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Biochar possesses unique characteristics, including a substantial surface area, a high carbon content, sufficient capacity for cation exchange, and a robust structure. However, biochar contains hazardous pollutants like volatile organic compounds that harm soil properties and functionality. Although several studies on biochar production from various feedstocks have been undertaken in recent years, several issues about feedstock preparation, economic feasibility, influencing factors, and the proper utilization of biochar production processes need to be addressed. This paper thus addresses these issues by providing potential solutions identified through a comprehensive review. Slow pyrolysis of lignocellulosic biomass and Acacia nilotica yields biochar from 20 to 52 wt% at various temperatures and residence times. Biochar yield varies from 29 to 48.3 wt% when waste tires and corn stalks are rapidly pyrolyzed at higher temperatures and for shorter periods. Torrefaction of algal biomass at moderate temperatures with different residence times can result in a substantial yield of 50–60 wt%. However, the variability and heterogeneity of waste feedstocks pose potential challenges affecting biochar's quality and properties. Given its widespread use in carbon sequestration, soil remediation, wastewater purification, and organic waste composting, the mechanisms of biochar production in environmental usage need to be investigated. [ABSTRACT FROM AUTHOR]

Using carbon-based materials (CBMs) to facilitate phytoremediation shows great promise for simultaneously enhancing the restoration efficiency of contaminated soil and reducing carbon dioxide in the context of global warming, which is still in the exploring and attempting phase. In addition to direct degradation or alteration of pollutant bioavailability, CBMs can enhance phytoremediation by alleviating plant nutrient deprivation and oxidative stress, as well as by modulating soil microbial communities and root secretions. Photosynthetic carbon fixation predominantly affects both phytoremediation efficiency and carbon cycle turnover in terrestrial ecosystems. In this regard, CBMs have extremely positive properties in facilitating plant carbon capture, with intrinsic mechanisms including (1) promoting photosynthetic pigment synthesis and acting as artificial built-in antennae to improve photon capture efficiency, (2) accelerating the photosynthetic electron transport rate in photosystems, (3) improving the Calvin cycle, and (4) maintaining the structural integrity of chloroplasts. Besides, as an ultra-stable type of CBM derived from waste biomass, biochar can preserve the native biomass carbon in the soil environment for decades and attenuate the rhizosphere priming effect by influencing the structure of rhizosphere soil aggregates and microbial communities, thus retarding the native soil organic carbon efflux. This review critically elaborates on the mechanisms by which CBMs assist in improving the efficiency of phytoremediation and their positive effects on the plant-root soil carbon balance. Additionally, a simple full-life cycle analysis encompassing cost analysis as well as ecological, economic, and social benefits is concluded to evaluate the feasibility and sustainability of CBMs-phytoremediation systems. [ABSTRACT FROM AUTHOR]

Microalgae technology is a viable solution for environmental conservation (carbon capture and wastewater treatment) and energy production. However, the nutrient cost, slow-kinetics, and low biosorption capacity of microalgae hindered its application. To overcome them, algal-biochar (BC) can be integrated with microalgae to treat textile wastewater (TWW) due to its low cost, its ability to rapidly adsorb pollutants, and its ability to serve as a nutrient source for microalgal-growth to capture CO2 and biodiesel production. Chlorella vulgaris (CV) and algal-BC were combined in this work to assess microalgal growth, carbon capture, TWW bioremediation, and biodiesel production. Results showed the highest optical density (3.70 ± 0.07 OD680), biomass productivity (42.31 ± 0.50 mg L−1 d−1), and dry weight biomass production (255.11 ± 6.01 mg L−1) in an integrated system of CV-BC-TWW by capturing atmospheric CO2 (77.57 ± 2.52 mg L−1 d−1). More than 99% bioremediation (removal of MB-pollutant, COD, nitrates, and phosphates) of TWW was achieved in CV-BC-TWW system due to biosorption and biodegradation processes. The addition of algal-BC and CV microalgae to TWW not only enhanced the algal growth but also increased the bioremediation of TWW and biodiesel content. The highest fatty acid methylesters (biodiesel) were also produced, up to 76.79 ± 2.01 mg g−1 from CV-BC-TWW cultivated-biomass. Biodiesel's oxidative stability and low-temperature characteristics are enhanced by the presence of palmitoleic (C16:1) and linolenic (C18:3) acids. Hence, this study revealed that the integration of algal-biochar, as a biosorbent and source of nutrients, with living-microalgae offers an efficient, economical, and sustainable approach for microalgae growth, CO2 fixation, TWW treatment, and biodiesel production. [ABSTRACT FROM AUTHOR]

Biochar, a carbon-rich material produced from biomass waste through thermal conversion, holds great environmental promise. This article offers a comprehensive overview of the various feedstocks used in biochar production, the different types of thermal degradation processes, biochar characterization, properties, modifications to engineered materials, and their applications in the environment. The quality of biochar, including surface area, pore size and volume, and functional group formation, is significantly influenced by the specific conditions under which thermal conversion takes place. Each of the diverse processes employed to produce biochar yields a distinct set of properties in the final product. In recent years, biochar has gained widespread recognition and utilization in diverse fields such as wastewater treatment, carbon sequestration, reduction of greenhouse gas emissions, biogas production, catalysis in biofuel industries, construction, and soil enhancement. In summary, biochar is a promising environmental mitigation tool to achieve a sustainable environment. In addition to its benefits, the application of biochar presents several challenges, including the selection of feedstocks, methods of biochar production, modifications to biochar, the properties of biochar, and the specific applications of biochar. The current review summarizes factors that could lead to significant advancements in future applications. Highlights: The feedstocks and production of biochar were discussed. Activation of biochar and properties of biochar were narrated and summarized. Application of biochar for sustainable environment was discussed. [ABSTRACT FROM AUTHOR]

Catalytic methane decomposition (CMD) stands out as a promising alternative for hydrogen production, distinguished by its ability to generate hydrogen with minimal byproducts. While some studies have explored the use of biochar as an alternative catalyst in the CMD process, the role of biochar surface functional groups and inherent properties have not been well understood. This study aimed to explore the influence of various woody biochar types, acidic sites, physicochemical properties, and operating temperatures on their catalytic activity in catalytic methane decomposition (CMD) process. Biochar derived from three biomass sources (pine, poplar, and bark) were examined at 600, 800, and 1000 °C reaction temperature. The findings revealed that heat-treated (HT) poplar biochar exhibited the lowest specific surface area (215.1 m2g⁻1) and the highest concentration of acidic sites. All samples exhibited improved performance at 1000 °C compared to other temperatures. The CH 4 conversion order was observed as HT poplar > HT red pine > HT bark, with the initial conversion of approximately 50%, 35%, and 25%, respectively. Additionally, employing genetic algorithms, kinetics models for the CMD reaction were developed. The study concluded a consistent second order reaction and an activation energy in the range of 300–330 kJ/mol for all three biochar samples. [Display omitted] • The role of acidic functional groups on biochar activity during CMD was revealed. • Poplar demonstrated the highest acidity and best catalytic performance at 1000 °C. • The O:C and H:C ratios suggested potential for carbon sequestration potential. • Biocarbon-catalyzed CMD exhibited an activation energy between 300 and 330 kJ/mol. [ABSTRACT FROM AUTHOR]

Green carbon-based materials (GCM), i.e., carbon materials produced using renewable biomass or recycled waste, ought to be used to make processes sustainable and carbon-neutral. Carbon nanomaterials, like carbon dots and the nanobichar families, and carbon materials, like activated carbon and biochar substances, are sustainable materials with great potential to be used in different technological applications. In this review, the following four applications were selected, and the works published in the last two years (since 2022) were critically reviewed: agriculture, water treatment, energy management, and carbon dioxide reduction and sequestration. GCM improved the performance of the technological applications under revision and played an important role in the sustainability of the processes, contributing to the mitigation of climate change, by reducing emissions and increasing the sequestration of CO2eq. [ABSTRACT FROM AUTHOR]

