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In recent years, the concept of green, low-carbon and clean energy consumption has been deeply rooted in the hearts of the people, and countries have actively advocated the use of new energy. In the face of problems such as resource shortage and environmental pollution, we began to explore the use of new fuels instead of coal for production. Biomass resources have the characteristics of being renewable and carbon neutral and having large output. As an energy utilization, it is helpful to promote the transformation of the energy structure in various countries. Applying it to ironmaking production is not only conducive to energy conservation and emission reduction in the ironmaking process but also can achieve efficient utilization of crop waste. By introducing the source and main preparation methods of biochar, this paper expounds the main links and advantages of biochar in the ironmaking process and puts forward the direction of biochar in ironmaking in the future. [ABSTRACT FROM AUTHOR]

Miscanthus × giganteus (M × g) is a promising energy crop in phytotechnology with biomass production. Despite considerable vegetation and harvest under varying climate conditions and across different soils, field-scale studies on utilising M × g remain scarce. Analysing the literature and our own findings, this study intends to highlight the potential of M × g phytotechnology for revitalising non-agricultural lands (NAL), including brownfields, and illustrate the expediency of applying biochar to enhance biomass yield, energy efficiency, and economic feasibility. To validate the feasibility of M × g production on brownfields, two scenarios within the value chain "biomass–biogas–electricity" for green harvest were examined. The assumptions were as follows: (1) a methane yield of 5134 m3 ha−1 y−1, and (2) substrate-specific methane yields of 247 and 283 mL (g oDM)−1 for the first and subsequent years, respectively. The findings suggest that Scenario 2 is better suited for cultivating M × g on brownfields/NAL, being more sensitive and eliminating inaccuracies and the generalisations of results. From the third year onward, the revenue of M × g production on biochar-amended brownfields showed greater potential for future profitability. Future research should confirm the positive trend in the energy efficiency ratio of M × g phytotechnology on a larger scale, particularly in real brownfield applications. [ABSTRACT FROM AUTHOR]

Aluminum production is a major energy consumer and important source of greenhouse gas (GHG) emissions globally. Estimation of the energy consumption and GHG emissions caused by aluminum production in China has attracted widespread attention because China produces more than half of the global aluminum. This paper conducted life cycle (LC) energy consumption and GHG emissions analysis of primary and recycled aluminum in China for the year 2020, considering the provincial differences on both the scale of self-generated electricity consumed in primary aluminum production and the generation source of grid electricity. Potentials for energy saving and GHG emissions reductions were also investigated. The results indicate that there are 157,207 MJ of primary fossil energy (PE) consumption and 15,947 kg CO2-eq of GHG emissions per ton of primary aluminum ingot production in China, with the LC GHG emissions as high as 1.5–3.5 times that of developed economies. The LC PE consumption and GHG emissions of recycled aluminum are very low, only 7.5% and 5.3% that of primary aluminum, respectively. Provincial-level results indicate that the LC PE and GHG emissions intensities of primary aluminum in the main production areas are generally higher while those of recycled aluminum are lower in the main production areas. LC PE consumption and GHG emissions can be significantly reduced by decreasing electricity consumption, self-generated electricity management, low-carbon grid electricity development, and industrial relocation. Based on this study, policy suggestions for China's aluminum industry are proposed. Recycled aluminum industry development, restriction of self-generated electricity, low-carbon electricity utilization, and industrial relocation should be promoted as they are highly helpful for reducing the LC PE consumption and GHG emissions of the aluminum industry. In addition, it is recommended that the central government considers the differences among provinces when designing and implementing policies. [ABSTRACT FROM AUTHOR]

