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Biochar modifications and fortifications are used to increase soil nutrient retention and increase crop yields, but the effects on phosphate (Pi) availability for plants are unknown for saline-alkaline soils. We used peanut shells (Peanut-S) as the starting material for biochar (Biochar) and MgO-modified biochar (MgO-Biochar) to study the Pi adsorption mechanisms under field conditions. Compared with Biochar and Peanut-S, MgO-Biochar adsorbed Pi in aqueous solution 20% better and reached equilibrium at twice the rate at twice the rate. MgO-Biochar also showed better Pi adsorption in saline soils and the maximum Pi adsorption capacity was 1.46 times higher than Biochar. We found that electrostatic attraction, precipitation and exchangeable anions contributed to the adsorption of phosphate and MgO-Biochar possessed the greatest adsorption capacity. MgO-Biochar application increased the soil available P content and resulted in higher rice yields in field experiments in the saline soil conditions found in the Yellow river delta region. Overall, our study offers a theoretical and practical foundation for the remediation of saline soil using MgO-modified biochar.

The present study investigated the potential tertiary treatment of wastewater by adsorption using rice husk biochar (RHC) obtained from microwave pyrolysis of rice husk. Adsorption experiments with RHC indicated phosphate and nitrate adsorption of 65% and 75% respectively. The adsorption kinetics indicated pseudo-second-order adsorption model for adsorption of nutrients on biochar with an R2 value more than 0.98. In addition, the Langmuir-Freundlich isotherm was observed to represent the adsorption of phosphate on RHC, whereas adsorption data of nitrate depicted Langmuir isotherm followed by Temkin and Dubinin-Radushkevich isotherms. The maximum phosphate and nitrate adsorption capacity were 71 mg/kg and 497 mg/kg respectively using Langmuir isotherm model. The desorption study indicated a release of 96.6% and 44.4% of adsorbed phosphate and nitrate, respectively. Hence, from 1 kg of nutrient loaded RHC about 68 mg of phosphate and 220 mg of nitrate can be extracted for land application.

In this study, the oxidation biochar supported magnetite particles (OBC-Fe3O4) was prepared to activate persulfate (PS) for antibiotic tetracycline (TC) degradation. The as-prepared OBC-Fe3O4 exhibited the better catalytic performance for PS activation due to its abundant oxygen-containing groups on the surface and Fe3O4 particles. In the OBC-Fe3O4/PS system, TC was degraded and removed through the synergistic effects of catalyst's adsorption and sulfate radical (SO4•−) oxidation. The optimum conditions were determined as pH 3.0, PS concentration 10 mM and OBC-Fe3O4 dosage 0.4 g/L, which resulted in 92.3% of TC removal within 2 h. The electron spin resonance (ESR) and radicals quenching studies revealed the mechanism of TC degradation in OBC-Fe3O4/PS system included the radical and nonradical pathway involving the generation of SO4•−, •OH and 1O2, while SO4•− and •OH radicals played more dominant role in the reaction. Moreover, the intrinsic atom arrangements of carbon hybridization, defective sites and persistent free radicals (PFRs) on the catalysts also related to its catalytic efficiency. Eight transformation products were identified which mainly derived from oxidation of double bonds, loss of dimethyl amino, dehydration, oxidation of aromatic ring and cleavage of carboatomic ring of TC. Consequently, a possible degradation pathway of TC was suggested. Overall, OBC-Fe3O4 could be an economic and high-efficiency heterogeneous catalyst for PS activation to remove organic pollutants in waste water.

Sustainable management of contaminated biomass derived from phytoremediation of metal(loid) polluted soil and water is of great importance to avoid environmental risks from secondary pollution of the contaminants. In this regard, pyrolysis technology may reduce the environmental risk of the contaminants and produce different bio-products from contaminated biomass. In this work, slow pyrolysis of Avicennia marina biomass was conducted to compare the pyrolysis properties of heavy-metal-contaminated and uncontaminated biomass and its potential to generate pyrolytic products, such as biochar, bio-oil and pyrolytic gas at a varying temperature range from 300 to 800 °C. The results indicated that the properties of biomass and derivatives were affected significantly by both pyrolysis temperature and the presence of heavy metal(loid)s. The heavy metal(loid)s in biomass contributed to higher biochar and pyrolytic gas yields at the expense of bio-oil. Increasing pyrolysis temperature induced the volatilisation of heavy metal(loid)s in biochar samples. At the same pyrolysis temperature, the contaminants significantly increased the ash content whilst decreased the fixed carbon content in biochars (p

An alginate gel bead composite adsorbent with polyethyleneimine (PEI) as a surface modifier and Eichhornia crassipes (EC) biochar, known as EC-alg/PEI-3, was added internally to the adsorb Cr(VI) from an aqueous environment. The functionalized gel beads were characterized using SEM, XPS, FTIR, and other techniques. The maximum adsorption capacities of EC-alg/PEI-3 were 714.3 mg g−1 at 10 °C and 769.2 mg g−1 at 25 °C. In the treatment of highly concentrated electroplating wastewater, EC-alg/PEI-3 can be dosed at 1.4 g L−1 to reduce the concentration of Cr(VI) to below 0.05 ppm. EC-alg/PEI-3 maintained a competitive adsorption capacity after six cycles. This spherical adsorbent material is easy to prepare, has a very high adsorption capacity, is environmentally friendly, and can be easily recycled. The EC-alg/PEI-3 gel beads are promising for the treatment of industrial wastewater. Errata: Yingnan He, Jianbing Chen, Jiapei Lv, Yimin Huang, Shuxing Zhou, Wenyan Li, Yongtao Li, Fengqin Chang, Hucai Zhang, Thomas Wågberg, Guangzhi Hu, Corrigendum to "Separable amino-functionalized biochar/alginate beads for efficient removal of Cr (VI) from original electroplating wastewater at room temperature". Journal of Cleaner Production, Volume 412, 2023, 137375. DOI: 10.1016/j.jclepro.2023.137375

In this study, we assessed the capacities of biochar derived from tea branches (hereafter referred to as biochar) and Fe–Mn-modified biochar (MnFe2O4-biochar) to immobilize Sb and Cd in contaminated soils and reduce the bioavailability of Sb and Cd in Lolium multiflorum Lam.. The results of pot experiments indicated that the application of biochar and MnFe2O4-biochar significantly (P

An innovative approach is developed to utilize the frass of mealworms (Tenebrio molitor Linnaeus 1758) for producing dye-removal biochar. Agricultural waste wheat straw (WS) was tested as feedstock versus wheat bran (WB) to rear mealworms for the production of insect biomass. Mealworms on WS grew at a slightly slower rate than those grown on WB for 32 days with ∼40% lignin removed at 25 °C. Biochars were generated using the frass of mealworms via pyrolysis. The best adsorption performance for three dyes, especially malachite green, a cationic dye, was the biochar of WS frass at 800 °C; it had better capacity (1738.6 mg/g) compared with the frass fed with bran, raw WS and raw WB as well as those reported in the literature. Adsorption of malachite green fits the Langmuir isotherm and the pseudo second order kinetic model, mainly due to chemisorption and electrostatic interaction. Our results demonstrated that the WS can be utilized to rear mealworms, and that frass of mealworms is an excellent raw material for generating high-efficiency bioadsorbents.