Human activities are responsible for emitting greenhouse gases (GHGs) that contribute to global warming and climate change. As the world's second-largest producer of staple food and the third-largest emitter of GHGs, India has been witnessing an increase in demand for food and energy, resulting in increased emissions. Thus, to achieve net carbon neutrality by 2070, India must focus urgently on climate change mitigation. Its agriculture sector has the potential to transition from being a net emitter to a net absorber of GHGs by adopting sustainable farming practices such as zero tillage, laser-assisted precision land leveling, direct seeding of rice, intercropping, biochar application, use of solar energy, and more efficient management of irrigation water, soil nutrients, livestock feed, and manure. To incentivize climate consciousness, a voluntary carbon credit trading system could be utilized in agriculture, supported by a measurement, monitoring, reporting, and verification platform. This system would also bring about social, environmental, and financial co-benefits for its stakeholders. Specifically, the agriculture sector could substantially reduce the country's annual emissions by 84% from 2019 to 2070. But to realize their potential, the carbon markets must overcome the limitations currently set by policy, economic, cultural, and biophysical factors. [ABSTRACT FROM AUTHOR]

Municipal sewage sludge (MSS) is an inevitable byproduct of wastewater treatment, with increasing amounts year by year worldwide. The development of environmentally and economically acceptable methods for the sustainable management of MSS is a major environmental challenge. Nowadays, sludge management practices, besides the commonly used stabilization methods, focus attention on alternative sludge-disposal pathways, which encompass enhanced energy and valuable-resource recovery. This review presents the recent advances in the recovery of selected value-added products from sludge. Because of the high nitrogen and phosphorus concentrations, waste MSS can be a nutrient source (e.g., struvite). This paper discusses the conditions of and advances in the technology of struvite recovery. As in the extracellular polymeric substances (EPSs) of biological sludge, alginate-like exopolymers (ALEs) are present in MSS systems that treat municipal wastewater. The yields, dynamics in content, and characterization of ALEs and their possible applications were analyzed. MSS is an important source of humic substances. Their occurrence, characterization, and yields in various types of MSS (e.g., untreated, composted, and digested sludge) and main methods of application are presented. The important aspects and trends of MSS pyrolysis, including the thermochemical conversion to biochar, are discussed in this review. The characterization of biochar derived from MSS and the assessment of the environmental risks are also covered. This paper explores the potential use of biochar derived from MSS in various applications, including soil amendment, carbon sequestration, and environmental remediation. [ABSTRACT FROM AUTHOR]

Biochar is a carbon-rich product obtained by biomass pyrolysis and is considered as a means of carbon sequestration. However, there is limited knowledge regarding responses of soil respiration and C-cycle enzyme activities to BC in a calcareous soil. In this study, different biochar AS, TS, PP, CS were applied to the soil at different rates (0.5, 1.0, and 1.5%) The highest increase in soil organic C content was observed in the TS treatment, while the AS treatment caused a slight increase of soil organic C. The highest MBC content was recorded in AS treatment and the lowest was observed in TS. The highest CO2-C emission was recorded in the TS treatment. In contrast, the lowest CO2-C emission was observed in the PP treatment due to its high recalcitrant C content and was attributed to a positive priming effect, stabilizing BC mineralization to improve the soil. The highest β-galactosidase enzyme activity was observed in the CS treatment and the lowest activity was observed in AS. The highest change in β-glycosidase enzyme activity was observed of PP treatment and the lowest was in AS biochar application. Thus, TS treatment is recommended to increase the organic C content of soils, and the PP biochar can be used to reduce CO2-C emission. The TS, PP, and CS can be applied to increase enzyme activities. The study clearly shows that the addition of BC to arid soils may have a high potential to improve soil enzyme activities and subsequent carbon sequestration and biochemical cycles. [ABSTRACT FROM AUTHOR]

Ensuring global food security under present and futuristic scenario of climate change accompanied by expanding population is of major concern worldwide. Researchers across the world are focusing on sustainable agronomic practices to combat climate change induced issues like desertification, reduction in crop yield, pest outbreaks, and reduction in soil health. Biochar has demonstrated positive effects on plant growth, development, fruit quality, carbon capture and sequestration. Studies indicate that biochar amendments to soil can enhance soil health, plant growth and development as well as help in combating abiotic stressors. Biochar has several properties that make it an attractive soil amendment, including high porosity, surface area, water-holding capacity, and the ability to increase soil microbiota, which in turn can promote nutrient uptake and reduce soil erosion. Environmentally, biochar's ability to degrade organic pollutant as well as sequester carbon makes it a very attractive addition to sustainable agriculture. Nonetheless, biochar has also been reported to have potential hazardous impacts on human health associated with possible leakage of toxic elements and particulate matter pollution. However, lack of exhaustive studies that detail all the major aspects of biochar application in agroecosystem impedes decision making on its overall usability in agriculture. There exists a need for comprehensive review that cover all the important aspects of biochar supplementation. This review provides a thorough overview of the multifaceted impacts of biochar, encompassing its positive effects on soil, plant growth, development and environment, while also exploring the limitations along with potential toxic effects associated with its application. [ABSTRACT FROM AUTHOR]

Carbon content is a key property of soils with importance for all ecosystem functions. Measures to increase soil carbon storage are suggested with the aim to compensate for agricultural emissions. In Norway, where soils have relatively high carbon content because of the cold climate, adapting management practices that prevent the loss of carbon to the atmosphere in response to climate change is also important. This work presents an overview of the potential for carbon sequestration in Norway from a wide range of agricultural management practices and provides recommendations based on certainty in the reported potential, availability of the technology, and likelihood for implementation by farmers. In light of the high priority assigned to increased food production and degree of self‐sufficiency in Norway, the following measures were considered: (1) utilization of organic resources, (2) use of biochar, (3) crop diversification and the use of cover crops, (4) use of plants with larger and deeper root systems, (5) improved management of meadows, (6) adaptive grazing of productive grasslands (7) managing grazing in extensive grasslands, (8) altered tillage practices, and (9) inversion of cultivated peat with mineral soil. From the options assessed, the use of cover crops scored well on all criteria evaluated, with a higher sequestration potential than previously estimated (0.2 Mt CO2‐equivalents annually). Biochar has the largest potential in Norway (0.9 Mt CO2‐equivalents annually, corresponding to 20% of Norwegian agricultural emissions and 2% of total national emissions), but its readiness level is not yet achieved despite interest from industry to apply this technology at large scale. Extensive grazing and the use of deep‐rooted plants also have the potential for increasing carbon storage, but there is uncertainty regarding their implementation and the quantification of effects from adapting these measures. Based on the complexities of implementation and the expected impacts within a Norwegian context, promising options with substantial payoff are few. This work sheds light on the knowledge gaps remaining before the presented measures can be implemented. [ABSTRACT FROM AUTHOR]

Organic soil amendments are a sustainable option for modifying soil structure and improving plant performance in the face of abiotic stressors such as drought and soil salinity. Of these amendments, biochar and compost have the added benefits of carbon sequestration and waste recycling. Establishment studies were conducted on tall fescue (Festuca arundinacea Schreb.) (syn., Schedonorus arundinaceus (Schreb.) Dumort and Lolium arundinaceum (Scop.) Holub) to assess the potential inhibition of establishment by compost and biochar products. Both green waste and biosolid compost impaired establishment rates, while biochar did not. In the field study, the green waste treatments were slower to reach 50% coverage than the untreated control or when biochar was added to the soil, but all treatments reached 75% and final coverage at a similar rate. Field application of compost had a positive effect on final root length and volume but a negative effect on tall fescue roots in the greenhouse. The negative effect of higher salts and volatiles in the biosolids compost was reduced when biosolids and biochar were incorporated into the soil simultaneously. This work represents one of the only large-scale field studies on turfgrass establishment comparing the impact of biochar and compost products on turfgrass establishment. [ABSTRACT FROM AUTHOR]

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. Highlights: K3PO4 promoted biochar precursor's dehydrogenation/polycondensation process to form fused-ring aromatic structures. K3PO4 increased recalcitrant carbon proportion and shielded biochar's active sites through the mineralization process. By adding 20 wt% of K3PO4, the thermal and chemical stability of biochar were enhanced by 11% and 7%, respectively [ABSTRACT FROM AUTHOR]

