Biochar最新文献

Cd contamination, especially in farmland soil, can pose serious threats to human health as well as ecological security. Stabilization is an important strategy for agricultural soil Cd remediation. In this study, a Cd-resistant strain (Cupriavidus B-7) was isolated and loaded onto cow manure (CDB), rice straw (RSB) and pine wood biochar (PB) to investigate its effects on Cd stabilization by a 60-day pot experiment. Results indicated that the Cupriavidus B-7-loaded biochar (labelled as CDBB, PBB and RSBB) reduced the CaCl₂-extractable Cd by 43.06–59.78%, which was significantly superior to individual applications of Cupriavidus B-7 and biochar. Likewise, the soil physicochemical properties, urease, catalase and phosphatase activities were improved, indicating improved soil health. Consequently, dry weights of pakchoi’s shoot and root were increased by 938.9–1230.9% and 149.1–281.2%, respectively, by applying CDBB, PBB and RSBB. Meanwhile, the Cd accumulation in pakchoi shoots decreased by 38.06–50.75%. Notably, the RSBB exhibited an optimal performance on pakchoi growth promotion and Cd accumulation alleviation. The structural equation model indicated the synergistic effect on pakchoi growth promotion and Cd accumulation decreased between biochar and Cupriavidus B-7. Our research provides some new insights into the development of strategies for green and sustainable remediation of Cd-contaminated soil.

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Environmental stressors such as drought, salinity, and heavy metals pose significant obstacles to achieving sustainable food security, necessitating the development of universally applicable and cost-effective solutions to ameliorate soil under stress. Biochar, an eco-friendly material to increase crop yield, has been researched for almost two decades and has great potential for global use in enhancing stress resistance. However, there hasn't been comprehensive research on the impact of biochar application on soil properties, and root and crop growth. To optimize and promote biochar application in agriculture under stress, this study integrates over 100 peer-reviewed articles to explain how biochar promotes crop growth by enhancing soil resistance to stress. Biochar's distinctive properties, such as porous structure, alkaline nature, enriched surface functional groups, and nutrient content, are responsible for the following soil environment benefits: improved soil physiochemical properties, increased nutrient cycling, and boosted microbial growth. Moreover, the research emphasizes that the enhanced stress resistance of biochar optimizes nutrient absorption, alleviates soil pollutants, and thereby enhances overall crop productivity. The study discusses the roles and mechanisms of biochar on soil under stress, as well as the challenges linked to the sustainable and economical implementation of biochar in extreme soil conditions. This review aims to provide a theoretical basis for the widespread and cost-effective use of biochar in improving soil under stresses, thereby enhancing soil health and food security.

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As for Atrazine (C₈H₁₄ClN₅) degradation in soil, iron (Fe)-manganese (Mn) bimetallic biochar composites were proved to be more efficient for persulfate (PS) activation than monometallic ones. The atrazine removal rates of Fe/Mn loaded biochar + PS systems were 2.17–2.89 times higher than Fe/Mn loaded biochar alone. Compared with monometallic biochar, the higher atrazine removal rates by bimetallic biochar (77.2–96.7%) were mainly attributed to the synergy degradation and adsorption due to the larger amounts of metal oxides on the biochar surface. Atrazine degradation in Fe-rich biochar systems was mainly attributed to free radicals (i.e., ({text{SO}}_{4}^{ cdot - }) and ·OH) through oxidative routes, whereas surface-bound radicals, ¹O₂, and free radicals were responsible for the degradation of atrazine in Mn-rich biochar systems. Furthermore, with a higher ratio of Fe(II) and Mn(III) formed in Fe-rich bimetallic biochar, the valence state exchange between Fe and Mn contributed significantly to the more effective activation of PS and the generation of more free radicals. The pathways of atrazine degradation in the Fe-rich bimetallic biochar systems involved alkyl hydroxylation, alkyl oxidation, dealkylation, and dechlorohydroxylation. The results indicated that bimetallic biochar composites with more Fe and less Mn are more effective for the PS-based degradation of atrazine, which guides the ration design of easily available carbon materials targeted for the efficient remediation of various organic-polluted soil.