Effective valorization of nutrient rich wastes for the fertilizer application is a promising method towards sustainable development. Nutrient rich wastes were mainly researched for production of biochar straight (single nutrient) fertilizer through slow pyrolysis. Appropriate waste feedstocks and cleaner thermal processing need to be explored for value addition. In present study, potassium (K) containing banana peduncle and phosphorus (P) rich effluent sludge (chemical fertilizer industry) wastes co-utilized for development of biochar complex fertilizer. Different thermal treatments viz slow pyrolysis (700 °C) and thermal plasma processing (1200–1500 °C) were trialed for production of biochars with desired characteristics. Plasma processing produced biochar with higher total P (8.53 – 11.81 %) and K (17.13 – 21.9 %) than slow pyrolysis (P-4.2 % and K-11.5 %). In contrast, slow pyrolysis resulted higher biochar yield (42 %) and total carbon content (34.1 %) than in plasma (28 – 34 % and 10.9 – 21.8 %). Bio-available phosphorus of effluent sludge (600 mg/kg) enhanced to 4500 – 6000 and 5600 mg/kg in plasma and slow pyrolysis biochars. XRD analysis indicates the presence of P as hydroxyapatite in sludge and biochars. The K was dominantly present as kalicinite (KHCO3) in slow pyrolysis and fairchildite [K2 Ca (CO3)2] specifically in plasma biochar. Biochars contained lesser total (0.18 –1.55 %) and leachable (0.014 – 0.034 %) fluoride than effluent sludge i.e. 3.45 and 0.076 %. These results demonstrate utilization potential of aforementioned wastes and thermal processes for the production of K and P enriched biochar complex fertilizer. Its application will be suitable for non-food crops and degraded soil reclamation due to toxic constituents.

In this study, the removal of zinc from plating wastewaters using fixed bed columns packed with hydrolyzed olive cake was investigated. This work discusses the significance of the scale-up and provides a brief overview of the potential uses of exhausted biosorbent for the generation of zinc-based materials. First, biosorption studies were performed to analyze biosorption behavior of hydrolyzed olive cake in different sized columns. Influence of important design parameters such as contact time, linear velocity and bed height/diameter ratio on biosorption performance was studied. Results indicated a significant effect of contact time on scale-up. Higher bed depths increased the biosorption capacity due to a larger dose of absorbent in the packed columns. As the flow rate increased, the breakthrough time decreased and the exhaustion of the column was reached faster. In addition, operating at the same contact time and bed height/diameter ratio and at a linear velocity much higher in the pilot column, the zinc uptake capacity was found to be higher. Better biosorption results could be due to velocity influencing the mass transfer and hydraulics improving the fluid dispersion. Finally, exhausted biosorbent was subjected to different thermal treatments. Preliminary tests showed that zinc-loaded solid can be recycled for the generation of zinc-based materials.

The use of abundant natural wastes as environmentally friendly products promotes a circular green economy and cleaner production. The potential use of natural waste materials without additional processing for the removal of priority pharmaceuticals from water was investigated. Here, the performance of selected low-cost biosorbents (biochar, macro-algae and wood chippings) was evaluated using two extensively prescribed model pharmaceuticals: diclofenac (DCF) and trimethoprim (TMP). The physicochemical properties of the biosorbents were examined (to shed light on likely biosorption mechanisms) using Brunauer–Emmett–Teller (BET) measurements, scanning electron microscopy (SEM), zero point of charge (pHzpc) measurements and Fourier transform infrared spectroscopy (FTIR). Experimental data from kinetic studies fitted a pseudo-second order model, and multiple diffusion steps limited the mass transfer of analytes. Intra-partile diffusion was the rate limiting step for biochar, while macro-algae and wood chippings were limited (mainly) by adsorptive attachment. The equilibrium data for most of the studied systems best fitted a Langmuir model, while the Freundlich model provided a better fit for TMP with wood chippings. At μg∙L−1 initial pharmaceutical loading levels, the maximum biosorption capacity for DCF was attained with biochar (7.25 × 103 μg g−1), while macro-algae performed best for TMP (7.14 × 104 μg g−1). Both chemical and physical interactions were likely responsible for the biosorption of pharmaceuticals. High removal efficiencies were achieved at the low initial loadings studied, indicating the potential application of those sustainable low-cost biosorbents at low (environmentally relevant) pharmaceutical concentrations.

Saffron (Crocus sativus L.) is a medicinal important plant with none information on cadmium (Cd) phytotoxicity. Therefore, this study for the first time elevated the effects of beeswax waste biochar (a novel organic amendment) on Cd uptake, biomass, antioxidant enzymes activities and some physiobiochemical characteristics in saffron exposed to Cd stress. The treatments were consisted four Cd concentrations (0, 3, 6 and 9 mg kg-1 soil) together with four biochar levels (0%, 1.5%, 3.0% and 6% w/w). The results showed that Cd uptake in saffron corm and leaf tissues was significantly elevated by increase in Cd stress, but this parameter in flower and stigma (as edible part of saffron) was unchanged. Application of Cd caused decrease in plant biomass which was found to recover with the amendment of biochar. The translocation factor values were less than 1 in all the treatments, demonstrating saffron can be considered as a candidate plant for cadmium phytostabilization. Cadmium-induced oxidative stress stimulated malondialdehyde content, and activity of superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase enzymes, while biochar application alleviated the oxidative damages. Crocin component was significantly raised along with increase in Cd concentration. Meanwhile, biochar application declined crocin and increased picrocrocin contents. In conclusion, beeswax waste biochar can mitigate Cd toxicity in saffron by inducing soil alkalinization, immobilizing Cd in soil, reducing Cd partitioning in the aboveground tissues and regulating Cd induced oxidative damage, consequently contributing to lowering the potential risks of Cd pollution.

Biochar is a carbon-rich material which can be prepared from various organic waste feedstock, such as agricultural wastes and municipal sewage sludge. Biochar has received increasing attention due to its unique feature such as high carbon content and cation exchange capacity, large specific surface area and stable structure. This review systematically analyzed and summarized the preparation, characterization, modification, and especially environmental application of biochar, based on more than 200 papers published in recent 10 year, to provide an overview of biochar with a particular on its environmental application. The physiochemical properties of biochar varies with the types of feedstocks. Pyrolysis, gasification and hydrothermal carbonization are the common methods for biochar preparation. Biochar can be modified by acid, alkali, oxidizing agents, metal ions, carbonaceous materials, steam and gas purging. The selection of modification methods depends on the environmental application fields. The biochar has been used for soil remediation and amelioration, carbon sequestration, organic solid waste composting, decontamination of water and wastewater, catalyst and activator, electrode materials and electrode modifier, which were discussed in detail. The application of biochar in the carbon sequestration should be further investigated at similar experimental conditions to obtain the consistent results. The effect of biochar on soil microbes should be further investigated to elucidate the dominant reason for the improvement of soil fertility based on different soil and feedstock. In addition, more attention should be paid to the release of heavy metals and polycyclic aromatic hydrocarbons (PAHs) from biochar to the environment when biochar is practically used for the environmental remediation. The relationship between biochar structure and activation capability should be further investigated to clarify the activation mechanism of persulfate by biochar when it is used as activator. In summary, biochar has wide application prospect in environmental remediation, and the mechanism of biochar in environmental application should be further investigated.

Rapid climate change mitigation requires carbon sequestration in addition to greenhouse gas emission reductions. Agriculture may have a high potential for carbon sequestration due to improved practices. However, it is not known how the global warming impacts of crop production could be mitigated especially within an agricultural system. The aim of this study is to evaluate possibilities to neutralize global warming impacts in crop production using biochar produced from side flows and buffer zone biomass. A life cycle assessment methodology is utilized in this research for oat production in the boreal climate zone. Global warming impact reductions are compared for three different side flow utilization options. Traditionally, side flows have been utilized in energy or fodder production, and these options are compared to biochar production at a system level. The potential to use buffer zone biomass for biochar production is also studied. Willow has been selected as a biomass source in buffer zones. Oat production leads to greenhouse gas emissions especially due to the use of fossil and mineral fertilizers in cultivation and heat energy, electricity and fuels in various process phases. The production of one metric ton of oat flakes from cradle to gate generates 700 kg of CO2eq emissions. Biochar and energy production from side flows enables a greater reduction in global warming impacts than the feed use of side flows. Buffer zones in willow biomass and biochar production may enable the full neutralization of the global warming potential of oat production within an agricultural system. Further research with actual measurements is required especially on biochar impacts on soil emissions such as N2O. This research shows that it could be possible to neutralize global warming impacts from crop production using available technologies and available biomass in agricultural systems. A framework is created for carbon neutral crop production using side flows and buffer zone biomass through biochar. Post-print / Final draft

