A systematic study on the chemical model of polycyclic aromatic hydrocarbons formation from nutrients (glucose, amino acids, fatty acids) in food

Polycyclic aromatic hydrocarbons (PAHs), prominent carcinogens formed during food processing, pose health risks through long-term consumption. This study focuses on 16 priority PAHs in the European Union, investigating their formation during pyrolysis. Glucose, amino acids and fatty acids are important food nutrients. To further explore whether these nutrients in food form PAHs during heating, a single chemical model method was used to heat these nutrients respectively, and GC-MS/MS was used to identify and quantify the obtained components. Glucose is the most basic nutrient in food, so the influence of water, pH, temperature and other factors on the formation of PAHs was studied in the glucose model. At the same time, the models of amino acids and fatty acids were used to assist in improving the entire nutrient research system. According to our results, some previously reported mechanisms of PAHs formation by fatty acids heating were confirmed. In addition, glucose and amino acids could also produce many PAHs after heating, and some conclusions were improved by comparing the intermediates of PAHs from three types of nutrients.

municipal solid waste and the use of the aqueous fraction produced for bovine mastitis control

The Terminalia catappa L. tree is an ornamental and shade tree producter of a large amount of biological waste sent to landfills. Therefore, this plant constitutes so-called municipal solid wood waste (MSWW), which causes undesirable impacts on the environment, such as the generation of methane through the action of microorganisms. Sustainable solutions for the proper use and disposal of MSWW are a topic that has assumed great relevance at present due to the high quantities of MSWW generated worldwide. Pyrolysis constitutes an attractive alternative for the sustainable use of MSWW to produce higher value-added products. This study investigated the slow pyrolysis of Terminalia catappa L. fruit and the use of the aqueous fraction produced for bovine mastitis control. We obtained four fractions from the pyrolysis process, with average yields of the aqueous phase (36.22 ± 2.0 %), bio-oil (5.52 ± 0.4 %), biochar (37.55 ± 2.8 %) and gas (20.71 ± 2.0 %). The aqueous fraction was extracted with organic solvents and analyzed by gas chromatography coupled to mass spectrometry (GC‒MS). The extracts were composed mainly of phenols (50 %), furan derivatives, cyclic ketones, and others with lower contents, such as alcohols and esters. The aqueous fraction had bactericidal activity against Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli, which are responsible for bovine mastitis. In addition, the fraction showed low cytotoxicity against a murine melanoma cell line from a C57BL/6J mouse, B16F10 cells and mouse peritoneal cells.

Eco-toxicological and climate change effects of sludge thermal treatments: Pathways towards zero pollution and negative emissions

The high moisture content and the potential presence of hazardous organic compounds (HOCs) and metals (HMs) in sewage sludge (SS) pose technical and regulatory challenges for its circular economy valorisation. Thermal treatments are expected to reduce the volume of SS while producing energy and eliminating HOCs. In this study, we integrate quantitative analysis of SS concentration of 12 HMs and 61 HOCs, including organophosphate flame retardants (OPFRs) and per- and poly-fluoroalkyl substances (PFAS), with life-cycle assessment to estimate removal efficiency of pollutants, climate change mitigation benefits and toxicological effects of existing and alternative SS treatments (involving pyrolysis, incineration, and/or anaerobic digestion). Conventional SS treatment leaves between 24 % and 40 % of OPFRs unabated, while almost no degradation occurs for PFAS. Thermal treatments can degrade more than 93% of target OPFRs and 95 % of target PFAS (with the rest released to effluents). The different treatments affect how HMs are emitted across environmental compartments. Conventional treatments also show higher climate change impacts than thermal treatments. Overall, thermal treatments can effectively reduce the HOCs emitted to the environment while delivering negative emissions (from about -56 to -111 kg CO2-eq per tonne of sludge, when pyrolysis is involved) and producing renewable energy from heat integration and valorization.

Noble metal-free FeCoNiMnV high entropy alloy anchored on N-doped carbon nanotubes with prominent activity and durability for oxygen reduction and zinc-air batteries

Efficient and stable oxygen reduction reaction (ORR) catalysts are essential for constructing reliable energy conversion and storage devices. Herein, we prepared noble metal-free FeCoNiMnV high-entropy alloy supported on nitrogen-doped carbon nanotubes (FeCoNiMnV HEA/N-CNTs) by a one-step pyrolysis at 800 °C, as certificated by a set of characterizations. The graphitization degree of the N-CHTs was optimized by tuning the pyrolysis temperature in the control groups. The resultant catalyst greatly enhanced the ORR characteristics in the alkaline media, showing the positive onset potential (Eonset) of 0.99 V and half-wave potential (E1/2) of 0.85 V. More importantly, the above FeCoNiMnV HEA/N-CNTs assembled Zn-air battery exhibited a greater open-circuit voltage (1.482 V), larger power density (185.12 mW cm-2), and outstanding cycle stability (1698 cycles, 566 h). This study provides some valuable insights on developing sustainable ORR catalysts in Zn-air batteries.

Comprehensive kinetic modeling and product distribution for pyrolysis of pulp and paper mill sludge

Pyrolysis holds immense potential for clean treatment of pulp and paper mill sludge (PPMS), enabling efficient energy and chemical recovery. However, current understanding of PPMS pyrolysis kinetics and product characteristics remains incomplete. This study conducted detailed modeling of pyrolysis kinetics for two typical PPMSs from a wastepaper pulp and paper mill, namely, deinking sludge (PPMS-DS) and sewage sludge (PPMS-SS), and analyzed comprehensively pyrolysis products. The results show that apparent activation energy of PPMS-DS (169.25-226.82 kJ/mol) and PPMS-SS (189.29-411.21 kJ/mol) pyrolysis undergoes significant change, with numerous parallel reactions present. A distributed activation energy model with dual logistic distributions proves to be suitable for modeling thermal decomposition kinetics of both PPMS-DS and PPMS-SS, with coefficient of determination >0.999 and relative root mean square error <1.99 %. High temperature promotes decomposition of solid organic materials in PPMS, and maximum tar yield for both PPMS-DS (53.90 wt%, daf) and PPMS-SS (56.48 wt%, daf) is achieved at around 500 °C. Higher levels of styrene (24.45 % for PPMS-DS and 14.71 % for PPMS-SS) and ethylbenzene (8.61 % for PPMS-DS and 8.33 % for PPMS-SS) are detected in tar and could be used as chemicals. This work shows great potential to propel development of PPMS pyrolysis technology, enabling green and sustainable production in pulp and paper industry.

An environmentally-friendly permeable liquid salt pyrolysis method based on capillary heat transfer for recycling waste insulator materials

Molten salt pyrolysis technology stands out as a potent approach for achieving efficient degradation and energy recovery of composite organic materials. Nevertheless, challenges such as the high melting point of molten salt, product destruction, and the complexities of treating waste salt pose significant limitations to the widespread application and popularization of this technology. To tackle these issues, this study proposes a salt-assisted pyrolysis method based on capillary heat transfer called permeable liquid salt pyrolysis. Focusing on abandoned power industry insulators, the research delves into the thermal and mass transfer model of cluster-embedded materials under non-molten salt conditions. The investigation reveals that the capillary between glass fiber and resin proves beneficial in enhancing heat transfer conditions by creating a novel phase known as permeate liquid. Results demonstrate that salt-assisted pyrolysis can substantially lower the required temperature and enhance the pyrolysis reaction rate, achieving a maximum degradation efficiency of 98.99 %. Additionally, the pyrolysis products undergo in-situ modification, with a notable reduction in benzene series compounds ranging from 68 % to 85 %. Furthermore, an erosion diffusion capillary mode is established. This study presents an environmentally-friendly approach to recycle and modify products derived from waste resin-based composite materials generated in the electric power industry.

