Effect Of Biochar Particle Size Research Articles

Size matters: Powder biochar promotes the elimination of antibiotics resistance genes and potential hosts during swine manure composting

Livestock manure faced acute environmental pollution and ecology risky caused by antibiotic resistance genes (ARGs). This study investigated the effects of biochar particle size including powder biochar (75 μm, PB), and granular biochar (2 mm, GB) on ARGs variation during the aerobic composting. The results showed that the total relative abundance (RA) of the ARGs decreased significantly in all the treatments after composting. While compared to the removal efficiency of total RA in the control (CK), PB decreased by 90.99 % and GB increased by 93.25 %, and both PB and GB removed MGEs completely. Sulfonamide antibiotic resistance genes were the main contributor of the ARGs rebounding. PB addition could hinder the rebounding of sulfonamide antibiotic resistance genes during the later stage of the composting. Co-occurrence network analysis showed that the addition of biochar (both types) increased the complexity of the microbial community the competition of inter-phylum, which was indicated by the higher number of edge and density and lower positive connection. The different ARGs removal efficiency in these two treatments might be that PB promoted the competition both inter-phylum and potential hosts-other microbes, resulted in fewer kinds and abundance of ARGs hosts, while GB increased the stability of ARGs hosts making it more resistant to environment changes. Totally, compared with the global adjustment strategy of microbial communities, more exclusive methods focusing on the controlling of ARGs hosts should be explored to decrease the ecological risk of composting products during composting process.

Effect of biochar content and particle size on mechanical properties of biochar-bioplastic composites

The recent increase in plastic use and the resulting pollution have put bioplastics in a strong position to expand. However, better understanding of bio-fillers and their effect on popular bioplastics, such as poly (lactic acid) (PLA), is required for this to occur. Biochar (BC), a stable form of carbon derived from high temperature conversion of organic material, has potential as a plastic filler. Although BC's effect on petroleum-based plastics has been widely studied, there are still major gaps in the literature surrounding BC use as a filler in PLA/starch composites. In this work, the effects of BC particle size and mass loading were examined when paired with a PLA/starch matrix. Mechanical and thermal testing was performed on composites that varied in filler loading (0–20 wt%), as well as particle size following a factorial design. At 20 wt% BC, the finer BC particles produced a drop in the viscosity, which could be attributed to degradation of polymer chains. Mechanical characterization showed that increasing the BC filler loading increased the stiffness of the composite. A similar effect was seen when decreasing the particle size of the BC at a constant loading. The most significant finding was that a combination of decreased particle size and filler loading of 5 wt%, increased the tensile strength by about 54% relative to the control (no BC) and slightly increased the elongation, thereby increasing the composites toughness. These results indicate that particle size and loading are important design considerations when using BC as a filler.

Effect of biochar with different particle sizes on the sorption-desorption characteristics of soil phosphorus.

The size of particles determines the adsorption reaction. In this study, three different particle sizes of biochar (0.25-1 mm, 0.075-0.25 mm, <0.075 mm) were produced from rapeseed straw (SBC) and chicken manure (MBC). The biochar was mixed with high phosphorus (P) soil and low P soil and then incubated for 30 days. We conducted isothermal P sorption and desorption experiments to evaluate the effects of biochar particle size on sorption-desorption characteristics of soil P, and analyzed soil properties associated with P sorption. The results showed that P sorption capacity of SBC and MBC in the water system was highest for the smallest particle size (<0.075 mm) (SBC: 43125 mg·kg-1, MBC: 20083 mg·kg-1), followed by the intermediate particle size (0.075-0.25 mm) (SBC: 37376 mg·kg-1, MBC: 13199 mg·kg-1) and the largest particle size (0.25-1 mm) (SBC: 27749 mg·kg-1, MBC: 12251 mg·kg-1). However, there was little difference in soil P sorption between the three particle sizes of the same biochar in the soil system. In comparison with no biochar treatment, the addition of SBC increased the Langmuir P sorption maximum (Smax) by 236.8%-755.7%, and decreased soil P desorption rate. The addition of MBC increased Smax, but the enhancement was less than that of SBC. Soil P desorption rate was increased by 7.2%-295.9%. Both SBC and MBC significantly increased the contents of soil total P, available P, and exchangeable calcium (Ca) and magnesium (Mg). The increases in Ca and Mg contents due to biochar addition was 64.0%-257.1% (SBC) and 39.1%-205.3% (MBC), respectively. The contents of soil exchangeable Ca and Mg were positively correlated with Smax. These results suggested that biochar particle size had little effect on soil P sorption, but the enrichment of Ca and Mg due to biochar addition played a critical role in regulating soil P sorption. The rapeseed straw biochar had a high adsorption capacity for soil P, making it suitable for improving the P fixation capacity of soil rich in P and reducing the loss of excess P. Chicken manure biochar could be used to improve the P availability of low P soils and increase the contents of available P.