To date, most studies have shown that biochar has great potential in carbon sequestration and reduction, as well as soil quality improvement. However, there is limited knowledge of its effect on soil organic carbon (SOC) fractions in tropical farmland. This study aimed to determine the impact of different types and rates of biochar applied in tropical farmlands on so SOC and its active fractions. The SOC, microbial biomass carbon (MBC), dissolved organic carbon (DOC), and soil mineralizable carbon (SMC) in the 0–30 cm soil layers under rice hull (R) and peanut shell (P) biochar treatments were measured. The results showed that the application of R and P biochar increased the contents, stocks, and cumulative stocks of SOC, MBC, and DOC in the 0–10 cm, 10–20 cm, and 20–30 cm soil layers. The contents, stocks, and cumulative stocks increased with increasing biochar application rates. Compared with CK, the ranges of the increased SOC, MBC, and DOC cumulative stocks were 10.76–46.36%, 30.04–195.65%, and 0.02–17.03%, respectively. However, the R60 and P60 had the lowest cumulative stocks of SMC, decreasing by 14.69% and 8.05%, respectively. The biochar treatment of more than 20 t ha−1 reduced the ratio of SMC:SOC and active fractions:SOC. Therefore, it can be inferred that the application of biochar improved the levels of SOC, MBC, and DOC, and the application of more than 20 t ha−1 biochar could decrease soil carbon mineralization, thus improving the stability of SOC in tropical farmlands. [ABSTRACT FROM AUTHOR]

Converting Sargassum horneri (SH)—a harmful marine stranding that can cause golden tide—to highly porous bio-adsorbent material (via one-step catalytic oxidative pyrolysis with K2FeO4) can be a strategically useful method for obtaining low-cost materials suitable for CO2 capture. In this manuscript, the behavior of different mass ratios of K2FeO4/SH precursor acting on the surface physicochemical properties of carbon materials are reported. The results suggest that specific surface area and total pore volume first increased to the mass ratio of K2FeO4/carbon precursor, then decreased. Among the samples prepared, the highest specific surface area was obtained with a K2FeO4/SH precursor ratio of 1:4 (25%-ASHC), and the CO2 adsorption performance was significantly increased and faster compared with the original biochar. The fitted values of the three kinetic models showed that the double exponential model provided the best description of carbon adsorption, indicating both physical and chemical adsorption; 25%-ASHC also exhibited excellent cyclic stability. The improved CO2 adsorption performance observed after K2FeO4 activation is mainly due to the increase in material porosity, specific surface area, and the enrichment of nitrogen and oxygen functional groups. [ABSTRACT FROM AUTHOR]

Bamboo biochar was modified by lignin impregnation and microwave irradiation to enhance its performance for CO2 capture. The pore structure of lignin-impregnated biochar was significantly affected by the impregnation ratio. The maximum specific surface area of 377.32 m2 g−1 and micropore volume of 0.163 cm3 g−1 were observed on the biochar with an impregnation ratio of 1:20 (mass ratio of lignin to biochar). Lignin impregnation increased the CO2 adsorption capacity of biochar up to 134.46 mg g−1. Correlation analysis confirmed the crucial role of biochar's pore structure in adsorption. The Avrami model fitted the CO2 capture curves well. The calculation of adsorption activation energy suggested that the adsorption process was dominated by physical mechanism assisted with partial chemical mechanism. Meanwhile, Langmuir isotherm analysis indicated that lignin impregnation transformed the larger pores of biochar into more uniform micropores, thereby making the adsorption process closer to monolayer adsorption. Both the high reusability (89.79–99.06%) after 10 successive cycles and the excellent CO2 selectivity in competitive adsorption confirmed that lignin-impregnated biochar is an outstanding adsorbent for CO2 capture. Highlights: Microwave energy absorbed by biochar carbonized the impregnated lignin to increase micropore structure. CO2 uptake on lignin-impregnated biochar reached 134.46 mg g−1 and was associated with micropore, alkalinity, and temperature. CO2 adsorption on lignin-impregnated biochar was governed by physisorption with slight chemisorption. Lignin-impregnated biochar demonstrated excellent reusability and selectivity in CO2 capture. [ABSTRACT FROM AUTHOR]

Mining sector has been the central attention of the business and public policy sustainable development scheme for several years. Reclamation territories are with potential carbon sequestration capacity in degraded mining areas and can be an impeccable option for achieving sustainable development goal-13. This paper made an investigation about the presence of heavy metals in reclaimed area possibilities to improve reclaimed soils with biochar with idea to enhance ecosystem carbon pool and atmospheric CO2 sequestration capacity to offset CO2 emission and soil organic carbon losses. The results show that the carbon content in biochar is 46.6 % and would be classified in class 2 according to the International Biochar Initiative. H/C and O/C atomic ratios could be useful for restoration of degraded poor mine soils through enhanced carbon sequestration. O/C ratio is 0.085 mol mol–1 and half-life of biochar is 2795.65 years, which confirm the biochar stability. For each kilogram of biochar incorporated into the soil, 144 g of carbon were sequestrated 52,8 % CO2 emission reduction. Hence, the biochar developed in this study can be used in carbon-deficient soils with the added benefit of long-term carbon storage. [ABSTRACT FROM AUTHOR]

Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. Biochar may be added to soils with the goal to improve the soil properties and relocate an amount of conventional fossil fuel based fertilizers and sequester carbon. Biochar production and incorporation in soil must play a role in climate change mitigation. The need for further clarity on optimizing biochar application to various crop yields is necessary if it is to gain widespread acceptance as a soil amendment. There is urgent need to intensify agricultural production to secure food supply for the ever increasing population especially in developing country like India of the tropics. Biochar proponents have placed on biochar stability in soil and it also includes increased soil fertility and water holding capacity, increased crop production and remediation of contaminated soils. The biochar have potential to feasibly and sustainably sequester/offset over 1 Pg of CO2-carbon equivalents annually. Current carbon market incentives are not sufficient to rapidly increase or maximize the initiation and development of biochar implementation. [ABSTRACT FROM AUTHOR]

The use of organic waste in agricultural soil can enhance crop yields, improve waste management, and boost soil carbon (C) sequestration. However, more field data are required to fully understand the impacts of pyrolyzed and unpyrolyzed animal manures. The objectives of this study were (i) to analyze the impact of two pyrolyzed and unpyrolyzed manures on soil properties, soil C storage, and clover productivity and (ii) to examine the biochar's movement through the soil profile. Poultry litter (PL), dairy manure (DM), poultry litter biochar (PLBC), and dairy manure biochar (DBC) were applied at rates of 8 t ha−1 in a field experiment with red clover (Trifolium pratense L. var. Quiñequeli) in an Andisol. We monitored changes in soil chemical properties, foliar properties, and crop yield after three clover cuttings. To examine the movement of biochars through the soil profile, we set up a lab experiment where field conditions were simulated. PLBC, DBC, and PL increased soil pH by 0.5 (6.44), 0.28 (6.22), and 0.25 (6.19) units, respectively. Soil available P increased in both pyrolyzed and unpyrolyzed PL treatments (by 8.53 mg P kg−1, on average). Clover yields only increased in treatments with amendments that provided more available P and increased the pH. The addition of DBC increased soil total C (30.3%). Both biochars added to the soil surface exhibited little movement through the soil profile (2 to 4 cm). In this study, the pyrolysis of manures emerged as an option for reducing waste volume from the farming industry. Manure biochars proved useful at low rates for enhancing crop yields (PLBC) and storing C in the soil (DBC). [ABSTRACT FROM AUTHOR]

This article describes the synthesis and characterization of porous carbon derived from waste banana peels by chemical activation with KOH or by activation KOH and urea modification. The as-synthesized samples were carefully characterized by various techniques. The prepared carbonaceous materials possess highly developed micropore and mesopore structures and high specific surface area (up to 2795 cm2/g for materials synthetized with KOH and 2718 cm2/g for activated carbons prepared with KOH and urea). A series of KOH-activated samples showed CO2 adsorption at 1 bar to 5.75 mmol/g at 0 °C and 3.74 mmol/g at 25 °C. The incorporation of nitrogen into the carbon sorbent structure increased the carbon uptake capacity of the resulting materials at 1 bar to 6.28 mmol/g and to 3.86 mmol/g at 0 °C and 25 °C, respectively. It was demonstrated that treatment with urea leads to a significant increase in nitrogen content and, consequently, CO2 adsorption, except for the material carbonized at 900 °C. At such a high temperature, almost complete decomposition of urea occurs. The results presented in this work could be used in the future for utilization of biomass such as banana peels as a low-cost adsorbent for CO2 capture, which could have a positive impact on the environment and human health protection. [ABSTRACT FROM AUTHOR]

