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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]

Enormous annual sewage sludge (SS) volumes pose global environmental challenges owing to contamination and significant greenhouse gas emissions. Here, we investigated the economic viability of co-pyrolyzing SS and biomass waste to produce biofuels (bio-oil and gas) and biochar. Net present worth (NPW) analysis, the sale product break-even price, and sludge handling price (SHP) were used to determine the profitability of co-pyrolysis compared with SS pyrolysis alone and conventional treatment methods. In this study, the sale prices of biochar based on quality (i.e., stability, carbon sequestration effectiveness, and heavy metal content) were estimated to be 2.24, 1.44, and 0.98 CAD/kg for high-, medium-, and low-grade biochar. The bio-oil prices, estimated based on the higher heating values of bio-oil and diesel, ranged from 0.80 to 1.22 CAD/kg. Sawdust (SD) and wheat straw (WS) were the chosen co-pyrolysis feedstocks, with four mixing ratios (20, 40, 60, and 80 wt%). Economically, SD (40 wt% mixing ratio) co-pyrolysis achieved the best performance, with a maximum NPW of 8.71 million CAD. SD single and co-pyrolysis were the only profitable scenarios. Moreover, SS single pyrolysis and WS co-pyrolysis exhibited higher profitability than conventional SS treatment methods, with SHPs of 65 and 40 CAD/1000 kg dry sludge, respectively. Sensitivity analysis highlighted the dependence of economic performance on biochar and bio-oil market value. This study offers the first economic analysis of this approach and enhances our understanding of the potential of co-pyrolysis for biofuel and biochar production, providing innovative solutions for the environmental challenges of SS disposal. [Display omitted] • Cost, operating expenses, and energy recovery of a pyrolysis plant were evaluated. • Co-pyrolyzing SS with sawdust SS showed the highest NPW of 8.71 million CAD. • All single and co-pyrolysis cases showed higher revenue than SS disposal methods. • Economic feasibility was dependent on bio-oil and biochar quality and sales price. [ABSTRACT FROM AUTHOR]

Involving biomass in the energy sector is a way to replace fossil fuels with renewable and CO 2 -neutral raw materials, reducing the negative impact on the environment. The energy application of agro-industrial waste is of particular interest, allowing one not only to obtain biofuel, but also to utilize by-products. The present work considers pine nut shells from a candy factory in relation to microwave processing into solid and gaseous fuels. The aim is to study the features of pine nut shells microwave pyrolysis, including the initiation mechanism and process behaviour, as well as the composition and characteristics of the resulting products. The study included experimentation in combination with application of high-speed video recording of the process and gas analysis, study of dielectric characteristics of raw materials, proximate and ultimate analysis of the obtained solid and gaseous products. At microwave pyrolysis, the conversion degree into liquid and gaseous products (76.9%) is much higher than, for example, at slow fixed bed pyrolysis (65.5%). The radiation absorption by the sample is nonlinear throughout the process and increases during the organic part degradation with the appearance of liquid and gaseous products. The gas obtained at microwave processing has a low ballast (share of CO 2 =3.5%) and a high hydrogen content (share of H 2 =19.3%) that results in a high heat of combustion (21.8 MJ·m−3), which is probably connected with interaction of pyrogenetic water and fuel carbon during plasma-chemical reactions. • Microwave pyrolysis of pine nut shells is caused by electric discharges. • Microwave radiation absorption by pine nut by shells is nonlinear over process time. • Microwave radiation absorption grows with increasing the yield of volatile products. • Interaction of pyrogenetic water and carbonaceous residue leads to high H 2 content. • Pyrolysis gas has a high heat of combustion (21.8 MJ·m–3) and low CO 2 content (< 3.5%). [ABSTRACT FROM AUTHOR]