The growing emphasis on indoor air quality and public health is fuelling the need for efficient yet affordable air purification techniques. In this study, the influence of biochar particle size on its adsorption efficiency toward airborne pollutants was examined. Bark-derived biochar particles were treated by grinding or ball milling, and then, seven samples with different particle size groups were separated. Biochar particles were characterized by particle size, proximate, SEM, XRD, and physisorption analyses. For adsorption efficiency, two different pollutants were tested at variable initial concentrations. The physical composition and XRD patterns of the biochar with different particle sizes were comparable. The ball-milled sample was an exception in that it had higher ash content and additional XRD peaks signifying contamination of the sample. The porosity of biochar was greater in smaller particles. Ball milling increased the specific surface area and total pore volume by 102% and 48%, respectively. Biochar with finer particle size exhibited the highest adsorption potential towards formaldehyde and methanol among other samples. It should be emphasized that simple mechanical grinding is preferred for reducing biochar size to avoid the risk of eventual contamination, greater energy consumption, and slower processing related to ball milling. When a low concentration of pollutant was tested (1 ppm formaldehyde), the effect of particle size on the adsorption efficiency was more noticeable. However, the effect of particle size was less dominant when higher concentrations of pollutants were tested. Smaller biochar particles (<100 μm) are more favourable for indoor air remediation given their superior adsorption efficiency of volatile organic compounds occurring at low concentrations in the buildings. [ABSTRACT FROM AUTHOR]

The paper presents characterization of chicken manure and mixture of chicken manure (CM) and beech wood (WB) carbonization at 450 and 600 °C. Experiments were carried out in small scale batch reactor. The obtained results indicate that increase in the amount of beech wood in the pellets caused increase in fixed carbon content and also affected increase in the calorific value of biochar. The results show that biochar obtained in the carbonization process of chicken manure cannot be used for the barbecue charcoal production, which is caused by low C fix and high ash content. Because of this, adding wood may be a good solution for the carbonization process. Experimental investigation showed that carbonization of pellets consisting of CM50 % and CM25 % lead to obtained biochar which meets standards for briquette barbecue production. Experimental results showed the possibility of using pyrolysis gases for energy purposes. Carbonization in different temperatures lead to production of pyrolysis gas mixtures with calorific value higher than the energy demand of the process. Moreover obtained energy contained in gases can cover the part of the heat demand of the farm. Analysis of heavy metals content showed that biochars meet the standards defined by the International Biochar Initiative. [ABSTRACT FROM AUTHOR]

Biomass derived from agricultural waste in Indonesia is abundant and has potential as a source of renewable energy feedstock. However, analysis is needed to determine the appropriate technology to convert potential biomass into consumable energy forms. This review summarises various data on Indonesia's potential biomass that can be used as a renewable energy feedstock. Biomass and biochar characteristics are systematically discussed, including proximate and ultimate analysis. We then summarise various biochar production technologies based on the biomass used and their yields. The characteristics of biochar produced in both proximate and ultimate analysis and the conversion of biochar into slurry fuel as one of the consumable forms of renewable energy were discussed. Slurry fuel is a potential use of biochar as a liquid fuel. The challenges of developing potential biomass-based bio-slurry production in Indonesia and the future work that needs to be done are presented. [ABSTRACT FROM AUTHOR]

Graphene, a two-dimensional carbon allotrope with a honeycomb structure, has emerged as a material of immense interest in diverse scientific and technical domains. It is mainly produced from graphite by mechanical, chemical and electrochemical exfoliation. As renewable energy and source utilization increase, including bioenergy from forest and woody residues, processed, among other methods, by pyrolysis treatment, it can be expected that biochar production will increase too. Thus, its useful applications, particularly in obtaining high-added-value products, need to be fully explored. This study aims at presenting a comprehensive analysis derived from experimental data, offering insights into the potential of biomass pyrolysis-derived biochar as a versatile precursor for the controlled synthesis of graphene and its derivatives. This approach comprehended the highest energy output and lowest negative environmental footprint, including the minimization of both toxic gas emissions during processing and heavy metals' presence in the feedstock, toward obtaining biochar suitable to be modified, employing the Hummers and intercalation with persulfate salts methods, aiming at deriving graphene-like materials. Material characterization has revealed that besides morphology and structural features of the original wooden biomass, graphitized structures are present as well, which is proven clearly by Raman and XPS analyses. Electrochemical tests revealed higher conductivity in modified samples, implying their graphene-like nature. [ABSTRACT FROM AUTHOR]