Effects of biochar particle size on sorption and desorption behavior of NH4+-N

Although optimizing of particle size was a simple and low-cost method for biochar modification, the insufficient understanding of biochar particle size on sorption and desorption performance has hindered its application. In this study, apple branch biochar was mechanically grinded and dry sieved into different particle sizes to investigate the sorption mechanism, sorption and desorption characteristics at various temperature, NH 4 + -N concentrations, contact time, biochar dosages and regeneration times. The particle size modification affected the physical properties of biochar but not the sorption mechanism, which was a comprehensive process involving physicochemical sorption. The result indicated that, for all three particle sizes, the sorption process was exothermic and the Langmuir, pseudo first and second order kinetic models can provide satisfactory descriptions. The sorption capacity increased with the rising of NH 4 + -N concentrations and contact time. The decreasing biochar particle size significantly increased the sorption capacity, desorption capacity and efficiency in the first 24 h, indicating that large particle size biochar had a better slow-release effect. Moreover, both sorption capacity and slow-release effect were also affected by the ratio of NH 4 + -N to biochar. High NH 4 + -N-biochar ratios were beneficial for increasing sorption and desorption capacity of biochar, while small NH 4 + -N-biochar ratios were beneficial for increasing the slow-release effect. Considering the nutrient supply and slow-release performance, the recommended NH 4 + -N-biochar ratios for fine, medium and coarse biochar were 0.013–0.016, 0.013–0.034, and 0.009–0.124, respectively. At the same slow-release effect, coarse biochar had better nutrient supply capacity, indicating that a greater application efficiency. Compared with traditional slow-release fertilizers, biochar had excellent regeneration performance, which could be enhanced by particle size modification. In conclusion, our research provides a theoretical basis for the necessity of biochar particle size optimization. • Fine biochar (＜0.25 mm) enhances sorption capacity but lowers slow-release effect. • NH 4 + -N-biochar ratio affects the biochar sorption and desorption performance. • The recommended NH 4 + -N-biochar ratio varies with the biochar particle size. • Coarse biochar (1–2 mm) is preferred for better efficiency and regeneration.

Effects of biochar particle size, biochar application rate, and moisture content on thermal properties of an unsaturated sandy loam soil