This overview addresses the formation of solid trash and the various forms of waste from a variety of industries, which environmentalists have embraced. The paper investigates the negative effects on the environment caused by unsustainable management of municipal solid trash as well as the opportunities presented by the formal system. This examination looks at the origins of solid waste as well as the typical treatment methods. Pyrolysis methods, feedstock pyrolysis, and lignocellulosic biomass pyrolysis were highlighted. Explain in detail the various thermochemical processes that take place during the pyrolysis of biomass. Due to its carbon content, low cost, accessibility, ubiquitousness, renewable nature, and environmental friendliness, biomass waste is a unique biochar precursor. This study looks at the different types of biomass waste that are available for treating wastewater. This study discussed a wide variety of reactors. Adsorption is the standard method that is used the most frequently to remove hazardous organic, dye, and inorganic pollutants from wastewater. These pollutants cause damage to the environment and water supplies, thus it is important to remove them. Adsorption is both simple and inexpensive to utilize. Temperature-dependent conversions explain the kinetic theories of biomaterial biochemical degradation. This article presents a review that explains how pyrolytic breakdown char materials can be used to reduce pollution and improve environmental management. [Display omitted] • Sources, synthesis and modification techniques of biochar are discussed. • Conversion of biomass into energy is more effective after being torrefied. • Appraisals on the activation energies during biochar preparation are made. • Torrefied biomass has environmental applications which are critically surveyed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Three types of biochar can efficiently activate hydrogen peroxide. • Biochar/H 2 O 2 systems exhibited high tetracycline degradation efficiency. • Catalytic property of biochar depends on the amounts of PFRs. • Biomass types and its compositions were crucial for the formation of PFRs. • Electron transfer pathways could be the catalytic mechanisms of biochar. Abstract Biochar, a green material that possesses high catalytic potential due to its persistent free radicals (PFRs), has attracted increasing attention in the removal of refractory pollutants from water. The influences of biomass types (bamboo, corn stalk, and pig manure) and its compositions (metals and phenolic compounds) on the formation of PFRs in biochar were investigated by electron paramagnetic resonance (EPR). It was found that the amounts of PFRs in biochar would decrease sharply with the decrease of the initial metals and phenolic compounds existed in biomass, and the effect of metals contents on PFRs formation was much greater than that of phenolic compounds contents. This finding was supported by the results obtained from elemental analysis and molar H/C analysis of three types of biochar, which suggested that pig-manure biochar (PM500) had the highest concentrations of PFRs of 14.13 × 1018 spins·g−1 due to the high content of metals and phenolic compounds in pig manure. The EPR trapping experiment and Linear sweep voltammetry (LSV) measurements in biochar/H 2 O 2 systems showed that OH was the dominant reactive radical and electrons transfer pathways might be responsible for the activation of H 2 O 2 by biochar. Possible degradation pathways of the tetracycline in biochar/H 2 O 2 systems were also proposed. Besides, high degradation efficiency and good stability were observed in real wastewater application of the PM500/H 2 O 2 system. These findings would provide a clearer insight into the formation mechanisms of PFRs in biochar, and also present a better strategy for biochar preparation and application in Fenton-like system. [ABSTRACT FROM AUTHOR]

Highlights • Biomass origin and structure affect composition and yield of pyrolysis biochar. • Operating conditions of thermal treatment affect composition and yield of pyrolysis biochar. • Further pyrolysis reactions modify young biochar structure and release gas products. • A predictive kinetic mechanism of biomass pyrolysis accounts for all these effects. • Large collection of literature experimental data supports the validation of the kinetic mechanism. Abstract Biomass is increasingly being recognized as a promising carrier for both heat, energy and chemicals production. However, several aspects still require intense research activity towards a better design and optimization of industrial combustors, gasifiers and pyrolyzer. The objective of this work is to update the CRECK kinetic mechanism of biomass pyrolysis, allowing a better prediction of both yield and composition of the solid residue (biochar). Moreover, further model modifications allow to better describe the variability of hemicellulose in different biomass. To this end, a large set of literature experimental data is collected and organized into a database, which is used to further tune and validate the proposed kinetic mechanism. Although the kinetic model maintains the previous agreement in respect of the rate of biomass pyrolysis, formation and distribution of gas and tar products, the novelty of this work is the greater attention to the predictions of biochar yield and composition, in a wide range of operative conditions. The model describes the solid residue as a mixture of pure carbon together with lumped metaplastic compounds, which represent the whole range of oxygenated and hydrogenated groups bonded to the carbonaceous matrix. These metaplastic species are released to the gas phase with their own kinetics and describe the change of both mass loss and elemental composition of the biochar. These comprehensive predictions of biochar composition are crucial for an accurate description of the successive oxidation and gasification processes. [ABSTRACT FROM AUTHOR]

