Pyrolysis Biochar Research Articles

Enhancing boreal forest resilience: A four-year impact of biochar on soil quality and fungal communities

Boreal forests commonly suffer from nutrient deficiency due to restricted biological activity and decomposition. Biochar has been used as a promising strategy to improve soil quality, yet its impacts on forest soil microbes, particularly in cold environment, remains poorly understood. In this study, we investigated the effects of biochar, produced at different pyrolysis temperatures (500 °C and 650 °C) and applied at different amounts (0.5 kg·m−2 and 1.0 kg·m−2), on soil property, soil enzyme activity, and fungal community dynamics in a boreal forest over a span of two to four years. Our results showed that, four-year post-application of biochar produced at 650 °C and applied at 1.0 kg·m−2, significantly increased the relative abundance of Mortierellomycota and enhanced fungal species richness, α-diversity and evenness compared to the control (CK) (P < 0.05). Notably, the abundance of Phialocephala fortinii increased with the application of biochar produced at 500 °C and applied at 0.5 kg·m−2, exhibiting a positively correlation with the carbon cycling-related enzyme β-cellobiosidase. Functionally, distinct fungal gene structures were formed between different biochar pyrolysis temperatures, and between application amounts in four-year post-biochar application (P < 0.05). Additionally, correlation analyses revealed the significance of the duration post-biochar application on the soil properties, soil extracellular enzymes, soil fungal dominant phyla, fungal community and gene structures (P < 0.01). The interaction between biochar pyrolysis temperature and application amount significantly influenced fungal α-diversity (P < 0.01). Overall, these findings provide theoretical insights and practical application for biochar as soil amendment in boreal forest ecosystems.

Enhancing Cd (II) immobilization with thiol-modified low-temperature pyrolysis biochar: Efficiency, mechanism, and applications

The fixation efficiency of thiol-modified lotus seedpod biochar on Cd (II) was assessed through a comprehensive investigation involving batch experiments and sediment cultivation experiments. The influence of thiol modification on the Cd (II) adsorption performance was investigated under different pyrolysis temperatures (550°C, 700°C, and 850°C). The physicochemical properties, adsorption kinetics, isotherms, and adsorption mechanisms of the modified biochar were studied. Oxidation and thiolation significantly reduced the specific surface area and total pore volume of the biochar, augmenting its hydrophilicity. High-temperature pyrolysis biochar was more suitable for oxidation modification than thiol modification. The abundant oxygen-containing functional groups in low-temperature pyrolysis biochar can serve as active sites for thiol loading. Therefore, it exhibited the highest grafting rate, the highest affinity for Cd (II), and the maximum Cd (II) adsorption capacity of 68 mg/g. Thiol-modified biochar primarily immobilized Cd (II) through chelation. Moreover, it significantly reduced the concentration of bioavailable Cd (II) in the sediment and enhanced enzymatic activity. These findings underscore the potential role of low-temperature pyrolysis thiol-modified biochar in addressing Cd (II) pollution in water and sediments.

Effect of pyrolysis temperature on the binding characteristics of DOM derived from livestock manure biochar with Cu(II).

Biochar-derived dissolved organic matter (BDOM) has the potential to influence the environmental application of biochar and the behavior of heavy metals. In this study, the binding properties of BDOM derived from livestock manure biochar at different pyrolysis temperatures with Cu(II) were investigated based on a multi-analytical approach. The results showed that the DOC concentration, aromatics, and humification degree of BDOM were higher in the process of low pyrolysis of biochar. The pyrolysis temperature changed the composition of BDOM functional groups, which affected the binding mechanism of BDOM-Cu(II). Briefly, humic-like and protein-like substances dominated BDOM-Cu(II) binding at low and high pyrolysis temperatures, respectively. The higher binding capacity for Cu(II) was exhibited by BDOM derived from the lower pyrolysis temperature, due to the carboxyl as the main binding site in humic acid had high content and binding ability at low-temperature. The amide in proteins only participated in the BDOM-Cu(II) binding at high pyrolysis temperature, and polysaccharides also played an important role in the binding process. Moreover, the biochar underwent the secondary reaction at certain high temperatures, which led to condensation reaction of the aromatic structure and the conversion of large molecules into small molecules, affecting the BDOM-Cu(II) binding sites.

