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Under the circumstances of serious environmental challenges and energy crises, it is of utmost importance to produce fuels and chemicals from renewable biomass and organic wastes. Biochar as a bioproduct from thermochemical conversion of biomass has attracted exponential research interest in recent years due to the abundance of its precursor (biomass resources) and its adaptability in different chemical reaction systems. Undoubtedly, it is essential to attain an in-depth understanding of the physiochemical properties and functionalization of biochar catalysts to further improve their catalytic activity, selectivity and stability in the reactions. However, until now, only a few reports are accessible on the use of biochar as a catalytic support material and/or a standalone catalyst in thermochemical biomass conversion to produce high-quality biofuels. Thus, the key objective of this review article is to summarize and discuss the latest progress in biochar production, modification, activation and functionalization by understanding its physical chemistry, composition and application in catalytic processes. This review article provides insights into the thermochemical and hydrothermal production of biochar as well as the engineering and process optimization aspects for value-added biofuel production and decarbonization. [Display omitted] • Effects of biomass composition and process conditions on biochar are reviewed. • Systematic discussion on biochar functionality as bio-based catalyst support is made. • Insights into the modification of biochar targeting optimal performance are shown. • Comparative analysis of biochar-based catalytic pyrolysis, gasification and liquefaction. • The significance of activation of biochar for enhanced functionality is justified. [ABSTRACT FROM AUTHOR]

Pyrogenic carbon capture and storage (PyCCS) based on biochar is considered a negative emission technology (NET) aimed at mitigating climate change, with the potential to reduce CO 2 by 0.3–2 gigaton/yr at the cost of $30–120/ton-CO 2. The annual biochar production needs a substantial scaling up of the current production rates (i.e., >150 million tons by 2050) to meet the above demand. However, current biochar production predominantly relies on a small-scale operation, which generally leads to high operational costs and limited control of the biochar properties. This work presents the operation of a state-of-the-art 1 ton/d pilot-scale Flexible Counter Flow Multi-Baffle (F-COMB) pyrolyzer designed for continuous biochar production, which is a prototype reactor for the scale-up. The F-COMB utilizes counter-flow and vortex mixing in a multi-baffle column structure to enable efficient contact of feedstock with hot gas. It boasts high energy efficiency and economic feasibility through a short residence time, reduced gas flow rate, and simple structure. It produces wood pellet biochar with accurate control of the reaction conditions such as temperature, retention time, hot gas flow rate, and feedstock loading. Moreover, continuous biochar production is done successfully with three flexible baffles configuration, demonstrating the significant potential for the scale-up. • Flexible Counter Flow Multi-Baffle (F-COMB) reactor is designed for pyrolysis. • F-COMB provides high energy efficiency via efficient contact of feedstock & hot gas. • Vortex mixing induced by multiple baffles gives the efficient contact. • Biochar production using a F-COMB was demonstrated at 1 ton/day scale successfully. • Continuous biochar production shows significant potential for the F-COMB scale-up. [ABSTRACT FROM AUTHOR]

The importance of combating the contamination of water resources with emerging pollutants must be kept all the more in view by scientists, since such pollutants are harmful and pose challenges for traditional water treatment methods. The current study was designed to scrutinize the adsorption properties of a low-cost biochar for two pharmaceuticals in both single and binary systems. The work was focused on understanding how paracetamol (PARA) and diclofenac (DIC) co-adsorb, and it can serve as a beacon for similar studies, especially in modeling the adsorption processes of such systems. Using a low-cost biochar from pepper stem (PS) with a high surface area = 727.5 m2/g as adsorbent, experiments were carried out in both the single and binary systems to investigate the adsorption behavior of the mentioned pharmaceuticals. Results showed that, in the single system, the PS biochar demonstrates a slightly greater adsorption capability for both PARA and DIC, with a capacity of 354.66 and 256.10 mg/g, respectively, compared to its capacity for each pharmaceutical in the presence of the other in the solution. Interestingly, the effect of the presence of one of the pharmaceuticals on the thermodynamic parameters (ΔGº, ΔSº, and ΔHº) of the other was ignorable, and interactions such as hydrogen bonding, π-π, n-π, and anion-π interactions were at work for the adsorption processes, with different extends in each pharmaceutical-biochar case. On the other hand, the presence of one of the pharmaceuticals was effective on the kinetics of the adsorption process of the other and caused a decrease in its adsorption rate, especially in the initial stage of the process. Overall, in addition to the suitability of pepper stem biochar for PARA and DIC, results showed that the presence of one pharmaceutical is not influential on all the adsorption properties of the other, and the results can be exploited for studding similar systems. [Display omitted] • The adsorption properties of a low-cost biochar for two pharmaceuticals were scrutinized. • The capacity of biochar for each pharmaceutical was depended on the adsorption mechanism. • The effect of presence of one of the pharmaceuticals on thermodynamics of the other was ignorable. • Kinetic and isothermal properties were different in single and binary systems. • The results can be exploited as a beacon for studding similar systems. [ABSTRACT FROM AUTHOR]

Torrefaction is an efficient pretreatment technology for large-scale and high-value utilization of biomass fuel. This study aims to enhance the understanding of the thermochemical conversion of torrefied biomass by delineating the role of potassium and torrefaction on primary/secondary charring reactions during pyrolysis of torrefied cellulose. Celluloses with varying potassium loading levels were torrefied at temperatures ranging from 200 to 320 °C and subsequently pyrolyzed at 1000 °C. Two contrasting pyrolysis conditions, i.e., limiting and enhancing transport resistance, were employed to tune the occurrence of secondary reactions, thereby determining the role of torrefaction and potassium on primary and secondary charring reactions. Potassium content, torrefaction severity, and pyrolysis conditions both profoundly affects char formation during pyrolysis of torrefied cellulose, resulting in a wide range of pyrolysis char yields from 1.95 wt% to 64.35 wt%. The structural changes induced by torrefaction, including the depolymerization of the carbohydrate structure and the formation of crosslinking structures, promote the char formation. Potassium enhances the char formation of torrefied cellulose in two ways: i) by catalyzing the transformation of the carbohydrate structure into the crosslinking structure during torrefaction, and ii) by catalyzing the charring reactions of both the carbohydrate and the crosslinking structures during pyrolysis. Raman spectral analysis of the char carbon structure indicates that increased potassium loading level and torrefaction severity enlarge the aromatic system of the char. The findings highlight the potential of optimizing biomass pyrolysis through controlled torrefaction and potassium, paving the way for more efficient biofuel production and high-quality biochar applications. • The role of potassium and torrefaction on char formation during pyrolysis is investigated. • A wide range of pyrolysis char yields from 1.95 to 64.35 wt% is reported. • Torrefied celluloses pretreated at different temperature exhibit different charring behavior. • Potassium can promote char formation by altering structure of torrefied cellulose. • A linear correlation is established between char yield and char carbon structure. [ABSTRACT FROM AUTHOR]

Lignin is a promising renewable alternative to fossil fuels for producing carbon materials such as carbon fibers, activated carbons, or carbon black. Despite extensive research, lignin-derived carbon materials show limited graphitization relative to comparable petroleum-derived carbons. Further, lignin-derived carbons show high variation in graphitization and electrical conductivity depending on the source of the lignin. Herein, nine lignins, derived from various feedstocks and isolation procedures, are pyrolyzed to produce biochar at 1100∘C. These lignins have a range of chemical compositions, carbon structures, and particle sizes. As a result, the pyrolysis behavior of these lignins varies, with powdered, clumped powder, and "foam" biochar morphologies resulting from finely powdered lignin. The produced biochars vary widely in both electrical conductivity, from 0.19 to 19 S/cm, and in-plane graphitic crystallite size, from 3.4 to 41.2Å. A significant decrease in electrical conductivity is identified when Na 2 SO 4 is removed from lignin, accompanied by an increase in graphitic crystallite size. Based on this finding, a quadratic relationship between biochar graphitic crystallite aspect ratio and electrical conductivity is proposed that builds on established quasi-percolation models for biochar electrical conductivity. • Electrical conductivity of lignin pyrolyzed at 1100 ∘C varies by a factor of 100. • Na 2 SO 4 in lignin increases the size of graphitic crystallites, decreases conductivity. • High aspect ratio graphitic crystallites are proposed as cause of this behavior. • Lignin-derived biochar carbon structure can be tuned by varying Na 2 SO 4 content. [ABSTRACT FROM AUTHOR]

Pyrolyzing waste biomass into functionalized biochar is aligned with the concept of the circular economy. The physicochemical properties of biochar are influenced by the type of biomass feedstock and pyrolysis parameters, necessitating significant time, energy, and resources for quantification. This study employed machine learning algorithms to predict the yield, elemental distribution, and degree of aromatization of biochar based on the physical and chemical properties, as well as the pyrolysis conditions of biomass. Support vector machines (SVM), multiple linear regression (MLR), nearest neighbor algorithm (KNN), random forest (RF), gradient boosting regression (GBR), and eXtreme Gradient Boosting (XGB) were comparatively analyzed. Among these algorithms, the XGB algorithm performed well in predicting biochar production and element distribution (R 2>0.99). Furthermore, PCC and SHAP analyses revealed a strong positive correlation between pyrolysis temperature and the degree of aromatization in biochar. Therefore, selecting the appropriate ML model can aid in predicting the physicochemical properties of biochar from diverse biomass sources without the necessity for complex and energy-intensive pyrolysis experiments. [Display omitted] • Machine learning for predicting the physicochemical properties of biochar. • Good prediction ability of the eXtreme Gradient Boosting. • Determining the significance of traits for various targets. • Strong correlation between pyrolysis temperature and aromaticity of biochar. [ABSTRACT FROM AUTHOR]