Formation of volatile chlorinated and brominated products during low temperature thermal decomposition of the representative PFAS perfluorohexane sulfonate (PFHxS) in the presence of NaCl and NaBr

Per- and polyfluoroalkyl substances (PFAS) are synthetic organofluorine compounds known for their chemical and physical stability as well as their wide range of uses. Some PFAS are widely distributed in the environment, leading to concerns related to both environmental and human health. High temperature thermal treatment (i.e., incineration) has been utilized for PFAS treatment, but this requires significant infrastructure and energy, prompting interest in lower temperature approaches that may still lead to efficient destruction. Lower treatment temperatures, however, increase the potential for incomplete PFAS mineralization and formation of volatile organofluorine (VOF) products. Herein, we report the formation of novel VOF products that include chlorinated and brominated compounds during the thermal treatment of potassium perfluorohexane sulfonate (PFHxS), a representative perfluoroalkyl acid (PFAA). By comparing the gas chromatography-mass spectrometry (GC-MS) results of known VOF stocks to evolved VOF during thermal treatment of PFAS, the formation of perfluorohexyl chloride and perfluorohexyl bromide was observed when PFHxS was heated at temperatures between 275 and 475 °C in the presence of NaCl and NaBr, respectively. To our knowledge, this is the first report of chlorinated or brominated VOF products during thermal treatment of a PFAA. These findings suggest that a range of mixed halogenated VOF may form during thermal treatment of PFAS at relatively low temperature (e.g., 500 °C) and that these can be a function of salts present in the matrix.

Formation mechanism of persistent free radicals during pyrolysis of Fenton-conditioned sewage sludge: Influence of NOM and iron

The present study provided an innovative insight into the formation mechanism of persistent free radicals (PFRs) during the pyrolysis of Fenton-conditioned sludge. Fenton conditioners simultaneously improve the dewatering performance of sewage sludge and catalyze the pyrolysis of sewage sludge for the formation of PFRs. In this process, PFRs with a total number of spins of 9.533×1019 spins/g DS could be generated by pyrolysis of Fenton-conditioned sludge at 400°C. The direct thermal decomposition of natural organic matter (NOM) fractions contributed to the formation of carbon-centered radicals, while the Maillard reaction produced phenols precursors. Additionally, the reaction between aromatic proteins and iron played a crucial role in the formation of phenoxyl or semiquinone-type radicals. Kinetics analysis using discrete distributed activation energy model (DAEM) demonstrated that the average activation energy for pyrolysis was reduced from 178.28 kJ/mol for raw sludge to 164.53 KJ/mol for Fenton conditioned sludge. The reaction factor (fi) indicated that the primary reaction in Fenton-conditioned sludge comprised of 27 parallel first-order reactions, resulting from pyrolysis cleavage of the NOM fractions, the Maillard reaction, and iron catalysis. These findings are significant for understanding the formation process of PFRs from NOM in Fenton-conditioned sludge and provide valuable insight for controlling PFRs formation in practical applications.

Kraft lignin fast (catalytic) pyrolysis for the production of high value-added chemicals (HVACs): A techno-economic screening of valorization pathways

This paper presents a techno-economic analysis (TEA) of six (6) scenarios of the kraft lignin catalytic (CFP) and thermal (TFP) fast pyrolysis towards the production of high value-added chemicals (HVACs) and electric energy, based on experimental data from our previous work. ASPEN PLUS was used to simulate the proposed plants/scenarios and retrofitted custom-based economic models that were developed in Microsoft EXCEL. The results showed that scenarios 1 and 2 in which the produced bio-oil is used as fuel for electricity production are the most cost-deficient. On the other hand, scenarios 3 and 6 that utilize the light bio-oil fraction to recover distinct HVACs, along with the use of heavier fractions for electricity production, have showed a significant investment viability, since profitability measures are high. Furthermore, scenarios 4 and 5 that refer to the recovery of mixtures (fractions) of HVACs, are considered an intermediate investment option due to the reduced cost of separation. All the proposed scenarios have a substantial total capital investment (TCI) which ranges from 135 MM€ (scenario 4) to 380 MM€ (scenario 6) with a Lang factor of 6.08, which shows that the CAPEX results are within reason. As far as the comparison of lignin CFP and TFP goes, it is shown that lignin CFP leads to the production of aromatic and phenolic monomers which have a substantial market value, while TFP can lead to important value-added chemicals with a lower OPEX than CFP. A target of return of investment (ROI) of 32% has been set for the selling prices of the HVACs. In summary, this study aims at listing and assessing a set of economic indicators for industrial size plants that use lignin CFP and TFP towards the production of high value-added chemicals and energy production and to provide simulation data for comparative analysis of three bio-oil separation methods, i.e. distillation, liquid-liquid extraction and moving bed chromatography.

Synthesis and Reactivity of Tricoordinate Organoberyllium Azides

A series of terminal mono- and disubstituted beryllium azides of the form [(CAAC)Be(N3)R] (R=CAACH, Dur; CAACH/CAAC=1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-yl/idene, Dur=2,3,5,6-tetramethylphenyl) and [L2Be(N3)2] (L=CAACNH=1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-imine, IiPrMe=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), respectively, were synthesized and characterized by NMR spectroscopy and X-ray crystallography. Thermolysis and photolysis products of these first examples of tricoordinate azidoberyllium complexes evidence extensive ligand scrambling and the formal insertion of nitrenes into the CAAC-Be bond, generating cyclic alkyl(amino)imine (CAAI) ligands. Furthermore, the reaction with a small N-heterocyclic carbene (NHC) leads to unexpected CAAC-NHC ligand exchange, while the reaction with pentaphenylborole yields the first γ-azide adduct of a borole, long postulated to be the first step in the synthesis of 1,2-azaborinines from boroles and azides.

Mechanism of soot and particulate matter formation during high temperature pyrolysis and gasification of waste derived from MSW

This research investigates the formation mechanism of soot and particulate matter during the pyrolysis and gasification of waste derived from Municipal Solid Waste (MSW) in a laboratory scale drop tube furnace. Compared with CO2 gasification atmosphere, more ultrafine particles (PM0.2, aerodynamic diameter less than 0.2 μm) were generated in N2 atmosphere at 1200℃, which were mainly composed of polycyclic aromatic hydrocarbons (PAHs), graphitic carbonaceous soot and volatile alkali salts. High reaction temperatures promote the formation of hydrocarbon gaseous products and their conversion to PAHs, which ultimately leads to the formation of soot particles. The soot particles generated by waste derived from MSW pyrolysis and gasification both have high specific surface area and well-developed pore structure. Compared with pyrolysis, the soot generated by gasification of waste derived from MSW had smaller size and higher proportion of inorganic components. The higher pyrolysis temperature led to the collapse of the mesoporous structure of submicron particles, resulting in a decrease in total pore volume and an increase in specific surface area. Innovatively, this research provides an explanation for the effect of reaction temperature/ CO2 on the formation pathways and physicochemical properties of soot and fine particulate matter.

Comparison of pyrolysis gasification of livestock manure, food wastewater, and their co-digested sludge

For energy recovery, anaerobic digestion is applied to organic waste, such as livestock manure (LM) and food wastewater (FW). Digested sludge(DS), a residue from the anaerobic co-digestion of LM and FW, is another type of organic waste that can be converted into energy through pyrolysis. This study compared the pyrolysis characteristics of LM, FW, and DS. The product content varied with the pyrolysis temperature, rate of temperature increase, reaction time, and final reaction temperature. Gas production from FW and DS was similar; however, gas production from LM was low. As the pyrolysis temperature increased, the H2 content increased, and the CO2 content decreased, respectively. At 1000 °C, the H2 content of LM increased to 45%, and FW produced the most gas but the lowest H2 content. The H2/CO ratios of LM and FW ranged from 3.5 to 5.2, while those of DS ranged from 5.5 to 12.4, with the highest values. The carbon conversion rate was the highest for the gaseous products of LM (30-54%) and lowest for the gaseous products of digested sludge (26-36%). Conversely, the cold gas efficiency was the highest for the DS and lowest for the LM. Following anaerobic digestion, the DS generated less tar than the untreated LM and FW, showed higher efficiency in gas generation and gas properties, and exhibited a higher value as a char fuel.