Sulfuric acid-assisted ball milling for the preparation of Si-O-enriched straw biochar: removal efficiency of rhodamine B and adsorption mechanism.

Traditional pyrolysis biochar has been widely employed to treat dye wastewater. However, there are some problems in the pyrolysis process, such as the generation of harmful gases and the low content of silico-oxygen functional groups to promote adsorption. Straw biochar (Ac-BCbm) was prepared by sulfuric acid co-ball milling method. The adsorption performance and adsorption mechanism of rhodamine B (RhB) under different preparation conditions and factors were investigated. The results showed that the adsorption rate of Ac-BCbm on RhB was up to 94.9%, which was 60.5% and 55.8% higher than that of ball-milling straw (STbm) and biochar prepared by pyrolysis (STBC600), respectively. The Ac-BCbm had better adaptability under different pH and common interfering ions for remove RhB. Characterization and DFT simulation analysis revealed that the sulfuric acid co-ball milling process promoted the formation of Si-OH and Si-O-CH3 oxygen-containing functional groups of Si component in straw, which enhanced the hydrogen bonding interactions and effectively improved the adsorption efficiency. This study investigated a new strategy for biochar preparation by sulfuric acid co-ball milling, which provides an additional development direction for the efficient resource utilization of straw.

Role of biochar pyrolysis temperature on intracellular and extracellular biodegradation of biochar-adsorbed organic compounds

Immobilizing organic pollutants by adsorption of biochar in farmland soil is a cost-effective remediation method for contaminated soil. As the adsorption capacity of biochar is limited, biodegradation of biochar-adsorbed organic pollutants was a potential way to regenerate biochars and maintain the adsorption performance of biochars to lower the cost. It could be affected by the biochar pyrolysis temperature, but was not evaluated yet. In this study, biodegradation of adsorbed phenanthrene on a series of biochars with pyrolysis temperatures from 150 to 700 °C by Sphingobium yanoikuyae B1 was investigated using batch experiments of biodegradation kinetics at 30 °C, to explore the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds. It was observed that 37.5–47.9% of adsorbed phenanthrene on moderate temperature-pyrolyzed biochars produced at 400 and 500 °C were biodegraded, less than that on high temperature-pyrolyzed biochars produced at ≥600 °C (48.8–60.8%) and low temperature-pyrolyzed biochars produced at ≤300 °C (63.4–92.5%). Phenanthrene adsorbed largely on the low temperature-pyrolyzed biochars by partition mechanism and thus is easily desorbed to water for a dominated intracellular biodegradation. On the high temperature-pyrolyzed biochars, phenanthrene is adsorbed largely by pore-filling mechanism and thus less desorbed to water for intracellular biodegradation. However, high temperature-pyrolyzed biochars can promote microbes to produce siderophore, H2O2 and thus release extracellular •OH for a dominated degradation of adsorbed phenanthrene by Fenton-like reaction. With the increase of biochar pyrolysis temperature, desorption and consequently the intracellular biodegradation of adsorbed phenanthrene on biochars decreased, while the secretion of siderophore and H2O2 by microbes on biochars increased to produce more extracellular •OH for degradation by Fenton-like reaction. The results could provide deep insights into the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds, and optimize the selection of biochar with higher adsorption performance and easier regeneration for soil remediation.

Petroleum-contaminated soil bioremediation and microbial community succession induced by application of co-pyrolysis biochar amendment: An investigation of performances and mechanisms