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Biochar application can alleviate the adverse effects of saline-alkali stress on crops. However, the long-term effects of one-off biochar application on soil physicochemical properties, salt concentration, nutrient availability, soil enzyme activities, and rice yield under highly saline-alkali paddy soils remain unclear. Here, a 6-year paddy field study was conducted in a saline-alkali paddy field using two nitrogen application levels (0 and 225 kg ha⁻¹) and four biochar application rates [0 (T0), 1.5% (T1.5), 3.0% (T3.0), and 4.5% (T4.5) biochar, w/w]. The results showed that compared with T0, the bulk density (BD) under T1.5, T3.0, and T4.5 treatments significantly decreased by 11.21%, 16.33%, and 25.57%, while total porosity (Tp) and saturated hydraulic conductivity (Ks) increased by 19.15–27.34% and 3217.78–5539.83%, respectively. Biochar consistently improved soil macro-aggregates, mean weight diameter (MWD), and the percentage of water-stable aggregates (PWSA) over the years. Additionally, one-off application of biochar continuously reduced the soil Na⁺ concentration, Na⁺/K⁺ ratio, Na⁺/Ca²⁺ ratio, saturated paste extract (ECe), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SARe). However, it reduced the pH in 2021 and 2022 only. It enhanced the concentration of K⁺, Ca²⁺, Mg²⁺, and cation exchange capacity (CEC) over the 6-year study, indicating its longer-term positive impact. Furthermore, the one-off biochar application, especially under high application rate treatments (T3.0 and T4.5), significantly and continuously improved nutrient availability and soil enzyme activities. However, alkali-hydrolysable nitrogen (AN) decreased in the initial year of biochar application. The grain yield of T1.5, T3.0, and T4.5 surpassed that of T0 by 116.38%, 141.24%, and 145.20%, respectively. Notably, the rice yield reached its peak with the treatment of 3.0% (w/w) in all 6 years of study period. These findings offered new perspectives on repairing and improving soil quality and production ability of highly saline-alkali paddy soils.

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The regulation of the pyrolysis process is a key step in increasing the carbon sequestration capacity of biochar. The effect of K₃PO₄ addition on the yield, chemical composition, characteristic functional groups, macromolecular skeleton, graphite crystallites, and stability of biochar was studied in this paper using two-dimensional infrared correlation spectroscopy (2D-PCIS), X-ray photoelectron spectroscopy, Raman spectrum, and other characterization methods combined with thermal/chemical oxidation analysis. It is discovered that adding K₃PO₄ may effectively minimize the graphitization temperature range and increase biochar's yield, aromaticity, H/C ratio, and proportion of refractory/recalcitrant organic carbon. The 2D-PCIS and Raman analysis revealed that K₃PO₄ mostly promoted the dehydrogenation and polycondensation process of the aromatic rings in the char precursor, transforming the amorphous carbon structure of biochar into an ordered turbostratic microcrystalline structure. K₃PO₄ enhanced biochar stability mostly at medium-high temperatures (350 ~ 750℃) by stimulating the transformation of unstable structures of biochar to stable carbon-containing structures or by inhibiting the interaction of its active sites with oxidants through the mineralization process. A 20% phosphorus addition increased biochar's refractory index (R₅₀) by roughly 11%, and it also boosted biochar's oxidation resistance (H₂O₂ or K₂CrO₄) efficiency, reducing carbon oxidation loss by up to 7.31%. However, at higher temperatures (> 750 ℃), the doping of phosphorus atoms into the carbon skeleton degraded the biochar structure's stability. The results of this study suggest that using exogenous phosphorus-containing additives is an efficient way to improve the stability of biochar.

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Limited information is available about potential physicochemical changes that can occur in hydrochar post-production, e.g. during drying and storage. Understanding these changes is crucial not just for shaping future research plans, but also for future practical applications. Here we studied the effect of moisture (69.2% and 2.4%) and three storage temperatures (− 18, 4, and 20 °C) over a year on selected organic and inorganic compounds in hydrochar produced from the Hydrothermal carbonization (HTC) of digested cow manure. Comparison of the control wet hydrochars (WHs) and dry hydrochars (DHs) showed changes in organic compound composition due to drying. Overall, the total amount of the selected organic compounds was notably greater in WH (15.2 g kg⁻¹ DM) compared to DH (11.8 g kg⁻¹ DM), with variations observed in individual compound concentrations. Drying, however, had no significant influence on the identified inorganic compounds. Storage caused significant changes in both WH and DH, particularly in organic compounds after 12 weeks. Sugars (2–sevenfold), acids (36–371%), and aromatics (58–120%) in stored samples at week 52 were significantly higher than their control values. Changes in the inorganic elements (e.g., Co, K, Mg, Mn, P, S, Sr, and Zn) occurred faster in WH, with significant differences starting from week 1 compared to their control values, while DH showed fewer changes. Based on these changes in both organic and inorganic content, we recommend the optimal storage conditions for future HTC studies to preserve hydrochar properties. Finally, we discussed potential applications for stored hydrochars, with DH showing greater stability, especially at − 18 °C, making it suitable for various applications.

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The development of efficient and sustainable composites remains a primary objective of both research and industry. In this study, the use of biochar, an eco-friendly reinforcing material, in additive manufacturing (AM) is investigated. A high-density Polyethylene (HDPE) thermoplastic was used as the matrix, and the material extrusion (MEX) technique was applied for composite production. Biochar was produced from olive tree prunings via conventional pyrolysis at 500 °C. Composite samples were created using biochar loadings in the range of 2.0–10.0 wt. %. The 3D-printed samples were mechanically tested in accordance with international standards. Thermogravimetric analysis (TGA) and Raman spectroscopy were used to evaluate the thermal and structural properties of the composites. Scanning electron microscopy was used to examine the fractographic and morphological characteristics of the materials. The electrical/dielectric properties of HDPE/biochar composites were studied over a broad frequency range (10^–2 Hz–4 MHz) at room temperature. Overall, a laborious effort with 12 different tests was implemented to fully characterize the developed composites and investigate the correlations between the different qualities. This investigation demonstrated that biochar in the MEX process can be a satisfactory reinforcement agent. Notably, compared to the control samples of pure HDPE, biochar increased the tensile strength by over 20% and flexural strength by 35.9% when added at a loading of 4.0 wt. %. The impact strength and microhardness were also significantly improved. Furthermore, the Direct current (DC) conductivity of insulating HDPE increased by five orders of magnitude at 8.0 wt. % of biochar content, suggesting a percolation threshold. These results highlight the potential of C-based composites for the use in additive manufacturing to further exploit their applicability by providing parts with improved mechanical performance and eco-friendly profiles.