Although biochar is considered as a potential soil amendment, the effect of its rates and particle sizes on soil properties such as soil thermal properties, especially in a light-textured soil has not been widely discussed. Due to the importance of soil thermal properties in many engineering, climatological and agricultural applications, this study aims to investigate and model the effects of biochar particle size, biochar rate, and soil moisture content on the thermal properties of a sandy loam soil through column experiments. The experiments were conducted using three biochar application rates (0 (as control), 1%, and 5% w/w), three biochar particle diameters (<0.15, 0.15–1, and 1–2 mm), and three water saturation (Sw) levels (0.07, 0.2, and 0.78) in three replicates. Given the experimental data, soil thermal properties were modeled using the Campbell, Zhao et al., and de Vries models. According to the results, a higher biochar application rate (i.e. 5%) significantly (P < 0.05) altered soil physical and chemical properties, i.e. bulk density, porosity, EC and pH, and soil thermal properties. Biochar particle sizes had a remarkable effect on soil thermal properties. Adding 5% biochar with particle sizes of < 0.15, 0.15–1 and 1–2 mm decreased soil thermal conductivity to 21%, 26%, and 32% at Sw= 0.07, respectively indicating a lower reduction of thermal conductivity when biochar with a smaller particle size (<0.15 mm) is applied. Applying 5% biochar of the smallest size decreased soil thermal conductivity and diffusivity, and heat capacity by 21%, 17%, and 9%, respectively, and increased thermal resistivity by 27% at Sw= 0.07. The effect of soil moisture on thermal properties (especially thermal conductivity and resistivity) was more robust than biochar amendment. Experimental modeling showed a linear relationship between soil moisture and thermal conductivity, diffusivity and heat capacity, and a power law relationship between soil moisture and thermal resistivity. Mathematical modeling showed the Campbell, de Vries, and Campbell/de Vries models perform the best in estimating thermal conductivity, heat capacity, and thermal diffusivity, respectively. The findings of this research could be used for controlling and predicting soil temperature, improving irrigating scheduling, and optimizing the quantity of biochar amendment required in agricultural fields.

Effects of biochar particle size and dosage on the desiccation cracking behavior of a silty clay.

Desiccation cracking can significantly change the integrity of soils, and potentially result in the instability of infrastructure as well as the migration of contaminants. Biochar is regarded as a promising low-carbon material for geotechnical applications, including cracking prevention. This study investigates the effects of biochar particle size and dosage on the desiccation cracking characteristics of a silty clay. For samples with fine biochar particles (<0.25 mm), coarser primary cracks initiate first, followed by finer secondary cracks regardless of biochar dosage. Quantitative analysis of the cracking characteristics at the stable stage shows that the surface crack ratio, the number of crack segments, the total length of cracks and the average width of cracks decreased by 31.29%, 30.78%, 14.18%, and 20.45% after 10% biochar addition. For samples with coarse biochar particles (>0.25 mm), cracks initiate simultaneously on the soil surface, and primary and secondary cracks are difficult to distinguish after drying, especially in high dosage samples. In the presence of 10% biochar, the surface crack ratio and average width of cracks decreased by 28.64% and 62.84%, but the number of crack segments and total length of cracks increased by 163.39% and 42.13%. Microstructure and image processing analysis of soil cracks indicate that biochar affects the crack initiation and propagation process by altering the soil microstructure and thereby the crack parameters. The contact between biochar and soil particles transitions from close contact to loose contact as the size of the biochar particles increases. In general, the application of 10% biochar with fine particle size had the best performance in inhibiting soil cracking.

Effect of production temperature and particle size of rice husk biochar on mercury immobilization and erosion prevention of a mercury contaminated soil

Mercury (Hg) contaminated soil is a potential hazardous material especially under soil erosion and surface runoff. This work aims to use rice husk biochar to immobilize Hg and prevent erosion, and find the optimal production temperature and particle size of the biochar. The biochars were produced at 300, 500, and 700 °C and sieved to three particle sizes ~20, < 2, and < 0.15 mm. They were applied to a Hg contaminated loamy sand (20.2 mg/kg) and undergone simulated rainfall erosion representing 7 years of heavy rain events in Beijing. All biochar amendments reduced the runoff volume by 5.1–15.4%. Hg amount in runoff were significantly reduced by 36.7–48.8% after the amendments of biochar. The Hg concentration of infiltration was reduced by biochar treatments except that produced at 300 °C, while its amount was increased due to larger infiltration volume. All biochar amendments significantly reduced soil loss in runoff by 43.5–77.2%. Hg was enriched in the sediments (39.7–46.8 mg/kg) compared with the parent soil (20.2 mg/kg) regardless of biochar treatment, but its bioavailability was low. Higher pyrolysis temperature of the rice husk biochars resulted in less runoff, more infiltration, and better erosion prevention, while the effect of biochar particle size is less significant.