Pyrolysis is one of the thermal conversion pathways to convert biomass into biochar. The characteristic of biochar depends on three parameters, i.e., before pyrolysis (drying methods of biomass), during pyrolysis (temperature), and after pyrolysis (activation agents). Thermal and non-thermal drying methods remarkably affected the psychochemical properties of biomass. Pyrolysis temperature significantly governed the biochar production. Temperature above 500 °C was required to convert biomass okara into biochar. Activation agent determined the pore characteristic of biochar. FT-IR, XRD, TGA-DSC, SEM, Raman, XRF, CHNOS Analyzer, Surface area analysis, and TEM characterizations of material confirmed that implemented the three parameters simultaneously were essential to achieved different properties of biochar that could be used in environmental remediation or energy-oriented field. • Non-thermal drying method generate biomass with higher lignocellulose level which led to higher carbon content of biochar. • Simultaneously varying biomass drying method, pyrolysis temperature, and activating agents provided various biochar character. • Acid activated biochar okara pyrolyzed at 800 °C possessed GO-like structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integrated HTC–PY technique was implemented to valorizes CS and YW. • HTC improved carbon content, deoxygenation, and higher heating value. • CSH and YWH hydrochars' co–pyrolysis modeled via hybrid RSM–ANN. • The pyrolysis of blends reduced the average activation energy. • Pyrolysis of hydrochars enriched bio–oil with hydrocarbons and phenols. Hydrothermal carbonization (HTC) presents a promising method for converting carbonaceous waste into renewable fuels, facilitating energy recovery. This study focuses on the HTC pretreatment of microalgae (Chlorella sorokiniana) and yard waste, examining their physicochemical structural changes, component migration, and potential for valorization via integrated HTC and pyrolysis processes. HTC notably enhances the carbon content while reducing oxygen and nitrogen levels in these feedstocks, producing a clean solid fuel with high energy density. The study investigates the pyrolytic behavior of hydrochars and their blends using different analytical techniques, kinetic modeling, and fixed–bed reactor experiments. The blends with 90% and 70% of microalgae hydrochar (CSH) exhibited the most significant synergistic effects during co–pyrolysis, evident in its devolatilization behaviors and reduced activation energies. Integrating artificial neural networks and response surface methodology models facilitated optimization of pyrolysis parameters and accurate prediction of bio–oil, biochar, and gas yields. The analytical techniques enabled characterization of pyrolysis products, revealing notable changes in bio–oil and biochar compositions, suggesting potential enhancements. The study comprehensively evaluates the HTC–pyrolysis approach's potential for converting microalgae and lignocellulosic biomass into eco–friendly biofuels for industrial applications. [ABSTRACT FROM AUTHOR]

The aim of the present study was to find environmentally friendly solutions for the disposal of problematic and toxic textile sludge (TS) by producing textile sludge biochar (TSB) by pyrolysis and evaluating its chemical properties, polycyclic aromatic hydrocarbon (PAH) content, heavy metals (HMs) speciation, environmental risks, and effects on seed germination. Pyrolysis of TS at temperatures ranging from 300 to 700 °C significantly reduced (85–95%) or eliminated certain PAHs in the biochar, enriched heavy metal content within land use limits, and increased bioavailability of HMs in biochar produced at 300 °C and decreased leaching capacity of HMs in biochar produced at 700 °C. The speciation of HMs and their bioavailability during pyrolysis processes was strongly temperature dependent, with lower temperatures increasing the toxic and bioavailable forms of Zn and Ni, while higher temperatures converted the bioavailable Ni to a more stable form, while Cu, Cr, and Pb were transformed from stable to toxic and bioavailable forms. The ecological risk index (RI) values of TSB-300 and TSB-700 are below the threshold value of 150, indicating a low-risk level, and the risk level decreases at temperatures above 500 °C. Further, the extracts of TSB-300 and TSB-700 had the highest percentage of germinating seeds, while the extracts of TS and TSB-500 inhibited seed germination by 20–30% compared to the control. These results indicate that pyrolysis effectively reduces PAHs and binds leachable HMs in biochar, however, the specific pyrolysis temperature influences metal speciation, bioavailability, seed germination, and environmental risk. [Display omitted] • Disposal of TS containing HMs poses a high environmental risk. • PAHs are reduced significantly by pyrolysis of TS into biochar. • Higher temperatures produce biochar with a stable form of Ni. • Environmental risk index of 700 °C biochar was the lowest. • Extracts of biochar produced at 700 °C promote plant growth. [ABSTRACT FROM AUTHOR]

As an effort to tackle some of the most pressing ecological issues we are currently experiencing, there has been an increasing interest in employing biomass-derived char products in various disciplines. Thermal combustion of biomass results in biochar production, which is a remarkably rich source of carbon. Not only does the biochar obtained by the thermochemical breakdown of biomass lower the quantity of carbon released into the environment, but it also serves as an eco-friendly substitute for activated carbon (AC) and further carbon-containing products. An overview of using biochar to remove toxic pollutants is the main subject of this article. Several techniques for producing biochar have been explored. The most popular processes for producing biochar are hydrothermal carbonization, gasification and pyrolysis. Carbonaceous materials, alkali, acid and steam are all capable of altering biochar. Depending on the environmental domains of applications, several modification techniques are chosen. The current findings on characterization and potential applications of biochar are compiled in this survey. Comprehensive discussion is given on the fundamentals regarding the formation of biochar. Process variables influencing the yield of biochar have been summarized. Several biochars' adsorption capabilities for expulsion pollutants under various operating circumstances are compiled. In the domain of developing biochar, a few suggestions for future study have been given. [Display omitted] • This survey looked into the production of biochar using various techniques. • Process variables that affect the yield of biochar were emphasized. • This article briefly describes the biochar synthesis mechanism. • Biochar application for the evacuation of organic and inorganic pollutants was briefed. • Synthesis and application of magnetic biochar was summarized. [ABSTRACT FROM AUTHOR]

A hybrid residual modeling approach was proposed by combining the residuals of the pyrolysis equilibrium model and the Random Forest model, and results indicated that the hybrid residual model provided a more accurate prediction of the biomass pyrolysis process compared with the separate models. [Display omitted] • A hybrid residual modelling approach predicts the yield and heating value of biochar. • First principles coupled with physical laws to establish a pyrolysis equilibrium model. • Equilibrium model residuals as an input feature improves the accuracy of ML model. Predicting biochar yield and heating value poses a great challenge due to the complexity of the biomass pyrolysis process. Here, we propose a hybrid residual (HR) modelling approach by combining the residual of the pyrolysis equilibrium model and the Random Forest (RF) model. Then, the separate pyrolysis equilibrium model and the RF model were also established for comparison. These three models were evaluated in terms of R2 and RMSE, and results revealed that the HR model exhibited the optimal performance with R2 values of 0.890 and 0.956 for yield and higher heating value (HHV) of biochar, respectively. Permutation importance analysis and SHAP value analysis were conducted to rank the feature importance of the HR model. The results indicated that the ash, pyrolysis temperature, and residual are important for biochar yield; the ash, carbon, and residual are crucial for the HHV of biochar in the biomass pyrolysis process. Furthermore, simplified interpretable equations were developed based on the identified features. In conclusion, this work demonstrated through simple case studies that combining a mechanism model with a machine learning model can accurately establish complex process modelling and offer simplified equations. [ABSTRACT FROM AUTHOR]

Moso bamboo is regarded as a kind of biomass resource with abundant reserves in nature, and how to achieve its high-value utilization is one of the important research topics widely concerned by the academic community. In this work, hierarchical porous graphene nanosheets with wrinkled structures derived from the natural moso bamboo is obtained via a compact two-step processing method including pyrolysis and chemical activation. The as-prepared ABC-950 possess a large specific surface area of 1758 m2 g−1, pore volume of 1.55 cm3 g−1, mesopores ratio of 75.5 % and high graphitization degree with I D /I G as low as 0.43. With these merits, as the electrode material for supercapacitor, the ABC-950 exhibits a high specific capacitance of 459.4 F g−1 at 1 A g−1 and an excellent rate performance of 82.3 % in 6 M KOH electrolyte. Moreover, the ABC-950 based symmetric supercapacitor shows superior specific capacitance of 112.3 F g−1 at 0.5 A g−1 and an attractive energy density of 15.6 Wh·kg−1 at 250 W kg−1. Moreover, outstanding capacitance retention of about 102.1 % even after 30,000 charge-discharge cycles at a large current density of 10 A g−1. Our work offers a promising method to easily transform moso bamboo into porous graphene nanosheets for the electric energy storage. • Wrinkle-like hierarchical porous graphene was prepared from the moso bamboo. • The porous carbon has an ultrahigh mesoporosity and degree of graphitization. • Great electron transfer efficiency and electrode kinetic performance are obtained. • Devices showed good rate capability and splendid long-term cycling stability. • High energy density of 15.6 Wh·kg−1 at 250 W kg−1 is achieved in 6 M KOH. [ABSTRACT FROM AUTHOR]

Biogas is a promising bioenergy source and its composition is based on methane (55–70% vol) but contains impurities such as CO 2 (30–45% vol). Various technologies are available to purify biogas and produce biomethane that can be injected into the existing natural gas network. In this work, the effectiveness of activated carbons (ACs) obtained by chemical activation from industrial food waste for CO 2 removal by adsorption was investigated. ACs with better textural development were obtained at higher activation temperature and dose of the activating agent (BET surface area and total pore volume up to 1446 m2/g and 0.589 cm3/g, respectively). The adsorbents exhibited a microporous character (micropore volume up to 0.472 cm3/g). The ACs were tested in high-pressure gas adsorption tests (CO 2 , CH 4 and H 2 up to 3, 8 and 4 MPa, respectively). All of them showed high, medium and low selectivity against for the adsorption of CO 2 , CH 4 and H 2 , respectively, although with different efficiencies. The adsorbent obtained under the most aggressive activation conditions (900 °C, 1:1 wt ratio) showed the greatest textural development and the maximum adsorption capacity for CO 2 (at 3 MPa) and CH 4 (at 8 MPa) (495 mgCO 2 /g and 126 mgCH 4 /g). Despite the porosity of the materials, all showed a very low affinity for hydrogen adsorption at 4 MPa (up to 3.71 mgH 2 /g). Taking the above into account, these activated carbons could be used in the purification of biogas and in the separation of CO 2 /H 2 mixtures to produce pure H 2 and obtain hydrogen-free CO 2 for capture and storage. [Display omitted] • Pomegranate peel residue char was used as a good precursor for activated carbon. • KOH chemical activation has been used to create effective microporous adsorbents. • BET surface area and total pore volume of up to 1446 m2/g and 0.589 cm3/g. • Activated carbons have potential for gas separation and biogas quality improvement. • A maximum adsorption capacity of 496 mg CO 2 /g and 126 mg CH 4 /g was achieved. [ABSTRACT FROM AUTHOR]

