Design constraints governing household-scale rice-straw biochar systems: The role of feedstock densification and particle-size selection

Biochar aging-driven cadmium release in paddy soils: Mechanistic insights into adsorption capacity loss and biochar feedstock-specific risks.

Remediation of pharmaceuticals in aquatic systems is crucial due to their substantial environmental and health impacts. In this study, a novel adsorbent from agricultural waste, activated rice straw residue biochar (activated RSR-BC), is developed to overcome the limits of existing water treatment technologies in eliminating sulfamethoxazole (SMX) and clindamycin (CLN) pollutants. Characterization of the synthesized activated RSR-BC adsorbent was done by XRD, SEM, BET, and FTIR to assess its physical and chemical properties. The BET-specific surface area increased after activation by 2.37 times, from 278.92 m2 g-1 to 662.51 m2 g-1, and the total pore volume increased. The Activated rice straw residue biochar (activated RSR-BC) showed excellent performance in removing (SMX) and (CLN). The adsorbent demonstrated a theoretical maximum adsorption capacity of 297.4 mg g-1 at pH 3 and 184.7 mg g-1 at pH 5 for SMX and CLN, respectively. Additionally, a prototype fixed-bed column system demonstrated high efficiency, removing 97.92% of SMX from continuous-flow wastewater effluent within 40 minutes. Beyond targeting specific contaminants, the activated RSR biochar also improved overall wastewater quality by significantly reducing total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), and total organic carbon (TOC). The main adsorption mechanisms identified include pore-filling, electrostatic attraction, hydrogen bonding, and π-π electron donor-acceptor (EDA) interactions, with chemisorption acting as the rate-limiting step. Moreover, activated RSR-BC material can be reused up to four times with 69.7% removal, highlighting its effectiveness in removing pharmaceuticals from water. Overall, this study demonstrates how agricultural waste, such as rice straw, can be valorized into a high-performance adsorbent for advanced water purification, supporting sustainable development goals (SDGs) and circular economy principles.

Optimizing Pyrolysis Temperature of Phosphoric Acid-Modified Rice Straw Biochar to Boost Nitrogen Utilization and Crop Yield in Saline-Alkali Soil

Industrial wastewater often contains colored toxic dyes and heavy metals that harm ecosystems and human health, highlighting the need for sustainable treatment strategies. This study aimed to develop a guar gum (GG)/polyacrylamide (PAAm)/rice straw biochar (RSBC) hydrogel grafted onto polyethylene terephthalate (PET) (GG/PAAm RSBC- g -PET) textile, and its structure was characterized through swelling behavior, FTIR-ATR spectroscopy, and Scanning Electron Microscopy (SEM) analysis. The modified GG/PAAm/RSBC- g -PET exhibits a significant increase in water absorption compared to GG/PAAm- g -PET. The alteration and shifted peaks were observed particularly at bands of 3441 cm -1 (RSBC), and 852 cm -1 (galactose and mannose units), imparting effective crosslinking. SEM analysis revealed a porous structure with irregular magnetite particles, enhancing the active surface area. The performance of the GG/PAAm/RSBC- g -PET composite was evaluated using industrial wastewater, which resulted in reduced turbidity (26.5 NTU) and color (~49.5 ADMI), compared to filtration with PET textile alone (47 NTU and ~69.5 ADMI). The GG/PAAm/RSBC- g -PET composite exhibits comparable yet inconsistent improvements, possibly due to particle release and pore blockage. These findings demonstrate the feasibility of the GG/PAAm/RSBC- g -PET textile for decolorization, indicating its potential application in wastewater remediation.

Rice straw biochar and mulched drip irrigation synergistically enhance nitrogen fixation and yield of peanut in a dryland cropping system

The biochar and microbial inoculant are commonly used amendments in soil improvement, but their effectiveness in protective agriculture is currently unclear. Based on this, this study takes the pepper vegetable greenhouse located in Zhuxi Town, Chongqing as the research object, and selects biochar prepared from corn straw and rice straw, as well as microbial inoculant, as the improvement materials. Five treatments were established, including corn straw biochar alone (CB), rice straw biochar alone (RB), microbial inoculant alone (CKM), combined corn straw biochar and microbial inoculant application (CBM), and combined rice biochar and microbial inoculant application (RBM), conventional fertilization was used as a control. This study explores the changes in soil physicochemical properties of protected vegetable production under different treatments at distinct time points (first, third, and fifth months after returning field) and soil depth (0-10cm and 10-20cm). The results demonstrated that the overall soil bulk density increased With the increase of returning time. There was no significant difference in the soil capillary porosity or mineral-associated organic carbon content (P > 0.05), whereas the other soil properties decreased with increasing return field time. In contrast, the soil bulk density (BD) increased with increasing soil depth. Except the capillary porosity, which exhibited no significant differences at different depths (P > 0.05), all the other soil properties demonstrated downward trends with increasing depth. After 5months of transplantation, the soil carbon pool management index of RBM treatment was higher than that of CBM treatment, with a 4.35% increase. The soil health index was 14.51% lower than that of CBM. However, the differences in soil carbon pool management index and soil health index between the two treatments did not reach a significant level. Overall, the RBM and CBM showed better improvement effects on soil carbon pool management index and soil health status, making them the better ratios for vegetable greenhouse farmland soil improvement in this study.