Transformation pathways of the carbon-containing group compounds during municipal sludge pyrolysis treatment

Municipal sludge contains abundant amounts of carbon, with contents ranging from 14 % to 38 %. The various carbon-containing group compounds can be converted into beneficial products, but pollutants and greenhouse gases are also released through the municipal sludge pyrolysis process. Ascertaining the pathways by which carbon-containing group compounds is converted and transformed is crucial for addressing pollution concerns and promoting recycling. This study explored the transformation pathways of carbon-containing group compounds during the pyrolysis process of municipal sludge. The results showed that the three major carbon-containing group compounds including protein (61 %), cellulose (9 %), and hemicellulose (7 %), had significantly different pyrolysis temperature of 600 °C, 400 °C and 300 °C. In terms of gas pollution, most carbon was fully pyrolyzed into CO2. While the temperature raised up to 500 °C, a part of the CO2 converted into CO. Meanwhile, the various carbon-containing compounds exhibited distinct effects on gas production, which CH4 was produced more with cellulose and protein presenting in the sludge. When temperature increased to 700 °C, the 60 % of the carbon-containing group compounds were transformed into liquid and solid. The pyrolysis liquid in the low-temperature stage (30-300 °C) contained a relatively high aliphatics content and lower organooxygen species (OOSs) content (at 200 °C), suggesting a potential for resource utilization. The yield of CO in the gas rapidly increased as the temperature increased in the high-temperature stage (500-700 °C). The insights from this study hold practical implications for enhancing municipal sludge pyrolysis efficiency, reducing pollution, and facilitating more sustainable and resource-efficient practices.

Preparation of Mn modified waste dander biochar and its effect on soil carbon sequestration

In order to reduce the mineralization of soil organic carbon (SOC) and enhance the ability of soil carbon sequestration. Mn-modified waste dander biochar (Mn-BC) was successfully prepared via impregnation and pyrolysis, and MnSO4 was formed on its surface. Mn-BC increases the carbon retention and reduces the emissions of CO2 and SO2 in way of forming CO, Mn-O-C bond and MnSO4. At the same time, the stability of the original biochar was reserved due to forming a conjugated structure (CC and pyridine-N bond), and the carbon sequestration content was increased to 25.63%. Importantly, the application of Mn-BC can directly regulate the transformation of microbial bacterial community and lead to create stable carbon dominant bacteria (Firmicutes). And the mineralization rate of SOC is reduced to 0.48 mg CO2/(g·d), together with an increased content of TOC (48.16%), thus the purpose of efficient carbon sequestration is achieved in soil.

Experimental investigation of products from thermal treatment of real-world mixed single-use and multi-layered waste plastics

The usage and disposal of highly abundant single-use and multilayered plastics contribute to significant ecological problems. The thermochemical recovery of these plastics to useful products and chemicals provides opportunity for positive economic and environmental impacts. Most previous research use idealised and unrepresentative feedstocks. To address this, various mixed waste plastics collected from the rejected fraction of a municipal waste recovery facility in Ghana were pyrolyzed at varying temperatures of 450, 500 and 550 °C and their yields compared. The obtained chemical products were analysed using several different techniques. Energy and carbon balances of the processes were produced using the CHNS and energy content of the oil fraction and the compositional results of the pyrolysis gas fraction, the latter of which was measured by Gas Chromatography Thermal Conductivity Detection (GC-TCD). The oils were further assessed via Gas Chromatography Mass Spectrometry (GC-MS) to identify the available valuable compounds. The formed oil contained approximately 40% light hydrocarbons (C6 - C11), 18% middle hydrocarbons (C11 - C16) and 42% heavy hydrocarbon compounds (C16+). The optimal oil yield of 65.9 ± 0.5% and low heating value of 44.7 ± 0.1 MJ/kg for single-use plastics were recorded at highest heating temperatures of 550 and 500 °C, respectively. The findings provide indication that pyrolysis is a fitting solution for energy recovery from waste plastics.

A comparative study of the pyrolysis and hydrolysis conversion of tire

In the present study, we pyrolyzed a waste tire at various temperatures under an N2 atmosphere and a water environment in an autoclave reactor to investigate the effect of water on tire degradation. The analysis involved a comparison of product distribution, char properties, oil composition, and the behavior of heteroatom elements (especially oxygen, nitrogen, and sulfur) under different atmospheres. Elemental analysis, functional-group identification, and chemical state analysis of sulfur were performed for chars. In addition, the chemical composition, elemental composition, and molecular weight of the produced oils were evaluated. The heavy fraction of oils, not detectable by gas chromatography-mass spectrometry (GC-MS), was analyzed through Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The findings revealed that high temperatures promoted oil cracking, resulting in the formation of light oils in both pyrolysis and hydrolysis processes. Compared to pyrolysis, hydrolysis generated a higher yield of low molecular-weight oil. Elevated hydrolysis temperatures promoted aromatization, yielding an oil with a low H/C ratio and a high double bond equivalent number. Consequently, the concentration of aromatics in the light fraction of oils generated from the hydrolysis process exceeded that in oils from the pyrolysis process. Temperature exhibited a limited impact on oil composition during the pyrolysis process. Hydrolysis promoted the release of heteroatom-containing compounds at low temperatures. During pyrolysis, nitrogen was gradually released from the solid phase, whereas nitrogen-containing compounds were released early during hydrolysis, with gas-phase nitrogen accounting for more than 50 wt% at 320 °C. A maximum D-limonene yield of 45.58% was obtained at 360 °C within 0 min of hydrolysis, with the potential conversion of D-limonene into aromatics at higher hydrolysis temperatures. These results contribute to the understanding of tire valorization via hydrolysis.

Investigating the adsorption potential of char derived from waste latex for methylene blue removal

This study presents the adsorption of methylene blue (MB) dye using latex char derived from pyrolysis of latex gloves. The adsorption process was investigated systematically using Response Surface Methodology (RSM) with a Central Composite Design (CCD). The effects of four key variables, namely pH, time, temperature, and adsorbent dosage, were studied using a factorial design enriched with center points and axial points. Experimental data were analyzed using a second-order polynomial regression model to construct a response surface model, which elucidated the relationship between the variables and MB removal efficiency. The study found that the char obtained at 800°C exhibited the highest adsorption capacity due to its increased carbonization, expanded surface area, and diverse pore structure. Analysis of Variance (ANOVA) confirmed the significance of the quadratic model, with remarkable agreement between predicted and experimental outcomes. Diagnostic plots validated the model's reliability, while 3D contour graphs illustrated the combined effects of variables on MB removal efficiency. Optimization using DoE software identified optimal conditions resulting in a 99% removal efficiency, which closely matched experimental results. Additionally, adsorption isotherms revealed that the Freundlich model best described the adsorption behavior, indicating heterogeneous surface adsorption with multilayer adsorption. This comprehensive study provides valuable insights into the adsorption process of MB dye using latex char, with implications for wastewater treatment and environmental remediation.

Pyrolysis of exhausted biochar sorbent: Fates of cadmium and generation of products

Biochar is a promising sorbent for Cd removal from water, while the disposal of the exhausted Cd-enriched biochar remains a challenge. In this study, pyrolysis was employed to treat the exhausted biochar under N2 and CO2 atmospheres at 600-900 °C, and the fate of Cd during pyrolysis and characteristics of high-valued products were determined. The results indicated that higher temperature and CO2 atmosphere favored the volatilization of Cd. Based on the toxicity characteristic leaching procedure (TCLP) results, the pyrolysis treatment under both atmospheres enhanced the stability of Cd, and the leached Cd concentration of regenerated biochar obtained at high temperatures (>800 °C) was lower than 1 mg/L. Compared with the pristine biochar, the regenerated biochar demonstrated higher carbon content and pH, whereas the contents of oxygen and hydrogen declined, and exhibited promising sorption properties (35.79 mg/g). The atmosphere played an important role in modifying biochar properties and syngas composition. The N2 atmosphere facilitated CH4 production, whereas the CO2 atmosphere increased the proportion of CO. These results implied that pyrolysis can be a valuable and environmental-friendly strategy for the treatment and reuse of exhausted biochar sorbent.

