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[Abstract:] Grasslands play a crucial role in European agriculture and ecology, but are often underutilized due to low-value end-products. The utilisation of late-harvest grass for biochar and heat generation on farm-level is being studied as a potential negative emissions technology. Technical (energy provision and carbon sink), economic (cost vs. benefit), political (regulatory framework) and social (SWOT) perspectives are being evaluated. Technical feasibility has been demonstrated with three different farm-scale technologies and the energetic and carbon-sink potential evaluated. When a continuously operating allothermal unit is evaluated, 35 % of the input biomass energy content can be utilized for heating a farm, in combination with the potential to provide a carbon sink. The cost-benefit analysis shows important monetary savings when including the agronomic value (based on the market price) of the produced biochar. An assessment of the regulatory framework of biochar production in Germany presents a multitude of regulations applying to such technologies some of which provide a hurdle to navigate and may incur excessive costs for farmers as small-scale biochar producers. A SWOT analysis of a case in Brandenburg, Germany highlights strengths and opportunities, but also obstacles such as lack of infrastructure and regulatory support. This study highlights the need for further development of suitable technology and research on the long-term economic and carbon sink potential of biochar. This work was performed within the GO-GRASS project and has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 862674. We thank all the partners who collaborated with the data collection. We would also like to thank Philipp Grundmann for the coordination of the GO-GRASS project.

Lignocellulosic biomass can be circulated to produce many materials and products, including biochar. This study analyzed five different types of biochar produced from agricultural wastes. The raw materials included three agricultural by-products: corncob, cassava rhizome, rice husk, and two types of wood residues: rain tree (Samanea saman (Jacq.) Merr.) and krachid (Streblus ilicifolius (Vidal) Corner.). The biochar were made in patented retorts with locally-appropriated technology at a temperature range of 450–500°C. This research focuses on the primary physicochemical properties and biochar components, allowing biochar to become a vital material to support sustainable agriculture and the environment. Biochar properties used for agriculture consist of specific surface area, total pore volume, average pore diameter, pH, electrical conductivity (EC), and cation exchange capacity (CEC). The properties that benefit the environmental purposes are the element: carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and the molar ratio of H/C, O/C, and C/N. The study found that all five types of biochar contained suitable properties for soil amendment and carbon sequestration. However, significant differences were shown in specific surface area, average pore diameter, pH, CEC, and EC of various biochar. Based on O/C and H/C ratios, all five types of biochar persisted in soil from 100 to over 1,000 years.

Herein, the aim was to develop an in-depth understanding of the kinetic behaviour of olive tree pruning residue (OTPR), an abundant agricultural waste, during pyrolysis. Thermal analysis at 1, 2, 4, 6 and 10 °C.min−1 was performed using TGA-thermogravimetric analysis, with the results subsequently used to determine the OTPR's kinetic thermal breakdown behaviour. Furthermore, advanced kinetics and technology solutions (AKTS) thermo-kinetic tool was applied to investigate the kinetic behaviour of OTPR and to generate kinetic predictions for various heating configurations. Friedman's method was the main approach used to evaluate the kinetic parameters. For comparison, other established kinetic modelling techniques, such as ASTM-E698 and Flynn-Wall-Ozawa (FWO) methods, were applied. The ASTM-E698 approach yielded an apparent activation energy (Ea) of 172.09 kJ.mol−1, whereas the FWO method yielded an Ea range from 38 to 172 kJ.mol−1. Finally, the differential iso-conversional approach yielded Ea values ranging between 85 and 191 kJ.mol−1. Kinetic predictions were then developed for isothermal, non-isothermal, and stepwise configurations using the kinetic parameters obtained via Friedman’s model. The forecasts shed light on optimising production throughput in a variety of reactor configurations.