Biochar is one of the most environmentally friendly and cost-effective materials that has shown potential properties for applications in various areas. Several studies have therefore been conducted in the past years, covering several aspects of biochar production, properties, and applications. This study employed both traditional and bibliometric methods to conduct a comprehensive review of the research field in the past decade (2013–2023). The Biblioshiny package in the R software and the VOSviewer tool were used for the analysis. Data from the largest research database, i.e., Scopus, was used for bibliometric analysis. The outcome of the study indicates that China sits on top in terms of research output and collaborations. An annual growth rate of 13.6 % is recorded for biochar research. The study also identified an evolution with respect to the themes studied in the past years to cover topics such as life cycle assessment, circular bioeconomy, and the techno-economics of biochar. Even though biochar's efficiency depends on the pyrolysis conditions and the nature of biomass, its development is also expected to focus on fine-tuning its properties. The environmental as well as the agronomical benefits of biochar have been well researched during the study period. This review provides stakeholders and researchers with the needed information on the most studied topics in feedstocks, production, and applications of biochar. • Recent advancements in the production and utilization of biochar are reviewed in this study. • The traditional and bibliometric review approaches were adopted for the study. • The study found an annual growth rate of 13.6 % for biochar research in the last decade. • It was found that research into biochar production and utilization has become more diversified in the last 3 years. • Most studies are focused on its utilization and economic viability in the last three years. [ABSTRACT FROM AUTHOR]

Recently, salt-assisted pyrolyzation has been deemed an emerging and efficient method for the preparation of biochars due to its facile operation as well as its good structural and chemical properties. In this work, biochars (MBCx) are prepared by heating bamboo powders in eutectic salts (Li2CO3 + K2CO3) at 500–600 °C in the air. Multiple technologies are employed to examine the physiochemical properties of bamboo biochars. Correlations between heating temperature and structural features and carbon dioxide uptakes of bamboo biochars have been investigated. The results show that heating temperature has a significant influence on the physicochemical properties of bamboo biochars. With the elevation of the heating temperature, the defect structures of bamboo biochars gradually ascend, especially when the heating temperature reaches 600 °C. MBCx biochars visibly exceed conventional bamboo biochar prepared via pyrolyzation in a nitrogen stream free of salt addition. Pyrolysis of bamboo in eutectic salts endows biochars with higher oxygen content and more carbon defects, which likely accounts for their better CO2 capture activities. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems (BESs) that combine electrochemistry with biological methods have gained attention in the remediation of polluted environments, including wastewater, sludge, sediments, and soils. The most attractive advantage of BESs is that the solid electrode is used as an inexhaustible electron acceptor or donor, and biocurrent directly converted from organics can afford the reaction energy of contaminant breakdown, crossing the internal energy barrier of endothermic degradation, which achieves a continuous biodegradation process without the simultaneous use of exogenetic chemicals and bioelectricity recovery. However, soil BESs are hindered by expensive electrode materials, difficult pollutant and electron transfer, low microbial competitive activity, and biocompatibility in contamination remediation. Fortunately, introducing biochar into soil BESs could reveal a high potential in addressing these BES inadequacies. The characteristics of biochar, e.g., conductivity, transferability, high specific surface area, high porosity, large functional groups, and biocompatibility, can improve the performance of soil BESs. In fact, biochar not only carries electrons but also transfers nutrients, pollutants, and even bacteria by facilitating transmission in the bioelectric field of BESs. Consequently, the abilities of biochar make for better functionality of BESs. This review collates information on the roles, application, and progress of biochar in soil BESs, and future prospects are given. It is beneficial for environmental researchers and engineers to extend BES application in environmental remediation and to assist the progress of carbon sequestration and emission reduction based on the inertia of biochar and the blocking of electron flow to form methane. A feature comparison between BES and conventional techniques was made. Biochar characteristics match the deficiencies of bioelectrochemical remediation. Behind roles of biochar in the contamination remediation were summarized. Application potential and direction of biochar in BES were emphasized. [ABSTRACT FROM AUTHOR]

Biomass valorisation for bioenergy is crucial for establishing a sustainable low-carbon circular bioeconomy and addressing societal and environmental challenges. As global demand for renewable energy grows, effective waste management using biomass becomes increasingly vital. However, successful implementation requires addressing specific local, scientific, and conceptual challenges, including technological intricacies, resource availability, scalability, and environmental impacts. Advancements in chemical looping gasification and chemical looping combustion are reviewed here as essential components of bioenergy with carbon capture and storage technologies. Chemical looping technologies have substantially contributed to decarbonising various industries, supported by precise trends. The review highlights the potential of chemical looping combustion and gasification in biomass utilisation for generating bioenergy and mitigating carbon emissions. Moreover, the advantages of chemical looping processes enhance their feasibility and applicability across different contexts including (1) significant increase in biomass conversion efficiency through chemical looping gasification, leading to substantial reductions in greenhouse gas emissions, (2) progress in chemical looping combustion, enhancing carbon capture and storage capabilities and contributing to a closed carbon cycle, (3) detailed insights into integrating chemical looping technologies into industrial sectors. [ABSTRACT FROM AUTHOR]

Biochar has been widely recognized for its potential to increase carbon (C) sequestration and mitigate climate change. This potential is affected by how biochar interacts with native soil organic carbon (SOC) and fresh organic substrates added to soil. However, only a few studies have been conducted to understand this interaction. To fill this knowledge gap, we conducted a 13C-glucose labelling soil incubation for 6 months using fine-textured agricultural soil (Stagnosol) with two different biochar amounts. Biochar addition reduced the mineralization of SOC and 13C-glucose and increased soil microbial biomass carbon (MBC) and microbial carbon use efficiency (CUE). The effects were found to be additive i.e., higher biochar application rate resulted in lower mineralization of SOC and 13C-glucose. Additionally, soil density fractionation after 6 months revealed that most of the added biochar particles were recovered in free particulate organic matter (POM) fraction. Biochar also increased the retention of 13C in free POM fraction, indicating that added 13C-glucose was preserved within the biochar particles. The measurement of 13C from the total amino sugar fraction extracted from the biochar particles suggested that biochar increased the microbial uptake of added 13C-glucose and after they died, the dead microbial residues (necromass) accumulated inside biochar pores. Biochar also increased the proportion of occluded POM, demonstrating that increased soil occlusion following biochar addition reduced SOC mineralization. Overall, the study demonstrates the additional C sequestering potential of biochar by inducing negative priming of native SOC as well as increasing CUE, resulting in the formation and stabilization of microbial necromass. Highlights: Biochar showed additional C storage ability by preserving SOC from mineralization (negative priming) and stabilizing added labile organic substrate Biochar (30 Mg ha−1) significantly increased microbial carbon use efficiency Biochar increased the formation of stable microbial residues (necromass) from a labile substrate (glucose) added to soil, as indicated by 13C recovery in amino sugars [ABSTRACT FROM AUTHOR]

The application of biochar and nitrogen fertilizer can increase rice yield, soil organic carbon (SOC) storage and reduce greenhouse gas (GHG) emissions. However, few studies have systematically evaluated the carbon footprint (CF) and net ecosystem economic benefits (NEEB) of paddy ecosystems under long‐term application of biochar and nitrogen fertilizer. Here, the life cycle assessment method was used to quantify the CF and NEEB of paddy fields under different biochar and nitrogen fertilizer application rates in 7 years. Three biochar rates of 0 (B0), 4.5 (B1) and 13.5 t ha−1 year−1 (B2) and two nitrogen fertilizer rates of 0 (N0) and 300 kg ha−1 year−1 (N) were set. The results showed that B2 significantly increased methane (CH4) emission by 38%, decreased nitrous oxide (N2O) emission by 29%, and significantly increased global warming potential by 27% compared with B0. Besides that, biochar application significantly increased ΔCSOC by 87%–173% and reduced CF by 1.6–1.8 Mg CO2 eq ha−1. Among them, CH4 and N2O emissions contributed 46%–95% of total GHG emissions, and the production and transportation of nitrogen fertilizer and biochar contributed 17%–52% of total GHG emissions. Nitrogen fertilizer application can significantly increase rice yield by 85% compared to the N0, which could bring the largest NEEB. Biochar application had a negative influence on the NEEB regardless of N application. This might be attributable to the fact that the economic gains from increased rice production and SOC caused by biochar cannot outweigh the high cost of biochar. These results suggest that the biochar application can significantly improve the SOC sequestration and reduce the CF, but also had negative effect on NEEB in paddy filed. [ABSTRACT FROM AUTHOR]