Reconstituted wood panels have several advantages in terms of ease of manufacturing, but their shorter life span results in a huge amount of reconstituted wood panels being discarded in sorting centers yearly. Currently, the most common approach for dealing with this waste is incineration. In this study, reconstituted wood panels were converted into activated biochar through a two-step thermochemical process: (i) biochar production using pilot scale fast pyrolysis at 250 kg/h and 450°C; and (ii) a physical activation at three temperatures (750°C, 850°C and 950°C) using an in-house activation furnace (1 kg/h). Results showed that the first stage removed about 66% of the nitrogen from the wood panels in the form of NO, NH3, and trimethylamine, which were detected in small amounts compared to emitted CO2. Compared to other types of thermochemical conversion methods (e.g., slow pyrolysis), isocyanic acid and hydrogen cyanide were not detected in this study. The second stage produced activated biochar with a specific surface area of up to 865 m²/g at 950°C. The volatile gases generated during activation were predominantly composed of toluene and benzene. This two-step process resulted in nitrogen-rich carbon in the form of pyrrolic and pyridinic nitrogen. Activated biochars were then evaluated for their SO2 retention performance and showed an excellent adsorption capacity of up to 2140 mg/g compared to 65 mg/g for a commercial activated carbon (889 m²/g). End-of-life reconstituted wood panels and SO2 gas are problematic issues in Canada where the economy largely revolves around forestry and mining industries. [ABSTRACT FROM AUTHOR]

With rapid increase in energy consumption around the world, usage of petroleum-based products has also been on the rise. Bitumen, a product of petroleum distillation is being widely used as the pavement material all around the world. Petroleum being a non-renewable source of energy and also an environment pollutant, there must be an alternative way to reduce its consumption. India is the world's largest producer of waste, specifically biowaste. Many industries are reducing the amount of waste in the atmosphere, which pollutes the environment. That is also why we use this waste as a substitute material for pavement construction. Sugar cane biowaste is 100 million metric tons per year produced, and that is why we use pyrolysis, which is the process of transforming biowaste to biochar using a binder as flexible pavement construction. This study aims to find out alternate materials in flexible pavement construction, focused on one potential replacement: Biochar, which is produced through pyrolysis of sugarcane waste. Biochar is replaced with bitumen in 0%,5%,10%,15%, and 20% and then tested to validate the performance of the Marshall specimens. However, it is important to ensure that the biochar used in the process meets the required standards for road construction. Henceforth the test results are evaluated on key properties like stability, flow and mix density. [ABSTRACT FROM AUTHOR]

This study investigates the suitability of different lignocellulosic sources, namely eucalyptus, apple bagasse, and out-of-use wood, for injection into blast furnaces (BFs). While wastes possess carbon potential, their high moisture renders them unsuitable for direct energy utilization. Additionally, the P and K impurities, particularly in apple bagasse, can pose operational and product quality challenges in BF. Thus, different thermochemical processes were performed to convert raw biomass into a more suitable carbon fuel. Low-temperature carbonization was selected for eucalyptus, yielding a biochar with properties closer to the low-rank coal. Hydrothermal carbonization was chosen for apple bagasse and out-of-use wood, resulting in hydrochars with enhanced fuel characteristics and fewer adverse inorganic species but still limiting the amount in binary PCI blends. Thermogravimetry evaluated the cause–effect relationships between coal and coal- and bio-based chars during co-pyrolysis, co-combustion and CO2-gasification. No synergistic effects for char formation were observed, while biochars benefited ignition and reactivity during combustion at the programmed temperature. From heat-flow data in combustion, the high calorific values of the chars were well predicted. The CO2-gasification profiles of in situ chars revealed that lignin-rich hydrochars exhibited higher reactivity and conversion than those with a higher carbohydrate content, making them more suitable for gasification applications. [ABSTRACT FROM AUTHOR]