This study aimed to remediate petroleum-contaminated soil using co-pyrolysis biochar derived from rice husk and cellulose. Rice husk and cellulose were mixed in various weight ratios (0:1, 1:0, 1:1, 1:3 and 3:1) and pyrolyzed under 500 °C. These biochar variants were labeled as R0C1, R1C0, R1C1, R1C3 and R3C1, respectively. Notably, the specific surface area and carbon content of the co- pyrolysis biochar increased, potentially promoting the growth and colonization of soil microorganisms. On the 60th day, the microbial control group achieved a 46.69% removal of pollutants, while the addition of R0C1, R1C0, R1C3, R1C1 and R3C1 resulted in removals of 70.56%, 67.01%, 67.62%, 68.74% and 67.30%, respectively. In contrast, the highest efficiency observed in the abiotic treatment group was only 24.12%. This suggested that the removal of petroleum pollutants was an outcome of the collaborative influence of co-pyrolysis biochar and soil microorganisms. Furthermore, the abundance of Proteobacteria, renowned for its petroleum degradation capability, obviously increased in the treatment group with the addition of co-pyrolysis biochar. This demonstrated that co-pyrolysis biochar could notably stimulate the growth of functionally associated microorganisms. This research confirmed the promising application of co-pyrolysis biochar in the remediation of petroleum-contaminated soil.

The Application of Pyrolysis Biochar Obtained from Waste Rapeseed Cake to Remove Copper from Industrial Wastewater: An Overview

Pyrolysis is a thermochemical technology for converting biomass into energy and chemical products consisting of bio-gas, bio-oil, and biochar. Several parameters influence the process efficiency and properties of pyrolysis products. These include the type of biomass, biomass preliminary preparation, gaseous atmosphere, final temperature, heating rate, and process time. This manuscript provides a general summary of the properties of the pyrolytic products of waste rapeseed cake, with particular emphasis on the sorption properties of biochar. Biochar, produced by the pyrolysis process of biomass, is emerging as a powerful tool for carbon sequestration, reducing greenhouse gas emissions, and purifying water from contaminants such as potentially toxic elements and antibiotics. The review found that the biochar obtained as a result of pyrolysis of chemically modified waste rapeseed cake is characterised by its excellent sorption properties. The obtained sorbents are characterised by sorption capacity relative to the copper(II) ion, ranging from 40 mg·g−1 to 100 mg·g−1, according to the pyrolysis conditions and chemical modification method. The purified pyrolysis gas obtained in the high-temperature process can be used to generate heat and energy. Bio-oil, with its significant combustion heat of 36 MJ·kg−1, can be a source of environmentally friendly green biofuel.

Can corn straw and its pyrolytic biochar be used to mitigate the toxicity of CuO NPs to wheat seedlings?

In order to understand whether corn straw (CS) and straw-derived biochar (CB) can be used as soil amendments to alleviate soil contaminated with metal oxide nanoparticles, CS and CB prepared by pyrolysis at 300 °C (with a weight ratio of 2% and 5%) were added to two types of soil contaminated with copper oxide nanoparticles (CuO NPs) to study the effects of CS and CB application on soil properties, wheat seedling growth, and metal transport. Our results showed that both 2% and 5% additions of CS and CB enhanced the nitrogen, phosphorus, and potassium fertility of both soils. In red earth (acidic), the addition of 2% and 5% of CB significantly increased soil pH (9.24% ~ 18.4%), wheat growth (12.2% ~ 14.9%), chlorophyll content (significantly increased by 32.3% for 2% CB treatment), and decreased antioxidant enzyme activity and membrane lipid peroxidation. In fluvo-aquic soil (alkaline), CS and CB did not increase soil pH, only 5% of CB significantly promoted wheat growth (by 11.0%), and decreased antioxidant enzyme activity, whereas 2% of CB reduced chlorophyll content (by 22.2%). Furthermore, 2% and 5% of CS and CB affected the transport of Cu in wheat, decreasing the translocation factor in red earth but increasing it in fluvo-aquic soil. Principal component analysis showed that 5% of CB had the best alleviating effect on CuO NPs toxicity in red earth, compared to CS. Taken together, CB obtained by pyrolysis at 300 °C appears to be an effective soil amendment specifically for red earth.Highlights• Corn straw (CS) and straw-derived biochar (CB) were used to mitigate CuO NP toxicity• 5% of CB showed the best mitigation effect on CuO NP toxicity in red earth• CS and CB had no significant mitigation on CuO NP toxicity in fluvo-aquic soilGraphical

Effects of biochar pyrolysis temperature on uranium immobilization in soil remediation: Revealed by 16S rDNA and metabolomic analyses