• Rice seedling suffered more inhibition than wheat and corn under biochar treatments. • Colloidal biochar can attach to root surface and affect nutrient absorption. • Biochar nanoparticles were only found in rice root cell. In recent years, biochar has attracted considerable attention for soil quality improvement and carbon sequestration due to its unique physicochemical properties. However, the mechanism by which biochar application negatively affects the growth of crop seedlings has not been fully investigated. In this study, a hydroponic experiment was conducted to evaluate the response of rice, wheat, and corn seedlings to biochar application (CK, 0 g/L; BC1, 0.5 g/L; and BC2, 1.0 g/L). Compared with the CK treatment, the BC1 and BC2 treatments decreased the fresh shoot and root weights of rice and corn seedlings (P < 0.05), but there was no significant effect on wheat seedlings (P > 0.05). For the contents of nutrient elements in seedlings, both BC1 and BC2 treatments hindered the roots from absorbing Fe and Cu and increased the uptake of Ca and Mn. Compared with the CK treatment, the translocation factor (TF) values of Ca, Mn, and Zn were significantly decreased especially in rice seedlings (35.3%-36.8%, 68.7%-76.5%, and 29.8%-22.0%, respectively) under the BC1 and BC2 treatments, while only Mn was significantly decreased in wheat and corn seedlings (P < 0.05). Transmission electron microscope (TEM) analysis of root cross-sections showed that nano-sized biochar particles (10∼23 nm) were found in the root cells under BC2 treatment conditions. Our findings reveal that a large amount of biochar application can reduce nutrient absorption and translocation, and hinder rice, wheat, and corn seedlings, particularly rice seedling, in hydroponic system. [Display omitted] [ABSTRACT FROM AUTHOR]

Sludge biochar, a carbonized product of raw sludge, contains porous architectures that can act as epicenters for adsorbing external molecules through physical or chemical bonding. Sludge biochar also immobilizes innate micropollutants, which is advantageous over conventional sludge disposal methods. To date, numerous strategies have been discovered to improve sludge biochar morphology, but the influential factors, pore tuning mechanisms, and process feasibility remain imprecise. This knowledge gap limits our ability to design a robust sludge-based biochar. Herein, we present state-of-the-art sludge biochar synthesis methods with insight into structural and chemical transformation mechanisms. Roadblocks and novel concepts for improving sludge biochar porous architecture are highlighted. For the first time, sludge biochar properties, adsorption performances, and techno-economic perspectives were compared with commercial activated carbon (AC) to reveal the precise challenges in sludge biochar application. More importantly, sludge biochar role in carbon sequestration is detailed to demonstrate the environmental significance of this technology. Eventually, the review concludes with an overview of prospects and an outlook for developing sludge biochar-based research. Highlights: Utilizing sludge's unique feature can unlock many new and feasible biochar modulation strategies. Sludge carbonization and activation mechanisms reveal the crucial factors for micropore decorating. Sludge biochar is compared with activated carbon to reveal requirements for practicality. Sludge-based biochar application supports carbon sequestration and economic sustainability. [ABSTRACT FROM AUTHOR]

Improving soil management to enhance soil carbon sequestration (SCS)—a cost-efficient carbon dioxide (CO2) removal approach—can result in co-benefits or trade-offs. Here we address this issue by setting up a modeling framework for Switzerland that combines soil carbon (C) storage, food production and agricultural greenhouse gas (GHG) emissions. The link to food production is crucial because crop types and livestock numbers influence soil organic C (SOC) stocks, through soil C inputs from plants and manure. We estimated SCS rates for the years 2020–2050 for three scenarios, each with two variants for biochar: cover cropping (0.30 t CO2 equivalents [CO2-eq] ha−1 yr−1), biochar addition (0.36–1.8 t CO2-eq ha−1 yr−1) and agroforestry-biochar addition (2.2–2.3 t CO2-eq ha−1 yr−1). Different limiting factors (land and biomass availability, population growth) affected SCS rates and indicated that they cannot be sustained until 2100 under all scenarios (cover cropping: 0.10 t CO2-eq ha−1 yr−1 [2051–2100]; biochar addition: 0.35–1.8 t CO2-eq ha−1 yr−1; agroforestry-biochar addition: 1.0–1.7 t CO2-eq ha−1 yr−1). This information together with the associated GHG emissions is critical for planning net zero strategies and highlights the importance of integrated assessments that capture links between SCS and the food system. [ABSTRACT FROM AUTHOR]

Global warming necessitates urgent action to reduce carbon dioxide (CO2) emissions and remove CO2 from the atmosphere. Biochar, a type of carbonized biomass which can be produced from crop residues (CRs), offers a promising solution for carbon dioxide removal (CDR) when it is used to sequester photosynthetically fixed carbon that would otherwise have been returned to atmospheric CO2 through respiration or combustion. However, high‐resolution spatially explicit maps of CR resources and their capacity for climate change mitigation through biochar production are currently lacking, with previous global studies relying on coarse (mostly country scale) aggregated statistics. By developing a comprehensive high spatial resolution global dataset of CR production, we show that, globally, CRs generate around 2.4 Pg C annually. If 100% of these residues were utilized, the maximum theoretical technical potential for biochar production from CRs amounts to 1.0 Pg C year−1 (3.7 Pg CO2e year−1). The permanence of biochar differs across regions, with the fraction of initial carbon that remains after 100 years ranging from 60% in warm climates to nearly 100% in cryosols. Assuming that biochar is sequestered in soils close to point of production, approximately 0.72 Pg C year−1 (2.6 Pg CO2e year−1) of the technical potential would remain sequestered after 100 years. However, when considering limitations on sustainable residue harvesting and competing livestock usage, the global biochar production potential decreases to 0.51 Pg C year−1 (1.9 Pg CO2e year−1), with 0.36 Pg C year−1 (1.3 Pg CO2e year−1) remaining sequestered after a century. Twelve countries have the technical potential to sequester over one fifth of their current emissions as biochar from CRs, with Bhutan (68%) and India (53%) having the largest ratios. The high‐resolution maps of CR production and biochar sequestration potential provided here will provide valuable insights and support decision‐making related to biochar production and investment in biochar production capacity. [ABSTRACT FROM AUTHOR]

Life cycle assessment (LCA) and techno‐economic analysis (TEA) models are developed for a tertiary wastewater treatment system that employs a biochar‐integrated reactive filtration (RF) approach. This innovative system incorporates the utilization of biochar (BC) either in conjunction with or independently of iron‐ozone catalytic oxidation (CatOx)—resulting in two configurations: Fe‐CatOx‐BC‐RF and BC‐RF. The technology demonstrates 90%–99% total phosphorus removals, adsorption of phosphorus to biochar for recovery, and >90% destructive removal of observed micropollutants. In this work, we conduct an ISO‐compliant LCA of a 49.2 m3/day (9 gpm) field pilot‐scale Fe‐CatOx‐BC‐RF system and a 1130 m3/day (0.3 MGD) water resource recovery facility (WRRF)‐installed RF system, modeled with BC addition at the same rate of 0.45 g/L to quantify their environmental impacts. LCA results indicated that the Fe‐CatOx‐BC‐RF pilot system is a BC dose‐dependent carbon‐negative technology at −1.21 kg CO2e/m3, where biochar addition constitutes a −1.53 kg/m3 CO2e beneficial impact to the process. For the WRRF‐installed RF system, modeled with the same rate of BC addition, the overall process changed from 0.02 kg CO2e/m3 to a carbon negative −1.41 kg CO2e/m3, demonstrating potential as a biochar dose‐dependent negative emissions technology. Using the C100 100‐year carbon accounting approach rather than Cnet reduces these CO2e metrics for the process by about 25%. A stochastic TEA for the cost of water treatment using this combinatorial P removal/recovery, micropollutant destructive removal, and disinfection advanced technology shows that at scale, the mean cost for treating 1130 m3/day (0.3 MGD) WRRF secondary influent water with Fe‐CatOx‐BC‐RF using the C100 metric is US$0.18 ± US$0.01/m3 to achieve overall process carbon neutrality. Using the same BC dose in an estimation of a 3780 m3/day (1 MGD) Fe‐CatOx‐BC‐RF facility, the carbon neutral cost of treatment is reduced further to US$0.08 ± $0.01 with added BC accounting for US$0.03/m3. Overall, the results demonstrate the potential of carbon negativity to become a water treatment performance standard as important and attainable as pollutant and pathogen removal. Practitioner Points: Life cycle assessment (LCA) of a pilot scale tertiary biochar water treatment process with or without catalytic ozonation at a WRRF shows a carbon negative global warming potential of −1.21‐kg CO2e/m3 while removing 90%–99% TP and >90% of detected micropollutants.Biochar‐integrated reactive filtration use can aid in long‐term carbon sequestration by reducing the carbon footprint of advanced water treatment in a dose‐dependent manner, allowing an overall carbon‐neutral or carbon‐negative process.A companion paper to this work (Yu et al., 2023) presents the details related to the process operation and mechanism and evaluates the pollutant removal performance of this Fe‐CatOx‐BC‐RF process in engineering laboratory pilot research and field WRRF pilot‐scale water resource recovery trials.Techno‐economic analysis (TEA) of this biochar catalytic oxidation reactive filtration process using Monte Carlo stochastic modeling shows a forecasted carbon‐neutral process cost with low P and micropollutant removal as US$0.11/m3 ± 0.01 for a 3780‐m3/day (1 MGD) scale installation with BC cost at US$0.03/m3 of that total.The results demonstrate the potential of carbon negativity to become a water treatmentperformance standard as important and attainable as pollutant and pathogen removal. [ABSTRACT FROM AUTHOR]