• Co-pyrolysis is an eco-friendly sewage sludge treatment process. • Mixing co-feed biomass with sewage sludge reduced the environmental burden. • All examined scenarios reduced the global warming potential. • All scenarios achieved positive energy balance with product energy recovery. • Transportation distance significantly affects scenarios' environmental outcome. To address the gaps in current research on sewage sludge (SS) pyrolysis, this study examined the feasibility of the environmental and energy demands of co-pyrolysis as an SS treatment process. The analyses included a cradle-to-gate life cycle assessment, carbon emission and credit assessment, energy recovery calculations, and sensitivity analysis. Sawdust (SD) and wheat straw (WS) were chosen as co-feeds for the co-pyrolysis scenarios; four mixing ratios (20, 40, 60, and 80 wt%) were examined for each co-feed. The functional unit was 1000 kg of bio-oil. Mixing the co-feed biomass with SS reduced the overall environmental burden by 58–83 %; WS/SS co-pyrolysis performed better than SD/SS in this respect. All examined scenarios reduced the global warming potential (GWP) and achieved a net positive energy balance; SD/SS co-pyrolysis was more desirable owing to high energy recovery. The additional gas turbine operation generated a process energy demand of 23–224 %. GWP and terrestrial ecotoxicity potential are indicators that are significantly affected by co-feed material transportation. Sensitivity analysis revealed that the transportation of feedstock and pyrolysis products should be prioritised to limit the environmental burden of the process. Co-pyrolysis is an eco-friendly SS treatment method, and its economic viability should be further investigated. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonisation was used to upgrade fuels from two types of agro-industrial wastes: olive tree trimmings and olive pulp. Hydrochar yield, elemental and proximate analyses, thermal stability, higher heating value (HHV), and energy yield at different reaction temperatures (120, 150, 180, 200, 220, 235 and 250 °C) and solid load (biomass to water ratios − B/W − equal to 7, 10, 15 and 25%) were assessed for a fixed reaction time of 30 min. HHV varied linearly with hydrochar mass yield and reaction temperature in the temperature range 180–250 °C. Solid load proved to be a crucial parameter in determining the energy properties of hydrochars. The higher B/W, the higher were the degree of carbonisation (in terms of fixed and total carbon), the hydrochar HHV, and the hydrochar yield. Elemental analysis showed that during HTC, olive pulp samples underwent a greater degree of carbonisation when compared to the corresponding olive tree trimmings residues. High solid load and high reaction temperature promoted secondary char formation. Secondary char showed a sphere-like structure formed by overlapping layers. EDS microanalysis showed that secondary char is characterised by a significantly higher carbon content than parent primary char, thus confirming its contribution towards enhancing the HHV of hydrochars. [ABSTRACT FROM AUTHOR]

Energy recovery via waste utilization in gasification process is an attractive alternative energy source which is expected to supersede part of the energy from fossil fuels. To enhance the H 2 -rich syngas production from residual biomass mixed with polymeric waste, a dual stage process involving catalytic steam gasification and tar cracking was integrated as a promising alternative technology for clean fuel production. Generally, the presence of tar causes syngas degradation and has been identified as one of the major impurities from the gasification process. This study shows the results obtained from an integrated process with optimization process conditions to enhance H 2 -rich syngas yield. Nickel and dolomite were used as cheap and effective catalysts in fluidized and fixed bed gasifiers respectively, which resulted in high-quality syngas production with a maximum hydrogen yield of 284.1 g H2 kg −1 feedstock and carbon conversion efficiency (CCE) of 92.4 wt%. Furthermore, the study eventuates the upgrading of the bio-char to carbon nano-tubes (CNT). In fact CNT could be further employed either in gasification process or as electrocatalyst supporting materials for low-temperature fuel cells. [ABSTRACT FROM AUTHOR]

It is a thorny issue to properly handle heavy metals-contaminated livestock manure. The transformation of the heavy-metals-contaminated livestock manure into valuable carbonaceous material has motivated our curiosity. Herein, this study provided a new concept of valorizing the contaminated manure into heavy metals-containing biochar catalysts for catalytic fast pyrolysis/gasification of biomass to manufacture phenols-enriched biofuel and H 2 -rich gas. The versatile Cu, Pb, and Zn-containing cow manure biochar catalysts were newly prepared from Cu, Pb, and Zn-contaminated livestock manure through a single-step energy-efficient thermal process. Cu and Pb-containing biochar catalysts prepared at 500 °C were more favorable for the production of bio-oil and organic phase, and up to 41.20% of phenolics was found in the bio-oil by using the Pb-containing biochar catalyst. The highest gas yield (51.55 wt%), equaling to 550 NmL/g WS , was observed in the presence of Cu-containing biochar catalyst prepared at 500 °C. Meanwhile, the H 2 concentration was elevated to 35.85 vol%, and the H 2 yield was correspondingly promoted to 197 NmL/g WS. Additionally, a deep knowledge of the reaction mechanisms regarding the catalytic fast pyrolysis/gasification of biomass over heavy metals-containing biochar catalysts was elucidated. Overall, this study provided a novel way to valorize heavy metals-contaminated livestock manure into effective biochar catalysts for catalytic fast pyrolysis/gasification of biomass to produce phenols-enriched bio-fuel or H 2 -rich gas. [Display omitted] • A new concept of valorizing heavy metals-contaminated manure into biochar catalysts. • Cu, Pb, and Zn-containing manure biochar catalysts were prepared at 500 °C and 800 °C. • Pb/CMBC-500 and Cu/CMBC-500 favored the production of bio-oils and liquid organics. • Up to 41.20% of selectivity toward phenolics was obtained by using Pb/CMBC-500. • The highest gas yield (51.55 wt%), i.e., 550 NmL/g WS , was gained over Cu/CMBC-500. [ABSTRACT FROM AUTHOR]