Present research aimed to investigate the interactive effects of rice straw biochar (RSBC) and heavy metals (cadmium (Cd) and lead (Pb)) on agronomic parameters, soil properties, gas exchange characteristics and metal uptake by wheat (Triticum aestivum L.) plants. The experiment involved a factorial design with two factors: biochar (No-BC and RSBC at a rate of 1%) and heavy metals (control, Cd, Pb, and Cd + Pb). The pre-analysis of RSBC showed high nutrient and mineral contents, especially silica rich minerals. Results indicated that RSBC application significantly improved plant growth parameters and mitigated negative effects of Cd and Pb on growth as compared to the control. The gas exchange characteristics were greatly improved with RSBC application under metal stress as compared to no-BC treatments. The RSBC reduced the concentrations of bioavailable Cd (24%) and Pb (18%) in soil. A significant reduction in metal accumulation was observed in grains (36 and 30% for Cd and Pb, respectively) and straw (55 and 88% for Cd and Pb, respectively) of wheat plants. The uptake of Cd and/or Pb was lower when applied alone as compared to Cd + Pb treatment. Results demonstrated the safe utilization of RSBC for enhancing crop resilience in metal-contaminated soils.

To enable the application of biomass pyrolysis products in sustainable pavements and inhibit volatile organic compound (VOC) emissions from reactive rejuvenated SBS-modified bitumen (SMB), six different biomass feedstocks were used to prepare biochar. The effects of biochar on the pavement performance and VOC emissions of the reactive rejuvenated SMB were analyzed. Results show that the biochar diminishes VOC concentration as well as its environmental and health risks, and the inhibition effect intensifies with increasing biochar dosage. Under the same pyrolysis conditions, the bamboo biochar exhibits the strongest inhibition of both the VOC variety and concentration, followed by the rice husk biochar and the corncob biochar, whereas the rice straw biochar shows the weakest effect. The adsorption of VOC by bamboo biochar involves physical and chemical mechanisms, which arise from its abundant pore structure and surface polar functional groups. Besides, the 3 wt % biochar dosage is the optimal choice for reactive rejuvenated SMB.

The poor quality and scarcity of soil used for raising seedlings are key issues holding back the further development of the rice industry. Artificial humic substances (A-HS) and artificial soils are attracting increasing attention due to their cost-effectiveness and significant potential to improve rice cultivation. This study used native soil (NS), engineered soil (ES) and rice straw to create artificial substrates (AES and ANS) using humification–hydrothermal carbonization technology (24 h treatment of NS and ES with rice straw at 200 °C and 2 MPa). Experiments on cultivation of the rice seedlings were conducted using initial soils (ES and NS) and artificial soils with addition of A-HS (AES+A-HS and ANS+A-HS). This study examined the nutrient content and microbial environment of the seedling substrates as well as the changes in growth and development of the rice seedlings. The combination of rice straw biochar in artificial soils (AES and ANS) with A-HS significantly increased the content of soil organic carbon (SOC) and enhanced the nutrient levels, such as total nitrogen and available phosphorus. Furthermore, it enhanced the microbial diversity, and it increased the abundance of microorganisms such as Actinomycetota, Chloroflexota, and Basidiomycota, thereby improved the soil microbial environment. An enhanced soil nutrient content and improved microbial environment effectively promoted the rice seedling growth. Compared to the original soils (ES and NS), before transplanting to paddy fields, the stem width of the seedlings increased by 5.1% (AES+A-HS) and 10.2% (ANS+A-HS), and their height increased by 18.7% (AES+A-HS) and 4.5% (ANS+A-HS). The rice seedling emergence increased by 6.1% (AES+A-HS) and 3.9% (ANS+A-HS), and the transplant survival rate also increased by 4.1% (AES+A-HS) and 2.9% (ANS+A-HS). This study provides an effective approach to alleviating the scarcity of rice seedling substrates and improving the quality of rice seedlings, and it provides an effective foundation for increasing the yield of rice.

Serpentine-modified biochar from dual wastes for enhanced copper removal: Performance and mechanism.