The safe disposal of sewage sludge (SS) and food waste digestate residues (DR) is a tough issue considering the difficulty of dewatering and the environmental risks from heavy metals and pathogens. This study combined hydrothermal pretreatment (HP), anaerobic digestion (AD), and pyrolysis to synergistically dispose of SS and DR to enhance dewaterability, recover energy, and prepare biochar with heavy metal immobilization. The results showed that the solid contents of centrifuged cakes increased after HP at 180 °C of SS with the addition of 25% and 50% mass fractions of DR. The centrate from co-HP had a high chemical oxygen demand (COD) and was further treated by AD at 37 °C, producing 193.75 and 210.39 mL/g COD input (25 °C and 1 atm) of cumulative CH 4 under the addition of 50% and 75% mass fractions of DR, respectively. The methanogenic types in AD converted from hydrogen utilization to acetic acid utilization with increasing DR ratio. Zn, Cu, Ni, and Pb were primarily left in the biochar after 50% mass fraction of DR was mixed in the HP combined with pyrolysis at 700 °C; the chemical fractionation of Zn, Cu, Cr, and Pb in the biochar increased to over 85% of the residual fractions, resulting in the lowest potential ecological risk index (15.22, low risk). The CH 4 produced from the AD of the co-HP centrate (50: 50, w / w) can supply heat for the HP process, reducing the energy input by 89%. This co-disposal strategy can effectively recover carbon resources from solid wastes to reduce carbon emissions. • HP, AD coupled with pyrolysis were used for synergistic treatment of SS and DR. • The dewaterability of SS improved after HP with the addition of DR. • The generated CH 4 can supply heat for the HP, reducing the energy input by 89%. • The biochar had a low heavy metal risk after HP combined with pyrolysis. [ABSTRACT FROM AUTHOR]

Recent research has found biochar to be a cost-effective adsorbent for removal of perfluoroalkyl substances in water. To promote cleaner production and sustainable waste management, this study explored the potential to produce activated biochars by co-pyrolyzing sawdust with iron-rich biosolids and polyaluminum sludge. The maximum capacity to adsorb perfluorooctanesulfonic acid (PFOS) reached 27.2 mg g−1 with biosolids-activated biochar and 19.2 mg g−1 with aluminum sludge-activated biochar, compared to 6.2 mg g−1 with sawdust biochar. The increased adsorption capacities were attributed to electrostatic interactions between the anionic PFOS and metal functionalities on the biochar surface. In contrast, hydrophobic interaction was the dominant adsorption mechanism of sawdust biochar. The presence of dissolved organic matter at 5–50 mg L−1 was found to inhibit adsorption of PFOS in water, while pH as low as 3.0 and sodium chloride concentrations up to 100 mM enhanced removal of PFOS by all the three adsorbents. In batch adsorption tests at environmentally relevant PFOS dosages and adsorbent dosage of 0.25 g L−1, the biosolids-sawdust biochar and Al sludge-sawdust biochar removed 71.4% and 66.9% of PFOS from drinking water and 77.9% and 87.9% of PFOS from filtrate of sludge digestate, respectively. The biosolids-sawdust biochar additionally removed Fe, although the Al sludge-sawdust biochar released Al into the alkaline drinking water and filtrate. Overall, this study proved co-pyrolyzing sawdust and Fe-rich biosolids to be an effective approach to activate sawdust biochar for enhanced removal of PFOS while recycling wastewater treatment residuals and sawdust. [Display omitted] [ABSTRACT FROM AUTHOR]

The utilization of waste lignin to produce bio-oil rich in aromatics aromatic hydrocarbons is promising and attractive for a wide range of applications. Fe-modified lignin biochar (xFe/ALC) prepared using a one-step method was utilized as catalysts to investigate their impact on product distribution, aromatic hydrocarbon generation, and pathways during ex-situ catalytic fast pyrolysis of enzymatic hydrolysis lignin. The results revealed that the addition of Fe enhanced the production of gas products such as H 2 , while decreasing bio-oil yield. The lowest bio-oil yield, at 12.10 wt%, was observed at a Fe loading of 25 wt%, however the relative content of aromatic hydrocarbons reached a maximum value of 16.24 area%. Compared to the pyrolysis of lignin alone, their contents increased by 2.46 times, with the content of monocyclic aromatic hydrocarbons (toluene, ethylbenzene, styrene, xylene) increasing by 1.5–3.8 times. Spent 25Fe/ALC had good stability on the production of aromatic hydrocarbons. Compared with non-catalytic pyrolysis of lignin, the aromatic hydrocarbons content for spent 25Fe/ALC after four cycles increased by 26.70%. [Display omitted] • Fe modified biochar was synthesized by enzymolysis lignin using a one-pot method. • The loading of Fe could regulate the structure and acidity of lignin biochar. • Fe/ALC catalysts were used for ex-situ catalytic pyrolysis of enzymolysis lignin. • The aromatics content for 25Fe/ALC was 2.46 times higher than that without catalysts. [ABSTRACT FROM AUTHOR]

This study addresses the preparation of sludge biochar through a procedure that combines steam pyrolysis in a wide range of temperature (500–900 ºC) and acid treatment with HCl (performed before or after the pyrolysis). The acid washing after the pyrolysis maximizes BET surface area due to pore unblocking, thus making visible the pore structure generated. The drawback of the acid washing is the lower yield obtained (compared to the acid pretreatment), as well as the loss of the magnetic properties of sludge biochar. The acid pretreatment requires temperatures above 700 ºC to have a beneficial effect, due to the occurrence of additional reactions of the incorporated HCl with sludge constituents. The pretreatment results in materials with a high degree of microporosity. Among the reactions favoured, of interest is the development of magnetite in the whole temperature range. The activation protocol used in this study (especially the procedure that includes the acid pretreatment) is effective to generate biochar with magnetic properties through the transformation of the Fe introduced during the water treatment process, without adding a source of Fe. The presence of magnetite is an advantage for the reuse of sludge biochars in wastewater treatment. • Acid washing after steam activation greatly enhances porosity due to pore unblocking. • Acid pretreatment produces biochars with a high degree of microporosity. • Acid pretreatment leads to the formation of magnetite in the whole temperature range. • The acid treatment results in the generation of C=O, -OH and -NH functionalities. • The activation protocol is effective to produce magnetic biochar without adding Fe. [ABSTRACT FROM AUTHOR]

The disposal of discarded disposable diapers (D3) is a critical eco-technological problem that is exacerbated by the exponential increase in global consumption each year. Global production of D3 is increasing exponentially and approximately 20 billion used diapers are sent to landfills each year, generating more than 3.5 million tonnes of diaper waste that requires almost 500 years to be fully decomposed. The disposal of D3 has resulted in significant environmental issues and public health hazards. The objective of this study was to provide a systematic review and in-depth discussion of the strategies, challenges, and recent breakthroughs in addressing the problems resulting from the generation and disposal of D3. A systematic literature search was conducted using three electronic databases (Google Scholar, Scopus, and ScienceDirect). Four peer-reviewed studies were selected from the 2287 articles found. Thermochemical technology is claimed to be suitable for the treatment and recycling of used diapers, especially with regard to the use of potentially safer and cleaner technologies with minimal costs. It was established that pyrolysis of D3 could yield useful end products with a wide range of applications, hence providing a future research direction to improve the efficiency of these processes in recycling this waste. • Production of D3 is increasing exponentially and approximately 20 billion used diapers are sent to landfills each year. • The temperature setting for the thermochemical procedure of D3 depends on the technique applied (200 – 900 ℃). • Chemical activation slightly enhanced lead removal from 96.2% to 98.2% (KOH) – 99.8% (ZnCl 2). • Reaction conditions (temperature, pressure, and time) are critical impact D3 biochar yield and product quality in pyrolysis. [ABSTRACT FROM AUTHOR]

Millions of tons of cotton textile waste are generated annually worldwide, and most of it enters the municipal solid waste (MSW) stream for landfill or incineration disposal, resulting in a significant waste of resources and environmental pollution. This article developed an innovative low-temperature pyrolysis process for producing artificial humic acid (HA) from waste cotton textiles. Subsequently, Al3+ was introduced for a secondary pyrolysis to prepare an Al-doped biochar (Al/BC) with superior adsorption properties. The experimental results show that the presence of Al3+ has an important influence on the pyrolysis process of cotton fabric and the formation and structure of Al/BC. This is the first time to synthesize low-cost adsorbent by pyrolysis and aluminum mixing process of waste cotton cloth and explains the mechanism. This increased in defects (I D / I G = 0.76 to I D / I G = 0.92), a larger specific surface area (6.47 m2/g to 566.94 m2/g), and an increase in oxygen-containing functional groups (from none to C-O-C, O C-O, etc.) when compared to the undoped Al3+ biochar. The optimum Al3+-doped biochar (Al/BC-15) prepared with HA as a precursor exhibited a superior adsorption capacity for Cr(VI) of up to 176.23 mg/g, surpassing the results reported for similar materials in the literature. The adsorption mechanism of Cr(VI) is primarily based on physical adsorption, with some chemical adsorption. At a lower pH, the Al/BC-15 surface exhibits a high positive charge (46 mV). The Al3+-O-Cr(VI) association group is formed through rapid electrostatic attraction between C-Al and Cr(VI). Due to the strong positive electronegativity of Al3+ and the negative electronegativity of C in the vicinity of Al, Cr(VI) is further reduced to Cr(III) by C-Al. Therefore, the method proposed in this paper for preparing Al-doped carbon materials from waste cotton fabric offers a new approach and potential application for the production of high-performance adsorbent materials from waste cotton fabric. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrolysis and activation in a dual fluidized bed was successfully operated. • Physical and chemical activation by flue gas and H 3 PO 4 occur simultaneously. • Maximum biochar yield and iodine number were 42.3 wt% and 648.5 mg/g, respectively. • Pyrolysis and activation of one-step method is superior to two-step method in DFB. • H 3 PO 4 favors formation of pores and surface functional groups with rising ratios. Interconnected pyrolysis and activation is a novel technology for combustible gas and biochar production in dual fluidized bed (DFB). The study proposed one-step and two-step methods for pyrolysis and activation of biomass in a pilot scale DFB with capacity of 100 kg/h. Physical and chemical activation occurred simultaneously in DFB system by phosphoric acid (H 3 PO 4) impregnation pretreatment of pear wood chips, and flowing hot flue gas and steam. Stable operating parameters were observed for both methods. The one-step method was superior to the two-step method in terms of the pyrolysis gas quality, biochar pore distribution, micro- and meso-pores structures of biochar, while one-step method reduced the biochar yields. As an activation agent, H 3 PO 4 increased the yields of biochar and pyrolysis gas, promoted formation of micropores and enriched the surface functional groups of biochar with increasing ratio of H 3 PO 4. H 3 PO 4 to biomass ratio of 1:5 reached the maximum biochar yield of 42.3 wt% and highest iodine adsorption value of 648.5 mg/g, increasing by 70.6 % and 90.3 % compared to the biochar without H 3 PO 4 pretreatment, respectively. This DFB system facilitated the diversified use of fluidized beds and the co-production of biochar and product gas with energy saving and CO 2 emission reduction. [ABSTRACT FROM AUTHOR]