Renewable energy sources such as biomass have been proven to be one of the promising sustainable alternatives to fossil fuels. However, using biomass directly as a fuel is less attractive due to its high moisture content, poor grindability, low bulk density, and low energy density nature. Hence biomass can be converted into biochar to overcome these challenges. In this study, biochar was derived from citrus peels biomass by slow pyrolysis over the temperature range of 300–700 °C. The effect of pyrolysis temperature on the quality of citrus peels-derived biochar was examined based on the physical and chemical properties obtained from various analyses. The citrus peels biomass and biochar were characterized by means of higher heating value (HHV) analysis, field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX), Fourier transform infrared ray (FTIR) analysis, proximate and thermogravimetric analysis. Based on the characterization results, the potential usage of the derived biochar as a solid fuel was discussed. Results obtained from the pyrolysis experiments indicated that a lower pyrolysis temperature produced a higher char yield. The carbon content and energy content of biochar were found to be increasing with pyrolysis temperature. Biochar produced at 500 °C presented the best fuel properties by having the highest value of HHV and carbon content. The results from this study provided great insights into biomass waste reutilisation to generate value-added biochar for renewable energy production in Malaysia. [Display omitted] • Promising potential for citrus peels biomass to biochar for energy conversion. • Higher heating value of citrus peels biochar comparable to sub-bituminous coal. • Carbon and energy content increased with increasing pyrolysis temperature. • Better combustion stability for biochar of higher pyrolysis temperature. [ABSTRACT FROM AUTHOR]

This work focuses in the application of the hydrothermal carbonization (HTC) technology as a possible moist agro-industrial waste management treatment. Through this technique, olive mill, canned artichoke and orange wastes (OMW, CAW and OJW, respectively) were carbonized in a lab-scale high pressure reactor at different temperatures (200–250 °C) and durations (2, 4, 8 and 24 h) in order to obtain useful bioenergy feedstocks. The effect of the residence time and temperature on the properties of the bio-char obtained was studied through different characterization techniques. Material and energy balances were also performed to determine the potential energy saving of hydrothermal carbonization versus dry thermal treatments like torrefaction (TF). It is found that the moisture content of HTC-hydro-chars decreases as the temperature and duration increase, which implies that wet biomass can be upgraded and, at the same time, dewatered through HTC. The best results are found for the OMW, whose moisture content decreases from over 70% to less than 30% for the experiments carried out under the more severe conditions. Consequently, it is be possible to reach energy savings over 50% by using HTC instead of TF technologies. Regarding the hydro-char properties, the hydrothermal carbonization of the three organic wastes treated leaded to hydro-chars that present carbon contents and heating values closed to those of brown coal and great energy densifications, depending on the type of waste. Accordingly, it can be concluded that it is feasible to manage moist agro-industrial wastes via HTC, which is ostensibly more efficient than TF in terms of energy consumption. [ABSTRACT FROM AUTHOR]

Biochar obtained from the pyrolysis of corn cob is used as the fuel of a direct carbon fuel cell (DCFC) employing a composite electrolyte composed of a samarium doped ceria (SDC) and a eutectic carbonate phase. An anode layer made of NiO and SDC is utilized to suppress the cathode corrosion by the molten carbonate and improves the whole cell stability. The anode off-gas of the fuel cell is analyzed with a gas chromatograph. The effect of working temperature on the cell resistance and power output is examined. The maximum power output achieves 185 mW cm −2 at a current density of 340 mA cm −2 and 750 °C. An anode reaction scheme including the Boudouard reaction is proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Conventional and microwave pyrolysis of biomass has been compared. [•] Conventional pyrolysis produces higher gas yield. [•] Microwave pyrolysis produces more char. [•] Two stages of gas release are seen, first CO & CO2 and second CH4 & H2. [Copyright &y& Elsevier]