Uranium-stressed soil caused by nuclear industry development and energy acquisition have attracted extensive attentions for a long time. This study investigated the effects of biochar application with different pyrolysis temperatures (300 ℃, 500 ℃ and 700 ℃) on remediation of uranium-stressed soil. The results showed that higher pyrolysis temperature (700 ℃) was benefit for ryegrass growing and caused a lower uranium accumulation in plants. At the same time, uranium immobilization was more effective at higher biochar pyrolysis temperature. Careful investigations indicated that activities of soil urease and sucrase were promoted, and bacterial diversity was strengthened in C700 group, which may contribute to uranium immobilization. The biochar application could activate metabolic of lipids and amino acids, organic acids and derivatives, and organic oxygen compounds. Nicotinate and nicotinamide metabolism, and Benzoxazinoid biosynthesis were unique metabolic pathways in the C700 group, which could enhance the uranium tolerance from different perspectives. Based on these results, we recommend to use biochar with 700 °C pyrolysis temperature when processing remediation of uranium-stressed soil. This study will facilitate the implementation of biochar screening and provide theoretical helps for remediation of uranium-stressed soil.

Adsorption Performance and Mechanism of Oxytetracycline in Water by KOH Modified Biochar Derived from Corn Straw

The pollution control of tetracycline antibiotics in the environment has become a hot topic, and biochar adsorption has become an important technology to remove organic pollutants. Pyrolytic biochars (BC400, BC500, and BC600) were prepared from corn straw and then were modified by KOH to obtain KBC400, KBC500, and KBC600. Among them, KBC400 was selected for secondary pyrolysis activation at 400-600℃ to obtain AKBC400, AKBC500, and AKBC600. The structure characteristics and surface properties of AKBC were also characterized. The adsorption kinetics and thermodynamic characteristics of oxytetracycline hydrochloride (OTC) in the solution by AKBC were investigated using batch experiments. Compared to that of BC400, the specific surface area and pore structure of AKBC were significantly improved, and the aromaticity was also enhanced, resulting in the notable enhancement of the adsorption capacities for OTC. The pseudo-second-order kinetics model could better fit the adsorption process, and AKBC500 had the largest adsorption rate constant and capacity. Both the intraparticle diffusion and film diffusion were the rate-limiting steps. The Langmuir, Freundlich, and Temkin models could fit the adsorption isotherms perfectly. The adsorption of OTC on AKBC was a spontaneous, endothermic, and entropy-increasing process by both physisorption and chemisorption. The pH values in the range of 3.0-7.0 were favorable for the adsorption of OTC by AKBC. The adsorption capacity decreased with the humic acid concentration over 10 mg·L-1. The adsorption mechanism of OTC by AKBC involved pore filling, hydrogen bonding, π-π conjugation, cation-π bond, and strong electrostatic effect. AKBC still had good reusability for OTC removal after five times of regeneration. The obtained AKBC is a potential adsorbent for OTC removal from water due to the good pore structure, high adsorption capacity, and stable adsorption effect.

In-depth study on the synergistic conversion mechanism of iron ore with waste biochar for co-producing directly reduced iron (DRI) and syngas

Waste biochar and waste iron ore sintering dust were synergistically resourced to produce directly reduced iron (DRI) and combustible syngas in this study. A solid product with 92.45 % metallization ratio and a combustible syngas (65.69 % CO, 8.03 % CH4) with a yield of 1170.9 ml/g were obtained at 1000 °C for 60 min with 1.2 mol(C/Fe). The CO production of biochar conversion was increased by adding iron ore sintering dust, about 769.3 mL/g at 1000 °C for 60 min, 7.17 times that of biochar pyrolysis alone (107.3 mL/g). The co-conversion was the generation, growth and aggregation of iron grains for the sintering dust. This synergistic conversion achieved the recycling of these two solid waste resources to produce high-value DRI and high-calorific-value syngas, as industrial raw materials and fuels, saving fossil resources and fuels. The biochar pyrolysis, gasification and the reconversion of pyrolysis products occurred during their co-conversion. The gas production of biochar pyrolysis and gasification were 280.7 ml/g and 933.8 ml/g, while the reduction degrees of iron ore by the gas and solid from biochar pyrolysis were 12.64 % and 79.98 %. Their well-mixed state during the co-conversion process facilitated the reconversions of pyrolysis products by improving diffusion efficiency.

