This paper deals with the state of the art biomass gasification technologies, evaluating advantages and disadvantages, the potential use of the syngas and the application of the biomass gasification. Syngas cleaning though fundamental to evaluate any gasification technology is not included in this paper since; in the authors' opinion, a dedicated review is necessary.     

Pyrolysis of agricultural residues from rape and sunflowers: Production and characterization of bio-fuels and biochar soil management

This research explores the opportunities of combining energy production with a biochar soil management using a pyrolysis process. Real-world issues justify this approach: the need to provide sustainable production systems that minimize on- and off-site pollution and soil degradation; and the demand for solutions to global warming. The proposed technology is a pyrolysis process that yields gas, bio-oil and biochar. The composition and heating value of the gas makes it suitable for use as a fuel. The bio-oil obtained may be evaluated as an environmentally friendly green biofuel candidate. The biochar product is carbon-rich and a potential solid biofuel. Other ways it might be used as a C and N source in soil amendment. This is a key to securing environmental benefits: the production of a biochar which can be applied to soil.