In this study, the torrefaction of food waste was carried out using a thermogravimetric analyzer (TGA) to produce biochar and assess its suitability as feedstock for steam gasification. Torrefaction was conducted at temperature from 230 to 290 °C and the heating rate from 10 °C/min to 30 °C/min. Subsequently, the detailed characterization was conducted using proximate, elemental, lignocellulosic, nutrient analysis, and TGA analysis. The proximate and elemental analysis showed that biochar had the highest fixed and elemental carbon at the highest temperature (290 °C) and lowest heating rate (10 °C/min). Similarly, TGA indicated that increase in temperature increased the mass loss, however, increase in heating rate did not yield much change in mass loss. Additionally, lignocellulosic and nutrient analysis showed that lignin fraction increased (up to 80%) with increases in severity of the torrefaction due to significant decomposition of hemicellulose, cellulose, starch, proteins, and lipids. Thereafter, the kinetic parameters (activation energy, pre-exponential factor) of torrefaction of food waste were determined using the two-step decomposition model which showed a good fit with experimental data. Finally, the biochar developed was used for energy production using steam gasification which produced syngas with maximum yield of 3.75 m3/Kg and having hydrogen fraction of around 65% at the optimal conditions (temperature: 290 °C, heating rate: 10 °C/min). Highlights: • Biochar was developed from food waste using torrefaction. • Biochar was characterized using various physico-chemical analysis along with kinetic study. • Steam gasification of biochar generated high quality syngas with 65% H2 fraction. [ABSTRACT FROM AUTHOR]

• Potential of biochar application in iron and steel industries is evaluated. • Comparison of biochar with coal-based fuels in view of physicochemical properties. • Evaluation of bio-coke production instead of coke in coke ovens. • Analysis of coke breeze replacement with biochar in sintering process. • Analysis of coke pulverized coal injection and coke with biochar in blast furnace. The iron and steel making is considered among the biggest industries which run the world. This industry contributes around 20% of global industrial-sector energy consumption that is provided significantly by coal and coke. The fossil-based fuels are consumed largely for heat generation and reducing agents in steel production processes which leads to huge global CO 2 emissions. This matter encourages to find an effective, environmentally friendly, and sustainable substitute instead of coke and coal. Recently, biochar has received lots of consideration as a possible replace since the acceptable adaptation and comparable metallurgical properties to coal and coke. However, the biomass application in iron and steel making manufactures is currently limited and it endures strong competition with coal-based fuels. This paper investigates the key challenges affected on the steel production plant and the ability of biochar to overcome these difficulties. This work evaluates coal and coke substitution with biochar, focusing on metallurgical, technical and environmental aspects with the view of gate-to-gate analysis, from industry entry gate (input feedstocks that are coal or biochar) to exit gate (that is steel production). Moreover, the opportunities and obstacles of biochar performance in energy-intensive processes in steel production such as coke-making, sintering and blast furnace are discussed and finally, the main questions regarding the evaluation of these alternatives and their impacts on the system are answered. [ABSTRACT FROM AUTHOR]

Biochar can be useful to overcome several environmental challenges in different sectors of energy, industry, and agriculture. However, there are currently only a limited number of studies with the employment of biochar for various applications and their environmental impacts. This study develops an LCA framework to evaluate the climate impacts of biochar production and its applications in soil enhancement and as a substitute for coal-based fuels in steel industries and then compares it with conventional biomass usage for energy production for Sweden, Italy, and Poland. Various pyrolysis operating temperatures are also considered to determine the optimal conditions for each location. The results show that biomass pyrolysis with biochar usage in the agricultural sector has the least environmental impact with the most significant potential in Poland followed by Italy. lower temperatures (around 350 °C) are more favorable for Sweden in terms of CO2 emissions, due to the country's renewable energy-based electrical system. Low to moderate temperatures (350–500 °C) are found to be optimal for pyrolysis temperature in Italy, while higher temperatures (around 650 °C) yield the highest GHG reduction for both biochar applications in Poland. [ABSTRACT FROM AUTHOR]