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The present study aimed to accelerate the humification and to investigate how MnO₂ modification of biochar (MBC) drives the humus formation during composting with chicken manure. In this study, compared with the control group (CK), the addition of MBC caused an increase in the concentration of both humus and humic acid (HA), with a respective enhancement of 29.1% and 37.2%. In addition, MBC also improved the stability of compost products. Hetero two-dimensional correlation spectra further exhibited that the MBC could alter the formation mechanism of humus fractions during composting. Random forest analysis showed that Microbacterium, Bacteroides, Kroppenstedtia, Gracilibacillus, and Lentibacillus were significantly related to humus formation (P < 0.05). MBC enhanced the absolute abundance of these five genera during composting. The structural equation model further confirmed that these five genera could be indirectly involved in humus formation, through the production of aromatic compounds via secondary metabolism. Additionally, these five genera could directly transform organic components into macromolecular humus structures. Therefore, the increase in these five genera might be a direct response to the acceleration of the humification during MBC composting. These findings demonstrate the potential value of MBC in harmless disposal of hazardous biowastes through composting.

Highlights

• MnO₂ modification of biochar changed the formation mechanism of humus fractions.

• Key genera involved in humus formation were identified.

• Among of MnO₂ modification of biochar, key genera and humus formation were revealed.

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This study investigated the effects of bamboo age, bamboo parts, and pyrolysis temperatures on the physiochemical properties of bamboo char throughout a series of pyrolysis processes spanning from 150 °C to 1000 °C. The results indicated that as the pyrolysis temperature increased from 150 °C to 500 °C, the yield of bamboo char experienced a rapid decline, settling at a maximum of 69%, with no significant impact from bamboo age and parts. Subsequently, as the pyrolysis temperature continued to rise from 500 °C to 1000 °C, the yield stabilized at 25.74–32.64%. Besides, fixed carbon (FC), volatile matter (VM), and ash content were temperature-dependent, while the H/C, O/C, (N + O)/C, and aromatic index kept constant after reaching 500 °C. Notably, 800 °C was confirmed to be a crucial turning point for physiochemical properties, at which the graphitic structural changes occurred, pore collapsed, and potassium salts released. Bamboo age was proved to enhance the stability. Pearson correlation coefficient (PCC) analysis revealed that the pyrolysis temperature was positively correlated (p < 0.01) with ash (0.76), FC (0.97), AI (0.81), R₅₀ (0.77), and C–C/C = C/C–H (0.87). Conversely, negative correlations (p < 0.01) were observed with VM (−0.91), O/C (0.88), H/C (−0.95), (N + O)/C (−0.87), C loss (−0.79), and labile organic-C (−0.78). Additionally, bamboo age was negatively correlated (p < 0.01) with C loss (−0.40), volatile organic-C (−0.63), labile organic-C (−0.45), and recalcitrant organic-C (−0.40), but positively associated with R₅₀ (0.54), refractory organic-C (0.42), and inorganic-C (0.52). Bamboo parts did not exhibit significant correlations with char properties.

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Pyrolysis is one method for treating sewage sludge, particularly in remote areas or decentralised systems. The end product of pyrolysis, sludge-char, can serve as a soil improver. However, there is a lack of comprehensive data on the organic pollutants’ behaviour in sludge-char. In our work, we focused on the behaviour of per- and polyfluoroalkyl substances (PFASs). Sludge was pyrolyzed at 200–700 °C to determine the minimum safe temperature for effective PFASs removal. It is important to note that PFASs may not only be mineralized but also cleaved to unanalyzed PFASs and other organofluorinated substances. To address this issue, we incorporated additional measurements of organic fluorine in the experiment using combustion ion chromatography (CIC). Due to the inherent heterogeneity of sludge, containing a variety of pollutants and their precursors, we conducted pyrolysis on artificially contaminated sand. This allowed us to assess and compare the behaviour of PFASs in a homogeneous matrix. Based on our analyses, we determined that a temperature greater than 400 °C is imperative for effective PFASs and organic fluorine removal. The results were verified by analyzing samples from a commercial sludge pyrolysis unit at the Bohuslavice-Trutnov WWTP, which confirmed our measurements. In light of these results, it becomes evident that sludge pyrolysis below 400 °C is unsuitable for PFAS removal from sewage sludge.

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