Effect of biochar and biochar particle size on plant-available water of sand, silt loam, and clay soil

Biochar is being used as a soil amendment to improve soil hydraulic properties. It has been reported that biochar increases plant-available water, particularly in coarse-textured soils; however, effects on fine-textured soils are less pronounced. Here, we quantified the effects of biochar particle size on plant-available water in sand, silt loam, and clay soils. We amended these soils with a hydrophilic biochar, and packed soil-biochar mixtures into columns of 5.35-cm diameter and 3.0-cm height. Biochar was produced by gasification of woody forest residues. We applied the biochar at two different rates (0.5% and 2% by weight of C) and with four different biochar particle-size fractions (<4.75, <2.0, <1.0 and <0.5 mm). Our results show that biochar amendments increased the plant-available water (when expressed gravimetrically) of all three soils, particularly at the highest biochar application rate. Although the absolute increase in plant-available water was largest for the silt loam soil, the relative increase of plant-available water was greater for the sand than for the silt loam and clay. When expressed in volumetric terms, however, the effects on water retention were less pronounced: the sand showed a small increase in plant-available water with biochar amendment, and no change was observed with the silt loam and clay. Particle size of biochar had little effect on plant-available water (when expressed in gravimetric terms) in the three soils, but silt loam and clay showed increased plant-available water (when expressed in volumetric terms) with decreasing biochar particle size, while no effect was observed for the sand. While our findings corroborate many of the previously reported effects of biochar on soil-water retention, we show that the effects and their magnitude depend on whether the results are reported in terms of gravimetric or volumetric water contents. Because bulk density tends to decrease with increasing biochar application, so will the volumetric water content, and thus the magnitude of the effect on plant-available water will be smaller when expressed in volumetric water content.

Influence of feedstock type and particle size on efficiency of biochar in improving tensile crack resistance and shear strength in lean clayey soil

The development of tensile stress can cause desiccation cracks, further increasing infiltration and inducing instability in green infrastructure (slopes and landfill liners). Recent research has promoted the use of biochar (i.e., stable carbon with a life period of more than 500 years) as an eco-friendly material that can provide simultaneous benefits in reducing tensile stresses and crack development, aiming to enhance landfill cover longevity. However, there is a lack of guidelines and criteria for selecting biochar (feedstock type and particle size) as landfill cover material. This study aims to investigate the effects of biochar particle size and feedstock type on cracking of soil. Two contrasting feedstock types (i.e., pig manure-based and wood-based) have been selected for amendment on lean clay soil. Laboratory experiments were conducted to monitor the cracks. The results show that wood biochar (WB) is more efficient in crack reduction than pig manure biochar (PMB). Moreover, it has been observed that fine-grained biochar is more suspectable to cracks formation regardless of biochar type. The cohesion and internal friction angle of biochar are dependent on the surface morphology of biochar. WB has more angularity and sharp edges, which can increase interlocking in soil, thereby enhancing shear resistance and, hence, soil stability. The comprehensive study can help narrow down the selectivity of biochar and its specifications to mitigate cracks and enhance the strength of landfill cover.