This study seeks to char and briquette various agricultural wastes to be used as fuel in cookstove. To realize this, charred briquettes were produced from various agricultural wastes such as rice husk, maize cobs, palm kernel shell, and sawdust using the fast pyrolysis method at three different particle sizes (0.6 mm, 1.8 mm, and 2.36 mm) and compacting pressures (10 MPa, 20 MPa, and 30 MPa). Fuel tests such as physical test, proximate, and ultimate analysis, combustion test, and mechanical test were determined to assess the quality and suitability of the charred briquettes for use as fuel in cookstoves. The findings show that for all the three factors considered, palm kernel shell briquettes recorded the highest calorific value of 20,836.32 kJ/kg, volatile matter content of 17.3%, and fixed carbon of 76.5% while recording the least amounts of ash content of 2.7% and moisture content 3.95% compared to the other briquettes. The water boiling test results revealed that Palm kernel shell and sawdust briquette fuels reached their boiling point of 100 ℃ at the fastest time of 10 minutes. Furthermore, palm kernel shell briquette of particle size of 0.60 mm and compacting pressure of 30 MPa exhibited an outstanding performance than the other briquettes with regard to the values of specific fuel consumption of 2.38 kg/liters, burning rate of 0.00428 kg/min, shatter index of 96.93%, impact resistance of 500%, relax density of 753,291 kg/m3 and water resistance of 92.9%. [ABSTRACT FROM AUTHOR]

The construction industry is responsible for a large amount of CO2 emissions and an intensive energy consumption. Cement production is the third largest source of anthropogenic CO2 emissions and is responsible for about 1.8 Gt of CO2 emissions into the atmosphere. The use of waste materials to replace a fraction of cement in the mortar makes it more economically and ecologically friendly. In this work, the main objective was to test incorporations of biochar produced at temperatures of 300, 350, and 400 °C, as a partial replacement for cement in the production of mortar. The materials used for the tests were residual lignocellulosic biomass (WBL) and electrical cable insulation waste (WIEC) mixed in a ratio of 1:1. The biochars produced were crushed and sieved after production to reduce the particles. A sample of biochar was used and tested under these conditions and another sample was washed in water and dried before being incorporated; all tests were carried out with a 5% replacement. Waste recovery tests were also carried out without thermochemical treatment. The specimens were studied for compressive strength and water absorption by immersion. All tests were replicated and were analyzed and compared with a control mixture with no incorporation of biochar in the mixture. It was possible to observe that the tests with the incorporation of biochars at 400 °C showed better results, with only a 24% reduction in resistance to compression. [ABSTRACT FROM AUTHOR]

The present work aims at (a) carbonizing agriculture biomass residue; (b) characterizing the obtained biochar; and (c) exploring its potential use for energy/resource recovery purposes. Six types of biomass were carbonized. The biochar was investigated through scanning electron microscopy with energy dispersive X-ray spectroscopy detector, thermogravimetric (TGA), proximate, ultimate, and Brunauer–Emmett–Teller analyses, along with bulk density, pH, electrical conductivity, and salt content measurements. The results served as input data for multi-criteria, multi-objective decision analysis of biochar, aiming to evaluate its best application prospective. The TGA identified two general stages: devolatilization (stage 2: 180–560 °C), and combustion (stage 3: 560–720 °C). The activation energy of stage 2 decreased with an increasing heating rate, but the opposite trend was observed for stage 3. The biochar CO2 adsorption suggested possible applications beyond energy conversion technologies. The decision support analysis revealed that peach stones, cherry stones, and grape pomace biochar achieved the most promising results for all evaluated applications (biofuel; catalyst; CO2 sequestration and soil amendment; supercapacitor) in contrast to colza, softwood, or sunflower husks char. [ABSTRACT FROM AUTHOR]