Numerous studies have unequivocally demonstrated that biochar and, to a lesser degree, earthworms can independently improve soil fertility and crop productivity, although information about their co-application effects on soil characteristics is limited. In this review, (1) earthworm biomarkers and underlying influencing factors, as well as the changes in the amended soil quality in response to co-application of earthworms and biochar are presented, (2) the functional interactions between earthworms and biochar in soil are summarized; (3) the principles governing the synergetic effects of biochar and earthworms on soil quality enhancement are probed; and (4) alternative strategies to optimize the efficacy of earthworm and biochar amendments are provided. It is noteworthy that while low doses of biochar can have a positive effect on various earthworm biomarkers, including growth and reproduction, restoration of the intestinal environment, and the mitigation of cellular organelle toxicity and genetic damage, high biochar dosages can yield adverse effects. Conversely, earthworms play a crucial role in distributing biochar particles deeper into the soil matrix, bolstering carbon sequestration potential, and enhancing the persistence and efficiency of biochar utilization. Moreover, earthworms stimulate the production of soil extracellular enzymes by microorganisms, which are pivotal to the processing, stabilization, and decomposition of soil organic matter, as well as nutrient cycling in terrestrial ecosystems. Additionally, they enhance the binding affinities of these enzymes to biochar. Significantly, changes in earthworm biomarkers in response to biochar integration are predominately governed by biochar properties and dosage, contact time, and soil type. Highlights: A lesser degree of biochar amendment had positive effects on earthworm metabolism. Earthworms homogenized biochar particles into soil matrix and increased biochar utilization efficiency. Earthworm biomarker responses was modulated by its types, biochar, contact time, and soils. Co-application of biochar and earthworms promoted soil health and fertility. [ABSTRACT FROM AUTHOR]

Biochar has gained significant attention in agricultural and environmental research over the last two decades. This comprehensive review evaluates the effects of biochar on soil organic carbon (SOC), emission of non-CO2 greenhouse gases, and crop yield, including related mechanisms and major influencing factors. The impacts of biochar on SOC, methane and nitrous oxide emissions, and crop yield are controlled by biochar and soil properties and management practices. High-temperature biochar produced from lignin-rich feedstocks may decrease methane and nitrous oxide emissions in acidic soils and strengthen long-term carbon sequestration due to its stable aromatic structure. In contrast, low-temperature biochar from manure may increase crop yield in low-fertility soils. Applying biochar to farmlands in China can increase SOC content by 1.9 Pg C and reduce methane and nitrous oxide emissions by 25 and 20 Mt CO2-eq year−1, respectively, while increasing crop yields by 19%. Despite the increasing evidence of the positive effects of biochar, future research needs to explore the potential factors that could weaken or hinder its capacity to address climate change and secure crop production. We conclude that biochar is not a universal solution for global cropland; however, targeted applications in fields, landscapes, or regional scales, especially in low fertility and sandy soils, could realize the benefits of biochar as a climate-smart measure. Highlights The findings of research on biochar's effects on soil C sequestration, GHG mitigation, and crop production were summarized. The factors influencing the impact of biochar on soil functioning were reviewed. The effects of biochar on soil C sequestration and GHG mitigation in farmlands of China were quantified. [ABSTRACT FROM AUTHOR]

Biochar soil amendments, along with non-tillage agriculture, are often proposed as a strategy for carbon sequestration. It is still questionable how the quality of biochar might influence the priming effect on soil organic matter and whether the addition of unprocessed organic amendments will affect biochar stability. In the study, six different biochars and three exogenous organic matter sources were added to two distinct arable soils. CO2 emission was monitored for 100 days of incubation and CO2 flux was estimated. Results showed that biochar increased soil CO2 fluxes. The highest peaks, up to 162 µg C-CO2 h−1 100 g−1, were recorded in treatments with food waste biochars, suggesting that they serve as a source of easily available carbon to soil microbes. Co-application of raw organic materials (manure and fresh clover biomass) enhanced CO2 emission and carbon losses, especially in sandy soil, where 0.85–1.1% of total carbon was lost in the short-term experiment. Biochar properties and content of labile C can stimulate CO2 emission; however, in a long-term period, this contribution is negligible. The findings of our study showed that more attention should be paid to priming effects caused by the addition of exogenous organic matter when applied to biochar-amended soils. [ABSTRACT FROM AUTHOR]

The conversion of residual biomass from fruit seeds into biochar can be achieved using MgCl2 as an activating agent and calcining at 700 °C. The resulting MgO‐biochars were employed in the aldol condensation reaction between furfural and acetone. This reaction is essential as the first step in the obtention of biofuels derived from biomass. The biochars were characterized through various physicochemical techniques, revealing that the presence of MgO nanoparticles deposited on the carbon surface modifies the structural and acidic‐basic properties of the carbonaceous materials with a graphitic structure. The biochar with a surface content of MgO of 0.34 % w/w enables the achievement of 100 % of selectivity towards 4‐(2‐furanyl)‐3‐buten‐2‐one (I) with quantitative conversions under optimized conditions. This property highlights the potential of using this type of biochar, commonly used for CO2 capture, as a versatile acidic‐basic catalyst, thereby introducing a novel approach to sustainable chemistry. [ABSTRACT FROM AUTHOR]

The Climate Change Conference of Parties (COP) 21 in December 2015 established Nationally Determined Contributions toward reduction of greenhouse gas emissions. In the years since COP21, it has become increasingly evident that carbon dioxide removal (CDR) technologies must be deployed immediately to stabilize concentration of atmospheric greenhouse gases and avoid major climate change impacts. Biochar is a carbon-rich material formed by high-temperature conversion of biomass under reduced oxygen conditions, and its production is one of few established CDR methods that can be deployed at a scale large enough to counteract effects of climate change within the next decade. Here we provide a generalized framework for quantifying the potential contribution biochar can make toward achieving national carbon emissions reduction goals, assuming use of only sustainably supplied biomass, i.e., residues from existing agricultural, livestock, forestry and wastewater treatment operations. Our results illustrate the significant role biochar can play in world-wide CDR strategies, with carbon dioxide removal potential of 6.23 ± 0.24% of total GHG emissions in the 155 countries covered based on 2020 data over a 100-year timeframe, and more than 10% of national emissions in 28 countries. Concentrated regions of high biochar carbon dioxide removal potential relative to national emissions were identified in South America, northwestern Africa and eastern Europe. Highlights: Biochar production via biomass pyrolysis is one of few carbon dioxide removal (CDR) technologies that can be deployed at scale. Modeled biochar CDR potential of nearly every country, based on available biomass residues and national average soil temperature. Biochar can offset over 10% of national emissions in many countries, with concentrated impacts in three global regions. [ABSTRACT FROM AUTHOR]

Cheap, efficient and eco‐friendly adsorbents have received great attention for CO2 capture. Nowadays, biochars are promising CO2 adsorbents with the advantages of their low‐cost, tunable porous structural characteristics, facile surface treatment and easy regeneration. In this work, biochar synthesized from wheat straw, an agricultural waste, by pyrolysis was used as a CO2 adsorbent. CO2 capture studies were conducted by thermogravimetric analyses (TGA) at 25 °C under 100 mL min−1 CO2 for 2 h. The CO2 adsorption capacity of the biochar was determined as 23.33 mg g−1. To enhance CO2 adsorption capacity, ultrasonication and urea treatment were applied to the biochar. With the combination of these treatment methods, CO2 adsorption capacity of the biochar increased to 73.56 mg g−1 due to an increase in its micro‐pore volume and presence of functional amine groups. Possible CO2 capture mechanisms were stated as pore filling with CO2 molecules, van der Waals forces, weak hydrogen bond, and Lewis acid‐base interactions in addition to reactions of amine groups with CO2 molecules. After five CO2 adsorption‐desorption cycles, ultrasonication assisted urea treated biochar was still used with over 90 % performance. The results show that the low‐cost and eco‐friendly physicochemical treated biochar is a favorable adsorbent for CO2 capture. [ABSTRACT FROM AUTHOR]