Synthesis of (FeCoNiCuMn)3O4 spinel-high entropy oxide and green carbon from agricultural waste for supercapacitor application.

This article highlights (FeCoNiCuMn)3O4 high-entropy oxide prepared via liquid state induction melting techniques for supercapacitor application. Nanostructured high entropy oxides have higher active sites to boost the surface redox process with transition metal cations, such as Fe2+, Mn3+, Ni2+, Co2+, and Cu+, which helps to improve specific power, long-term cyclic stability, and specific capacitance. Melted and ball-milled HEA Nps were annealed to form the high entropy oxide, which uses a positive electrode for supercapacitor application; this results in the highest specific capacitance of 313 F g-1 for a current rate of 5 mV s-1 for the optimized 3 M KOH electrolyte. The biochar prepared through the pyrolysis of rice straw biochar shows a maximum specific capacitance of 232 F g-1 for 5 mV s-1. The fabricated aqueous devices display the highest specific capacitance of 83 F g-1 at 2 A g-1 with a specific energy of 33.4 W h kg-1 at 1700 W kg-1.

Development of biochar/HDPE composites and characterization of the effects of carbon loadings on the electromagnetic shielding properties

The aim of this research is to develop high carbon-yielding biochar from pinewood, coffee husk, sugarcane bagasse, and maize cob and to characterize the biochar/HDPE composites for electromagnetic (EM) shielding application. During the biochar/HDPE composites fabrication, slow pyrolysis and compression molding manufacturing were used. The enhanced properties characterizations were conducted by using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), differential thermal analysis (DTA), Fourier transform spectrometry (FTIR), Brunauer-Emmet-Teller (BET) analysis, digital multi-meter, and proximity analysis. The results of biochar pyrolysis showed the maximum carbon yield of 74.6 %, 68.9 %, 68.4 %, and 40 % for pine wood, maize cob, sugarcane bagasse, and coffee husk respectively. The BET analysis showed the maximum specific surface area (734.5 m2/g), pore volume (0.2364 cm3/g), and pore radius (9.897 Å) from the pine wood biochar. The biochar loading analysis results showed that the 30 % and 40 % pine wood biochar significantly enhanced the electrical conductivity, thermal conductivity, thermal stability, crystallinity, and EM shielding effectiveness (SE) of the biochar/HDPE composites. In particular, the biochar/HDPE composite with 30 wt% pine wood biochar showed the highest thermal conductivity of 2.219 W/mK, and the 40 wt% pine wood biochar/HDPE composite achieved the highest electrical conductivity of 4.67 × 10−7 S/cm and EM SE of 44.03 dB at 2.1 GHz.

Minimum Concentrations of Slow Pyrolysis Paper and Walnut Hull Cyclone Biochars Needed to Inactivate Escherichia coli O157:H7 in Soil

Antimicrobial properties of biochar have been attributed to its ability to inactivate foodborne pathogens in soil, to varying degrees. High concentrations of biochar have reduced E. coli O157:H7 in soil and dairy manure compost, based on alkaline pH. Preliminary studies evaluating 31 different biochars determined that two slow pyrolysis biochars (paper biochar and walnut hull cyclone biochar) were the most effective at inactivating E. coli in soil. A study was conducted to determine the lowest percentages of paper and walnut hull cyclone biochars needed to reduce E. coli O157:H7 in soil. A model soil was adjusted to 17.75% moisture, and the two types of biochar were added at concentrations of 1.0, 1.5, 2.0, 2.5, 3.5, 4.5, 5.5, and 6.5%. Nontoxigenic E. coli O157:H7 were inoculated into soil at 6.84 log CFU/g and stored for up to 6 weeks at 21°C. Mean E. coli O157:H7 counts were 6.01–6.86 log CFU/g at all weeks between 1 and 6 in soil-only positive control samples. Populations in all soil amended with 1.0 and 1.5% of either type of biochar (as well as 2.0% of the walnut hull biochar) resulted in ≤0.68 log reductions at week 6, when compared with positive controls. All other concentrations (i.e., ≥2.0% paper and ≥2.5% walnut hull) inactivated ≥2.7 log at all weeks between 1 and 6 (p < 0.05). At the end of 6 weeks, E. coli O157:H7 declined by 2.84 log in 2.0% paper biochar samples, while concentrations of between 2.5 and 6.5% paper biochar completely inactivated E. coli O157:H7, as determined by spiral plating, at weeks 5 and 6. In contrast, 2.0% walnut hull biochar lowered populations by only 0.38 log at week 6, although 2.5–6.5% concentrations of walnut hull biochar resulted in complete inactivation at all weeks between 3 and 6, as assessed by spiral plating. In summary, ≥2.5% paper or walnut hull biochar reduced ≥5.0 log of E. coli O157:H7 during the 6-week storage period, which we attribute to high soil alkalinity. Amended at a 2.5% concentration, the pH of soil with paper or walnut hull biochar was 10.67 and 10.06, respectively. Results from this study may assist growers in the use of alkaline biochar for inactivating E. coli O157:H7 in soil.