The possibility of applying biochar in mild torrefaction treatment to improve the thermochemical characteristics of ground biomass was the focus of the study. Camelina straw and switchgrass were torrefied in a reactor using microwave irradiation at torrefaction temperatures of 250 °C and 300 °C with residence times 10, 15 and 20 min, under nitrogen-activated inert conditions. Both biochar addition of more than 10% and residence time significantly affected the product yields, as MW torrefaction temperatures shifted from 250 °C to 300 °C. Overall, the results indicated a slight increase in ash content, mass loss percentage intensification, heating values, and fixed carbon, while moisture content and volatile matter decreased in camelina straw and switchgrass, with or without biochar. Biochar addition with a long residence time (20 min) at 250 °C reduced energy requirement during the microwave torrefaction process. The combustion index values showed that torrefied camelina straw or switchgrass with biochar addition suits co-combustion with coal in a coal-fired plant and is a potential biomaterial for biofuel pellets. [ABSTRACT FROM AUTHOR]

To maximise the use of biomass for energy purposes, there are various options for converting biomass to biofuels through thermochemical conversion processes, one of which is torrefaction. Higher utilisation of waste from the aspiration cleaning of grains, such as wheat or maize, could be one of the means through which the dependence on fossil fuels could be reduced in the spirit of a circular economy. In this study, the effect of torrefaction on fuel properties of agricultural residues was investigated. The tested materials were waste by-products from the aspiration cleaning of maize grains and waste from wheat. The materials were treated by torrefaction under a nitrogen atmosphere (225 °C, 250 °C, and 275 °C), over a residence time of 30 min. During the treatment, weight loss was monitored as a function of time. Proximate and elemental composition, as well as calorific values, were analysed before and after torrefaction. Torrefaction has a positive effect on the properties of the fuels in the samples studied, as shown by the results. The carbon content increased the most between temperatures of 250 °C and 275 °C, i.e., by 11.7% wt. in waste from maize. The oxygen content in the maize waste samples decreased by 38.99% wt. after torrefaction, and in wheat waste, it decreased by 37.20% wt. compared to the original. The net calorific value increased with increasing temperatures of process and reached a value of 23.56 MJ·kg−1 at a peak temperature of 275 °C in by-products from maize. To express the influence of the treatments on combustion behaviour, stoichiometric combustion calculations were performed. Differences of up to 20% in stoichiometric combustion parameters were found between the two types of waste. A similar case was found for fuel consumption, where a difference of 19% was achieved for torrefaction at a temperature of 275 °C, which fundamentally differentiated these fuels. [ABSTRACT FROM AUTHOR]

To assuage global consumer demand for energy, there is a need for increased biofuel production. Flash pyrolysis is an important technique for biomass conversion into eco-friendly biofuels. This review discusses the research progress and key findings made over the years on the flash pyrolysis of biomass. Flash pyrolysis oil yields can be as high as 60–75 wt% at optimised conditions. For the process to be effective, temperature, heating rate and residence time would be within the range of 450–600 °C, 10 3 - 10 4 °C/s and < 1 s. Flash pyrolysis oil is characterised by high water content (usually > 15 wt%). The main pyrolysis products of lignin part biomass are phenols. The phenolic part includes phenols, hydroxylphenols, meothoxyphenols, dimethoxyphenols. Flash pyrolysis products of biomass (as with other pyrolysis types) must be upgraded before use. They are unstable, re-polymerised and are not miscible with hydrocarbons. The future of the technology is promising as products obtained can serve as better feedstock for other re-refining processes (compared to other pyrolysis process types). Furthermore, it is faster and can handle higher feedstock volumes at similar reactor volumes and process intricacies. Due to the advantages of product yield, it is an important technology that should be explored for energy conversion of biomass and can also serve as a solid waste management technique. [ABSTRACT FROM AUTHOR]