The relevant effect of marine salt and epiphytes on Posidonia oceanica waste pyrolysis: Removal of SO2/HCl emissions and promotion of O/HCOOH formation

Significant quantities of Posidonia oceanica deposit on some beaches and coastlines every year, which generates high costs associated with the disposal of this waste. Pyrolysis may be an adequate way for its valorization. However, it would imply to know how the process takes place and if the removal of its natural detrital inorganic matter (epiphytes, marine salt and sand) is necessary, which are the objectives of this research. Pyrolysis by thermogravimetry-mass spectrometry was carried out on both the washed and unwashed samples. During this waste pyrolysis, the following occurs: (i) the high alkali metal chloride content promotes fragmentation reactions of carbohydrates and O formation, which increases HCOOH intensities at temperatures between 250 and 360 °C; (ii) from 500 °C to 650 °C, Fe2O3 and decomposition of carbonates seem to be involved in reactions that produce O release and steam and CO2 reforming of hydrocarbons and oxygenated organic compounds with H2 generation; (iii) from 650 °C to 750 °C, Fe2O3, high alkali metal content and carbonate decomposition generate char gasification, an increase in O release, SO2 capture and HCOOH formation. In general, the abundance of inorganic matter (chlorides, carbonates, etc.) minimizes the release of various compounds during pyrolysis, including SO2 and HCl, while increasing HCOOH production. Thus, this high content of inorganic matter may represent an advantage for its pyrolysis, producing value-added chemical products with a reduced environmental impact. Therefore, this study may be the starting point for defining the optimal pyrolysis conditions for this waste valorisation.

Untapped potential of food waste derived biochar for the removal of heavy metals from wastewater

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.

Promotion of levoglucosan production from biomass pyrolysis by hydrogen peroxide pre-oxidation

Due to the complexity of biomass structures, the conversion of raw biomass into value-added chemicals is challenging and often requires efficient pretreatment of the biomass. In this paper, a simple and green pre-oxidation method, which was conducted under the conditions of 2 wt% H2O2, 80 min, and 150 °C, was reported to significantly increase the production of levoglucosan (LG) from biomass pyrolysis. The result showed that the LG yield significantly increased from 2.3 wt% (without pre-oxidation) to 23.1 wt% when pine wood was employed as a sample for pyrolysis at 400 °C, resulting from the removal of hemicellulose fraction and the in-situ acid catalysis of lignin carboxyl groups formed during the pre-oxidation. When the conditions for pre-oxidation became harsher than the above, the LG yield reduced because the decomposition of cellulose fraction in biomass. The study supplies an effective method for utilization of biomass as chemicals.

Additive manufacturing-derived free-standing 3D pyrolytic carbon electrodes for sustainable microbial electrochemical production of H2O2

Producing H2O2 via microbial electrosynthesis is a cost-effective and environmentally favorable alternative to the costly and environmentally hazardous anthraquinone method. However, most studies have relied on carbon electrodes with two-dimensional (2D) surfaces (e.g., graphite), which have limited surface area and active sites, resulting in suboptimal H2O2 production. In this study, we demonstrate the enhanced efficiency of microbial H2O2 synthesis using three-dimensional (3D) electrodes produced through additive manufacturing technology due to their larger surface area than conventional carbon electrodes with 2D surfaces. This work innovatively combines 3D printed pyrolytic carbon (3D PyrC) electrodes with highly defined outer geometry and internal mesh structures derived from additive manufacturing with high-temperature resin precursors followed by pyrolysis with microbial electrochemical platform technology to achieve efficient H2O2 synthesis. The 3D PyrC electrode produced a maximum of 129.2 mg L-1 of H2O2 in 12 h, which was 2.3-6.9 times greater than conventional electrodes (e.g., graphite and carbon felt). Furthermore, the scalability, reusability and mechanical properties of the 3D PyrC electrode were exemplary, showcasing its practical viability for large-scale applications. Beyond H2O2 synthesis, the study explored the application of the 3D PyrC electrode in the bio-electro-Fenton process, demonstrating its efficacy as a tertiary treatment technology for the removal of micropollutants. This dual functionality underscores the versatility of the 3D PyrC electrode in addressing both the synthesis of valuable chemicals and environmental remediation. This study shows a novel electrode design for efficient, sustainable synthesis of H2O2 and subsequent environmental remediation.

Ammonia hydroxide and citric acid modified wheat straw-biochars: Preparation, characterization, and environmental applications

This study presents an assessment of inorganic and organic modification of biochar on physicochemical properties, dissolved organic carbon (DOC) release, sorption efficiency towards enrofloxacin (E) and silver nanoparticles (Ag-NPs), as well as an evaluation of addition of prepared materials on hydro-physical properties and adsorption capacity of montmorillonite (M). The biochar was derived from wheat straw at 650 °C. An inorganic modification was performed using ammonia hydroxide, whereas an organic modification, using citric acid. The ammonia hydroxide and citric acid changed the biochar nature and surface chemistry by introducing amino and ester groups. The lowest DOC release was from ammonia-biochar (BCN) and the highest, from citric acid-biochar (BCC). The adsorption data were better described by pseudo-II order equation and Marczewski-Jaroniec isotherm. Results showed that BCN exhibited the highest efficiency in adsorption of E and Ag-NPs. It also improved the adsorptive abilities and saturated hydraulic conductivity of M. This provides the chemically modified biochars have an excellent potential to improve pollution removal from aqueous media and hydro-physical/sorption properties of soil sorption complex. They can be used with advantageous in environmental applications.

Microbial synthesis of antimony sulfide to prepare catechol and hydroquinone electrochemical sensor by pyrolysis and carbonization

The application of antimony sulfide sensors, characterized by their exceptional stability and selectivity, is of emerging interest in detection research, and the integration of graphitized carbon materials is expected to further enhance their electrochemical performance. This study represents a pioneering effort in the synthesis of carbon-doped antimony sulfide materials through the pyrolysis of the mixture of microorganisms and their synthetic antimony sulfide. The prepared materials are subsequently applied to electrochemical sensors for monitoring the highly toxic compounds catechol (CC) and hydroquinone (HQ) in the environment. Via cyclic voltammetry (CV) and impedance testing, we concluded that the pyrolytic product at 700 °C (Sb-700) demonstrated the best electrochemical properties. Differential pulse voltammetry (DPV) revealed impressive separation when utilizing Sb-700/GCE for simultaneous detection of CC and HQ, exhibiting good linearity within the concentration range of 0.1-140 μM. The achieved sensitivities of 24.62 μA μM-1 cm-2 and 22.10 μA μM-1 cm-2 surpassed those of most CC and HQ electrochemical sensors. Meanwhile, the detection limits for CC and HQ were as low as 0.18 μM and 0.16 μM (S/N = 3), respectively. Additional tests confirmed the good selectivity, reproducibility, and long-term stability of Sb-700/GCE, which was effective in detecting CC and HQ in tap water and river water, with recovery rates of 100.7%-104.5% and 96.5%-101.4%, respectively. It provides a method that combines green microbial synthesis and simple pyrolysis for the preparation of electrode materials in CC and HQ electrochemical sensors, and also offers a new perspective for the application of microbial synthesized materials.

Pressurized pyrolysis of mattress residue: An alternative to landfill management

Mattresses are a difficult waste to manage in landfills due to their large volume and low density. Pyrolysis treatment could reduce its volume while producing fuel or products valuable for the chemical industry. Pressurized pyrolysis at 400, 450, and 500 °C is carried out in a lab-scale autoclave at initial pressures 4.2, 8.4, and 16.8 bar. Product gas yield increases slightly along with elevated pressure as well as temperature. However, beyond 8.4 bar the initial pressure makes no discernible differences. CO and CO2 are the major gas species followed by CH4. CO contributes the most to the product gas energy content followed by C3 species, C2H6, and H2. Calculated energy content (heating value) is between 2 and 15 MJ·Nm-3. In terms of product gas energy content, low pressure pyrolysis is favorable over high pressure pyrolysis. According to integration areas of chromatographic measurements the liquid phase contains up to 25 % of N-compounds, with benzonitrile being the most abundant, followed by toluene, o-xylene, and ethylbenzene. The solid char maintains constant properties across operating conditions, with carbon and energy contents of approximately 75 wt% and 30 MJ·kg-1, respectively.