Biochar is an effective soil amendment with capabilities of boosting carbon sequestration and enhancing soil fertility, thus enhancing plant growth and productivity. While numerous studies have documented the positive effects of biochar on improving soil properties, a number of studies have reported conflicting results. Therefore, the current study was conducted to evaluate the impact of Prosopis juliflora biochar (0, 2.5, 5.0, and 7.5 t ha−1) on soil biochemical properties in Coastal Kenya to ascertain biochar's potential for soil fertility improvement. A randomized complete block design was used for setting up the experiment with three replicates, while Casuarina equisetifolia L. was planted as the test crop. Soil sampling for nutrient analysis was conducted quarterly for 12 months to assess nutrient dynamics under different biochar rates in the current study. Compared to soil untreated with Prosopis juliflora biochar, the results showed that there was a significant increase in soil pH by 21% following biochar utilization at the rate of 7.5 t ha−1. Total nitrogen was increased by 32% after the biochar application, whereas the total organic carbon was increased by four folds in comparison to biochar-untreated soil. Available phosphorus was increased by 264% following biochar application in comparison to the control treatment. In addition, the application of biochar resulted in an increment in the soil exchangeable cations (Ca2+, K+, Mg2+) across the assessment periods. Soil cation exchange capacity (CEC), bacteria and fungi were enhanced by 95, 33 and 48%, respectively, following biochar application at 7.5 t ha−1 in comparison to untreated soil. In conclusion, these results strongly suggest improvement of soil biochemical properties following Prosopis juliflora biochar application, thus providing potential for soil fertility improvement in regions such as the one in the study. [ABSTRACT FROM AUTHOR]

Biochar has gained increasing attention as a potential adsorbent for the sequestration of carbon dioxide (CO 2) and enhancement of soil fertility. Biochar pH and stability are important adsorbent properties as they indicate the affinity of biochar for CO 2 and its potential to be applied in soil for long periods. These attributes are influenced by the feedstock composition and pyrolysis conditions. Therefore, it is important to develop a model that can elucidate the underlying trends and inherent relationships between feedstock composition and pyrolysis operating parameters on biochar pH and stability. In this work, rough set machine learning (RSML) tools have been used to develop a model to quantify this relationship because of the interpretable nature of RSML. RSML is a rule-based prediction model that categorizes the biochar properties by utilizing 'if. then' rules to conditional attributes. In this study, the feedstock properties such as elemental (carbon, hydrogen, oxygen and nitrogen) composition, fixed carbon, ash content, volatile matter, and operating conditions such as residence time, heating rate, and temperature were the conditional attributes while pH, ash content and O/C ratio of biochar were considered the decision attributes. The rules generated from RSML were validated and evaluated for scientific coherency. Thus, this approach provided a model which could reflect on the physical phenomena at varying process conditions. As a result, it was recommended that the pyrolysis temperature is in between 375 and 475 °C, the ash content in the feedstock is between 2.59 and 3.55 wt% and volatile matter in the feedstock is in between 68.9 and 73.8 wt% to obtain biochar with minimum ash content (0–5 wt%), minimum O/C ratio (0–0.2), and high pH (9−11). [Display omitted] • Rough-set ML to predict biochar pH and stability from pyrolysis and feedstock. • Rules with certainties >60% and ensured its scientific coherency. • Higher T for higher pH and O/C ratios; low T for biochar ash content. • Higher AC leads to higher O/C ratios and biochar ash content. • Low VM leads high biochar pH and low ash content. [ABSTRACT FROM AUTHOR]

The growing demand for biomass is forcing attention toward alternative resources, including agricultural by-products such as fiber hemp (Cannabis sativa L.). Growing hemp for seed produces about 10 tons of dry matter by-products per hectare. Processing-conversion technologies used in practice change the properties of primary raw materials, give them higher added value, and prepare them for various needs. In addition to economic benefits, biochar contributes to carbon sequestration and increases the sustainability of agricultural production. This study evaluated the effect of thermochemical treatment in an oxygen-free environment on some physicochemical properties of the fiber hemp by-products of the Felina 32 variety. At a heating temperature of 700 °C, the biomass yield of biochar from stems was 28.4 ± 0.5% and from seed husks was 30.6 ± 0.6%. At that time, the carbon concentration in fiber hemp stems biochar increased 1.82 times, from 45.0 ± 2.26% to 81.9 ± 8.46%, and in seed husk biochar by 1.20 times, from 56.5 ± 11, 6% to 67.9 ± 7.47%. Furthermore, the changes in the fractional composition, density, calorific value, ash content, and ash melting characteristics that occurred during the conversion of primary raw material of fiber hemp into biochar were evaluated. [ABSTRACT FROM AUTHOR]

In a laboratory experiment, the effect of biochar (BC) on substrate-induced respiration (SIR) of soils was studied. In the experiment, 10 samples of BC obtained from woody and herbaceous materials in two modes of pyrolysis were used. The SIR was determined after 3 days and after 3 and 6 months of incubation. During short-term incubation, no effect of BC on SIR was observed. The exception was the corn-based BС application, when there was a 34.6% increase in SIR. After incubation for 3 months, a significant increase in SIR was found (from 30.4 to 54.8%) for five BCs were added. After incubation for 6 months, a significant increase in SIR (from 30.4 to 65.9%) was observed when eight BCs were applied. LASSO regression and 23 parameters of BC properties were used as potential predictors to evaluate BC properties that affect SIR. It was found that during three-day incubation, the following properties of BС have a positive effect on SIR: the contents of oxidizable organic matter (OM) and exchangeable calcium and the pH of water suspension; the content of exchangeable sodium had a weak negative effect. At incubation for 3 months there is a positive effect of oxidized OM; and after 6 months, the ash content. Since only a positive statistically significant effect of BC on SIR was observed in the experiments, it was concluded that in order to objectively assess the efficiency of BC use for CO2 sequestration in soils, balance calculations are necessary. In these calculations, along with the amount of stable carbon introduced into soils with BC, a potential increase in CO2 emissions from soils due to the activation of soil saprophytic microbiota should be taken into account. [ABSTRACT FROM AUTHOR]

Drought is a major stressor of tree seedlings regarding both natural and artificial regeneration, especially in excessively drained, sandy outwash soils. While climate change is expected to cause an increase in the total annual precipitation in the Upper Midwest, USA, the timing of the precipitation is predicted to result in longer periods of drought during the growing season. Biochar, a material created through the pyrolysis of organic matter, such as wood waste, has been proposed as a soil amendment that may increase the water holding capacity of a soil. Biochar has mostly been studied in agricultural settings, and less is known about the impact of biochar on forest soils and tree seedlings. We used a greenhouse experiment to test the ability of biochar to improve the drought tolerance of jack pine (Pinus banksiana) seedlings via increased soil water holding capacity. The seedlings were planted in sandy soil treated with three levels of biochar (none, 3% by weight, and 6% by weight) in two experiments, one manipulating the timing of drought onset and the other controlling the amount of water that seedlings received. Our results showed no significant effects of biochar on seedling survival, growth, or physiology under drought conditions. While this outcome did not support the hypothesis that biochar would increase seedling performance, the biochar amendments did not negatively affect seedlings, indicating that biochar may be added to soil for carbon storage without having negative short-term impacts on tree seedlings. [ABSTRACT FROM AUTHOR]

CO2 capture is a practical approach to mitigating the impacts of global warming. Adsorption‐based carbon capture is a clean and potentially energy‐efficient method whose performance greatly depends on adsorbent design. In this study, we explored the use of jute‐derived carbon as a high‐performance adsorbent for CO2 capture. The carbons were produced by pyrolyzing powdered jute sticks with NaHCO3 as an activating agent at 500–700 °C. Impressive adsorption capacities of up to 2.5 mmol ⋅ g−1 and CO2/N2 selectivities of up to 54 were achieved by adjusting the pore size distribution and surface functionalization. Based on the isotherm results, the working capacities, regenerabilities, and potentials for CO2 separation were determined for a practical vacuum swing adsorption process. The adsorbent materials were characterized by XRD, FTIR, Raman, FESEM and N2 sorption at 77 K. This study provides a general approach for designing adsorbents for various gas‐separation applications. [ABSTRACT FROM AUTHOR]