To achieve a closed nutrient cycle and more sustainable food production, enhanced nutrient recycling in the agri-food system is a necessity. Pyrolysis is an emerging technology to recycle the nutrient content of sewage sludge. The produced biochar can be used to reduce the need for mineral fertilizers; in addition, pyrolysis can also handle potential pollutants such as microplastics and pathogens present in sewage sludge. In this research, a life cycle assessment (LCA) was carried out to determine the environmental impact of sewage sludge pyrolysis as an alternative to current practices of two different cases of sewage sludge treatment in two municipalities in Sweden. The results indicated that avoiding mineral fertilizer production by using biochar has a significant influence on the environmental benefits. Furthermore, it showed that an integrated system of anaerobic digestion followed by pyrolysis could perform as the most environmental-friendly option for sewage sludge treatment with a lower risk of transferring pollution to the soil. [Display omitted] • Life cycle assessment has been performed to compare the current practice of sewage sludge treatment with alternative of pyrolysis. • Midpoint impact assessments results have been combined with analysis of other factors such as contamination transfer risk to soil, carbon sequestration and legislative aspects. • Avoided mineral fertilizer production shows a significant contribution to the environmental benefit of treatment methods. • Results show that pyrolysis could be an environmental preferable treatment for sewage sludge. • Future research should focus on innovative solutions of sewage sludge treatment which satisfy environment and human health simultaneously. [ABSTRACT FROM AUTHOR]

The presence of heavy metals in water pose a serious threat to both public and environmental health. However, the advances in the application of low cost biochar based adsorbent synthesize from various feedstocks plays an effective role in the of removal heavy metals from water. This study implies the introduction of novel method of converting food waste (FW) to biochar through pyrolysis, examine its physiochemical characteristics, and investigate its adsorption potential for the removal of heavy metals from water. The results revealed that biochar yield decreased from 18.4 % to 14.31 % with increase in pyrolysis temperature from 350 to 550 °C. Likewise, increase in the pyrolysis temperature also resulted in the increase in the ash content from 39.87 % to 42.05 % thus transforming the biochar into alkaline nature (pH 10.17). The structural and chemical compositions of biochar produced at various temperatures (350, 450, and 550 °C) showed a wide range of mineralogical composition, and changes in the concentration of surface functional groups. Similarly, the adsorption potential showed that all the produced biochar effectively removed the selected heavy metals from wastewater. However a slightly high removal capacity was observed for biochar produced at 550 °C that was credited to the alkaline nature, negatively charged biochar active sites due to O-containing functional groups and swelling behavior. The results also showed that the maximum adsorption was recorded at pH 8 at adsorbent dose of 2.5 g L−1 with the contact time of 120 min. To express the adsorption equilibrium, the results were subjected to Langmuir and Freundlich isotherms and correlation coefficient implies that the adsorption process follows the Freundlich adsorption isotherm. The findings of this study suggest the suitability of the novel FW derived biochar as an effective and low cost adsorbent for the removal of heavy metals form wastewater. [Display omitted] • Biochar was successfully produced from food waste at various pyrolysis temperatures. • Temperatures significantly affect the physiochemical characteristics of biochar. • Biochar showed effective adsorption capacity towards the removal of heavy metals. • pH 8, 2.5 g L−1 adsorbent dose and 120 min contact time showed high adsorption. • Adsorption equilibrium fitted best with Freundlich adsorption isotherm model. [ABSTRACT FROM AUTHOR]

This study evaluates pyrolysis products obtained from biomasses (silver grass, pine, and acacia) harvested from heavy-metal-contaminated soil. To do so, we utilized two methods: a batch one-stage pyrolysis, and a continuous two-stage pyrolysis. The study results show that the yields and characteristics of bio-oils and biochars varied depending on the pyrolysis process and the type of biomass. The two-stage pyrolysis having two reactors (auger and fluidized bed reactors) appeared to be very suitable for specific chemicals production such as acetic acid, acetol, catechol, and levoglucosan. The biochar obtained from the fluidized-bed reactor of two-stage pyrolysis had high thermal stability, high crystallinity, high inorganic content, and a small number of functional groups. In contrast, the biochar obtained from the one-stage pyrolysis had low thermal stability, low crystallinity, a high carbon content, and a large number of functional groups. The biochar obtained from the two-stage pyrolysis appeared to be suitable as a material for catalyst support and as an adsorbent. The biochar obtained from one-stage pyrolysis appeared to be a suitable as a soil amendment, as an adsorbent, and as a precursor of activated carbon. All biochars showed a negative carbon footprint. In the end, this study, which was conducted using two different processes, was able to obtain the fact that products of pyrolysis biomass contaminated with heavy metals have different characteristics depending on the process characteristics and that their utilization plans are different accordingly. If the optimal utilization method proposed through this study is found, pyrolysis will be able to gain importance as an effective treatment method for biomass contaminated with heavy metals. [Display omitted] • Results of one-stage and two-stage pyrolysis of contaminated biomass were compared. • Two-stage pyrolysis turned out to be suitable for specific chemicals production. • Biochar from fluidized-bed reactor has potential as catalyst support and absorbent. • Biochar from fixed-bed reactor has potential as soil amendment and absorbent. • All biochars seemed to be applicable in construction field as sustainable materials. [ABSTRACT FROM AUTHOR]

Carbon dioxide methanation is a promising approach to convert captured CO 2 into green natural gas. Developing high performance biochar-supported nickel catalysts promotes a circular economy and the application of sustainable catalysts. Western red cedar biochar was produced via pyrolysis at 400, 500, and 600 °C and loaded with nickel via incipient wetness impregnation. Methanation was done at 400, 500, and 600 °C with the highest methane yield of 59% achieved at 500 °C with 10 wt.% Ni loading. This is comparable to a γ-Al 2 O 3 supported catalyst prepared and tested similarly, which achieved a methane yield of 53%. Biochar-supported catalysts showed deactivation whereby methane yield decreased from 59% to 51% over 5 h, likely due to coking and/or the sintering of nickel. Various space velocities were tested, and results demonstrated that with a space velocity of 37.5 mL/g.min methane selectivity was 89% after 1 h on stream compared to methane selectivity of 42%, which was achieved at a space velocity of 112.5 mL/g.min. This shows that a much higher rate of deactivation is observed at higher space velocities. Increasing the nickel loading from 5 wt.% to 10 wt.% increased methane yield from 40% to 58% after 1 h on stream. The higher loading also showed significantly less deactivation. Future work focusing on the extent and impact of metal-support interactions and metal dispersion on catalytic performance and deactivation during CO 2 methanation is recommended. [Display omitted] • Biochar catalysts perform comparably to alumina catalysts for CO 2 methanation. • 58% CH 4 yield was reached at 10 wt.% Ni loading and 500 °C methanation temperature. • Deactivation was observed over 5 h likely due to sintering and/or coking. • Pyrolysis temperature from 400 to 600 °C did not significantly affect performance. • Methanation performed at 500 °C balanced thermodynamic and kinetic limitations. [ABSTRACT FROM AUTHOR]

The perpetual market demand for polystyrene results in the gradual accumulation of polystyrene waste, placing a serious burden on the environment. This study proposed a promising method to upcycle polystyrene for styrene-derived monomers through catalytic fast pyrolysis. The metals-incorporated biochar catalysts were synthesized from heavy metals-contaminated manure waste for catalytic fast pyrolysis of polystyrene. The experimental results showed that the bimetallic biochar-derived catalyst containing Zn and Cr (Zn-Cr/C) was more conducive to the liquid production, with an extremely high yield of 88.22 wt%. Monometallic Pb-incorporated biochar catalyst (Pb/C) and bimetallic Zn-Cu co-doped on biochar (Zn-Cu/C) were more favorable for the production of pure styrene, with the mass yield of 61.26 wt% and 60.39 wt%, respectively. Additionally, the study elucidated a deep understanding of the reaction mechanisms involved in the catalytic fast pyrolysis of polystyrene. Simply put, this study introduced a new concept to convert heavy metal-contaminated animal manure into metal-incorporated biochar catalysts for catalytic conversion of polystyrene waste in pure styrene-based monomers. [Display omitted] • A new concept of upcycling polystyrene into pure monomers. • Mono-/bi-/tri-metallic Zn, Cu, Pb, Cr-containing biochar catalysts were prepared. • Bimetallic Zn-Cr/C favored the liquid production, with the high yield of 88.22 wt%. • Pb/C was more favorable for pure styrene production, reaching 61.26 wt%. • Trimetallic Zn-Cu-Pb/C had an obviously negative impact on the liquid production. [ABSTRACT FROM AUTHOR]