This study presents a new bottom-up biofabrication method to produce highly porous magnetic biochar from waste-derived fungal biomass. Neurospora crassa was grown in iron containing coagulation backwash (BW) diluted with primary effluent (PE) wastewater in two ratios of 1:4 (PE-BW 1:4) and 3:4 (PE-BW 3:4). The fungi encapsulated iron directly into biomass hyphae and carbonization resulted in one-step biochar preparation and maghemite (Fe2O3) formation. The morphology and structure of the materials were investigated using a suite of characterization tools. Results indicated that the physiochemical properties of each char were dependent on the blend used for fungal cultivation. PE-BW 1:4 had much larger average pore diameters (13.2 nm vs. 6.1 nm), less elemental surface carbon (2.1% vs. 23.7%), and more expansive Fe2O3 formation. Batch phosphorus adsorption experiments were conducted in the range of 0–90 mg-P/L, and a maximum adsorption density of 23.9 mg/g was achieved. Langmuir, Freundlich and Temkin isotherms were used to describe the interactions of the phosphate on the absorbents and an in-depth error analysis was conducted. Further characterization of the P-loaded chars indicated adsorption primarily via P-OH bonding on the surface of the materials. This new biofabrication method showed great potential to magnetic biochar production with excellent phosphorus adsorption, which can be effectively used in wastewater resource recovery.

The enhancement of surface functional groups of biochar is essential to improving the biochar contaminant adsorption. Current pyrolysis methods that are accompanied by activation are energy consuming and costly. Herein, a novel wet-pyrolysis system that was carried out in open air, with simultaneous conversion and modification to produce an effective biochar adsorbent, is described. Within this system, the surface of the biochar was oxidized partially to produce sufficient functional groups at the surface, whereas carbonization of the biomass (miscanthus sacchariflora) occurs under an acidic catalyst. The characteristic results confirmed the attachment of abundant surface functional groups, including hydroxyl and carboxyl groups, which increased in content with the ongoing reaction time. Neutralization with sodium carbonate removed the hydrogen bonds and enhanced the adsorption properties. The biochar that was obtained by using this technique exhibited an excellent cadmium adsorption capacity of 197 mg .g−1 and a high removal efficiency of 99%. Analysis of the Cd-loaded biochar indicated that adsorption occurred via ion exchange, and formed cadmium complexes. It could be concluded that this novel wet-pyrolysis system is a promising approach to produce biochar efficiently and cost-effectively for heavy-metal remediation.

Municipal solid waste incinerator fly ash (IFA) is categorized as a hazardous waste, which requires proper treatment prior to landfilling due to its high concentrations of toxic elements. This study developed an innovative and cleaner method for stabilization/solidification (S/S) of IFA by the incorporation of supplementary cementitious materials (SCMs) and green stabilizers. Quantitative X-ray diffraction and thermogravimetric analyses indicated that toxic elements in IFA inhibited the cement hydration. Therefore, the single use of cement (10 wt%) was not efficient for the immobilization of toxic elements, especially for Pb. The incorporation of SCMs (20 wt% of binder) such as silica fume facilitated the formation of additional cement hydrates and reduced Pb leachability by 36.3%. The addition of green stabilizers such as potassium dihydrogen phosphate (KDP) and wood waste-derived biochar also improved the immobilization of toxic elements. KDP directly combined with Pb2+ to form a precipitate of Pb3(PO4)2, whereas biochar promoted the generation of cement hydrates for S/S via the effect of internal curing. The incorporation of silica fume (40 wt%) in the binder was the most effective. Overall, this study demonstrated that the selected green binders can serve as low-carbon and high-efficient material for S/S of hazardous ash residue such as IFA.

High sodicity and Low nutrient retention in bauxite-processing residue sand (BRS) disposal areas restrict sustainable vegetation management in this highly alkaline environment. Although previous investigations have reported the beneficial effect of organic amendments on BRS rehabilitation, little is known about the underlying mechanisms of this complicated process, particularly after supplementary leaching of biochar amended BRS. We have investigated the coupled effect of supplementary leaching process, biochar [aged acidic (AC) vs alkaline pine (PC)] amendment and di-ammonium phosphate (DAP) fertilisation on rhizosphere nutrient dynamic and ryegrass performance in a 116-day glasshouse study. Biochar amendment in DAP + PC and DAP + AC treatments significantly increased and decreased pH (0.3–0.5 units) in all BRS rhizosphere and root-free zones, respectively. The application of alkaline and acidic biochars to BRS have reduced ammonia volatilisation (25–80%) and increased nitrogen retention (9–72%) in comparison with DAP treatment. Supplementary leaching had no significant effect on BRS rhizosphere pH, but reduced the EC values by ca. 62% in biochar-amended treatments. The leachates’ pH remained unchanged (ca. 8) throughout the experiment, while their EC reduced in AC (6 folds) and PC (9 folds) amended treatments, with lower reduction in rhizosphere than root-free zones. The interaction of applied biochars and plant roots generally decreased nutrient leaching from rhizosphere in comparison with root-free zones. Sodium was the dominant cation in the leachate of all treatments and cumulative abundance of exchangeable cations were in the order of Na+ > Ca2+ > K+ > Mg2+ > Al3+. The reduction of BRS salinity has increased plant biomass (ca. 47%) in biochar amended treatments by improving the capacity of fresh BRS rhizosphere for plant establishment.

Walnut shell is a common agricultural by-products for the production of biochar. In this study, the walnut shell was investigated by thermoanalytical methods to evaluate its thermal behavior; and the biochar was prepared from the pyrolysis at 600 °C. Biochar characterization was studied in detail, and proximate analysis result indicates that the biochar obtained from walnut shell has a high fixed carbon content, lower ash content. The biochar was used as a reductant to reduce the waste copper slag for recovering iron. The reduction process of copper slag by biochar was analyzed theoretically, and the iron in the slag was recovered efficiently by reduction and magnetic separation method. The phase transformation of the reduced slag and the kinetics of reduction process were analyzed during the reduction process with biochar. The research results suggest that biochar derived from walnut shell can be used as a green reductant to reduce iron phase in the waste copper slag and realize the clean utilization of hazardous waste.

Biochar has been widely studied as a soil amendment to improve soil properties. When different feedstocks are used to produce biochar under different pyrolysis conditions, the resulting biochar would typically differ in physicochemical properties, which consequently impact the agricultural and environmental performance of biochar in its real-world applications. In this work, based on previously reported data from independent studies, different biochar properties were synthesized as a continuum of pyrolysis temperature and feedstock type. Despite the fact that other factors besides pyrolysis temperature and feedstock type might also impact biochar properties, given the same category of feedstock, many critical properties such as biochar yield, pH, cation exchange capacity, specific surface area, ash content, volatile matter content, and elemental composition have been found to well correlate with pyrolysis temperature, showing p-values smaller than 0.05. At the same time, through meta-analyses, the effects of pyrolysis temperature and feedstock type on the agricultural and environmental impacts of biochar, including nitrogen retention, nitrous oxide emission and crop production, have been evaluated. The study has demonstrated that quantitative approaches such as data syntheses and meta-analyses are potential for revealing predictive relationships that can link biochar production with its properties and performance in real-world applications.