Transforming to biochar provides an environmentally friendly approach for crop residue reutilization, which are usually applied as sorbent for heavy metal removal. As typical silicon-rich material, the specific sorptive mechanisms of rice straw derived biochar (RSBC) are concerned, especially at the low concentration range which is more environmentally relevant. In the present study, Cd sorption onto RSBCs at the concentration of ≤ 5 mg/L was investigated. The sorptive capacity was positively correlated with the pyrolytic temperature of the biochar and the environmental pH value. Water soluble minerals of the RSBCs played the dominant roles in Cd sorption, contributing 29.2%, 62.5% and 82.9% of the total sorption for RSBCs derived under 300°C, 500°C and 700°C, respectively. Increased number of cations, dominantly K+, were exchanged during the sorption. Coprecipitation with cations and carbonates may also be contributive to the sorption. The dissolution of silicon-containing minerals was found to be declined during sorption, suggesting its involvement in the sorption process, possibly through precipitation. Whilst, the sparingly soluble silicate crystals may impose ignorable role in the sorption. Complexation with organic groups is only a minor mechanism in Cd sorption, compared to the much more dominant roles of the inorganic ashes.

Considerable research efforts have been devoted to increase phosphorus (P) availability during aerobic composting. However, there is little discussion weather the dissolved organic carbon (DOC) controls the transformation among P-fractions. Thus, we investigated the changes in DOC compositions and P-fractions during biochar-amended composting (wet weight basis, 5% and 10%). TP content continuously increased since the ‘concentration effect’ during aerobic composting. NaHCO3-Pi, NaOH-Pi and HCl-Pi were main P-fractions, and biochar can improve P-bioavailability by transforming NaOH-Pi and HCl-Pi into NaHCO3-Pi. Structure equation models (SEMs) indicated that biochar enhanced the P-bioavailability through regulating the decomposition of DOC. Our results at least hint that the activation mechanism on P under the influence of DOC during biochar-amended composting.

Acid mine drainage (AMD) is a multi-factor pollution formed from complex chemical, physical, and biological interactions that takes place under ambient conditions in abandoned and active mines. Over the years, researchers have been investigating ways to mitigate its potential impact on the environment through various treatment technologies. The aim of this review was to critically analyze the broad spectrum of treatment methods that have been engaged in published literature on the remediation of AMDs. Adsorption treatment using zeolites, fly ash, biochar activated carbon, clay-based minerals and biomass-based adsorbents was discussed. Given an appropriate choice of adsorbent, ions in AMD can be reduced between 50% and 99%. Membrane separation processes like nanofiltration, reverse osmosis and hybrid systems were discovered to be more effective than adsorption and can effect over 90% rejection at optimized conditions. Biological processes showed a far wider range of performance amongst all treatment types due to the selectivity in performance of the different micro-organisms used although Advanced Oxidation Process (AOPs) have been shown to achieve>80% ions removal. In all biological processes studied ranging from wetlands to bioreactors, algal bioreactors seemed the most effective in this domain. Most of these treatment technologies are corrective while preventive techniques can be explored to prevent the production of AMD. Despite the positive outcomes of the different types of treatment, they have associated technical issues. It is recommended that more preventive techniques be explored to reduce the production of AMD. The review discussed how AMD treatment would affect environmental protection and water resource management.

Nowadays, the harm of antibiotics residues in environments to human health and ecological safety has been causing more and more attention. In this paper, a biochar based iron material (MBC) was used to activate persulfate (PS) for the removal of sulfadiazine (SDZ) from aqueous solution. Experiment results indicate that the degradation and mineralization of SDZ by MBC/PS system reached 91.79 and 60 % within 60 min under the optimal reaction conditions, respectively. MBC/PS system exhibited a better performance on SDZ removal compared with MBC/H2O2 system. The addition of Cu2+ ion could enhance the degradation of SDZ by MBC/PS system. PO43-, Cl- and SO42- had a certain degree of inhibitory effect on the SDZ degradation. Both radicals and non-radical species such as SO4•-, •OH and 1O2 participated in the degradation reaction of SDZ by MBC/PS system, but •OH was the main radical species responsible for SDZ degradation. The liquid chromatograph-mass spectrometer (LC-MS) technique was used to identify the intermediate products of SDZ, and it was proposed that the degradation of SDZ might be achieved through hydrolyzation, hydroxylation, deamination and amino-oxidization processes. A possible reaction mechanism involving a synergistic effect between PS homogeneous and heterogeneous activation processes as well as both radicals and non-radicals reactions was finally proposed.