Sustainable valorization of macroalgae residual biomass, optimization of pyrolysis parameters and life cycle assessment

The major challenges for the current climate change issue are an increase in global energy demand, a limited supply of fossil fuels, and increasing carbon footprints from fossil fuels, which have necessitated the exploration of sustainable alternatives to fossil fuels. Biorefineries offer a promising path to sustainable fuel production, converting biomass into biofuels using diverse technologies. Aquatic biomass, such as macroalgae in this context, represents an abundant and renewable biomass resource that can be cultivated from water bodies without competing with traditional agricultural land. Despite this, the potential of macroalgae for biofuel production remains largely untapped, with very limited studies addressing their viability and efficiency. This study investigates the efficient conversion of unexplored macroalgae biomass through a biorefinery process that involves lipid extraction to produce biodiesel, along with the production of biochar and bio-oil from the pyrolysis of residual biomass. To improve the effectiveness and overall performance of the pyrolysis system, Response Surface Methodology (RSM) was utilized through a Box-Behnken design to systematically investigate how alterations in temperature, reaction time, and catalyst concentration influence the production of bio-oil and biochar to maximize their yields. The results showed the highest bio-oil yield achieved to be 36 %, while the highest biochar yield reached 45 %. The integration of Life Cycle Assessment (LCA) in the study helps to assess carbon emission and environmental burdens and identify potential areas for optimization, such as resource efficiency, waste management, and energy utilization. The LCA results contribute to the identification of potential environmental hotspots and guide the development of strategies to optimize the overall sustainability of the biofuel production process. The LCA results indicate that the solvent (chloroform) used in transesterification contributes significantly to greenhouse gas emissions and climate change impacts. Therefore, it is crucial to explore alternative, safe solvents that can mitigate the environmental impacts of transesterification.

Enhancing fuel characteristics and combustion performance of cellulose-rich straws through CO2-assisted torrefaction

Cellulose-rich straws of corn and rice were torrefied under carbon dioxide, and the fuel characteristics and combustion performance of the obtained biochar were investigated. A high severity resulted in surface collapse, greater pore volume, elimination of oxygen, elevated calorific value, and improved hydrophobicity in biochar. Following carbon dioxide torrefaction, the cellulose content in solid biochar experienced a slight decrease when the temperature was raised to 220 °C for longer residence durations. At 300 °C, the cellulose content in the biochar was nearly eliminated, while the relative proportion of non-sugar organic matter in corn stover and rice straw increased to 87.40 % and 77.27 %, respectively. The maximum calorific values for biochar from corn and rice straws were 22.38 ± 0.03 MJ/kg and 18.72 ± 0.05 MJ/kg. The comprehensive combustion indexes of rice and corn straw samples decreased to 1.06 × 10-7 and 1.31 × 10-7 after torrefaction at 300 °C, respectively. In addition, the initial decomposition temperatures increased by 38 °C and 45 °C, while the ultimate combustion temperatures rose by 13 °C and 16 °C for corn and rice straws, respectively. These results imply an extended combustion timeframe for the torrefied samples.

Stabilization of heavy metals in solid waste and sludge pyrolysis by intercalation-exfoliation modified vermiculite

Increasing amounts of solid waste and sludge have created many environmental management problems. Pyrolysis can effectively reduce the volume of solid waste and sludge, but there is still the problem of heavy metal contamination, which limits the application of pyrolysis in environmental management. The intercalated-exfoliated modified vermiculite (IEMV) by intercalators of sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide were used to control the release of Cd, Cr, Cu, Zn and Pb during pyrolysis process of sludge or solid waste. The retention of heavy metals in sludge was generally better than that in solid waste. The IEMV by octadecyltrimethylammonium bromide as the intercalator calcined 800 °C (STAB-800) was the best additive for heavy metal retention, and the retention of Cr, Cu and Zn was significantly better than that of Pb and Cd. Cr, Cu, Zn and Pb were at low risk, while Cd had considerable risk under certain circumstances. New models were proposed to comprehensively evaluate the results of the risk and forms of heavy metals, and the increasing temperature was beneficial in reducing the hazards of heavy metals by the addition of STAB-800. The reaction mechanism of heavy metals with vermiculite was revealed by simulation of reaction sites, Fukui Function and Frontier Molecular Orbital. Thermal activation-intercalated-exfoliated modified vermiculite (T-IEMV) is more reactive and had more active sites for heavy metals. Mg atoms and outermost O atoms are the main atoms for T-IEMV to react with heavy metals. The Cr, Cu and Zn have better adsorption capacity by T-IEMV than Pb and Cd. This study provides a new insight into managing solid waste and sludge and controlling heavy metal environmental pollution.

Kapok fiber composites minimizing secondary waste and disposal costs for large-scale radioactive liquid treatment

Conventional liquid treatments for large-scale, low-level radioactive wastewater, such as ion exchange and waste solidification, face challenges due to the large amounts of secondary waste and high disposal costs. A new large-scale decontamination method is proposed that uses kapok fiber composites for rapid radionuclide adsorption and high volume reduction to minimize secondary waste. The composite consists of natural zeolite and kapok holocellulose, which has high water-soaking ability and low-temperature pyrolysis. The kapok composites, fabricated using a commercial wet-laid nonwoven manufacturing process, absorbs 99% of low-level radioactive cesium in 20 min, reducing the volume by 98% and the weight by 47% at 300 °C. The low-temperature pyrolysis process below 300 °C prevents cesium desorption and gasification by avoiding zeolite destruction. The mass-producible kapok composites can be used for adsorbing various radionuclides in large-scale wastewater by attaching specific adsorbents for target isotopes to the composites.

Uncovering nano-bonechar for attenuating fluoride in naturally contaminated soil

Fluoride ion (F-) is one of the major geogenic contaminants in water and soil. Excessive consumption of these geogenic contaminants poses serious health impacts on humans and plants. In this study, a novel carbonaceous material, nano-bonechar, was synthesized from cow bones and applied as a soil amendment at rates of 0, 0.5, 1, and 2% to remediate and revitalize naturally F--contaminated soil. The results revealed that the nano-bonechar significantly reduced the mobility and bioavailability of F- by 90% in the contaminated soil, and improved the soil quality by increasing the soil water holding capacity, soil organic matter, and the bioavailable contents of PO43-, Ca2+, and Na+. Subsequently, the pot experiment results showed a significant reduction in the uptake of F- by 93% in Zea mays plants. Moreover, the nano-bonechar application improved the plant's growth, as indicated by the higher fresh and dry weights, root and shoot lengths, and total content of PO43-, Ca2+, and K+ than those of un-amended soil. The F-immobilization in soil was mainly due to the presence of the hydroxyapatite [Ca10(PO4)6(OH)2] mineral in the nano-bonechar. Ion exchange between OH- (of nano-bonechar) and F- (of soil), and the formation of insoluble fluorite (CaF2) contributed to the attenuation of F- mobility in the soil. It is concluded that nano-bonechar, due to its size and enrichment in hydroxyapatite, could successfully be utilized for the rapid remediation and revitalization of F--contaminated agricultural soil.

Turning plastics/microplastics into valuable resources? Current and potential research for future applications

Plastics are a wide range of synthetic or semi-synthetic materials, mainly consisting of polymers. The use of plastics has increased to over 300 million metric tonnes in recent years, and by 2050, it is expected to grow to 800 million. Presently, a mere 10% of plastic waste is recycled, with approximately 75% ended up in landfills. Inappropriate disposal of plastic waste into the environment poses a threat to human lives and marine species. Therefore, this review article highlights potential routes for converting plastic/microplastic waste into valuable resources to promote a greener and more sustainable environment. The literature review revealed that plastics/microplastics (P/MP) could be recycled or upcycled into various products or materials via several innovative processes. For example, P/MP are recycled and utilized as anodes in lithium-ion (Li-ion) and sodium-ion (Na-ion) batteries. The anode in Na-ion batteries comprising PP carbon powder exhibits a high reversible capacity of ∼340 mAh/g at 0.01 A/g current state. In contrast, integrating Fe3O4 and PE into a Li-ion battery yielded an excellent capacity of 1123 mAh/g at 0.5 A/g current state. Additionally, recycled Nylon displayed high physical and mechanical properties necessary for excellent application as 3D printing material. Induction heating is considered a revolutionary pyrolysis technique with improved yield, efficiency, and lower energy utilization. Overall, P/MPs are highlighted as abundant resources for the sustainable production of valuable products and materials such as batteries, nanomaterials, graphene, and membranes for future applications.