Positive roles and mechanisms of sea rice straw biochar in accelerating sulfamethoxazole biodegradation in coastal saline soils

Abstract Traditional agricultural practices have various ecological and environmental challenges. This study examined the effects of rice straw biochar on the physico-chemical properties and water retention capacity of sandy soil under rain-fed lowland rice cultivation using FARO 44 and FARO 52 rice varieties. The study also considered the environmental impact of open-burning, emphasizing the need to transit to cleaner technology. The experiment was conducted using complete randomize experimental design. The biochar-soil mixture was applied at various rates (biochar: 0 g/5 kg, 20 g/5 kg, 60 g/5 kg, 100 g/5 kg, 120 g/5 kg) for the physicochemical characterization and replicated four times. 0 g/5 kg, 20 g/5 kg, 60 g/5 kg and 100 g/5 kg experimental mixture biochar and soil was used for water content and plant growth parameters experiments. The impact of biochar was assessed on various soil properties such as organic matter, soil bulk density, pH, cation exchange capacity (CEC), and macro-nutrients, also data on the plant performance such as tiller number, plant height, root biomass and shoot were collected. Statistical analysis was conducted on the result using analysis of variance, also significant means were separated using Tukey HSD test at 0.05 significance levels. The result revealed that the 100 g/5 kg treatment showed the best output, achieving 97.7% water retention and a pH of 7.00 ± 0.57. Both rice varieties had improved growth and biomass yield, with FARO 44 reaching an average plant height of 2.32 ± 0.46 m. The study also showed a significant reduction in the emission of the GHGS from adoption of biochar technology compared to open field burning method indicating a more environmentally friendly method of disposing the rice straw. These results highlight rice straw biochar as a sustainable soil amendment that improves sandy soil fertility, environmental friendly and enhances rice productivity.

The widespread presence and persistence of organic pollutants in aquatic environments have raised serious concerns worldwide due to their adverse ecological and health impacts. Therefore, there is an urgent need to develop efficient and sustainable degradation technologies. In this study, a novel photocatalyst composed of rice straw biochar and rare-earth europium comodified ZnIn2S4 was synthesized. The degradation efficiency of pristine ZnIn2S4 for metronidazole (MNZ) under visible light reached 70.5%. Subsequent modification with rice straw biochar and rare-earth europium resulted in a highly efficient degradation performance, achieving a degradation efficiency of 99.8%. Notably, the composite also demonstrated effective MNZ degradation under natural sunlight. Mechanistic investigations revealed that the comodification with rice straw biochar and europium synergistically enhances light absorption, facilitating charge separation. This study offers a feasible strategy for the rational design of highly efficient photocatalysts and underscores their potential for practical applications in antibiotic-contaminated water treatment.

Comprehensive evaluation of the toxicological effects of biochar on rice physiology, enzymology, and transcriptome.

Abstract Salinity is an abiotic stress that can increase Aminocyclopropane carboxylic acid (ACC) levels, leading to reduced plant growth. This study aimed to determine the effect of applying ACC deaminase-producing bacteria and organic amendments on the growth of red spinach ( Amaranthus tricolor L.) under salinity stress. The study was carried out in the greenhouse at the Faculty of Agriculture, Universitas Sumatera Utara, utilizing a factorial randomized block design with two experimental factors: bacterial isolates (no bacteria, Bacillus cereus, Priestia flexa, Achromobacter xylosoxidans ) and organic amendments (none, rice straw compost, and rice straw biochar). The results indicated that organic amendments had a significant effect on vegetative plant growth, and there was an interaction between ACC deaminase-producing bacteria and organic amendments. The best treatment was the combination of B. cereus and rice straw biochar.

Characteristics of tetracycline adsorption by different embedded biochar materials.

Understanding the stoichiometric characteristics of phosphorus and extracellular enzyme activity in paddy soil under the application of different types of biochar can improve phosphorus management and nutrient utilization efficiency. A two-year field experiment was conducted with treatments including no fertilization (CK), chemical fertilizer (NPK), and biochar amendments based on NPK: perishable organic waste biochar (WB), rice straw biochar (SB), and pig manure biochar (MB). Combined with enzyme vector analysis, we explored the effects of different biochar types on soil phosphorus availability and microbial carbon, nitrogen, and phosphorus-related enzyme activities. Results showed that the NPK treatment increased total phosphorus, available phosphorus, and crop yield by 39.8%-73.1%, 128.5%-131.0%, and 27.0%-33.9%, respectively. Compared to NPK, all three biochar treatments consistently elevated soil total phosphorus, with MB>WB>SB, where MB significantly increased by 108.8% and 156.0%. The MB treatment enhanced soil available phosphorus and phosphorus activation capacity by 297.1%-388.4% and 53.3%-143.1%, respectively, leading to average annual improvements of 12.1% in rice yield and phosphorus use efficiency. Biochar application boosted β-glucosidase (BG), N-acetyl-β-glucosaminidase (NAG), and leucine aminopeptidase (LAP) activities by 43.9%-90.4%, 15.7%-77.6%, and 84.5%-173.4%, respectively, but inhibited alkaline phosphatase (ALP) activity by 41.8%-54.9%. Soil enzyme carbon-phosphorus ratios in biochar treatments were significantly higher than in NPK, while carbon-nitrogen ratios were lower. Biochar application effectively alleviated microbial phosphorus limitation and may have shifted to nitrogen limitation. There were significant positive associations between soil total phosphorus and available phosphorus with BG, LAP activity, rice yield, and phosphorus use efficiency, but negative associations with ALP activity. In summary, biochar application enhances soil phosphorus availability and extracellular enzyme activity, mitigated microbial phosphorus limitation, an increased rice yield. The MB performed the best.