Inactivation of harmful cyanobacteria Microcystis aeruginosa by Cu2+ doped corn stalk biochar treated with different pyrolysis temperatures

In this study, biochars (BCs) derived from corn stalk treated at various pyrolysis temperatures (350–950 °C) were prepared and then loaded with Cu2+ to form highly efficient algaecide, i.e. Cu2+-doped BC composites (Cu-BCs). The results showed BCs pyrolyzed at higher temperatures suppressed the growth of Microcystis aeruginosa in the order of BC550 ≫ BC750 > BC950, while BC350 accelerated cell growth due to the release of inorganic nutrients. The difference could be attributed to the physicochemical characteristics, including specific surface area, adsorption capacity of nutrients and the presence of particularly persistent free radicals. Furthermore, Cu-BCs exhibited the improved inactivation performance, but the 72 h growth inhibition rates and reaction activities of Cu-BCs were still influenced by the Cu2+ loading ratio and pyrolysis temperature. These results, reported for the first time, demonstrated the algae inactivation efficiency of pristine BCs, and Cu-BCs were principally manipulated by the biochar pyrolysis temperature.

Comparison of Ca-Based Commercial and Natural Catalysts Performance on Olive Pomace Pyrolysis Process

Physicochemical treatment was applied with 20 mg/L alum to the marble processing effluents as 5 minutes 200 rpm mixing, 25 minutes 15 rpm mixing and 60 minutes settling and marble sludge (MS) was produced. Catalytic performance of MS in olive pomace (OP) pyrolysis process was evaluated and compared to commercial Ca(OH)2 since it mainly comprises of different AAEMs (especially Ca and its forms such as CaCO3, CaO) functioned as catalyst. Catalytic pyrolysis was conducted at 600°C and 5°C/min heating rate with 5% and 10% catalyst (MS or Ca(OH)2) dosages. Although both catalysts had important effect on pyrolysis product yields, Ca(OH)2 was found as good alternative for higher gas production and MS was introduced as better option for the higher char production comparing to the conventional OP pyrolysis. Pyrolysis biochars produced with MS were in higher thermal strength than the biochars generated with Ca(OH)2. Moreover, biooils of OP+MS include different organic compounds, such as 9 heptadecanol, 1-eicosanol, ethyl linoleate, ethyl oleate, addition to the compounds observed in pyrolysis liquids of OP and OP+ Ca(OH)2. All detected organic components have diverse usage areas. Ca(OH)2 provided more decrement in the percentages of oxygenated compounds as compared to the MS. Consequently, it can be stated that MS can be used successfully as an alternative to Ca-based commercial catalyst in OP pyrolysis.