FeCx-coated biochar nanosheets as efficient bifunctional catalyst for electrochemical detection and reduction of 4-nitrophenol

Herein, we present the exceptional performance of FeCx-coated carbon sheets (FC) derived from the pyrolysis of waste biomass as a bifunctional catalyst for electrochemical detection and catalytic reduction of 4-nitrophenol (4-NP). Despite having a lower surface area, larger particle size, and lesser N content, the FC material prepared at a calcination temperature of 900 °C (FC900) outperforms the other samples. Deeper investigations revealed that the FC900 efficiently facilitates the charge transfer process and enhances the diffusion rate of 4-NP, leading to increased surface coverage of 4-NP on the surface of FC900. Additionally, relatively weaker interactions between 4-NP and FC900 allow the facile adsorption and desorption of reaction intermediates. Due to the synergetic interplay of these factors, FC900 exhibited a linear response to changes in 4-NP concentration from 1 μM to 100 μM with a low limit of detection (LOD) of 84 nM (S/N = 3) and high sensitivity of 12.15 μA μM-1 cm-2. Importantly, it selectively detects 4-NP in the presence of five times more concentrated 2-aminophenol, 4-aminophenol, catechol, resorcinol, and hydroquinone and ten times more concentrated metal salts such as Na2SO4. NaNO3, KCl, CuCl2, and CaCl2. Moreover, FC900 can accurately detect micromolar levels of 4-NP in river water with high recovery values (99.8-103.5 %). In addition, FC900 exhibited outstanding catalytic activity in reducing 4-NP to 4-aminophenol (4-AP), achieving complete conversion within 8 min with a high-rate constant of 0.42 min-1. FC900 also shows high recyclability in six consecutive catalytic reactions due to Fe magnetic property.

A novel strategy of tannery sludge disposal - converting into biochar and reusing for Cr(VI) removal from tannery wastewater

Tannery sludge with high chromium content has been identified as hazardous solid waste due to its potential toxic effects. The safety disposal and valorization of the tannery sludge remains a challenge. In this study, the chromium stabilization mechanism was systematically investigated during chromium-rich tannery sludge was converted to biochar and the removal performance of the sludge biochar (SBC) for Cr(VI) from tannery wastewater was also investigated. The results showed that increase in pyrolysis temperature was conductive to the stabilization of Cr and significant reduction of the proportion of Cr(VI) in SBC. It was confirmed that the stabilization of chromium mainly was attributed to the embedding of chromium in the C matrix and the transformation of the chromium-containing substances from the amorphous Cr(OH)3 to the crystalline state, such as (FeMg)Cr2O5. The biochar presented high adsorption capacity of Cr(VI) at low pH and the maximal theoretical adsorption capacity of SBC produced at 800°C can reach 352 mg Cr(VI)/g, the process of which can be well expressed by Langmuir adsorption isotherm and pseudo second order model. The electrostatic effect and reduction reaction were dominantly responsible for the Cr(VI) adsorption by SBC800. Overall, this study provided a novel strategy for the harmless disposal and resource utilization for the solid waste containing chromium in leather industry.

Thermo-chemical behaviour of Dunaliella salina biomass and valorising their biochar for naphthalene removal from aqueous rural environment

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 (Ea). 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.

Detection of nanoplastics released from consumer plastic food containers by electromagnetic heating pyrolysis mass spectrometry

Nanoplastics released from consumer plastic food containers are emerging environmental pollutants and directly ingested as part of the diet. However, quantification methods for nanoplastics are still lacking. Herein, a rapid identification and mass quantification approach was developed for nanoplastics analysis by combining electromagnetic heating with pyrolysis mass spectrometry (Eh-Py-MS). The pyrolysis products directly entered into the MS, which omits the gas phase separation process and shortens the detection time. A compact pyrolysis chamber was used and this increased the sample transfer efficiency and lowered power requirement. The operational parameters were systematically examined. The influence of nanoplastic size, additive, humic acid, and aging on detection was investigated, and it was concluded that environmental factors (humic acid, aging) and plastic properties (size, additives) did not influence the detection. The developed chamber showed that the limit of detection of polystyrene (PS) nanoplastics was 15.72 ng. Several typical food packages were demonstrated with satisfactory recovery rates (87.5-110%) and precision (RSD ≤11.36%). These results suggested that the consumer plastic food containers are a significant source of direct exposure to nanoplastics in humans from the environment.

Thermochemical conversion of silkworm by-product into syngas

This study explored the valorisation of silkworm by-product, a major by-product of the silk industry (sericulture), which amounts to 16 million tonnes annually. The focus was on transforming waste into energy resources through pyrolysis under CO2 conditions. In one-stage pyrolysis, the evolution of syngas under N2 was found to be comparable to that under CO2. A notable allocation of carbon to biocrude rather than syngas was observed. The two-stage pyrolysis resulted in increased syngas production. However, achieving a homogeneous reaction between CO2 and the volatiles liberated from silkworm byproduct proved challenging. Indeed, the reaction kinetics governing CO2 reactivity was not fast although the temperature windows of the reaction were aligned in the two-stage pyrolysis. To address this issue, pyrolysis was performed using a Ni-based catalyst to expedite the reaction kinetics. Consequently, syngas formation, particularly CO formation, was significantly enhanced under CO2 conditions compared to that under N2 conditions. The syngas yield under CO2 was 36.42 wt% which was 2-fold higher than that of N2. This suggested the potential of CO2 altering the carbon distribution from biocrude to syngas. This strategy would contribute to the establishment of sustainable production of silk by converting sericulture by-product into energy/chemical resources.

Low-cost pyrolysis of biomass-derived nitrogen-doped porous carbon: Chlorella vulgaris replaces melamine as a nitrogen source

Porous carbon generated from biomass has a rich pore structure, is inexpensive, and has a lot of promise for use as a carbon material for energy storage devices. In this work, nitrogen-doped porous carbon was prepared by co-pyrolysis using bagasse as the precursor and chlorella as the nitrogen source. ZnCl2 acts as both an activator and a nitrogen fixer during activation to generate pores and reduce nitrogen loss. The thermal weight loss experiments showed that the pyrolysis temperatures of bagasse and chlorella overlap, which created the possibility for the synthesis of nitrogen-rich biochar. The optimum sample (ZBC@C-5) possessed a surface area of 1508 m2g-1 with abundant nitrogen-containing functional groups. ZBC@C-5 in the three-electrode system exhibited 244.1F/g at 0.5A/g, which was extremely close to ZBC@M made with melamine as the nitrogen source. This provides new opportunities for the use of low-cost nitrogen sources. Furthermore, the devices exhibit better voltage retention (39%) and capacitance retention (96.3%). The goal of this research is to find a low cost, and effective method for creating nitrogen-doped porous carbon materials with better electrochemical performance for highly valuable applications using bagasse and chlorella.

Techno-economic and environmental analyses of the pyrolysis of food waste to produce bio-products

Food waste has become a source of concern as it is generated abundantly worldwide and needs to be valorised into new products. In this study, cucumber, tomato, and carrot wastes were investigated as pyrolysis feedstocks as a single component (cucumber), a binary component mixture (cucumber and tomato), and a ternary component blend (cucumber, tomato, and carrot). Fourteen scenarios were simulated and evaluated based on varying the feedstock blend (single, binary, and tertiary), temperature (300 and 500 °C), and feedstock moisture content (5, 20, and 40%). Using an established empirical model, the effect of these parameters on product yields, techno-economic implications, energy requirements, and life cycle analysis (LCA) outcomes were investigated. The best performers of each scenario were determined, and their strengths and weaknesses were identified and compared with other scenarios. In terms of product yields, all three systems (single, binary, and tertiary) followed a similar pattern: bio-oil yields increased as temperature and feedstock moisture content increased, while biochar yields decreased as temperature and feedstock moisture content increased. The production of syngas, on the other hand, was only observed at elevated temperatures. The total energy requirement exhibited an increase with increasing temperature and feedstock moisture content. The economic evaluation revealed that the return on investment (ROI) value for the single component at 5% moisture content at 300 °C is 29%, with a payback period (PB) of only 3.4 years, which is potentially very appealing. The water footprint increased with increasing pyrolysis temperature but decreased with increasing moisture content in all scenarios. The land footprint is observed to remain constant despite changes in process conditions. The study's findings contribute to the pyrolysis process's scalability, technological advancement, and commercialisation.