Influence of biochar particle size on the hydraulic conductivity of two different compacted engineered soils

Biochar is a recalcitrant material obtained after pyrolysis of labile biomass under oxygen-limited condition. The conversion of biomass into biochar is considered to be a sustainable way of generating bioenergy, minimizing the emission of greenhouse gases and managing the waste. Recently, the amendment of biochar in soil gained attention due to its multiple soil ameliorating features. Many studies have investigated the effect of biochar particle size on the physicochemical and hydraulic properties of relatively loose agricultural soil. However, such study is rarely conducted for compacted soil suitable for bioengineered structures. The objective of the current study is to investigate the effect of biochar particle size on the hydraulic conductivity of compacted soil for bioengineered structures. Saturated hydraulic conductivity (Ksat) of different compacted soils amended with biochar of different particle sizes ranging from 0.075 to 4.75 mm has been investigated. The results showed that the amendment of 5% to 15% (w/w) biochar of different particle sizes led to the change in Ksat of the silty sand. When compared with bare soil, a higher Ksat with biochar of particle size larger than 0.425 mm and a lower Ksat with particles of size smaller than 0.425 mm was observed. However, in pure sand, a lower Ksat irrespective of particle size of biochar was observed and the lowest Ksat was noted with biochar of particle size smaller than 150 mm. These changes in the Ksat after biochar amendment were attributed to the alteration of pore structure mainly, inter-pores of the soil, which is controlled by the particle size of the biochar. The findings of the present study could be useful for the field application i.e. in bioengineered structures.

Effect of biochar particle size on water retention and availability in a sandy loam soil

The ability of biochar to enhance the physical and hydrological properties of light textured soils is highly dependent on the characteristics of biochar including its particle size. To investigate the effect of biochar particle size on water characteristics and soil structure of a sandy loam soil, date palm biochar prepared at a pyrolysis temperature of 450–500 °C was fractioned by dry sieving into four sizes: 2–1, 1–0.5, 0.5–0.1, and <0.1 mm, and mixed in soil pots with a sandy loam soil at an application rate of 4%. The soil pots were incubated in a greenhouse for 120 days, and water content was kept at field capacity throughout the experiment. Water retention, hydraulic conductivity, and soil structure parameters were measured. Results showed that the largest increase in both water content at field capacity and available water content was observed with the smallest biochar particle size due to increased microporosity as a result to the larger internal surfaces and the porous structure of the biochar particles. Condense particle packing and increased tortuosity due to increased microporosity resulted in a reduction in saturated hydraulic conductivity and bulk density of the soil and biochar mixtures. Soil structure was improved in the soil and biochar mixtures at all biochar particle sizes, nevertheless, no significant increase in soil structures was observed among biochar particle sizes < 1 mm. The application of biochar with particle sizes < 1 mm can enhance the physical and hydrological properties of light textured soils and increase water conservation in the soil, which will help to reduce the amount of water required for irrigation. However, assessment under field conditions is required to assess the long-term effect of biochar on water characteristics and soil structure.

Adsorption of Lead, manganese, and copper onto biochar in landfill leachate: implication of non-linear regression analysis

The feasibility of using wood-derived biochar (BC) to remove Pb, Mn, and Cu from landfill leachate was investigated and modeled in this study. BC was produced under the pyrolytic temperature of 740 °C. The effect of contact time, BC dosage and particle size on adsorption of the heavy metals onto BC was examined. BC was used in two forms i.e., pulverized (PWB) and crushed (CWB) to evaluate the effect of BC particle size on adsorption characteristics. The kinetics of Pb, Mn, and Cu adsorption onto PWB and CWB were assessed using the pseudo second-order and Elovich models, where both applied models could well describe the adsorption kinetics. Removal efficiencies of the heavy metals were increases by 1.2, 1.4, and 1.6 times, respectively, for Pb, Mn, and Cu, when PWB content of the leachate increased from 0.5 to 5 g L− 1. Equilibrium adsorption capacity of the heavy metals onto BC in leachate system was evaluated using the Langmuir, non-linearized Freundlich, linearized Freundlich, and Temkin isotherms and found to have the following order for PWB: Non-linearized Freundlich > Temkin > Langmuir > Linearized Freundlich. The Langmuir and linearized Freundlich models could not adequately represent adsorption of the heavy metals onto BC, especially for CWB. The highest removal of 88% was obtained for Pb, while the greatest adsorption intensity was found to be 1.58 mg g− 1 for Mn. Using the non-linearized Freundlich isotherm significantly reduced adsorption prediction error. The adsorption affinity of PWB for Pb, Mn, and Cu was greater than that of CWB in all treatments. Wood-derived BC is suggested to be used for the removal of heavy metals from landfill leachate as an economical adsorbent.