This review systematically examines the role of Computational Fluid Dynamics (CFD) in enhancing the understanding of microwave-assisted pyrolysis (MAP) for efficient biomass conversion into valuable chemicals. By critically analyzing recent advancements in CFD modeling, this paper highlights the significant contributions of CFD to optimize process parameters, improve reactor designs, and predict the yield and quality of bio-oil, biochar, and syngas. The synthesis of literature reveals key insights into the microwave energy absorption mechanisms, thermal and electromagnetic field distributions, and their impact on pyrolysis outcomes. The novelty of this review lies in its comprehensive aggregation of CFD-based studies, offering a holistic understanding of MAP processes, identifying gaps in current research, and proposing future directions for integrating CFD simulations with experimental studies to advance biomass conversion technologies. • Simulations and modeling: Understand and optimize microwave-assisted pyrolysis (MAP). • Optimization: Power, biomass type, reactor design influence MAP efficiency. • Addressing challenges: Limited simulation studies, need for further research. • Bio-oil, activated carbon, biofuels from waste biomass showcase MAP potential. • Future: Optimize conditions, explore feedstocks, integrate technologies, and scale-up. [ABSTRACT FROM AUTHOR]

To elucidate the impact of a modified reaction medium on the hydrothermal carbonization (HTC) coupled pyrolysis process, a two-stage conversion of rice straw (RS) was investigated in the present work. RS was initially treated hydrothermally in a conventional medium (water) and a modified reaction medium (metal chlorides and ammonium persulfate AP), followed by an upgrade of the obtained hydrochar via pyrolysis. The characteristics of the modified hydrochar and the pyrolysis biochar were examined. It was shown that a modified reaction medium promoted a higher mass yield of hydrochar. Compared to conventional hydrochar, modified hydrochar exhibited higher ash and fixed carbon content, and lower carbon and oxygen content. Furthermore, the pyrolysis behavior of modified hydrochar was more complex. Not only the DTG curve entirely different was, but the values of activation energy and pre-exponential factor also significantly increased. Ultimately, the modified medium enhanced the adsorption capacity of the HTC coupled pyrolysis biochar. Among them, B-HTC-AP had the highest S BET (544.83 m²/g) and the largest pore volume (0.4644 cm³/g). The TC adsorption capacity of B-HTC-AP reached 187.31 mg/g. The pseudo-second-order kinetic model and the Freundlich isotherm model provided a better description of the TC adsorption process on B-HTC-AP. Possible adsorption mechanisms of B-HTC-AP could encompass pore filling, electron transfer, hydrogen bonding, and π-π interactions. Therefore, the use of a modified reaction medium in the two-stage process could be an effective strategy for upgrading biomass. • Modified medium increased the yield of hydrochar. • HTC-MgAl exhibited the highest apparent activation energy. • Modified medium enriched the metals contents in hydrochar and biochar. • Modified medium enhanced the BET surface area of biochar. • Modified medium enhanced the adsorption capacity of biochar. [ABSTRACT FROM AUTHOR]

The development and utilization of biomass play a vital role in reducing fossil fuel dependency and mitigating greenhouse gas emissions. High-temperature pyrolysis provides a promising route for converting biomass into valuable products without tar formation. Kinetic models are essential for understanding biomass pyrolysis processes, aiding reactor design and optimization. In this study, rice husk (RH) and corn straw (CS) are selected, which exhibit significant differences in ash content but are widely present. Pyrolysis is performed using a thermogravimetric analyzer coupled with a mass spectrometer (TGA-MS). The results show a rapid decrease in solid residue oxygen content at elevated temperatures, which stabilized after reaching 900°C, accounting for about 8–10%. MS quantification indicates increased release of H 2 O and CO during this stage. Fourier transform infrared spectroscopy (FTIR) analysis on the biochar unveils that this phenomenon is attributed to the stretching vibration of C-O bonds and the conversion of -OH groups. The remaining oxygen primarily exists as carbonyl and carboxyl groups. Subsequently, the CRECK-S-B biomass pyrolysis kinetic model is updated, specifically targeting the transformation mechanism of oxygen-containing solids at high temperatures to improve the prediction of biochar yield and elemental composition. The relative error of oxygen content prediction is less than 10%. The accuracy of the model is validated through experimental data and an extensive literature database, leading to the establishment of a comprehensive database. The updated model demonstrates significantly enhanced prediction accuracy for pyrolysis temperatures above 800°C, expanding its applicability range. Moreover, it achieves an accuracy rate exceeding 80% for char yield and elemental content in the temperature range of 200–1000°C, including torrefaction conditions. It provides a theoretical foundation for the effective utilization of high-temperature biochar, offers a novel insight into biomass thermochemical conversion, and contributes to the sustainable development of biomass energy. • The distinct thermal behaviors at high temperatures are revealed. • The remaining oxygen exists as carbonyl and carboxyl groups in the solid residue. • The CRECK-S-B biomass pyrolysis kinetic model is updated. • A comprehensive database comprising pyrolysis experiments is established. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient co-valorization of waste cooking oil into biofuel and carbon nanotubes. • Natural biochar shows excellent deoxygenation performance and good stability. • Correlation between AAEM in biochar and selectivity of A&E and HCs in bio-oil. • Potential for obtained biofuel to serve as a precursor for jet fuel. • Feasibility and profitability of integrated production process demonstrated. Valorizing renewable precursors into high-quality biofuel and functional carbon nanomaterials can considerably improve the economic viability. Here, we propose a process for integrated production of high-quality biofuel and carbon nanotubes from waste cooking oil via catalytic pyrolysis coupling with chemical vapor deposition (CVD) technology. The natural biochar catalyst demonstrates excellent deoxygenation performance and good stability in catalytic pyrolysis process. The alkali/alkaline earth metal species (AAEMs) content in biochar catalysts has a strong correlation with the selectivity of esters and hydrocarbons in bio-oil. The biofuel obtained under optimal conditions exhibited potential as a precursor for jet fuel. The CVD process convert pyrolysis gas into carbon nanotubes with yield of 2.13%. The technical–economic analysis demonstrated the feasibility of the integrated process, projecting profitability and substantial total profit over a ten-year period. Overall, this study improves the economic viability of the waste cooking oil pyrolysis process and supports its wider commercial application. [ABSTRACT FROM AUTHOR]

Pyrolysis could be one of the promising ways for polyethylene terephthalate (PET) waste-based char production, while the adherence environmental persistent free radicals (EPFRs) brought the risks for the wide application. Co-pyrolysis was employed as the potential way to reduce the EPFRs and improve the char quality simultaneously with the introduction of sewage sludge (SS), and the optimization reaction conditions and the relative mechanisms were proposed in this work. EPFRs in PET-based char were found to decrease from 1.07 × 1018–4.84 × 1018 spins·g−1 to 2.17 × 1017–4.90 × 1017 spins·g−1, with 38.86–48.55% reduction at the mass ratio of 1:1 (PET:SS). The corresponding activation energy decreased by 78.83% with 30.93% higher biochar yield rate due to the synergistic effects. Co-pyrolysis facilitated the decomposition of benzoic acid and its derivatives by enhancing the cleavage of oxygen-containing functional groups and led to the binding of nitrogen with more pyrolysis intermediates, resulting in a reduction of precursors for oxygen/oxygenated-carbon centered radicals. More phenyl radicals were polymerized into carbon-centered radicals through hydride transfer and crosslinking in the mixed system. The additive of SS promoted the aromatization degree, enhanced the defect and pore structure of the biochar, and led to a 43.62-fold increase in the surface area of PET-based char at 400 °C. This work provides a potential approach to reduce EPFRs from the pyrolysis of plastic waste and to deal with multiple waste streams in venous industry park under the implementation of zero waste cities construction. [Display omitted] • Sludge additives contributed to 15.59–48.55% of EPFRs reduction for PET pyrolysis. • Co-pyrolysis reduced the EPFRs through the change of EPFRs types and precursors. • Co-pyrolysis increased the aromatization degree and defects in the carbon matrix. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrolysis coupled with in situ condensation method is developed. • Volatiles are cycled back to be fixed on biochar surface by re-polymerization. • Yield of biochar from pyro-condensation doubles that from pyrolysis. • Condensed volatiles are returned to biochar, enhancing biochar yield to > 60 %. • Pyro-condensation shows lower environmental impact than pyrolysis. Biochar is a carbonaceous material produced from pyrolysis of biomass in oxygen-deficient atmosphere, which is the feedstock for production of numerous functional carbon materials. Yield of biochar from biomass in the upstream determines cost in manufacturing downstream biochar-derived materials. In pyrolysis, dominance of cracking reactions removes not only oxygen, hydrogen but also carbon, diminishing biochar production. Therefore, retainment as many carbon-containing organics as possible in pyrolysis is the key for improving yield of biochar. In this study, pyrolysis coupled with in situ condensation (pyro-condensation) method is developed, in which the volatiles are cycled back to surface of biochar constantly. This leads to the re-polymerization of the volatiles after the cracking, which increases molecular sizes of the volatiles and eventually transforms them into part of the biochar, maximizing biochar production while minimizing bio-oil formation. The typical biochar yield reaches 60% for the pyro-condensation of poplar sawdust at 450 °C, doubled that from traditional pyrolysis. Additionally, universality of pyrolysis-condensation method for enhancing biochar yield was confirmed by the use of 25 different types of biomasses as research substrates. The biochar is highly aliphatic, rendering it versatile applications as a reductant, solid fuel, adsorbent for pollutants, or a soil conditioner with a high water retention rate. The configuration of the reactor for pyro-condensation is very simple, and the process shows lower environmental impacts than traditional pyrolysis. [ABSTRACT FROM AUTHOR]