The elevated presence of metal(loid)s in the environment significantly impacts ecosystems and human health and is generally largely due to industrial and mining activities. Thus, in the current study, we investigated and proposed an environmentally friendly method (phytomanagement) aimed at reducing the negative impacts associated with metal(loid) pollution through the use of soil amendments (biochar and compost) to permit Ailanthus altissima growth on a highly contaminated mining Technosol, with arsenic (As) and lead (Pb) contents of 539.06 and 11 453 mg kg–1, respectively. The objective was to examine the impacts of three biochars and compost on i) the physicochemical characteristics of soil, ii) metal(loid) immobilization in soil, and iii) A. altissima growth. We revealed that the application of biochar as a soil amendment improved soil conditions by increasing soil electrical conductivity, pH, and water-holding capacity. Moreover, concomitantly, we observed a large reduction (99%) in Pb mobility and availability following application of the hardwood biochar in combination with compost (HBCP). Thus, this combined soil amendment was most effective in promoting A. altissima growth. In addition, the HBCP treatment prevented As translocation in the upper parts of plants, although soil pore water As concentration was not diminished by amendment application.

Co-pyrolysis of feedstock with varied compositions is a common practice, during which cross-interaction of volatiles from single feedstock requires particular attentions as it may affect the product properties. In this study, co-pyrolysis of swine manure and pinewood sawdust was conducted. The results proved the interaction of volatiles from pyrolysis of swine manure with pinewood sawdust and their significant impact on the evolution of pyrolysis products. The interaction effect favored the formation of bio-oil and biochar but diminished the production of gases, as the cross-interaction transformed the gaseous precursors into heavier organics. Although cross-interaction facilitated the formation of organics with π-conjugated structures, The Fourier transform ion cyclotron resonance-mass spectrometry (FT-ICR MS) characterization showed that the chemical species with large carbon number in the sawdust-derived bio-oil were transferred into the carbonaceous substance. The bio-oil from co-pyrolysis was thus lighter, and the interaction effect also inhibited the generation of nitrogenous species. The cross-interaction of volatiles made the biochar oxygen-rich and enhanced the thermal stability. Furthermore, in situ Diffuse Reflection Infrared Fourier Transform Spectra (DRIFTS) results indicated that the interaction of volatiles resulted in the formation of more functionalities like –OH, -C-H and C O on the biochar.

The co-pyrolysis of sewage sludge and biomass is considered a promising technique for reducing the volume of sewage sludge, adding value, and decreasing the risk associated with this waste. In this study, sewage sludge and cotton stalks were pyrolyzed together with different amounts of K2CO3 to evaluate the potential of chemical activation using K2CO3 for improving the porosity of the biochar formed and immobilizing the heavy metals present in it. It was found that K2CO3 activation effectively improved the pore structure and increased the aromaticity of the biochar. Moreover, K2CO3 activation transformed the heavy metals (Cu, Zn, Pb, Ni, Cr, and Cd) into more stable forms (oxidizable and residual fractions). The activation effect became more pronounced with increasing amount of added K2CO3, eventually resulting in a significant reduction in the mobility and bioavailability of the heavy metals in the biochar. Further analysis revealed that, during the co-pyrolysis process, K2CO3 activation resulted in a reductive atmosphere, increased the alkalinity of the biochar, and led to the formation CaO, CaCO3, and aluminosilicates, which aided the immobilization of the heavy metals. K2CO3 activation also effectively reduced the leachability, and thus, the environmental risks of the heavy metals. Thus, K2CO3 activation can improve the porosity of the biochar derived from sewage sludge/cotton stalks and aid the immobilization of the heavy metals in it.