Biochar holds great promise for carbon sequestration but is restricted by high costs. Here, we introduced the water–fire coupled method and developed a mineral coating technique for biochar production from paulownia waste (Paulownia fortune). Exposure time and mineral (lime) coating were assessed for their impacts on biochar properties. The former had a dominant adverse effect on carbon content, specific surface area, and carbon capture capacity of the biochar. In contrast, the latter alleviated the adverse impact on carbon capture capacity and specific surface area, the highest being 67.07% and 176.0 m2 g−1, respectively. Without a mineral coating (B), biochar functional groups reduced at the exposure time of 0–4 min (-COOH from 0.50 to 0.19 mol/kg, phenolic-OH from 0.43 to 0.14 mol/kg). In contrast, a mineral coating (B-Ca) increased -COOH from 0.25 to 0.83 mol/kg and phenolic-OH from 0.19 to 0.72 mol/kg. The pyrolysis process with a mineral coating is conceptualized as (1) wrapping the paulownia branch with the mineral, (2) enabling oxygen-limited pyrolysis inside the branch, and (3) ending the pyrolysis with water to form biochar. Ca2+ played multiple functions of ion bridging, complexation, and reduction of COx gas formation, thus enhancing the carbon capture capacity (the ratio of C in biomass converted to biochar) to 67%. This research would improve the feasibility of biochar use for carbon sequestration and climate change mitigation. [ABSTRACT FROM AUTHOR]

The article discusses the importance of soil carbon sequestration (SCS) as a tool to mitigate climate change. The authors estimate that agricultural soils have the potential to sequester 3-14 Gt CO2/year by 2050 through SCS practices. They emphasize that SCS should be implemented alongside emission reductions in all sectors. The article also highlights the need for better estimates of biomass availability for SCS practices and acknowledges the variability in carbon loss and saturation levels. The authors argue that undervaluing the potential of SCS can lead to inaction on climate change. [Extracted from the article]

A field experiment was carried out to elucidate the effect of elevated carbon dioxide (eCO2 – 550 ± 30 ppm) on soil enzymes (dehydrogenase, β-glucosidase, fluorescein diacetate, urease, acid and alkaline phosphatase), soil carbon pool (Soil Organic Carbon (SOC), Microbial Biomass Carbon (MBC), oxidizable carbon, humic acid (HA), fulvic acid (FA) fractions), microbial population dynamics (heterotrophs, fungi, actinobacteria, diazotrophs, methanotrophs, and total anaerobes), carbon sequestration and yield in a flooded paddy soil in open top chambers (OTCs) in relation to rhizospheric and bulk soil. Responses of most of the observed parameters to eCO2 with biochar application in rhizosphere soil were significantly higher. The carbon (C) sequestration potential was found higher in the biochar applied plot under eCO2 with 0.59 Mg C sequestered ha−1. The same recorded the highest biomass yield and grain yield which is 12.8 and 30.8% higher than the control. Principal Component Analysis (PCA) recognized soil dehydrogenase, β – glucosidase, SOC, FA, Substrate Induced Respiration (SIR), metabolic quotient (qCO2) and counts of heterotrophs as key drivers of variability. The current study thus provides some dependable biological indicators to assess the paddy ecosystems, vis-à-vis anticipatory climate change. [ABSTRACT FROM AUTHOR]

Alternate wetting and drying irrigation (IAWD) is one type of water-saving technology to repeatedly dry and re-flood the fields. However, the frequent alternate aerobic and anaerobic environment under IAWD has increased the reactive nitrogen gas emission in rice fields. Fortunately, biochar has been widely used to improve land productivity (including crop production, carbon sequestration, mitigation of GHG, and remediation of heavy metal pollution) in agricultural soil amendment. However, little information is available on the effects of biochar on NH3 volatilization, N2O emissions, and reactive nitrogen gas emissions in paddy rice systems, especially under IAWD. This study aims to explore the response mechanism of reactive nitrogen gas emissions to the biochar application under IAWD conditions. A two-year field split-plot experiment was conducted with the biochar application rates (0 and 20 t/hm² ) under two irrigation regimes (continuously flooded irrigation, ICF and IAWD). Two irrigation regimes were used as the main plots, whereas, two biochar additions were the subplots. Each plot was in the size of 3 m (width) × 6 m (length) that separated by the PVC barrier at a depth of 30 cm. in order to avoid the lateral flow of nutrients and water. The results showed that the IAWD increased yields by 1.7% to 5.1% (P>0.05), NH3 volatilization by 6.6% to 11.6%, and N2O emissions by 157.1% to 116.7%, compared with the ICF (P>0.05). Biochar addition at the rate of 20 t ha−1 significantly reduced the NH3 volatilization by 10.8% to 25.2% and N2O emissions by 21.6% to 24.2% (P>0.05). There was an increase in the yield by 0.2% to 12.5% and a reduction in the reactive nitrogen gas emissions by 6.1% to 11.7% in biochar combined with the IAWD, compared with the control (ICFB0). Furthermore, the inorganic nitrogen existed mainly in the form of NH4 + -N in the soil environment of rice fields, accounting for 80% to 90%. The IAWD had no significant impact on the soil NH4 + -N, compared with the ICF, whereas, a significant increase was found in the content of surface soil NO3 − -N by 50.3% to 74% and the oxidationreduction potential by 47.6% to 54.1% (P>0.05). Moreover, the biochar addition increased the soil NH4 + -N by 25.9% to 52.41% (P>0.05), and pH by 0.6% to 1%, compared with the biochar-free treatment. Principal component analysis showed a strong negative correlation between NH3 volatilization and soil NH4+ -N content, yield, and aboveground nitrogen accumulation. It indicated that the biochar addition significantly improved the soil adsorption capacity for the inorganic nitrogen, thereby reducing the NH3 volatilization losses and increasing aboveground nitrogen accumulation, ultimately leading to an increase in the yield. N2O emissions were strongly positively correlated with the oxidation-reduction potential and soil NO3 − -N. Therefore, the frequent alternate aerobic and anaerobic environment under IAWD increased the concentration of soil NO3 − -N and the oxidation-reduction potential, thereby increasing denitrification substrates and N2O emissions. Anyway, the biochar addition coupled with alternate wetting and drying can be expected to promote rice production with water saving, carbon sequestration and emission reduction, while reducing the environmental costs associated with the reactive nitrogen emissions in the paddy field. [ABSTRACT FROM AUTHOR]

Biochar amendment is one of the most promising agricultural approaches to tackle climate change by enhancing soil carbon (C) sequestration. Microbial‐mediated decomposition processes are fundamental for the fate and persistence of sequestered C in soil, but the underlying mechanisms are uncertain. Here, we synthesise 923 observations regarding the effects of biochar addition (over periods ranging from several weeks to several years) on soil C‐degrading enzyme activities from 130 articles across five continents worldwide. Our results showed that biochar addition increased soil ligninase activity targeting complex phenolic macromolecules by 7.1%, but suppressed cellulase activity degrading simpler polysaccharides by 8.3%. These shifts in enzyme activities explained the most variation of changes in soil C sequestration across a wide range of climatic, edaphic and experimental conditions, with biochar‐induced shift in ligninase:cellulase ratio correlating negatively with soil C sequestration. Specifically, short‐term (<1 year) biochar addition significantly reduced cellulase activity by 4.6% and enhanced soil organic C sequestration by 87.5%, whereas no significant responses were observed for ligninase activity and ligninase:cellulase ratio. However, long‐term (≥1 year) biochar addition significantly enhanced ligninase activity by 5.2% and ligninase:cellulase ratio by 36.1%, leading to a smaller increase in soil organic C sequestration (25.1%). These results suggest that shifts in enzyme activities increased ligninase:cellulase ratio with time after biochar addition, limiting long‐term soil C sequestration with biochar addition. Our work provides novel evidence to explain the diminished soil C sequestration with long‐term biochar addition and suggests that earlier studies may have overestimated soil C sequestration with biochar addition by failing to consider the physiological acclimation of soil microorganisms over time. [ABSTRACT FROM AUTHOR]