Background: Economic benefit has been analyzed for the yield of farming products when designing a farming system, while waste treatment also generates profitable energy products for this system. The economic factor is decisive in decision-making for applying waste treatment solutions for a small-scale farming system. A household farming system in the Mekong Delta generates many kinds of organic wastes, but most of the agricultural waste resources are disposed of into the environment. Methods: This study approaches an analysis of economic–environmental–energy (EEE) efficiency for waste treatment of an integrated livestock-orchard (LO) system on a household scale in the Mekong Delta. This novel analysis method is based on the energy content of biomass and its cost. The EEE efficiency is optimized to gain objective functions regarding energy yield efficiency, system profit, and CO2 sequestration for the treatment model. The algorithms are built for optimizing these objective functions. Results: The optimization results show the treatment model of pyrolysis and pelleting gain all the objective functions with high efficiency. The model is efficiently applied for the LO system that generates more than 100 kg of orchard residues and 3000 kg of pig manure. The system with a charcoal oven and pellet machine is capable to gain energy efficiency due to its potential biofuel products, such as biochars and pellet products. A treatment model of composting, pyrolysis, and pelleting gives the best performance of overall EEE efficiency. Conclusions: This work has proven economic benefits from integrating biogas tank, charcoal oven, and pellet machine in an integrated LO system. The system contributes not only for reducing CO2 emissions but also for supplementing secondary renewable bioenergy, as well as for increasing incomes and thus supporting livelihoods for the local farming households. [ABSTRACT FROM AUTHOR]

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[Display omitted] • A microwave multiphysics model with dynamic permittivity of biochar was constructed. • Attenuation of electric field intensity caused the temperature gradient distribution. • The generation mechanisms and the spatial distribution of the hotspots were explored. • Regulation of the hotspots optimized the pore structure and graphitization of the biochar. • The interaction between the formation of the biochar and the microwave energy loss was explored. The microwave pyrolysis of biomass and the directional design of biochar structure are examined in this study by exploring the internal connection between energy conversion and biochar structure evolution. Through the optimization of process parameters (microwave power and sample volume), the average utilization efficiency of microwave energy increased from 11.96% to 32.84%, and the specific surface area of the biochar increased from 453.89 m2/g to 638.82 m2/g. According to the simulation results of the COMSOL Multiphysics software, the distribution of the temperature field was closely related to the evolution of the microwave electric field intensity. The local high temperature areas (hotspots) were primarily located in the center of the biochar, and the temperature distribution gradually decreased from the inside to the outside. The hotspots contributed to the promotion of the conversion of amorphous carbon to graphite carbon. Meanwhile, the graphite carbon with a stronger microwave absorption capacity formed a local hotspot and promoted the growth of the pore structure. The rich pore structure of the biochar facilitated the multiple reflection of microwave energy and prolonged the microwave residence time. Graphite carbon can absorb microwave energy and convert it into heat energy to improve the utilization efficiency of microwave energy. This paper combined the experimental and simulation results to reveal the heat transfer mechanism in the microwave pyrolysis process, which provided a new perspective for the directional reduction of microwave pyrolysis energy consumption and the optimization of the microstructure of biochar. [ABSTRACT FROM AUTHOR]

Climate change and energy demand are calling for more sustainable fuels such as biomethane produced by anaerobic digestion of organic waste. Biochar addition to waste is presumed to enhance the efficiency of methane production, yet individual reports disclose contradictory results. Therefore, we performed a meta-analysis of 27 selected publications containing 156 paired measurements of control and biochar-amended treatments to assess the impact of biochar on the methanogenic performance. Results show that biochar promotes biomethane production substantially with a high Hedge's d value of 5.7 ± 1.04, yet sporadic publications report a methane decline. Methanogenic performance is statistically controlled by feedstock type, pyrolysis temperature and biochar concentration, but not controlled by pH, size, surface area and methanogen species. These findings should help to tune the parameters of anaerobic digestion with biochar to optimize biomethane productions. Moreover, our results cast some doubt on the efficiency of adding biochar to soil to sequester carbon in soils because biochar promotes methane generation and, in turn, emissions of methane, a greenhouse gas, to the atmosphere. [ABSTRACT FROM AUTHOR]