The study reports an investigation into the effects of temperature and duration of the pyrolysis on the yield and properties of the rice straw biochar and their optimization for application in soil based on the results of seed germination test. As a continuation, the effects of rice straw biochar on the growth of mung beans germinated using extracts of biochar, which were maintained at different pHs was studied. Biochar solvent extraction was done by mixing a predetermined dose of rice straw biochar to solutions initially maintained at five different pH conditions (4, 6, 7, 8, and 10). The biochar extracts were also characterized for their pH, electrical conductivity, and nutrient values and correlated with the germinated seed lengths. Further, this study based on the results of seed germination optimized the rice straw biochar production conditions with such properties to promote maximum seedling growth. Results showed that the yield of biochar decreased from 45.04% to 33.45% as temperature raised from 400 °C to 700 °C. The properties of biochar are primarily affected by the temperature as compared to the heating duration of the pyrolysis. The crystallinity index in the rice straw biochar decreased by 15.25% with the increase in the temperature from 400 °C to 700 °C. Correlation test among seed lengths and biochar extracts properties showed that the seed growth was directly correlated with the increase in the nutrient values at all pH conditions. Based on the germination test, the optimized conditions for the maximum seedling growth observed as for high nutrients, carbon (35–40%) and moderate nitrogen (3–4%), ash (32–35%), yield (35–40%) and cation exchange capacity (40–45 cmol/kg), carbon-nitrogen ratio (22–25:1), low oxygen-carbon ratio (0.7–0.8), ideal pH (8–9), and low volatiles (44–48%). The optimized pyrolytic temperature and duration to produce rice straw biochar with above-listed properties modelled as 500–600 °C and 80–100 min respectively.

Many studies identified the optimum temperature to maximise bio-oil/biochar yield using fast pyrolysis from woody biomass. However, the optimum mix of biochar and bio-oil production and their final utilisation to achieve optimal environmental and economic benefits are yet to be investigated. Hence, the aim of this study was to identify the optimum mix and utilisation using life cycle assessment and costing approach. Two utilisation scenarios were analysed: Scenario 1 considered terrestrial carbon sequestration through spreading biochar in corn fields while Scenario 2 assumed the co-combustion of biochar to displace coal in a coal-fired power station. In both scenarios, bio-oil was assumed to substitute heavy fuel oil in an industrial boiler. The functional unit used in the study was 1 Mg of green thinned logs from hardwood plantations. Scenario 1 showed outstanding greenhouse gas emissions offset (1680 kg-CO2-eq per function unit). However, this scenario lagged behind when considering other environmental impacts. Scenario 2 delivered more modest greenhouse gas offset, but it had better overall environmental and economic performance. The results indicated that the overall environmental performance of Scenario 2 decreased with increasing pyrolysis temperature due to the decline in biochar yield as well as the increased energy consumption during the pyrolysis process. Meanwhile, lifecycle cost reduced when the pyrolysis temperature increased because of the increased bio-oil production, which has higher economic value than biochar. Assuming equal weights for the environmental and economic functions, the optimal performance of Scenario 2 is likely to be achieved when the pyrolysis process is run at 500 °C with the bio-oil and biochar yields being 64% and 22%, respectively. Monte Carlo Analysis revealed that for balanced environmental and economic weights (30%–70%) the solution is robust. The Monte Carlo Analysis results suggested that under the optimal conditions, there is 97.5% likelihood that Scenario 2 would achieve 1050 kg-CO2-eq greenhouse gas emissions offset and realise $25.8 life cycle cost savings per functional unit. This study demonstrates an easy method to incorporate life cycle assessment and costing into an optimisation decision making framework. Thus, allowing a more comprehensive assessment of policies incorporating multiple environmental impacts (criteria). It contributes to the debate about the economic and environmental validity of using forestry by-products, as well as other low cost woody biomass as a renewable energy source.

The effectiveness of biochar produced from used tea waste was investigated as a potential in-situ amendment for Cd immobilization using a study design based on sediment-water meso-microcosm with 14-days of incubation. The optimum condition for biochar production was evaluated as a function of size, pyrolysis temperature and time. The highest monolayer uptake capacity was found as 42.01 mg/g for selected tea biochar (TB). The TB was mixed with sediment at the ratios of 0%, 2.5%, 5%, and 10%. As compared to the control (0% TB dose), in TB treated sediments, mobile fraction of Cd in sediment was considerably reduced which ultimately decrease the amount of Cd uptake by biota. The efficiency of Cd immobilization increased with the amendment dosage. Overall, sediment treated with 10% TB led to a reduction of Cd by 67.7% in the exchangeable fraction. Additionally, uptake of Cd in mollusc tissue was successfully reduced by 83%, while in case of Eichhornia crassipes root and shoot 75% and 87%, correspondingly. The tea waste biochar had shown its potential to immobilize the Cd from contaminated sediment as an economically and feasible method of abatement.

The main problem and also challenge was to find a satisfactory effective tool for real-time control the torrefaction/pyrolysis process of biomass and to evaluate (also in real-time conditions) biochar quality. This paper presents results from investigation on a new method for both evaluating biochar quality and control biomass thermal processing at temperatures of 300, 350 and 400◦C. Thermal processing of biomass in this temperature range is torrefaction and pyrolysis. Investigation was focused on processing Virginia Mallow (Sida Hermaphrodita) energetic crops. Several strong correlations were observed as follows: carbon and hydrogen content in biochar (charcoal), oxygen content, ash and volatile matter from biochar, calorific value and temperature of the process and finally, acetic acid in condensate and carbon content in the biochar. The results show that the content of acetic acid, being one of the major compounds present in the condensate (black liquor, biooil), is in satisfactory linear correlation with the process temperature and furthermore, with carbon content in biochar. The mathematical description for this polynomial function was proposed as follows: Carbon (%) = 0.6e-3 x Acetic Acid (ppm)+49.5. The correlation between acetic acid in black liquor and carbon in biochar was used to introduce a new method which can be considered as a diagnostic tool for determining biochar quality in real-time conditions during biomass thermal processing. Hence, carbon content in biochar as well as its calorific value can be determined by measuring percentage of acetic acid in the condensate. This correlation was considered as the main novelty presented here. This method provides relatively fast evaluation of quality of biochar produced in industrial scale torrefaction systems, what makes it possible to optimize process parameters (temperature, retention time) in real time conditions and improve biochar production process in this way.

The application of biochar to soil is a potentially significant way to achieve negative net emissions. Photosynthesis fixes carbon from the atmosphere during plant growth; subsequently, pyrolysis stabilizes the carbon in biomass into recalcitrant form, which results in long-term storage when the carbonized product is put in soil. However, effective planning of such Biochar-based Carbon Management Networks is needed to ensure that benefits are maximized, and that adverse consequences are mitigated. The objective of this work is to develop a P-graph methodology for planning Biochar-based Carbon Management Networks, where pyrolysis plants act as sources, while the agricultural lands that receive the biochar act as sinks. Two problem variants are considered. In the first case study, the allocation of biochar is constrained by the presence of contaminants that exist naturally in the biomass or are formed during pyrolysis, such that only 72.5% of the available biochar is applied to soil. In the second case study, the distribution of biochar is limited both by the ultimate soil carbon limit, as well as annual application rates at each site; 88.9% of the available biochar is used in the optimal solution. The P-graph framework also generates near-optimal network topologies, which present alternative solutions that can be useful for the large-scale implementation of Biochar-based Carbon Management Networks.

The effectivity of biochar as soil amendment depends on its physical and chemical characteristics, related to the type and features of the thermal production process, such as peak temperature, heating rate, holding time, as well as on the used feedstock. The textural characteristics of biochar in terms of surface area, pore size and pore volume distribution, important for its physicochemical properties, are critically dependent on the feedstock type, the production process, and possible further activation methods. This study was based on a single biochar type, resulting from slow pyrolysis at the working temperature of 550 °C of raw material from coppiced woodlands, as well as on a single experiment. For the first time, controlled hydrodynamic cavitation was proven as a fast and effective way to enhance the surface area of biochar by as much as 120%, while preserving or improving the respective chemical composition. The introduced technique, while easily applicable and scalable, showed far higher efficiency than the conventional method of increasing the working temperature of the pyrolysis process, with higher process yields by at least an order of magnitude. Moreover, hydrodynamic cavitation processes could be straightforwardly integrated with other consolidated methods, such as hydrothermal carbonization and chemical activation, possibly leading to effective synergism.