• An integrated framework for optimizing waste valorisation methods is developed. • Three technologies are evaluated: pyrolysis, liquefaction and gasification. • The framework considers technical, economic and environmental factors. • The model supports stakeholders' decision-making on waste management strategies. Waste is the most abundant biomass worldwide for renewable energy and value-added products generation. While technologies for the treatment of multiple waste categories continue to evolve, frameworks that facilitate strategic decision-making within bio-economies are required. Therefore, the aim of this research is to develop a framework that can identify optimal processing route for converting different biomass wastes into valuable products. This study considers five different waste types available in Qatar, including date seed, camel manure, municipal solid waste (MSW), food waste, and sewage sludge. Whereas the investigated technologies include pyrolysis, gasification, and hydrothermal liquefaction (HTL). The three processes were simulated in Aspen Plus® and evaluated in terms of their technical, environmental, and economic performance for the different selected biomass feedstocks. A two-stage optimisation framework was then developed to identify the optimal processing technology for each biomass considering multiple products generation (i.e., syngas, biochar, and bio-oil). Investigating the waste to energy pathways, the presented model maximised net profit and energy generation while minimised the total associated emissions. The model indicated that gasification is the optimal processing technology to achieve higher economic return. While pyrolysis is recommended for the achievement of highest energy return. Nevertheless, HTL exhibited the best environmental performance with the lowest associated emissions. In addition, various wastes such as MSW and food waste are best processed by gasification to fulfil the environmental and economic criteria, while pyrolysis is more energy efficient in processing these wastes. Whereas HTL has been recommended only for high moisture containing biomass like manure and sludge, demonstrating relatively high energy efficiency, but lower economic return relative to gasification and pyrolysis. The presented optimisation framework may provide insights for decision-makers to optimally valorise waste considering national priorities. [ABSTRACT FROM AUTHOR]

Thermo-chemical behavior of a microalgal biomass; Dunaliella salina was investigated through thermo-gravimetric analyses. Fully-grown D. salina biomass were subjected for biochar conversion using pyrolytic treatment at three distinct heating rates such as 2.5, 5, and 15 °C min−1. The kinetic appraisals were explained by using model-free kinetics viz., Kissinger-Akahira-Sanose, Flynn-Waal-Ozawa and Starink iso-conversional correlations with concomitant evaluation of activation energies (E a). The Ea value is 194.2 kJ mol−1 at 90% conversion in FWO model, which is higher as compared to other two models. Moisture, volatile substances, and other biochemical components of the biomass were volatilized between 400 and 1000 K in two separate thermo-chemical breakdown regimes. Microscopic and surface characterization analyses were carried out to elucidate the elemental and morphological characteristics of the biomass and biochar. Further, the proficiency of the prepared biochar was tested for removing naphthalene from the watery media. The novelty of the present study lies in extending the applicability of biochar prepared from D. salina for the removal of a model polyaromatic hydrocarbon, naphthalene. [Display omitted] • Prepared microalgal biochar exhibited superior naphthalene sorption from aqueous media. • Utilized Freundlich isotherm and pseudo-second order kinetics to elucidate sorption. • D. salina -derived biochar's surface complexation facilitated naphthalene sorption. • Prepared biochar combines microalgal biomass valorization with pollution reduction. [ABSTRACT FROM AUTHOR]

Volatile-char interaction is almost unavoidable in pyrolysis, which is part of the process shaping composition of bio-oil/gases and properties of char. In this study, the influence of the char from sawdust/spinach/rice /spirulina /pig manure on pyrolysis of poplar sawdust was investigated at 500 °C, aiming to understand the impact of the char of same or varied origin on formation of volatiles/gases and change of the char catalysts themselves from the volatile-char interaction. The results suggested that the sawdust-, spinach- or rice-char catalyzed cracking of volatiles, reducing formation of heavy tar, decreasing production of bio-oil (28.6–35.5 % vs 49.4%) while enhancing gases generation (36.9–44.0 % vs 22.4%). The spirulina - and manure-char enhanced secondary condensation of volatiles, producing more heavy tar, more bio-oil, and additional oxygen-rich carbonaceous deposit with highly aliphatic nature. This reduced thermal stability, the C/O ratio of the char catalyst, and also led to coverage of char surface, especially for the manure-char catalyst. The in-situ IR techniques showed that manure-char catalyzed formation of abundant ketones and esters/lactones in intermediates, which further involved in polymerization. In comparison, the sawdust-char catalyst catalyzed cracking and aromatization of the volatiles of same origin, producing carbon- and hydrogen-rich carbonaceous solid, enhancing aromatic nature of the char catalyst, which was actually a real process for evolution of structure of biochar in pyrolysis of the sawdust. [Display omitted] • Sawdust-, spinach- and rice-char enhances cracking, producing more gases but less/lighter bio-oil. • Spirulina- and manure-char enhances polymerization, forming more bio-oil and heavy tar. • Volatiles-char interactions forms deposits over spinach-, spirulina- and especially manure-char. • The O-rich deposits are very aliphatic, reducing thermal stability of spent manure-char. • Volatiles-char interactions over sawdust-char of same origin forms deposit of highly aromatic nature. [ABSTRACT FROM AUTHOR]

Immobilizing organic pollutants by adsorption of biochar in farmland soil is a cost-effective remediation method for contaminated soil. As the adsorption capacity of biochar is limited, biodegradation of biochar-adsorbed organic pollutants was a potential way to regenerate biochars and maintain the adsorption performance of biochars to lower the cost. It could be affected by the biochar pyrolysis temperature, but was not evaluated yet. In this study, biodegradation of adsorbed phenanthrene on a series of biochars with pyrolysis temperatures from 150 to 700 °C by Sphingobium yanoikuyae B1 was investigated using batch experiments of biodegradation kinetics at 30 °C, to explore the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds. It was observed that 37.5–47.9% of adsorbed phenanthrene on moderate temperature-pyrolyzed biochars produced at 400 and 500 °C were biodegraded, less than that on high temperature-pyrolyzed biochars produced at ≥600 °C (48.8–60.8%) and low temperature-pyrolyzed biochars produced at ≤300 °C (63.4–92.5%). Phenanthrene adsorbed largely on the low temperature-pyrolyzed biochars by partition mechanism and thus is easily desorbed to water for a dominated intracellular biodegradation. On the high temperature-pyrolyzed biochars, phenanthrene is adsorbed largely by pore-filling mechanism and thus less desorbed to water for intracellular biodegradation. However, high temperature-pyrolyzed biochars can promote microbes to produce siderophore, H 2 O 2 and thus release extracellular •OH for a dominated degradation of adsorbed phenanthrene by Fenton-like reaction. With the increase of biochar pyrolysis temperature, desorption and consequently the intracellular biodegradation of adsorbed phenanthrene on biochars decreased, while the secretion of siderophore and H 2 O 2 by microbes on biochars increased to produce more extracellular •OH for degradation by Fenton-like reaction. The results could provide deep insights into the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds, and optimize the selection of biochar with higher adsorption performance and easier regeneration for soil remediation. [Display omitted] • 37.5–92.5% of phenanthrene on biochar was biodegraded by Sphingobium yanoikuyae B1. • Biodegradation of phenanthrene on biochar (400–500 °C) was the minimum (37.5–47.9%). • Phenanthrene on biochar (≤300 °C) was easily desorbed for intracellular degradation. • Biochar (≥600 °C) promoted microbe to produce extracellular siderophore, H 2 O 2 ,.•OH. • Phenanthrene on biochar (≥600 °C) was degraded by extracellular Fenton-like reaction. [ABSTRACT FROM AUTHOR]

A large amount of manure is generated from concentrated animal feeding operations (CAFOs), leading to serious environmental issues and hazardous risks from pathogens, such as methicillin-resistant Staphylococcus aureus. Therefore, developing an effective method for manure disposal is essential. Thus, in this study, we suggest the use of CO 2 in pyrolysis of hen manure (HM) as an effective method to convert the carbon in HM into syngas (especially carbon monoxide (CO)). HM was used and tested as the model compound. From the results of thermo-gravimetric analysis, the decarboxylation of CaCO 3 in HM in the presence of N 2 was realized at temperatures ranging from 638 to 754 °C. The Boudouard reaction was observed at ≥ 664 °C in the presence of CO 2. Despite the lack of occurrence of the Boudouard reaction, more CO formation was observed in the presence of CO 2 at ≥ 460 °C. This was deemed as a homogeneous reaction induced by CO 2. Considering the high Ca content of HM, HM biochar in N 2 and CO 2 were used as adsorbent for removal of Cadmium (Cd), which is toxic heavy metal. The adsorption capacities of HM_N 2 and HM_CO 2 were 302.4 and 95.7 mg g−1, respectively. The superior performance of HM_N 2 is mainly attributed to the presence of Ca(OH) 2 , which provides favorable (alkaline) conditions for precipitation and ion exchange. Our results indicate the environmental benefits from using CO 2. Specifically, CO 2 (representative greenhouse gas) converted into fuel. Given this, pyrolysis of HM in the presence of CO 2 was achieved at ≤ 640 °C, and the atmospheric condition should be switched from CO 2 to N 2 at ≥ 640 °C to ensure the decarboxylation of CaCO 3. [Display omitted] • Thermochemical conversion of hen manure (HM) was attempted using N 2 and CO 2. • The formation of CO under CO 2 conditions was enhanced compared to that of N 2. • Because HM biochar contained high Ca, the biochar was used to adsorb cadmium. • Pyrolysis of HM in CO 2 is preferable at ≤ 660 °C and should be switched from CO 2 to N 2 at ≥ 660 °C. [ABSTRACT FROM AUTHOR]