Effect of pickling on pyrolysis characteristics and adsorption properties of biomass

ABSTRACT In order to explore the influence of pickling on the pyrolysis characteristics and adsorption performance of biomass, this paper used pickled rice husk as raw material, and used TG-FTIR coupling instrument to explore the pyrolysis characteristics and product changes of rice husk; The Coats-Redfern (C-R) method was used to analyze the pyrolysis kinetics, and the adsorption performance of pyrolysis biochar on heavy metal Cu was investigated. The results show that pickling can effectively reduce AAEMs, change the pyrolysis path, increase the release of volatiles, and increase the calorific value of raw materials by about 17.10%. The surface of rice husk retains abundant functional groups, and the vibration of characteristic peaks is more intense. The C-R kinetic analysis showed that the pyrolysis process was consistent with the reaction order n = 1, and the influence on the activation energy of rice husk was sulfuric acid > phosphoric acid > nitric acid. The pickling pyrolysis biochar can promote the adsorption of heavy metal Cu2+ in the aqueous phase, the adsorption capacity is up to 41.4 mg·g−1, and the adsorption efficiency is up to 82.8%.

Biochar enhances microbial degradation of phenol in water: Response surface optimization

The utilization of biochar-immobilized microorganisms is an effective method for eliminating phenol from water. However, the main challenge to the practical implementation of this method is the high susceptibility of bacteria to environmental factors. In this study, biochar was used to reduce microbial susceptibility to high concentrations of phenol. Demineralized biochar obtained at high temperatures (600/800/1000 °C) was used to immobilize phenol-degrading bacteria (PDB) and enhance phenol removal. Biodegradation was inhibited by high concentrations of phenol (>1300 mg/L). In contrast, when microorganisms were combined with biochar, up to 82.4% phenol removal occurred, surpassing the efficacy of phenol degradation by a single microorganism (42%). Characterization techniques such as SEM, XRD, and XPS were used to analyze the properties and immobilization effect of biochar. The addition of biochar altered the dominant species of PDB to include Serratia, Ralstonia and Enterobacter. Response surface analysis indicated that both biochar pyrolysis temperature and experimental temperature significantly influenced the phenol removal rate. Thus, this paper provides methodological guidance for the application of biochar-immobilized microorganisms for phenol wastewater treatment.

Characterization and kinetics of iron oxide reduction by corn straw biochar prepared by pyrolysis using superheated steam atmosphere and hydrothermal processes

Current research on using biochar as foaming agents in electric arc furnace (EAF) steelmaking is limited to pyrolysis biochar treated with nitrogen. Therefore, this study used pyrolysis corn stalk biochar treated with nitrogen (PN) as a reference, the physical and chemical properties, the ability to reduce iron oxide, and the reaction mechanism of pyrolysis corn stalk biochar treated with superheated steam (PSS) and hydrothermal corn stalk biochar (HC) were investigated. HC contains a large number of hydrogen-containing functional groups, which can release large amounts of H2 during the reduction of iron oxide, while PSS has a higher fixed carbon content and produces higher amounts of CO and CO2 gas. Dividing the thermogravimetric results into three reduction stages, the results show that the large amount of volatile fraction contained in HC contributes to Stage 1 and that the gasification reaction ability of PSS is stronger than that of PN. The results of the kinetic analysis showed that the best reaction mechanism for the three reduction stages of the three biochars was the Jander diffusion equation. This work provides theoretical guidance for the use of PSS and HC as foaming agents in EAF steelmaking.

Mechanical strength characterisation of pyrolysis biochar from woody biomass

In order for biochar (which is produced via waste wood pyrolysis) to be used in sustainable energy or material production, it is crucial to determine certain properties, such as its mechanical strength. Consequently, in this paper, municipal waste wood (MWW)11Municipal waste wood. and forestry residue biomass (FRB)22Forestry residue biomass. – as a point of reference – are examined in an autothermal pyrolysis unit. The mechanical strength of the biochar is analysed via an uniaxial compression experiment. The present paper proposes an advanced method to investigate the strength of pyrolysed biochar in a representative and comprehensive manner, since no standards are available in literature. It has been found that firstly, the mechanical biochar’s strength decreases with increasing temperature, and secondly, that biochar prepared from FRB shows a higher breaking strength than biochar produced from MWW. Furthermore, an approximately linear progression between degree of pyrolysis and the mechanical strength is observable. Successful experiments on the gasification of MWW confirm the results obtained in this study. Additional allothermal pyrolysis experiments reveal higher strength values and reflect the more precise temperature adjustment. These results can be used as a point of reference in future research on alternative biogenic energy carriers and biochar products.