Application of Artificial Neural Network (ANN) as a predictive tool for the removal of pharmaceutical from wastewater streams using biochar: a multifunctional technology for environment sustainability

This study investigates biochar as an attractive option for removing pharmaceuticals from wastewater streams utilizing data from various literature sources and also explores the sensitivity of the characteristics and implementation of biochar. ANN 1 was designed to determine the optimal biochar characteristics (Surface Area, Pore Volume) to achieve the maximum percentage removal of pharmaceuticals in wastewater streams. ANN 2 was developed to identify the optimal biomass feedstock composition, pyrolysis conditions (temperature and time), and chemical activation (acid or base) to produce the optimal biochar from ANN 1. ANN 3 was developed to investigate the effectiveness of the biochar produced in ANN 1 and 2 in removing dye from water. Biomass feedstock with a high lignin content and high volatile matter at a high pyrolysis temperature, whether using an acid or base, achieves a high mesopore volume and high surface area. The biochar with the highest surface area and mesopore volume achieved the highest removal percentage. Regardless of hydrophobicity conditions, at low dosages (0.2), a high surface area and pore volume are required for a high percent removal. And with a higher dosage, a lower surface area and pore volume is necessary to achieve a high percent removal.

Revolutionizing soil heavy metal remediation: Cutting-edge innovations in plant disposal technology

Soil contamination with heavy metals has emerged as a global environmental threat, compromising agricultural productivity, ecosystem integrity, and human health. Conventional remediation techniques often fall short due to high costs, operational complexities, and environmental drawbacks. Plant-based disposal technologies, including biochar, phytometallurgy, and phrolysis, have emerged as promising solutions in this regard. Grounded in a novel experimental framework, biochar is studied for its dual role as soil amendment and metal adsorbent, while phytometallurgy is explored for its potential in resource recovery and economic benefits derived from harvested metal-rich plant biomass. Pyrolysis, in turn, is assessed for transforming contaminated biomass into value-added products, thereby minimizing waste. These plant disposal technologies create a circular model of remediation and resource utilization that holds the potential for application in large-scale soil recovery projects, development of environmentally friendly agro-industries, and advancement in sustainable waste management practices. This review mainly discussed cutting-edge plant disposal technologies-biochar application, phytometallurgy, and pyrolysis-as revolutionary approaches to soil heavy metal remediation. The efficacy, cost-effectiveness, and environmental impact of these innovative technologies are especially evaluated in comparison with traditional methods. The success of these applications could signal a paradigm shift in how we approach both environmental remediation and resource recovery, with profound implications for sustainable development and circular economy strategies.

The application of P-modified biochar in wastewater remediation: A state-of-the-art review

Phosphorus modified biochar (P-BC) is an effective adsorbent for wastewater remediation, which has attracted widespread attention due to its low cost, vast source, unique surface structure, and abundant functional groups. However, there is currently no comprehensive analysis and review of P-BC in wastewater remediation. In this study, a detailed introduction is given to the synthesis method of P-BC, as well as the effects of pyrolysis temperature and residence time on physical and chemical properties and adsorption performance of the material. Meanwhile, a comprehensive investigation and evaluation were conducted on the different biomass types and phosphorus sources used to synthesize P-BC. This article also systematically compared the adsorption efficiency differences between P-BC and raw biochar, and summarized the adsorption mechanism of P-BC in removing pollutants from wastewater. In addition, the effects of P-BC composite with other materials (element co-doping, polysaccharide stabilizers, microbial loading, etc.) on physical and chemical properties and pollutant adsorption capacity of the materials were investigated. Some emerging applications of P-BC were also introduced, including supercapacitors, CO2 adsorbents, carbon sequestration, soil heavy metal remediation, and soil fertility improvement. Finally, some valuable suggestions and prospects were proposed for the future research direction of P-BC to achieve the goal of multiple utilization.

Production of light olefins and monocyclic aromatic hydrocarbons from the pyrolysis of waste plastic straws over high-silica zeolite-based catalysts

Owing to the ever-increasing generation of plastic waste, the need to develop environmentally friendly disposal methods has increased. This study explored the potential of waste plastic straw to generate valuable light olefins and monocyclic aromatic hydrocarbons (MAHs) via catalytic pyrolysis using high-silica zeolite-based catalysts. HZSM-5 (SiO2/Al2O3:200) exhibited superior performance, yielding more light olefins (49.8 wt%) and a higher MAH content than Hbeta (300). This was attributed to the increased acidity and proper shape selectivity. HZSM-5 displayed better coking resistance (0.7 wt%) than Hbeta (4.4 wt%) by impeding secondary reactions, limiting coke precursor formation. The use of HZSM-5 (80) resulted in higher MAHs and lower light olefins than HZSM-5 (200) because of its higher acidity. Incorporation of Co into HZSM-5 (200) marginally lowered light olefin yield (to 44.0 wt%) while notably enhancing MAH production and boosting propene selectivity within the olefin composition. These observations are attributed to the well-balanced coexistence of Lewis and Brønsted acid sites, which stimulated the carbonium ion mechanism and induced H-transfer, cyclization, Diels-alder, and dehydrogenation reactions. The catalytic pyrolysis of plastic straw over high-silica and metal-loaded HZSM-5 catalysts has been suggested as an efficient and sustainable method for transforming plastic waste materials into valuable light olefins and MAHs.

Recovery of energy and carbon fibre from wind turbine blades waste (carbon fibre/unsaturated polyester resin) using pyrolysis process and its life-cycle assessment

Recovery of carbon fibres and resin from wind turbine blade waste (WTB) composed of carbon fibres (CF)-reinforced unsaturated polyester resin (UPR) has been environmentally challenging due to its complex structure that is not biodegradable and that is rich in highly toxic styrene (main component of UPR). Within this framework, this paper aims to liberate CF and UPR from WTB using a pyrolysis process. The treatment was performed on commercial WTB (CF/UPR) up to 600 °C using a 250 g reactor. The UPR fraction was decomposed into liquid and gaseous phases, while CF remained as a residue. The composition of gaseous phase was monitored during the entire treatment using a digital gas analyser, while gas chromatography-mass spectrometry (GC-MS) was used to characterize the collected liquid phase. CF fraction was collected and exposed to additional oxidation process after treatment at 450 °C for purification propose, then it was analysed using FTIR and SEM-EDX. Finally, the life cycle assessment (LCA) of the CF/UPR pyrolysis was studied using SimaPro software and the results were compared with landfill disposal practices. The pyrolysis results manifested that 500 °C was sufficient for UPR decomposition into styrene-rich oil and gaseous products with yields of 15.23 wt% and 6.83 wt%, respectively, accompanied by 77.93 wt% solid residue including CF. The LCA results showed that pyrolysis with oxidation process has high environmental potential in WTB recycling with significant reduction in several impact categories compared to landfill. However, the pyrolysis scenario revealed several additional environmental burdens related to ecosystems, acidification, Ozone formation, and fine particulate matter formation that must be overcome before upscaling.