This work investigated the optimization of process parameters in the upgrading of the oil extracted from Scenedesmus obliquus microalgae using a novel nickel-impregnated biochar catalyst. The effects of temperature, dodecane-to-oil mass ratio and pressure on the upgraded liquid-phase biofuel yield were evaluated and optimized by central composite design of the response surface methodology (RSM). The model equation generated from RSM showed that dodecane-to-oil mass ratio and pressure, as well as the quadratic effects of all the three factors, were significant model terms in predicting the yield of upgraded liquid-phase biofuel. Maximum liquid biofuel yield was attained at 246.89 °C, 3.72 (w/w) dodecane-to-oil mass ratio, 3.84 MPa hydrogen pressure and 6 h processing time. Validation runs resulted in an upgraded biofuel yield of 69.4%, which was in close agreement with predicted values generated by RSM. The upgraded biofuel comprised of 100% green liquid hydrocarbons containing 94% alkanes and 6% alkenes. Its main fuel properties, such as heating value (43.78 MJ kg−1), elemental composition, density, and viscosity, exceeded those of the fatty acid methyl ester standard and were found comparable to those of petroleum diesel. More importantly, the results of the ultimate analysis and confirmed by the findings from Fourier transform infrared and gas chromatography – mass spectroscopy analyses, showed significantly low oxygen and nitrogen content and absence of sulfur in the upgraded biofuel.

Emerging contaminants have recently been recognized as new and significant water pollutants and gained great of concerns because of their considerable effects on ecosystems and human health. Current conventional wastewater treatment technologies are not efficient at removing these trace contaminants; novel and lower cost approaches are required. Biochar is well-known as an effective adsorbent for the removal of complex inorganic contaminants and organic contaminants from water. This review provides a summary of recent research on the underlying mechanisms controlling the presence of emerging contaminants in water, as well as their removal and the environmental treatment of soil by biochar. A range of information is also presented regarding the application of this resource; it is clear that a variety of cheap, efficient, modified, and composite biochar that is able to remove emerging contaminants will be required to further advance research progress.

Meticulous research has been done to observe and measure the impact of biochar on soil-water retention properties. On the contrary, very little research is conducted on quantifying cracking in soil biochar composites. Investigation of crack intensity factor is essential as it affects permeability and hence, overall water balance in agricultural fields. It is well known that cracking of soil is influenced by suction and water content but their interactive effects are not very well understood. This technical note aims to investigate the cracking of soil amended with biochar made out of water hyacinth, an invasive weed, with focus on analysing interactive effects of water content and soil suction. An integrated reduced scale monitoring and modelling using artificial neural networks have been adopted. A series of tests were conducted to monitor suction, water content and crack intensity factor in soils mixed with four different compositions i.e. 0%, 2%, 5% and 10% by weight of biochar for around 3 months. The measured results have been evaluated first, and eventually modelled using artificial neural networks to predict crack intensity factor as function of water content and suction for all composites. In most of the cases it has been found that suction is more influential than water content. However, the relative significance of suction to water content in determining crack intensity factor decreases with increase in biochar content of soil. It is concluded that the optimum biochar content is 10% for most of the agricultural purposes based on the water retention capacity and cracking. The probability distribution of crack intensity factor is found to be normal for case with 5% biochar and while for others, it is skewed negatively. A simple cost based analysis taking in context of a small developing urban city of India, showcased a cost savings in irrigation of urban infrastructure by around 63,000 US dollars for a particular summer.

Low-cost materials are promising aqueous pollutant adsorbents but when batch adsorption method is employed, separation of pollutant-loaded-adsorbents from water is a major challenge especially when dealing with a large volume of wastewater. Thus, biomass and biochar from Quercus robur fruits were valorized via magnetization (for easy post-adsorption separation) to prepare optimized biomass-magnetic hybrid (BMM 0.5:1) and biochar-magnetic hybrid (BCM 1:1). The BMM 0.5:1 and BCM 1:1 were employed for Pb(II) and Cd(II) removal from simulated contaminated water. The hybrids exhibited higher values of cation exchange capacity (CEC), BET surface area and pore sizes, as well as better thermal stability and the presence of pure spinal structures of Fe3O4, along with the characteristic functional groups of biomaterials (such as the hydroxyls, amides and carboxyls). The adsorption equilibria for both cations were attained within 180 min. Adsorption mechanism involved electrostatic interactions on both external and pore surfaces, with Pb(II) data fitting the Langmuir adsorption isotherm model while Cd(II) data fitted the Freundlich. The adsorption process was spontaneous and exothermic as solution temperature was increased from 292 to 310 and 328 K. The adsorption of Cd(II) initially increased with temperature but decreased on further temperature rise by similar percentages for both adsorbents. In contrast, adsorption of Pb(II) decreased continuously but the decrease was higher for BMM 0.5:1 than BCM 1:1 implying BCM is a more promising adsorbent. Adsorption capacities for BMM 0.5:1 are 63.6 and 21.0 mg/g, while BCM 1:1 has 58.2 mg/g and 21.3 mg/g for Pb(II) and Cd(II), respectively. These adsorption capacities were better than many low-cost adsorbents in literature. Thus magnetic valorization, apart from easing separation, enhances the adsorption capacity of low-cost adsorbents.

Mixed wood sawdust is a common waste material in many parts of the world. This study characterized biochar that was produced from locally available mixed wood sawdust with respect to its capability to perform Direct Air Capture of ambient carbon dioxide. Specifically, the impact that pyrolysis temperature, heating rate and ambience carbon dioxide concentration have on the carbon capture and sequestration capability of this biochar is evaluated. In addition, the reduction in this capability due to contamination by indoor particulate matter was studied. Results showed that pyrolysis temperature is the only significant factor that determines the carbon capture and sequestration capability of the biochar produced. Furthermore, by exposing biochar samples to an indoor environment containing particulate matter with a minimum size of 0.35 μm, carbon capture and sequestration capability of the biochar was shown to be reduced by about 8.33 times, under an ambient environment of 600 ppm of carbon dioxide. These findings hold important lessons on how biochar can be deployed for Direct Air Capture in the field, and as a mean for enhancing indoor air quality in buildings.

Ammonia nitrogen inhibition is a well-known issue in the anaerobic digestion of food waste. This study aims to investigate the influence of biochar on the performance and the microbial community structure of a controlling internal circulation (CIC) reactor for food waste treatment in presence of 1500 mg/L of ammonia nitrogen. When ammonia nitrogen concentration increased to 1500 mg/L in the influent, chemical oxygen demand (COD) removal efficiency was reduced to 76%, the fluorescence peaks of aromatic proteins disappeared, and the intensity of coenzyme F420 was reduced in the three-dimensional excitation emission matrix (3D-EEM) spectra of soluble microbial products (SMP) and tightly-bound extracellular polymeric substances (TB-EPS). The band intensity at 1635 cm−1, attributed to the C=O stretching vibrations, reduced, and the broad band values of 3400 cm−1 implied a sharp peak of the amino group in the fourier transform infrared (FTIR) spectra of TB-EPS. In the CIC reactor, COD removal efficiency reached to about 90% with biochar. High-throughput sequencing revealed that the abundance of Clostridiales, Lactobacillales and Methanoculleus increased, while the abundance of Syntrophomonas decreased at high ammonia nitrogen concentrations. In presence of biochar, the abundance of Methanoregulaceae, Bacteroidales, Anaerolineales, and Syntrophobacterales increased. It was concluded that biochar addition could alleviate the inhibitory effect of high ammonia nitrogen concentration.

The present study aimed to determine the sorption behaviour of crystal violet (CV) dye on mango leaves biochar (MLBC) prepared at 400 °C, 600 °C and 800 °C. Response surface methodology (RSM) was executed to evaluate the interactive effect of four process variables on the sorption of CV dye using Box-Behnken design. The quadratic model showed significance of model for the responses which were validated by analysis of variance (ANOVA). Maximum sorption (99.85%) of CV dye (2500 mg/L) was demonstrated on MLBC (800 °C) within 48 min of incubation at pH 8 and 47 °C temperature. The point of zero charge (pHpzc) and Brunauer-Emmett-Teller surfaces (BET) of MLBC were 7.7 and 168.23 m2 g−1, respectively. In addition, fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), total organic carbon (TOC) and atomic absorption spectroscopy (AAS) techniques were employed to characterize the biomass and MLBC. Toxicological studies of residual CV dye were executed using seed germination and tilapia fish model. Histological assessment of the gills showed no alterations in the gills architecture of fishes exposed to MLBC treated residual CV dye solution. Therefore, the present experimental results strongly revealed the strategies for utilizing low-cost biomass to treat waste water containing hazardous textile dyes.