Limestone calcined clay cement (LC3) typically exhibits low early-age strength, limiting its practical use in construction. To address this, the present study performs a comparative assessment of three waste-derived siliceous additives; rice husk ash (RHA), rice husk biochar (RHB), and rice straw biochar (RSB), to enhance early strength development. A comprehensive experimental program evaluated their effects on consistency, compressive strength, ultrasonic pulse velocity (UPV), microstructure, and hydration products using TGA/DTG, FTIR, XRD, and SEM analyses. Results showed that LC3-RHA significantly improved compressive strength at 7 and 28 days. It has been observed that LC3-RSB exhibited the highest early strength gain (3 d), attributed to enhanced pozzolanic activity, pore refinement, and internal curing. The hybrid analytical approach, based on qualitative and quantitative analysis, has been employed and it was observed that LC3-RSB supersede the LC3 strength by 29%, 14% and 19%, at 3, 7, and 28 days, respectively. And have marginal difference form the ordinary Portland cement (OPC) strength. TGA and FTIR analyses confirmed increased carbonate formation, evidenced by mass retention in the 700 to 850 °C range and characteristic bands at 1410 to 1500 cm−1, indicating CO2 capture via physical adsorption and mineralization. RSB outperformed RHB in carbonation potential due to its higher porosity and favorable ash composition. Overall, biochar-modified LC3 offers a sustainable, carbon-negative binder solution by valorizing agro-waste, reducing clinker content, and improving environmental performance.

To understand the effects of different types of biochar application on the physical and chemical properties of saline-alkali soil and the growth of plants in the Wuliangsuhai Lake Basin， corn stalk biochar （A）， corn cob biochar （B）， and rice straw biochar （C） were used as experimental materials， and the saline-alkali soil in the Wuliangsuhai Lake Basin was used as the experimental soil. A pot experiment using Helianthus tuberosus was conducted with a blank control （CK） and three biochar application ratios. The results showed that： ① The application of biochar could significantly increase the plant height and ground diameter of H. tuberosus， with the increased range being 106.8%-151.7% and 104.1%-153.0%， respectively， compared with those in the control group， and there was a negative correlation with the application rate of biochar. ② The application of biochar could improve soil salinity and alkalinity. The application rate of 1% of corn stalk biochar could significantly reduce soil pH， with the reduction range being 0.08-0.28 compared with that of the control group， while the application rate of 5% of corn stalk biochar could significantly reduce soil electrical conductivity， with the reduction range of 32.9%-47.9% compared with that of the control group. ③ Applying biochar could significantly reduce soil bulk density and increase soil moisture content. The improvement effect was most obvious in the 5% application rate of corn stalk biochar， and the improvement effect was positively correlated with the biochar application rate. The reduction range of bulk density was 22.5%-28.9%， and the increase range of moisture content was 19.6%-38.4%. ④ The application of biochar could increase the nutrient content of saline-alkali soil. Among them， the 5% application rate of corn stalk biochar had the most obvious effect on increasing soil organic matter content， with the increased range being 170.0%-308.4% compared with that of the control group. The 5% application rate of corn cob biochar had an excellent effect on increasing soil ammonia nitrogen content， with the increased range of 34.9%-227.3%. The 3% corn cob biochar application ratio had a significant effect on increasing soil available phosphorus content， with an increase range of 13.6% to 40.1% compared to that in the CK group. In addition， the 5% application rate of rice straw biochar had a more obvious effect on increasing soil available potassium content， with the increased range of 80.4%-189.1%. In conclusion， the application of biochar can promote the growth of H. tuberosus to a certain extent and improve the physical and chemical properties of saline-alkali soil， which can provide a theoretical basis for the management of saline-alkali land in the Wuliangsuhai Lake Basin.