Effects of biochar particle size and concomitant nitrogen fertilization on soil microbial community structure during the maize seedling stage.

Biochar is widely used as a soil amendment, either alone or in association with fertilizer. However, the effects of biochar particle size on the soil microbial community are largely unclear. Biochar was divided into two groups according to diameter sizes: < 1mm and 2.5-5mm (labeled as CB1 and CB5, respectively). A pot experiment was established in which maize (Zea maize L.) was treated with CB1, CB5, and/or external nitrogen (N, NH4NO3). At the end of the seedling period (45days), analyses of soil microbial community structure and other soil and crop properties were conducted. The biochar (regardless of N addition) enhanced microbial biomass and activity. CB1 had a stronger capacity than CB5 to modify soil microbial community structure by promoting soil microbial groups (e.g., fungi, Gram-negative bacteria), which is likely due to CB1 undergoing a series of more intense processes (e.g., nutrient release, mineralization) than CB5. However, this difference was diminished or disappeared when N was added, mainly due to the masking effect of soil acidification that was induced by N fertilization. Collectively, fine biochar has a stronger effect on soil microbial community than coarse biochar. Particle size only affects soil microbial community structure when biochar is applied alone; it has no effect when biochar is applied in association with chemical N fertilizer, at least during the seedling period. The relationship between particle size and soil microbial community needs to be considered when using biochar for soil amendment.

Effects of Biochar Particle Size on Methane Emissions from Rice Cultivation

Biochar amendment is generally recognized as an effective mitigation option of methane (CH4) emissions from rice cultivation. Although its mitigation mechanisms are not well understood, the potential relevance of surface area and porosity of biochar has been discussed. This study aimed to evaluate the application of different biochar particle sizes on CH4 production, oxidation, and emissions from rice cultivation in a clay loam soil, based on the assumption that porosity and surface area of biochar are directly related to its mitigation effects. Rice was grown under greenhouse conditions for two growing seasons, either with 0.5–2 mm (small, SB) or with 2–4 mm (large, LB) biochar. The results show that both sizes of biochar increased soil pH and redox potential (Eh) during rice growth. Soil dissolved organic carbon (DOC), nitrate (NO3− ), and sulfate (SO42−) also increased under both biochar amendments, but size effects were not observed. SB and LB suppressed the abundance of CH4 producers (methanogens) but stimulated the abundance of CH4 consumers (methanotrophs). The increase of soil Eh and electron acceptors (NO3− and SO42− ) indicated the increase in soil oxidation capacity is a barrier to CH4 production by methanogens in both biochar treatments. Laboratory incubation experiments showed that CH4 production activity was significantly (p ≤ 0.05) reduced by 18.5% using SB and by 11.3% using LB compared to the control. In contrast, the stimulation of methanotrophs promoted greater CH4 oxidation activity by 15.0% in SB and 18.7% in LB compared to the control. It shows that CH4 production was reduced more by larger surface area biochar (SB), while a greater increase in CH4 oxidation was found using larger pore volume biochar (LB). The effects on CH4 production were more pronounced than those on CH4 oxidation, resulting in a greater reduction of cumulative CH4 emissions by SB than LB (by 26.6% and 19.9% compared to control, respectively).