Application of wood ash on forest and agricultural soils can provide nutrients and increase soil pH, however, it changes the soil chemistry rapidly and temporarily, often resulting in reduced plant growth and potassium leaching. Biochar from woody materials are nutrient poor and need nutrient enhancement prior to soil application. In this study, spruce residues were mixed with spruce/pine ash in different ratios (0–50%) to produce biochar-ash composites at 450 °C. The biochar yield (ash-free basis) increased by 80–90% with the addition of 50% ash due to catalytic biochar formation. Consequently, nearly half the amount of wood is needed to produce the same amount of (ash-free) biochar. Mineral release was moderated in the composites compared to pure ash, demonstrated by a lower electric conductivity and % available K content (a factor of 2.5–4.4 lower than in wood ash). Furthermore, the % available chromium content, which is a key potentially toxic element in wood ash, decreased by a factor of 50–160. Soil application of biochar-ash composites decreases the risk of Cr toxicity, salinity stress and leaching of K in soil substantially compared to ash application. Biochar-ash composites are a novel product with vast unexplored potential for use in forestry and agriculture.

This study reports a novel method using microwave vacuum pyrolysis combined with sodium-potassium hydroxide mixture (NaOH-KOH) activation to produce highly porous activated carbon (AC) from palm residue (i.e. palm kernel shell, PKS) – a solid residue constantly produced in large volume by palm industry. The yield and properties of AC produced were found significantly influenced by two key process parameters - type of activating agent and chemical impregnation ratio. The pyrolysis provided fast heating rate (60 °C/min), high temperature (607 °C), and short process time (35 min) to convert PKS into biochar, and the subsequent activation by NaOH-KOH mixture at 1.0 of chemical impregnation ratio resulted in 84 wt% yield of AC. The AC possessed high BET surface area (1320 m2/g) and highly porous structure formed by micro- and meso-pores, thus showing high adsorption capacity. The adsorption capacity of AC was examined via impregnation with nickel and aluminium atoms (termed “Ni/AC” and “Al/AC”) followed by application in treating industrial effluent abundantly released from palm oil mill (termed ‘palm oil mill effluent, POME). Both Ni/AC and Al/AC showed high removal efficiency in reducing the total suspended solid (TSS), oil and grease (O&G), biochemical (BOD) and chemical oxygen demand (COD) in POME. Higher removal efficiency on BOD and COD was observed for Ni/AC and Al/AC than normal AC (non-metallic AC). The production cost of AC using this pyrolysis method was estimated to be ranged from 4 to 10 USD/kg. The results show the exceptional promise of this pyrolysis method as an approach to transform PKS into highly porous AC for utilize as an adsorbent to treat POME.

A parametric study employing Taguchi's design of experimental technique was conducted to produce a value added novel biochar mix from three different origin feedstock and evaluate the effect of process parameters on biochar quality. Three feedstocks sourced from different origins (macroalgae: Sargassum sp, agricultural waste: rice husk and lignocellulosic waste: pine wood) were mixed in a definite proportion and pyrolyzed following the L4 experimental layout. Results indicated that temperature and mixing ratio were the most influential contributing factor. A temperature of 500 °C and 70% algae mix was the optimum condition to get an enhanced biochar in terms of thermal stability, aromaticity, pH balance, ash content and yield. Among the 4 Taguchi combination char S3 stands out as the best condition that resulted in high aromaticity, 40% high ash content, highly alkaline pH (10.3), 1–2% higher nitrogen and sulfur content. Potential application of biochar in agronomy as a soil ameliorant and/or in contaminant remediation as an adsorbent is suggested.

A 2-year field study was conducted with wheat (Triticum aestivum L.) - green gram (Vigna radiata L.) crop rotation in an inceptisol to compare the effect of vermicompost and biochar on soil organic carbon (SOC), its fractions and carbon mineralization when applied with inorganic fertilizers. Experimental treatments used were only inorganic nitrogen, phosphorus and potassium (NPK) at recommended dose as control, 50% N + PK, NPK + vermicompost (2.5 t ha−1), NPK + biochar (2.5 t ha−1), 50% N + PK + vermicompost (5 t ha−1) and 50% N + PK + biochar (5 t ha−1). Compared to lone application of inorganic fertilizers, application of organic amendments significantly increased the total organic carbon (4–10%), particulate organic carbon (POC) (5–21%), microbial biomass carbon (MBC) (40–55%), recalcitrant carbon (F4) (16–67%), humic acid carbon (HAC) (2–12%) and fulvic acid carbon (FAC) (8–37%). Higher concentration of labile carbon fractions (F1 and F2), POC and MBC were noted with vermicompost application while addition of biochar produced more stable carbon fractions (FAC, HAC and F4). Vermicompost application increased (5–15%) the C mineralization rate with higher (29–55%) soil respiration, and lower (35–58%) C half-life compared to biochar. Principal component analysis confirmed a close association among the stable C fractions (FAC, HAC and F4) and degree of humification. Labile carbon fractions (F1, F2 and MBC) indicated higher sensitivity to the applied fertilizers. Biochar application promoted higher leaf and root biomass in the tested crops whereas the grain yields were not significantly (P ≤ 0.038) different suggesting equal potentiality of both the amendments towards productivity. The benefit cost ratio was higher (1.89 and 2.89) for application of vermicompost but greater agronomic efficiency (0.10 and 0.12 kg kg−1) and lower (10–22%) soil available nitrogen content were noted with biochar application, which indicates environmental sustainability. Thus, biochar introduction into the fertility program of wheat-green gram crop rotation along with inorganic fertilizers would be a better option which not only uphold crop productivity but also sequester higher SOC compared to vermicompost.

Many food manufacturers in the U.S. are attempting to reduce the environmental footprint of their high biological oxygen demand (BOD) effluents due to increased risk of financial surcharges from publically owned treatment works, water scarcity issues and changes in societal opinions about large scale biodegradable waste releases. Managers at these firms are often reluctant to consider on-site processing due to their fear of committing to unfamiliar and complex wastewater treatment processes with excessive capital expenditures. While an abundance of research has been performed on the use of biochar (i.e. charcoal intended to be used for agricultural purposes produced from organic waste feedstocks via pyrolysis) to mitigate the problem of heavy metal ions from traditional manufacturing effluents by filtration, little is known on biochar's potential to treat high BOD industrial aqueous food wastes. This paper attempts to fill this gap by gauging the environmental and financial sustainability of a vertically integrated biochar filtration system, wherein maple wood biochar is used to treat high BOD tofu whey effluent and subsequently re-utilize that material as an enriched value-added soil amendment to improve crop quality and yields in basil and lettuce. Results show whey filtered biochar significantly increased fresh weight in basil and lettuce above the no biochar and unfiltered biochar controls. This novel approach could potentially help food and beverage manufacturers sustainably reduce their carbon and water footprints by harvesting and monetizing the nutrients found in their wastewaters, while allowing farmers to close regional nutrient cycles by returning nutrient rich carbon to the soil and reduce the use of synthetic fertilizers or costly peat moss or perlite soil amendments in greenhouses.