Highlights: [•] Properties of products properties obtained during co-pyrolysis were studied with polypropylene addition. [•] Were observed synergistic effects to the product yield from biomass co-pyrolysis process with polypropylene addition. [•] Describe differences in properties of products obtained during co-pyrolysis with polypropylene addition. [•] Were observed relationship among of polypropylene addition and differences in the high heats of products. [ABSTRACT FROM AUTHOR]

The depletion of fossil fuels as well as the greenhouse gas emissions from fossil fuel use have led to growing interest in biofuel production from biomass. A new technology, thermo-catalytic reforming (TCR), is one of the contributing interests. TCR technology integrates intermediate pyrolysis with a post-reforming stage to convert biomass into a high-quality bio-oil, biochar, and syngas. In this study, experiments were carried out using three Alberta-based biomass feedstocks – hardwood pellets, softwood pellets, and chips – in a 2 kg h−1 laboratory-scale TCR plant. The results show that the composition of the biomass has little effect on product yield and quality. The TCR gases had a higher heating value of 12.5–12.8 MJ kg−1 and a hydrogen content of 13–15 vol %. The produced TCR bio-oil had low water content (~5 wt %) and a heating value of 32–34 MJ kg−1. The high quality of the bio-oil is reflected in the low O/C ratio of 0.15 and TAN of 6–15 mg KOH g−1. The TCR biochar from all three feedstocks had a high heating value and a high carbon content, as well as low O/C and H/C ratios. A parametric study was conducted for the softwood pellets to observe the effect of reformer temperature (500–700 °C) and reactor temperature (400–550 °C). It was observed that at a reformer temperature of 700 °C, the gas yield increases at the expense of a reduction in bio-oil and biochar. The optimum reactor temperature for the TCR of softwood pellets was found to be 500 °C, in terms of both bio-oil quality and yield. • Thermo-catalytic reforming (TCR) technology incorporates intermediate pyrolysis with high temperature reforming. • The TCR bio-oil had low TAN (6–15 mg KOH/g), and high HHV (32–34 MJ kg−1). • The TCR gases had a hydrogen content of 13–15 vol % and HHV of 12–14 MJ kg−1. • Higher reforming temperature led to increase in gases at the expense of bio-oil. [ABSTRACT FROM AUTHOR]

In the current scenario of climate change, the search for alternative energy sources is very important to reduce the use of fossil fuels. Undesired biomass (weed) from agricultural fields can be used to produce biofuels through nano catalysts enhanced gasification and process. Lignocellulosic part of weedy plants represents a potential alternative feedstock for economic production of bioethanol. Large numbers of weedy plant species are growing all over the world. However, high energy requirements and poor-quality biofuel products are the major constraints for utilization of this technology. Nanomaterials could be used as a catalyst to enhance the energy use efficiency and product quality. So, present study was conducted to produce bio-gas, bio-diesel and bio-char from mixed weed biomass of weeds like Carthamous oxyacantha, Asphodelus tenuifolius and Chenopodium album through gasification process using nano-materials as catalysts. Nickel and cobalt nano-particles were used as nano-catalysts to expedite the bio-chemical reactions for the generation of these products at lower temperatures i.e. (400 C°) in a muffle furnace. Further, these products were characterized using GC-MS analysis. It was observed that biodiesel contained 65.47% esters, which indicates its better quality than the normally produced biodiesel having 15–20% esters contents. Similarly, GC-MS analysis of biogas produced from mixed weed biomass showed 3.76% Methane, 8.32% Propane, 50.16% Ethene, 3.12% Propyne and 34.64% Methanol. The present results clearly exhibited the improved product quality and better energy use efficiency in gasification of weed biomass for bioenergy production. Image 1 • Strategic recycling of weed biomass into useful biofuels and biochar using nano-catalysts. • Nano-catalysts can accomplish gasification of weed biomass at lower temperatures. • Biodiesel of weed biomass is of better quality and environment friendly. • The biochar produced from weed biomass can be used as soil amendment. • Biogas produced from weed biomass is a good source of hydrocarbon fuel gases. [ABSTRACT FROM AUTHOR]