The influence of biochar particle size and concentration on bulk density and maximum water holding capacity of sandy vs sandy loam soil in a column experiment

Biochar application to agricultural soils has been proposed as a way to increase crop production by improving soil chemical and physical properties. Liming potential and improved nutrient exchange on biochar surfaces are the most reported mechanisms. Wherever crops experience drought stress, improvements in soil water holding capacity (WHC) might also be an important mechanism. However, reported effects on soil structure and WHC are mixed. Therefore, we studied the effects of biochar on soil bulk density (BD) and WHC in a laboratory column study using two agricultural soils from Portugal: a sandy and a sandy loam soil. Mixed woody feedstock was pyrolysed at 620 °C, creating a wettable biochar that was used unsorted as well as sieved into large (2–4 mm) and small (0.05–1.00 mm) particles, mixed into the soils at 1, 5, 10 and 20% (by volume), and incubated for 10 days at field capacity to allow aggregation. Soil samples were analysed for BD and WHC using soil columns.We found biochar to decrease soil BD and increase maximum WHC, expressed as gravity-drained equilibrium water content, for both soils. The sandy soil was more responsive with significant effects at the lowest application rate (1%), while the sandy loam soil started to show significant effects at 5% biochar. Small biochar particles reduced the BD of sandy soil more, while large biochar particles caused a greater reduction in the BD of the sandy loam soil. The effect of biochar particle size on WHC was less clear, except for small particles at 20% volumetric concentration, which showed a 60% increase in gravimetric WHC. When expressed as total soil water storage (SWS), 20% biochar incorporation to 15 cm depth would increase the total SWS of sandy soil from 0.56 mm (control) to 0.83–0.91 (mm), and of the sandy loam soil from 0.56 to 0.79–0.96 (mm), depending on biochar particle size. Our results suggest that biochar particle sizes can be used to achieve specific effects in soils, while mechanisms and trade-offs (agro-economic and environmental) need further exploration.

Effect of Biochar Particle Size on Physical, Hydrological and Chemical Properties of Loamy and Sandy Tropical Soils

The application of biochar is promising for improving the physical, chemical and hydrological properties of soil. However, there are few studies regarding the influence of biochar particle size. This study was conducted to evaluate the effect of biochar size on the physical, chemical and hydrological properties in sandy and loamy tropical soils. For this purpose, an incubation experiment was conducted in the laboratory with eight treatments (control (only soil), two soils (loamy and sandy soil), and three biochar sizes (&lt;0.15 mm; 0.15–2 mm and &gt;2 mm)). Analyses of water content, bulk density, total porosity, pore size distribution, total carbon (TC) and total N (TN) were performed after 1 year of soil–biochar-interactions in the laboratory. The smaller particle size &lt;0.15 mm increased water retention in both soils, particularly in the loamy soil. Bulk density slightly decreased, especially in the loamy soil when biochar &gt; 2 mm and in the sandy soil with the addition of 0.15–2 mm biochar. Porosity increased in both soils with the addition of biochar in the range of 0.15–2 mm. Smaller biochar particles shifted pore size distribution to increased macro and mesoporosity in both soils. Total carbon content increased mainly in sandy soil compared to control treatment; the highest carbon amount was obtained in the biochar size 0.15–2 mm in loamy soil and &lt;0.15 mm in sandy soil, while the TN content and C:N ratio increased slightly with a reduction of the biochar particle size in both soils. These results demonstrate that biochar particle size is crucial for water retention, water availability, pore size distribution, and C sequestration.

Effect of biochar particle size on hydrophobic organic compound sorption kinetics: Applicability of using representative size

Particle size of biochar may strongly affect the kinetics of hydrophobic organic compound (HOC) sorption. However, challenges exist in characterizing the effect of biochar particle size on the sorption kinetics because of the wide size range of biochar. The present study suggests a novel method to determine a representative value that can be used to show the dependence of HOC sorption kinetics to biochar particle size on the basis of an intra-particle diffusion model. Biochars derived from three different feedstocks are ground and sieved to obtain three daughter products each having different size distributions. Phenanthrene sorption kinetics to the biochars are well described by the intra-particle diffusion model with significantly greater sorption rates observed for finer grained biochars. The time to reach 95% of equilibrium for phenanthrene sorption to biochar is reduced from 4.6–17.9days for the original biochars to <1–4.6days for the powdered biochars with <125μm in size. A moderate linear correlation is found between the inverse square of the representative biochar particle radius obtained using particle size distribution analysis and the apparent phenanthrene sorption rates determined by the sorption kinetics experiments and normalized to account for the variation of the sorption rate-determining factors other than the biochar particle radius. The results suggest that the representative biochar particle radius reasonably describes the dependence of HOC sorption rates on biochar particle size.