High efficiency and stable CaO-based catalysts which used rice husk biochar as a carrier were utilized to catalyze transesterification of vegetable oil with methanol. The properties of the synthesized catalyst were determined using XRD, TGA, FT-IR, SEM, EDX, N2 adsorption/desorption, XPS and the Hammett indicator method. The influences of catalyst preparation, reaction parameters and reusability of catalyst were also investigated. The results indicated that the catalyst activity mainly depended on the pretreatment temperature, structure and basicity of the catalysts. The maximum yield could reach 93.4% under the prepared conditions of 30% CaO loading and 700 °C calcination temperature. Meanwhile, after being reused for 10 cycles, there was no noticeable loss of catalyst activity in biodiesel yield (above 85%). The appearance of Ca O Si bond on the catalyst surface was the main reason for high stability. The findings suggested that the rice husk biochar based catalyst was a very promising choice for biodiesel production.

In this study, the usage of biomass-based materials as co-catalysts was tested for simultaneous sugar industry wastewater treatment/hydrogen production by catalytic wet air oxidation and the final product distribution in gas and liquid effluents were investigated. For this purpose, biochar (BC) and graphene oxide-like biomass derivative (BGO) were synthesized from corncob and coupled with LaCoO3 (LC). LaCoO3-Biochar (LC/BC) catalyst was determined as the most compatible one with pure LC in terms of removal efficiencies which were approximately 100% for total saccharide (TSC), 90% of total organic carbon (TOC) and chemical oxygen demand (COD) removal, respectively. This shows that biochar is a promising alternative to replace metal catalysts. The catalyst reusability was examined and the fresh and used catalysts were characterized by SEM-EDX, XRD, and BET analyses. There were slight decreases in catalytic activities of all catalysts including LC which were associated with the chemical and morphological alterations supported by the characterization analyses as a result of formation of acidic intermediates some of which were identified as formic acid and acetic acid in the liquid effluent. The formation of CO2 was determined as proportional with TOC reduction but the behaviour for H-2 production was the opposite as a result of total oxidation in which the final products are CO2 and H2O. Although the amount of H-2 produced was relatively lower for the selected catalyst LC/BC with higher treatment performance, the produced H-2/initial sucrose ratio equal to 0.109 was considered as promising., Ege University Scientific Research Project Coordination [17-MUH-040], This work was supported by Ege University Scientific Research Project Coordination (Grant number: 17-MUH-040). The authors would like to thank for the analyses in characterization studies which were performed in Ege University Central Research Test and Analysis Laboratory Application and Research Center, Middle East Technical University Central Research Laboratory, and Recep Tayyip Erdo.gan University Central Research Laboratory Application and Research Center. The authors would also like to thank to Ege University Chemistry Department for gas product analyses and Ege University Chemical Engineering Department for liquid product analyses which are gratefully acknowledged.

To reduce and recycle manure, conversion of livestock manure to hydrochar through hydrothermal carbonization (HTC) could fix carbon and reduce pollution. The properties of hydrochar largely determined its application; thus, it is significant to comprehensively assess the manure-derived hydrochars (MHCs). However, relatively few systematic studies on MHCs are insufficient to support agricultural research on MHCs. This study investigated the basic properties, nutrient composition and speciation, and heavy metal content in pig/cattle manure and its MHCs (PCs and CCs). Results showed that MHCs were neutral and weakly acidic, which were milder than its alkalinity manure, and could not change the soil acidity too much when applied to the soil. After HTC, nitrogen (N) and phosphorus (P) contents were enriched in CCs with 3.47–21.5% N and 69.6–135% P, and in PCs with 74.1–132% P. MHCs prepared at higher temperature had stronger resistance to degradation due to rich ash content, which was conducive to carbon sequestration as soil remediation agents. Besides, the MHCs with rich ash content could also supplement macro/micronutrients for plant growth. More calcium-bound P content (2.26–2.44 times for PCs, 4.78–5.38 times for CCs) suggested that HTC promoted P fixation in MHCs, further reduced nutrient loss, and solved the problem of eutrophication. Most concentrated heavy metals in MHCs were still up to the biochar-based organic fertilizer standard, which could not increase heavy metal risk compared with manure. Overall, the MHCs as energy-saving and value-added products with sufficient and balanced nutrients and limited heavy metal pollution risk can yield valuable agricultural potential. This research would provide theoretical support for the agricultural utilization of MHCs.

© 2021 Elsevier LtdCiprofloxacin, a second-generation synthetic fluoroquinolone derivative widely used in human and veterinary medicines, has the potential to pose a serious risk to aquatic organisms and humans. The current research investigated the removal of ciprofloxacin using biochar treated with clay mineral and subsequently activated with carbon dioxide (CO2) produced at two different pyrolysis temperatures (350 and 650 °C). Batch adsorption experiments were carried out to assess the removal efficiency of ciprofloxacin by as-synthesized materials. The effects of various factors, such as pH, contact time, adsorbent dose, initial ciprofloxacin concentration, and temperature were studied during the removal process. The physicochemical characterization results verified the successful loading of clay minerals on biochar. Non-linear adsorption models were employed to understand the nature of adsorption processes however, the Pseudo-second-order kinetic and Freudlich and Redlich Peterson isotherm models best fitted with the adsorption data. These findings indicated that the adsorption did not follow an ideal monolayer adsorption suggesting hybrid chemical adsorption process that was spontaneous and endothermic. The maximum adsorption (50.32 mg g−1) of ciprofloxacin was achieved by CO2 activated biochar-clay mineral composite prepared at 350 °C, and was almost two times higher than the pristine biochar at neutral pH and 40 °C. The possible proposed mechanisms involved for the removal of ciprofloxacin were electrostatic attraction, cation exchange, pore-filling effect, and π-π interactions. Our findings demonstrate that application of CO2 activated biochar-clay mineral composite is a promising technique for efficient removal of ciprofloxacin from aqueous solution.

Renewable and sustainable energy production is essential for future technological requirements, owing to the ever-increasing environmental pollution caused by the use of non-renewable fossil fuels. The conversion of abundant solar energy to solar fuels by photocatalysis has been suggested as an adequate and alternative route to address the aforementioned issue. A wide range of catalysts have been studied, but their low photocatalytic efficiency due to rapid electron-hole recombination (e.g., C3N4) and high cost (e.g., Pt) have limited their commercialization. There is an urgent need to develop economically/eco-friendly, highly efficient, and robust catalysts for enhanced photocatalysis to tackle the energy crisis and environmental issues. Semiconductor-based catalysts are commonly used as excellent compound materials for photocatalytic reaction applications because of their tunable energy band edge potential, abundance, and less poisonous characteristics. On the other hand, these have limitations due to charge recombination, poor stability, and low conductivity. The current review emphasizes the recent progress on semiconducting materials integrated with carbon (biochar) materials, which are a good choice to minimize these issues. This review summarizes the progress of recent research works for the development of highly active biochar-based composite systems to promote further developments of biochar-modified semiconductors in photocatalytic applications. Biochar has played a pivotal role in photocatalysis because of its fascinating benefits, such as a good support material, enhanced the specific surface area, and numerous surface active sites. These properties have led to high charge shuttling and acting as an electron reservoir, promoting greater charge separation and reducing the energy bandgap. The typical applications of biochar-modified photocatalytic materials are reviewed mainly in photocatalytic hydrogen production and other energy and environmental areas, such as carbon dioxide photo-reduction and the abatement of polluted water/air treatment under solar light irradiation. This review focuses on the recent trends and future prospects for the development of ecofriendly biochar-modified semiconductor photocatalysts.

Coastal salt marshes have been significantly suffering degradation worldwide, turning these wetlands from carbon sink to carbon source. The additions of carbon-rich substrates in degraded coastal wetlands have been documented to alleviate this situation; however, the microbial responses as well as their carbon metabolisms to the input are not well explored. Here, we investigated the effects of different addition levels (0.1%, 1%, and 3%) of reed straw and biochar addition on microbial communities (bacteria and fungi) and predicted functions of carbon metabolism in degraded coastal salt marshes. The effects of the carbon-rich substrates on microbial communities are more pronounced under 3% of reed straw and biochar than other levels, straw increased opportunistic bacteria (e.g., Bacillus and Cellvibrionaceae) and biochar increased low carbon turnover bacteria (e.g., Acidobacteria and Actinobacteria). The addition of higher doses of reed straw and biochar promoted the carbon metabolism of soil bacteria as predicted by the PICRUSt 2. Interestingly, the addition of reed straw increased the abundance involved in fungal carbon metabolism, but this was not the case for the biochar input. The addition of reed straw and biochar promoted the growth of some bacteria (e.g., Rhizobiales and Bacillus) that are beneficial to plant growth, and decreased some fungal pathogen (e.g., Magnaporthaceae and Phaeosphaeria). Our findings revealed that the carbon-rich substrates addition can reshape the microbial structure and shift their carbon metabolisms, specially, biochar has a higher potential to improve the ecosystem services, such as blue carbon sequestration, of these degraded coastal salt marshes.