Solar energy and biomass produce energy, which is sustainable and does not harm our environment. This characteristic of the two-energy feedstock is harnessed using the pyrolysis method to produce liquid and gaseous fuel that is transportable while bio-char regarded as a by-product has found usefulness in soil amendments. Solar-biomass pyrolysis technology combines these two low-density energy feedstock to produce high energy density fuel. The effectiveness of this process depends not only on the feedstock or reaction dynamics but also on the solar-thermal systems and reactor configuration. This review addressed the benefits of solar-biomass pyrolysis, available optical concentrating device, conceptual heating modes, the existing configuration of solar-thermal and reactor orientations, and some basic model equations applied in solar biomass pyrolysis. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are critical environmental concerns due to their intrinsic toxic aromatic nature and concomitant circumstances that potentially harm the ecological and human health. In this study, converting mahogany (Swietenia macrophylla King) pericarps to value-added biochar by pyrolysis for evaluating the potential formation/destruction of biochar-bound PAHs was studied for the first time. This study designed and optimized the thermal processing conditions at 300–900 °C in the CO 2 or N 2 atmosphere, and heteroatoms (N, O, B, NB, and NS) were modified for mahogany pericarps biochar (MPBC) production. The MPBC500 exhibited significantly higher pyrolysis products of PAHs (2780 ± 38 ng g−1) than that of MPBC900 (78 ± 6 ng g−1) under N 2 without introducing modified elements. Specifically, the inhibition capacity of MPBC500 for PAHs under CO 2 was improved most efficiently by the active nitrogen species of the pyridinic N and pyrrolic N groups. The pyrolysis conditions and heteroatom modification of MPBC altered its physicochemical properties, that is, aromaticity and hydrophobicity, affecting the PAH concentration and composition in the pyrolysis products. This study reveals sustainable approaches to reduce the environmental footprint of biochar by focusing on increases in PAHs pollution in sustainable biochar produced from a low-carbon bioeconomy perspective. [Display omitted] • Biochar produced at 500 °C in the presence of CO 2 led to high polycyclic aromatic hydrocarbons yield. • Naphthalene was the dominant biochar-bound polycyclic aromatic hydrocarbon. • Pyrolysis in N 2 reduced the level of polycyclic aromatic hydrocarbons in unmodified biochar at 900 °C. • Doping with N effectively suppressed polycyclic aromatic hydrocarbons formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • P recovery from SS char in amended process was 48 % higher than control process. • SS amendment led to AP to NAIP conversion which enhanced P recovery from char. • Higher P recovery from chars prepared at 400 °C than at 600 °C and 900 °C. • Excess Al inhibited the formation of less soluble P species in amended process. • Immobilization of P in the carbon matrix of char prepared at ≥ 600 °C. Phosphorus (P) recovery from sewage sludge (SS) (or its ash/char) is challenging due to the presence of heavy metals (HMs) in SS. This study proposed the integration of SS, alum sludge (AS), sequential wet extraction, and pyrolysis for P recovery without simultaneous HM extraction. SS + AS mixture (P:Al molar ratio = 3:1) was first acid pretreated to obtain amended SS, then pyrolyzed, and finally, P was extracted from the char using an alkali. Pyrolysis was conducted at low (400 °C), medium (600 °C), and high (900 °C) temperatures. The highest alkaline P recovery efficiency was 88 % from the amended SS char, while 32 % from the unamended SS char (both prepared at 400 °C). Overall, the highest P recovery in the amended process was 48 % higher than the unamended process despite 11 % P loss during acidic pretreatment. Standards measurements and testing (SMT) protocol and solid-state NMR (31P and 27Al) analyses revealed that acidic pretreatment of SS with AS induced apatite phosphate (AP) to non-apatite inorganic phosphate (NAIP) conversion in SS. As NAIP is more soluble in alkali than AP and HMs, higher alkaline P recovery was achieved for amended SS char than unamended SS char, without HM contamination. However, higher pyrolytic temperatures impaired P recovery due to the immobilization of P in the char carbon matrix and the formation of recalcitrant P phases. These findings were corroborated by complementary characterization techniques such as XPS, XRD, and FTIR. Some major HMs in SS and AS were concentrated in char, except Zn, which partially volatilized above 600 °C. This study demonstrated the applicability of AS for extracting P from SS, offering a potential pathway for the synergistic management of sludge waste streams. [ABSTRACT FROM AUTHOR]

Following the Paris Agreement's climate targets and the modelling community's scenarios of how to reach them, carbon dioxide removal is gaining increasing importance in national climate policies. This is also the case in Denmark – considered by itself and others a climate frontrunner – where biochar is envisioned to cover 10% of the 2030 reduction goal. However, apart from research experiments and test sites, biochar is at the time of research not employed in Denmark, raising the question how it came to constitute a large part of the national goal. This paper explores how biochar, as a method for carbon removal, comes into being as a relevant solution in Danish climate policy, and what this means for emission reduction efforts. Through document analysis, participatory observation, field visits and semi-structured interviews, I employ the framework of the dramaturgical regime and analyse how biochar is enacted as a climate solution through policy documents, conferences, media and network meetings. Here the concept of enactment indicates that different people's actions are not overtly coordinated, and the effects of such actions are not necessarily fully intentional, but they are nevertheless political. I argue that through different scientific, administrative, political, and media practices, biochar is enacted as a viable climate solution that enables the continuation of current forms of production and consumption. As biochar likely substitutes for emission reductions and is in risk of failing to deliver the anticipated amount of carbon removals, the enactment of biochar as a climate solution in Danish climate policy possibly constitutes a case of mitigation deterrence. • Biochar is enacted as a relevant solution in Danish climate policy. • This occurs in policy documents, conferences, media and network meetings. • Enactments enable a continuation of current forms of production and consumption. • Including biochar in Danish climate policy is possibly a case of mitigation deterrence. • Enactments can show how mitigation deterrence can come about as an emergent effect. [ABSTRACT FROM AUTHOR]

Wood boards used in construction are generally treated with toxic chemicals, making them unsuitable for further use and causing environmental pollution. This study evaluates the possibility of using catalytic torrefaction as a pretreatment to improve wood pyrolysis and combustion for greener biochar production. Waste beech boards were impregnated with different K 2 CO 3 solutions (0–0.012 M), then torrefied between 5 and 60 min at 275 °C. The ICP-AES showed that the board's surface held more potassium than the core. Torrefaction coupled with potassium decreased the C–O and –OH stretches. Thermogravimetric analysis of torrefied wood showed that the board's internal heating degraded the core more than the surface. The exothermic reactions made potassium's catalytic action more efficient in the core. Interactions between the potassium content and torrefaction duration decreased the pyrolysis' maximum devolatilization temperature. During combustion, potassium decreased the ignition temperature by up to 9% and 3% at the surface and core, respectively, while the torrefaction increased it. The catalytic torrefaction significantly decreased the devolatilization peak during combustion, thus making the wood's combustion similar to that of coal, having only the char oxidation step. These findings highlight the advantages and challenges of waste wood's catalytic-torrefaction for biochar production to reduce environmental pollution. [Display omitted] • Catalytic torrefaction produces biochar with environmental remediation potential. • Wood board's torrefaction is heterogeneous between the surface and core. • Potassium increases the exothermic reactions at the core during torrefaction. • Interactions between potassium content and torrefaction duration are significant. [ABSTRACT FROM AUTHOR]

Waste biochar from biomass power generation and sintering dust from ferrous metallurgy were skillfully used to produce direct reduced iron (DRI) and syngas via a synergetic conversion in this study. The thermodynamic analysis of their related reactions, biochar conversion and reduction behavior of sintering dust were investigated. The biochar gasification and reduction of sintering dust were coupled and promoted by each other at 1000 °C for 60 min with 1.2 mol (C/Fe). For biochar conversion, adding sintering dust deepened the pyrolysis of the volatiles in the waste biochar to generate more CH 4 , and it provided more oxygen atoms, gasifying carbon atoms in the fixed carbon to generate more CO. The CO and CH 4 yield from biochar conversion with iron oxides of sintering dust increased by 633.8% and 41.5% to its pyrolysis alone. For the reduction of sintering dust, the whole conversion process of sintering dust was the generation, aggregation and growth of the iron grains, including the generation of metallic iron grains, forming curved bars and composite flocculent metallic iron, and its larger lumps particles finally. A DRI with a 92.4% metallization ratio, meeting the requirements of the subsequent electric arc furnaces, was obtained at 1000 °C for 60 min with 1.2 mol (C/Fe). This study achieves an efficient and reciprocal conversion of these two solid waste resources. It offers an essential research reference for fuel gasification and DRI processes. [ABSTRACT FROM AUTHOR]

In this study, oxidative torrefaction (OT) was used as the pretreatment process for the pyrolysis of Clitocybe maxima stipe (CMS) which is one kind of typical mushroom wastes, in order to evaluate the influence of OT on pyrolysis behaviour of torrefied CMS and products' properties. The experimental results demonstrated that OT enhanced the degree of aromatization, and improved the thermal stability of the torrefied CMS compared with inert torrefaction (IT). The biochar (T9-P 700) obtained by OT (9% oxygen) coupled pyrolysis (700 °C) had the improved pore structure with the highest specific surface area of 661.61 m2/g, while the obtained liquid products were less acidic with an increased formation of N-containing compounds (up to 19.15%) and phenolic compounds (8.08%). Furthermore, T9-P 700 had a higher adsorption efficiency and adsorption capacity (147.31 mg/g) for Pb(Ⅱ). C-O, C O, -COOH, and -OH on the obtained biochar participated in the adsorption process of Pb(Ⅱ), attributing to the adsorption mechanism interpreted as physical adsorption, precipitation, and functional group complexation. Higher oxygen concentrations increased the severity of torrefaction, which facilitated a better pore structure in the CMS biochar generated during the subsequent pyrolysis process and the generation of liquid products with better qualities. Therefore, OT coupled pyrolysis may be an effective way to improve the quality of pyrolysis products. [Display omitted] • OT modified elemental and compositional properties more effectively. • OT increased the E α and thermal stability of torrfied CMS pyrolysis. • OT coupled pyrolysis biochar had better pore structure and higher S BET. • Liquid products obtained from OT coupled pyrolysis had lower acidity. • OT improved the adsorption performance of CMS biochar for Pb(Ⅱ). [ABSTRACT FROM AUTHOR]

[Display omitted] • Pine needle biochars were prepared at different temperatures for PMS activation. • With temperature increasing, the degradation rates increase then slightly decrease. • BC-300 has more oxygenic groups/PFRs, BC-700 has higher porosity/graphitization. • 1O 2 plays important role in both BC/PMS systems. • Electron transfer is the key factor of the superior degradation rate of BC-700. In order to gain insights into the critical impact of pyrolysis temperatures, a series of pine needle biochars were prepared by one-step pyrolysis method at different temperatures, and were applied for peroxymonosulfate activation to degrade enrofloxacin. Interestingly, with the increase of temperature, the degradation efficiencies increase first, then slightly decrease. BC-700 (biochar synthesized at 700 °C) exhibited best performance, and the degradation rate could reach 97.7 % within 180 min under the optimized conditions. Characterization results demonstrated biochar synthesized at relatively low temperature exhibited more oxygen-containing functional groups and persistent free radicals, while biochar synthesized at high temperature contained more pore structure and higher graphitization degree. Mechanism studies demonstrated that biochar synthesized at relatively low temperature tend to generate transient radicals, while biochar synthesized at high temperature exhibited better electron transfer capability, which might be the key factor of the superior degradation rate of BC-700. In addition, singlet oxygen played an important role in both systems. [ABSTRACT FROM AUTHOR]