Impacts of Woody Biochar Particle Size on Porosity and Hydraulic Conductivity of Biochar-Soil Mixtures: An Incubation Study

ABSTRACTBiochar improves soil performance by altering soil physical characteristics. To understand the effect of biochar particle size on soil hydrology, we measured the hydraulic conductivity (Ks) of biochar-soil mixtures. To better understand how physical properties influenced Ks, skeletal and (bulk density (, the water saturation (S), and the porosity (Ф) of mixtures were measured. A sandy loam soil was mixed with two woody biochar particle sizes (1–2 and <1 mm). All used biochars significantly decreased Ks compared to soil but this reduction for finer biochars was more distinct. When finer particles of low and high-tempered biochars were applied Ks decreased 14.3% and 18.9% while coarser particles reduced Ks 13.9% and 17.5%, respectively. Also, all biochars increased total, effective, inter and intraporosity of mixtures compared to control after 180 days. Negative correlation between Ks and porosity demonstrates the increase of porosity isn’t necessarily providing flow paths and thus doesn’t have a positive influence on Ks. Decrease of Ks through the addition of fine biochars was because they filled spaces between soil particles, which increased tortuosity and reduced pore throat size. Also, the decrease of Ks associated with coarser biochars was caused by the bimodal particle size distribution, resulting in more compact packing and tortuosity.

Phosphorus Removal from Wastewater in Biofilters with Biochar Augmented Geomedium: Effect of Biochar Particle Size

The use of biochar as a filter medium amendment has shown potential for removing organic and inorganic pollutants from wastewater. The purpose of this study was to investigate the effect of biochar particle size on: (i) removal efficiency of total phosphorus (TP) from wastewater; (ii) stability of the system under overloading and flooding conditions; and (iii) desorption potential of phosphorus from the filtration medium under inundation conditions. Biochar was prepared in two different sizes: fine and coarse with a mean diameter size of 0.31 and 0.49 mm, respectively. Two treatments using sand augmented with 8% by weight fine biochar (sand–FBC) and sand augmented with 8% by weight coarse biochar (sand–CBC) were tested. The TP removal efficiency of sand–CBC was 10% higher than sand–FBC medium. The average removal efficiencies were 83.3 ± 3.2 and 75.7 ± 7.4% for sand–CBC and sand–FBC media, respectively. Positive correlations between TP load and removal efficiencies were observed. All treatments showed resilience to overloading, flooding, and inundation conditions.

Biochar particle size, shape, and porosity act together to influence soil water properties.

Many studies report that, under some circumstances, amending soil with biochar can improve field capacity and plant-available water. However, little is known about the mechanisms that control these improvements, making it challenging to predict when biochar will improve soil water properties. To develop a conceptual model explaining biochar’s effects on soil hydrologic processes, we conducted a series of well constrained laboratory experiments using a sand matrix to test the effects of biochar particle size and porosity on soil water retention curves. We showed that biochar particle size affects soil water storage through changing pore space between particles (interpores) and by adding pores that are part of the biochar (intrapores). We used these experimental results to better understand how biochar intrapores and biochar particle shape control the observed changes in water retention when capillary pressure is the main component of soil water potential. We propose that biochar’s intrapores increase water content of biochar-sand mixtures when soils are drier. When biochar-sand mixtures are wetter, biochar particles’ elongated shape disrupts the packing of grains in the sandy matrix, increasing the volume between grains (interpores) available for water storage. These results imply that biochars with a high intraporosity and irregular shapes will most effectively increase water storage in coarse soils.