Pyrolysis of mixed engineering plastics: Economic challenges for automotive plastic waste

Chemical recycling of complex plastic waste via pyrolysis can reduce fossil resource dependence of the plastics value chain and greenhouse gas emissions. However, economic viability is crucial for its implementation, especially considering challenging waste streams with high shares of engineering plastics that have lower pyrolysis product quality than standard thermoplastics waste. Thus, this study conducts a techno-economic assessment determining the profitability factors of pyrolysis plants for automotive plastic waste in Germany including different plant capacities and calculating cost-covering minimum sales prices for the resulting pyrolysis oil. Main findings are that due to economies of scale, the cost-covering minimum sales prices vary between 1182 €/Mg pyrolysis oil (3750 Mg input/year) and 418 €/Mg pyrolysis oil (100,000 Mg input/year). The pyrolysis technology employed must be robust and scalable to realize these economies of scale. Large plant capacities face challenges such as feedstock availability at reasonable costs, constant feedstock quality, and pyrolysis oil quality, affecting pyrolysis oil pricing. Due to the limited yield and quality of pyrolysis oil produced from these technically demanding feedstocks, policy implications are that additional revenue streams such as gate fees or subsidies that are essential to ensure a positive business case are necessary. Depending on the assessed plant capacity, additional revenues between 720 and 59 €/Mg pyrolysis oil should be realized to be competitive with the price of the reference product heavy fuel oil. Otherwise, the environmental potential of this technology cannot be exploited.

Prediction of MSW pyrolysis products based on a deep artificial neural network

Pyrolysis is a promising method for recovering resources and energy products from municipal solid waste (MSW). Predicting MSW pyrolysis products is crucial for establishing an efficient pyrolysis system for resource recovery. In this study, a database was established based on MySQL to record relevant information on MSW pyrolysis, which includes the MSW ultimate analysis results, proximate analysis results, parameters of pyrolysis operation and yields of pyrolysis products, etc. Based on the database and with help of a deep artificial neural network (ANN) which contains 10 hidden layers, a prediction model was successfully established to predict the yield of char, liquid and gas products from MSW pyrolysis. The results showed that the coefficients of determination for predicting the yields of char, liquid and gas from the MSW pyrolysis are 0.841, 0.84, and 0.85, respectively; these values demonstrate an accuracy comparable to that achieved for product prediction from single biomass, indicating a successful model performance. The results also show that ash content and temperature are the most important input factors influencing the outputs, namely, yields of char, liquid and gas. The results of this study can help to achieve a more efficient design of the pyrolysis system and improve the recovery of the desired pyrolysis products.

Migration of phosphorus in pig manure during pyrolysis process and slow-release mechanism of biochar in hydroponic application

Pyrolysis is an effective method for treating of livestock and poultry manure developed in recent years. It can completely decompose pathogens and antibiotics, stabilize heavy metals, and enrich phosphorus (P) in biochar. To elucidate the P migration mechanism under different pig manure pyrolysis temperatures, sequential fractionation, solution 31P nuclear magnetic resonance, X-ray photoelectron spectroscopy, X-ray diffraction, and K-edge X-ray absorption near-edge structure techniques were used to analyze the P species in pig manure biochar (PMB). The results indicated that most of the organic P in the pig manure was converted to inorganic P during pyrolysis. Moreover, the transformation to different P groups pathways was clarified. The phase transition from amorphous to crystalline calcium phosphate was promoted when the temperature was above 600 °C. The content of P extracted by hydrochloric acid, which was the long-term available P for plant uptake, increased significantly. PMB pyrolyzed at 600 °C can be used as a highly effective substitute for P source. It provides the necessary P species (e.g. water-soluble P.) and metal elements for the growth of water spinach plants, and which are slow-release comparing with the Hogland nutrient solution.

Total Capital Investment of plastic recycling plants correlates with energy losses and capacity

Plastic pollution is a generational problem, and stakeholders are turning to chemical recycling as a potential solution. However, decision-makers necessitate quick and reliable capital investment estimations to evaluate innovative technologies, especially in the early project stage, when limited historical data are available. To address this need, we built a database of 160+ chemical recycling plants, querying for nominal capacity, year and place of construction, total capital investment (TCI), number of long-term jobs and opportunity of subsidies. Then, we compared conventional association of the advancement of cost engineering AACE class 5 estimation methods, with literature estimates, and commercial capital expenditure confidence intervals for pyrolysis, gasification, solvolysis, and selective dissolution. We demonstrate the unreliability of classic methods, and we propose ballpark correlations based on the plant capacity, or the energy loss. Chemical recycling plants suffer from poor economy of scale (with current technologies), and capacity is not always the best indicator for TCI estimation. Pyrolysis and gasification are energy-driven technologies, and their TCI correlates very well (R2 =0.91-0.92) with the total energy losses. Solvolysis and selective dissolution, instead, are at an earlier development stage, so cost engineers or researchers will have to accept less certain TCI vs capacity (R2 =0.60).

Simultaneous removal of brominated and chlorinated species during the production of oils by e-waste plastics catalytic hydropyrolysis

The production of added-value chemicals via pyrolysis of plastic wastes, such as those from electrical and electronic equipment (WEEE), needs addressing their usual contamination with halogens (mainly Br and Cl). This work compares the conversion via pyrolysis and hydropyrolysis of a real WEEE plastic, having a complex composition, in two different reactor configurations: down-flow (DF) and up-flow (UF). Likewise, the effects of incorporating a Pd/Al2O3 catalyst and using two different pressures (1 and 6 bar) have been assessed. With the DF mode, pyrolysis at 1 bar leads to an oil yield above 80 wt% and a total halogen content of about 600 ppm (vs 1600 ppm in the water-washed WEEE plastic). Under DF catalytic hydropyrolysis at 6 bar, this high oil yield is maintained while its dehalogenation degree is improved (142 ppm). Operating with the up-flow configuration, under 6 bar and H2 presence, leads to some reduction in the oil yield (about 70 wt%) but significantly decreases the oil halogen content (55 ppm Cl and total elimination of Br). These results have been related to the slower pyrolysis and longer residence time in the thermal zone of the UF configuration, which favours the halogen-trapping effect of the char fraction, and the pressure-enhanced hydrodehalogenation activity of the catalyst. This study highlights the environmental benefits of the proposed process, emphasizing the lower halogen content in the resulting oils and promoting a more sustainable approach to plastic waste valorisation.

Potential use of Ulva intestinalis-derived biochar adsorbing phosphate ions in the cultivation of winter wheat Tristicum aestivum

In this work, the properties of biochar produced from green macroalga Ulva intestinalis by pyrolysis were studied at temperatures of 300, 500, and 700 °C. This biochar was characterized in terms of multielemental composition, BET surface area, total pore volume, and biosorption properties toward phosphate ions. Biochar produced at 700 °C-25 m2/g had the highest surface area. The kinetics and isotherms of sorption processes of phosphate ions as sorbate by these sorbents were investigated. Modified biochar was able to remove 84.3% of phosphate ions from wastewater, whereas non-modified biochar-only 40.6%. Hence, biochar enriched with phosphate ions can serve as a valuable soil amendment. Pot experiments performed on winter wheat (Triticum aestivum) with a 3% addition of dry Ulva intestinalis, pristine biochar, and Mg-modified biochar enriched with phosphate ions showed that these amendments stimulated plant growth (length and fresh weight of plants) as well as enlarging the chlorophyll content in leaves. Our results indicate that the production of biochar (pristine and Mg-impregnated) is a sustainable option to valorize the biomass of seaweeds, and to recycle phosphorus from wastewater.

Developing a sorptive material of cadmium from pyrolysis of hen manure

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 CO2 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 CaCO3 in HM in the presence of N2 was realized at temperatures ranging from 638 to 754 °C. The Boudouard reaction was observed at ≥ 664 °C in the presence of CO2. Despite the lack of occurrence of the Boudouard reaction, more CO formation was observed in the presence of CO2 at ≥ 460 °C. This was deemed as a homogeneous reaction induced by CO2. Considering the high Ca content of HM, HM biochar in N2 and CO2 were used as adsorbent for removal of Cadmium (Cd), which is toxic heavy metal. The adsorption capacities of HM_N2 and HM_CO2 were 302.4 and 95.7 mg g-1, respectively. The superior performance of HM_N2 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 CO2. Specifically, CO2 (representative greenhouse gas) converted into fuel. Given this, pyrolysis of HM in the presence of CO2 was achieved at ≤ 640 °C, and the atmospheric condition should be switched from CO2 to N2 at ≥ 640 °C to ensure the decarboxylation of CaCO3.