Soils in which fresh produce is grown can become contaminated with foodborne pathogens and are sometimes then abandoned or removed from production. The application of biochar has been proposed as a method of bioremediating such pathogen-contaminated soils. The objectives of the present study were to evaluate three fast-pyrolysis-generated biochars (FPBC; pyrolyzed in house at 450, 500, and 6008C in a newly designed pyrolysis reactor) and 10 United Kingdom Biochar Research Center (UKBRC) standard slow-pyrolysis biochars to determine their effects on the viability of four surrogate strains of Escherichia coli O157:H7 in soil. A previously validated biocidal FPBC that was aged for 2 years was also tested with E. coli to determine changes in antibacterial efficacy over time. Although neither the UKBRC slow-pyrolysis biochars or the 450 and 5008C FPBC from the new reactor were antimicrobial, the 6008C biochar was biocidal (P, 0.05); E. coli populations were significantly reduced at 3 and 3.5% biochar concentrations (reductions of 5.34 and 5.84 log CFU/g, respectively) compared with 0.0 to 2.0% biochar concentrations. The aged 5008C FPBC from the older reactor, which was previously validated as antimicrobial, lost efficacy after aging for 2 years. These results indicate that the biocidal activity of FPBC varies based on production temperature and/or age. [ABSTRACT FROM AUTHOR]

Biochar is a carbon-rich solid formed from the organic residue by pyrolysis. The productivity of biochar relies on feedstock type and pyrolysis conditions. Studies on biochar were discussed relating its application and production as a source of soil remediation and bioeconomy. Pyrolysis conditions, gasification, hydrothermal carbonization were discussed in this study in obtaining biochar for remediation of soil. Biochar have made substantial breakthroughs in reducing greenhouse gas emissions and global warming, reducing soil nutrient leaching losses, sequester atmospheric carbon into the soil, increasing agricultural productivity, reducing bioavailability of environmental contaminants and subsequently, becoming a value-added product sustaining bioeconomy. Bio-economy implies the exploration and exploitation of bio-resources, which involves the use of biotechnology to create new bio-products of economic value. Biochar is a marketable bio-product, which can be used in agriculture, industries and energy sector. Thus, biochar production can enhance soil property and provide opportunities for additional income. This review presents the production, agronomic and economic benefits of biochar. [ABSTRACT FROM AUTHOR]

• BC700 can efficiently activate persulfate for clofibric acid (CA) degradation. • C–OH and π-π* transitions in aromatic rings are accounted for radical generation. • Surface-bound reactive radicals are mainly responsible for CA oxidation. • The catalytic activity of reused BC700 was largely recovered by thermal treatment. Wood-based biochars were fabricated at different pyrolysis temperatures of 400–700 °C and used to activate peroxydisulfate (PDS) for the degradation of clofibric acid (CA). Biochar pyrolyzed at 700 °C (BC700) showed more excellent catalytic performance toward CA removal (97.8% in a 60 min reaction) than other BCs. The BC700/PDS process performed efficiently at initial pH range of 4.0–9.0. The effects of PDS concentration and BC700 dosage on CA removal were also examined. Radical quenching experiments and electron paramagnetic resonance (EPR) spectra were applied to identify the reactive radicals generated in the BC700/PDS system. The role of persistent free radicals (PFRs), oxygen functional groups and π-π* transitions in aromatic rings of BC700 for the PDS activation was explored. The reaction intermediates of CA were identified by liquid chromatography–mass spectrometry (LC–MS) and the corresponding degradation pathway was proposed. This study contributes to the development of green materials for sustainable remediation of organic contaminants in water and provides support for further studies. [ABSTRACT FROM AUTHOR]

Sustainable management of contaminated biomass derived from phytoremediation of metal(loid) polluted soil and water is of great importance to avoid environmental risks from secondary pollution of the contaminants. In this regard, pyrolysis technology may reduce the environmental risk of the contaminants and produce different bio-products from contaminated biomass. In this work, slow pyrolysis of Avicennia marina biomass was conducted to compare the pyrolysis properties of heavy-metal-contaminated and uncontaminated biomass and its potential to generate pyrolytic products, such as biochar, bio-oil and pyrolytic gas at a varying temperature range from 300 to 800 °C. The results indicated that the properties of biomass and derivatives were affected significantly by both pyrolysis temperature and the presence of heavy metal(loid)s. The heavy metal(loid)s in biomass contributed to higher biochar and pyrolytic gas yields at the expense of bio-oil. Increasing pyrolysis temperature induced the volatilisation of heavy metal(loid)s in biochar samples. At the same pyrolysis temperature, the contaminants significantly increased the ash content whilst decreased the fixed carbon content in biochars (p < 0.05). Furthermore, it was noticed that the quality of bio-oils was improved by the presence of metal(loid)s, as the pyrolysis of contaminated biomass produced 8–11% hydrocarbons in the bio-oil samples with less oxygenated compounds as compared to uncontaminated biomass that produced only 4–5.8% hydrocarbons in the bio-oil. Moreover, biomass abound with trace metal(loid)s produced more H 2 and CO 2 during pyrolysis compared to uncontaminated biomass. Overall, this study demonstrated that pyrolysis is an efficient way for converting heavy metal contaminated biomass obtained from phytoremediation into valuable products, contributing to the sustainability of phytoremediation. Image 1062189 • Contaminated and uncontaminated biomass and pyrolytic products were studied. • Temperature and contaminants affected biomass and pyrolysis products properties. • The biochar yield was significantly increased with presence of heavy metal(loid)s. • Heavy metal(loid)s were enriched in biochars by pyrolysis at lower temperatures. • Hydrocarbons in bio-oils increased greatly with presence of heavy metal(loid)s. [ABSTRACT FROM AUTHOR]

• Fast pyrolysis of mannan-rich ivory nut was performed at 350 °C and 500 °C. • Pyrolysis liquids (yield 58–60 wt%) were rich in levomannosan and 5-hydroxymethyl furfural. • Biochar and non-condensible gases (NCGs) were characterized. • Biochar holds potential for e.g. soil applications, NCGs hold potential for e.g. syngas processes. Ivory nut residues from the palm Phytelephas aequatorialis were converted via fast pyrolysis into a set of valuable biorefinery products, being (i) pyrolysis liquids rich in levomannosan and 5-hydroxymethyl furfural (5-HMF), (ii) biochar, with potential for soil applications, (iii) and non-condensable gases with potential for upgrading and syngas processes. The ivory nut residues were mannan-rich leftovers from button manufacturing in Ecuador. A handful of studies, dating back from the 20th century, have investigated gram-scale valorization of ivory nut to e.g. mannose. Nevertheless, advances in science and technology on biorefinery products called for a comprehensive reassessment of the valorization potential of this underutilized feedstock. A fully equipped, continuously operated lab-scale reactor (200 g.h−1 feed) was used for pyrolysis at 350 °C and 500 °C. The pyrolysis liquid yield was 57.53 wt% at 350 °C and 60.36 wt% at 500 °C. The aqueous phase obtained at 350 °C contained 17.5 wt% (d.b.) anhydrosugars, of which 90% was levomannosan, and contained 11.6 wt% (d.b.) furans, of which 56% was 5-HMF and 17% furfural. The carbon stability of the biochars, measured with the Edinburgh accelerated ageing tool, were 40.6% and 64.6%, respectively. Non-condensable gases during pyrolysis at 350 °C only were composed of CO 2 and CO (CO 2 :CO molar ratio of 4:1), while at 500 °C, gases were obtained with a CO 2 :CO:H 2 :CH 4 molar ratio of 9:9:4:1. Overall, the results demonstrate that pyrolysis of ivory nut holds potential as starting point for valuable biorefinery products. [ABSTRACT FROM AUTHOR]

• Stability of biochars produced at low-medium vacuum was investigated. • Both temperature and vacuum were the most influential factors affecting stability. • Low and medium-vacuum pyrolysis had an overriding effect on biochar characteristics. • Biochar produced under low and medium-vacuum pyrolysis were preferable to biochar stability. Vacuum carbonization is considered to be an effective and promising thermochemical-tool for resource and energy recovery by collecting and reusing pyrolysis products and volatiles. In this study, thermochemical conversion of orange peel to biochar under low- and medium-vacuum pyrolysis conditions were investigated for product distribution and stability characteristics of biochar. The pyrolysis experiments were executed under three different conditions i.e., N 2 atmosphere (without vacuum), low-vacuum (1013.2 Pa) and medium-vacuum (101.3 Pa) in the temperature range of 300–700 °C. The derived biochars were characterized for its aromaticity, polarity, elemental composition, pH, electrical conductivity, surface area, thermal decomposition, FTIR spectroscopy and chemical oxidation properties. Results revealed that low and medium-vacuum pyrolysis had an overriding effect on the H/C (aromaticity) and O/C (polarity) ratios, surface functional groups, as well as on the chemical oxidation potential of derived biochars. A significant reduction in biochar yield (1.1–1.9 folds), increased aromaticity with low H/C (1.3–2.0 folds) and O/C (1.95–4.75 folds) values was observed with increased pyrolysis temperature, under low- and medium-vacuum pyrolysis compared to the N 2 atmosphere. It was also found that biochar produced in the temperature range of 300–700 °C, under low and medium-vacuum pyrolysis were comparatively preferable to biochar stability. It is concluded that biochar produced at low-medium vacuum pyrolysis conditions shows higher carbon sequestration potential compared to the N 2 atmosphere. [ABSTRACT FROM AUTHOR]