Efficient removal of oxytetracycline hydrochloride (OTC) from wastewater is of great significance but extremely challenging. Herein, a novel adsorbent lignin-based multi-metal ferrite biochar (FeNiZn-LBC) was synthesized through pyrolysis with controllable temperature and hydrothermal reaction using lignin of sinocalamus oldhami as raw material. The adsorption property of FeNiZn-LBC for OTC was systematically researched, and the results displayed that adsorption of FeNiZn-LBC to OTC accorded with the Langmuir model and the equilibrium adsorption capacity was 476 mg g−1. Notably, FeNiZn-LBC can be regenerated with 0.100 mol L−1 NaOH. Additionally, we raised rational explanations for the mechanisms of adsorption behavior based on the zeta potential and XPS spectra. The adsorption of FeNiZn-LBC for OTC was mainly controlled by the electrostatic interactions, hydrogen bonds and complexation involving FeNiZn-LBC and OTC, especially the metal-oxide bond (M-O) generated after loaded with multi-metal ferrite played a positive role in the removal of OTC from water. Our work highlighted the potential of FeNiZn-LBC for excellent adsorption of OTC in next generation.

It is necessary to explore alternative resources for phosphorus (P) in an effort to address the lack of available P source for crops in an agricultural sector. In this study, bacterial biomass waste of Escherichia coli from a fermentation industry was converted to “P-enriched biochar”, and its possibility as a P fertilizer was assessed. Biochar yields (5.2 ± 0.74% to 19.7 ± 1.54%) highly depended on pyrolysis conditions such as initial weight of feedstock and residence time. Inorganic elemental analysis revealed that the biochar did not consist of any elements with high toxic concentration levels regardless of its yield and that it was rich in P. Biochar with lower yield showed higher water soluble P. Subsequently, a rapid P-release in water and citric acid was initially observed, and a gradual decline one day later was followed. The extractable P in water and citric acid reached 52% and 61%, respectively, of initial P content (84.7 mg g−1) in the biochar in five days. Scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) results showed that P was evenly distributed in macropore-sized biochar matrix, and the contents of P and O decreased after P release into water. Fourier transform infrared spectroscopy (FT-IR) revealed that the peaks related to phosphate form significantly decreased after P release. SEM-EDS and FT-IR results indicated that released form of P was phosphate. Hydroculture bioassay showed that biochar had a positive effect on the early growth of Lactuca sativa. This study suggested that conversion of bacterial waste to the P-enriched biochar could be a feasible strategy for recycling P source as a P fertilizer as well as valorization of wastes from fermentation industry.

Abundant wastes of barley straws were utilized as precursor to prepare biochar adsorbent through thermal pyrolysis. Pore characteristics, morphology, and attraction extent of the prepared adsorbent toward salicylic acid were identified. The obtained biochar had a surface area of 435.52 m2/g, a pore volume of 0.241 cm3/g, and an average pore width of 22.16 A. The effects of batch adsorption variables, such as initial salicylic acid concentration (50–250 mg/L), contact time (0–24 h), initial pH (3–11), and temperature (25 °C–45 °C) on the biochar performance were tested. Equilibrium data analysis revealed the best correlation of the Langmuir isotherms, with maximum salicylic acid uptakes of 189.12, 197.43, and 210.56 mg/g at 25 °C, 35 °C, and 45 °C, respectively. The salicylic acid/biochar system exhibited spontaneous, chemisorption, and endothermic natures. Considering its favorable pore characteristics and high attraction performance, barley straw biochar could be a suitable adsorbent to eliminate salicylic acid from wastewaters.

Ragweed (Ambrosia artemisiifolia L.), a metal-accumulator invasive species, was pyrolyzed under a range of pyrolytic conditions to investigate their influence on immobilization and environmental safety of potentially toxic elements (PTEs) in the produced biochar. Conditions tested included temperature, retention time, heating rate, gas flow rate and particle size. Temperature and particle size had pronounced effects on product yields and physico-chemical characteristics of the produced biochar. All PTEs were enriched in the biochar, and the effect was more pronounced with higher temperature over 500 °C. However, fractionation of PTEs in biochar by following the sequential extraction process indicates that the mobile (bioavailable) fraction of most of the PTEs was transformed into more stabilized (residual) form (P

Competitive utilization of straw is a challenge faced by developing countries such as China with the increase of crop production. Biochar, briquette fuel and combined heat and power generation are the three main new measures for straw utilization in recent years; however, there is still a knowledge gap for environmental and economic effects of these utilizations in China. To address this issue, combined life-cycle analysis and cost-benefit analysis was employed to assess the environmental impacts and economic benefits of biochar, briquette fuel and combined heat and power generation applications based on three cases in China. The results suggested that biochar was the most promising technology for straw utilization in China for its highest greenhouse gas mitigation potential i.e. −0.94 t CO2 equivalent (CO2e) per ton straw utilized and high profit with a net present value per ton straw of 20.98 U.S. dollars with the baseline of crop straw return including carbon revenue. Briquette fuel also deserves to achieve a best net present value ratio of 5.06 and GHG abatement potential being −0.9 t CO2e t−1 straw. However, the waste of straw ash could bring some pollution risk without suitable treatment. The economic potential of the combined heat and power generation project that produces bioelectricity, is not considerable with a very low net present value ratio of 0.007 and a mitigation potential of −0.03 tCO2e t−1 straw due to low energy utilization efficiency of direct combustion. Biochar could be one of the most potential economic and environmental sustainable straw utilization technologies in China though the wide production and application is still a big challenge in future.

The influences of pyrolysis conditions on the products yield distribution and physico-chemical characteristics of biochar derived from peanut shell in a fixed-bed reactor were investigated in this study. The pyrolysis conditions included the pyrolysis temperature (300–700 °C), retention time (15–90 min), heating rate (1–10 °C min−1), gas flow rate (20–200 mL min−1) and feedstock particle size (

Sewage sludge has gained increasing attention as one of the most intractable environmental concerns. Pyrolysis is a promising technology that can convert the sewage sludge into biochar and the produced biochar has been increasingly used as adsorbents for heavy metal remediation. However, further environmental problems will be generated from the accumulation of spent biochar after metal adsorption. This work involved a series of experiments to study the adsorption of hazardous copper on the sewage sludge-derived biochar. A novel method was then proposed to stabilize the adsorbed copper in the biochar matrices. The results showed a growth in copper adsorption capacity with an increase in the initial pH of the solutions, and positive effects on copper adsorption were detected from the mineral constituents (e.g., silicon, aluminium, iron and calcium) of the sludge biochar. Furthermore, after copper adsorption, the spent biochar was thermally sintered, and the hazardous copper was found to be incorporated into a CuAl2O4 spinel phase through thermal reactions between copper and the mineral constituents. The stabilization effect on copper was further evaluated in the sintered ceramic products, and copper leachability was found to decrease by a factor of approximately 65 when samples were subjected to a leaching fluid with a pH of 2.9. A series of copper-enriched biochars was prepared to further explain the reaction mechanisms, which showed that aluminium-containing minerals and iron oxide were the most important constituents for copper stabilization. Through this study, a dual effect of the mineral constituents in the biochar was reported on both copper removal and further stabilization, which suggested a strategy to achieve sustainable waste management in an effective and environmentally friendly way.