This study investigated the effectiveness of carbon adsorbents as remediation material for sediments contaminated with heavy metals and the feasibility of utilizing diffusive gradients in thin films (DGT) as a biomimetic tool to estimate the accumulation of heavy metals in Venerupis philippinaram (Manila clam). The results showed that carbon materials had significant inhibitory effects (14.0–53.0%) on the enrichment of heavy metals in organisms and the order of increasing overall inhibitory effect was: charcoal, peat, activated carbon, and biochar. There were significant correlations (P

The bio-wastes pyrolysis is a waste to energy strategy that converts bio-wastes into valuable products (bio-char, bio-oil) with wide use in the agri-food sector. However, limited efforts are paid to the investigation of its environmental sustainability: in this context, the study contributes the need towards the assessment of a wide range of environmental impacts for the pyrolysis process of different types of bio-wastes under different operating conditions. The study estimates the potential environmental impacts related to bio-char production from the pyrolysis of several different agro-industrial residues and different temperatures and identifies the process “hot spots”. The analysis is carried out through the life cycle assessment methodology. The functional unit for the analysis is 1 MJ of thermal energy potentially released during the complete combustion of bio-char obtained from the pyrolysis process. The study highlights that, under the examined conditions, the type of biomass affects the environmental impacts of the pyrolysis process more than the peak pyrolysis temperature. Among the biomasses tested, bio-char obtained from orange peels has the lower environmental impacts, with an average percentage difference of about 16% compared to bio-char obtained from olive tree trimmings that has the worst environmental performance. For each biomass, the impacts associated to bio-char obtained with different operational temperatures have percentage differences in general lower than 5%. A contribution analysis shows that the electricity consumed during the operational phase is responsible for the largest impacts in all the examined impact categories, followed by bio-wastes transportation. In detail, the contribution of the electricity to the total impact ranges from minimum values of about 44% (for cumulative energy demand) up to 91% (for terrestrial eutrophication), while transportation contributions range from a minimum of about 4% (for terrestrial and marine eutrophication) to 36% for mineral, fossil and renewable resource depletion. Therefore, the use of more energy efficient processes and technologies and the diffusion of distributed pyrolysis systems near farms can significantly improve the environmental performance of the system examined.

The use of bioretention areas is common in urban stormwater management, but their performance varies significantly depending on rainfall characteristics and design conditions. In this study, a pilot experiment using bioretention columns with different media (commercial activated carbon and river sediment-derived biochar) investigated the influence of rainfall on bioretention performance. The results indicated that the runoff volume retention ratio (Rv), which included the runoff purified and discharged at the bottom of the column, and the runoff retained in media during rainfall event, decreased significantly with increases in the rainfall event return period (p 0.05). The addition of adsorptive material, such as activated carbon and biochar, may not be the key factor for improving nitrogen and COD removal under heavy rain that exceeds the 2-yr return period. The bioretention performance of phosphorus removal from urban stormwater runoff could be improved by replacing or adding media with high adsorption capacity, but these improvements would not be significant under heavy rain that exceeds the 2-yr return period. The results provide some reference for evaluating bioretention performance and optimizing bioretention design in the future.

Nowadays, iron ions as a ubiquitous heavy metal pollutant are gradually concerned and the convenient and quick removal of excessive iron ions in groundwater has become a major challenge for the safety of drinking water. In this study, boron-doped biochar (B-BC) was successfully prepared at various preparation conditions with the addition of boric acid. The as-prepared material has a more developed pore structure and a larger specific surface area (up to 897.97 m²/g). A series of characterization results shows that boric acid effectively activates biochar, and boron atoms are successfully doped on biochar. Compared with the ratio of raw materials, the pyrolysis temperature has a greater influence on the amount of boron doping. Based on Langmuir model, the maximum adsorption capacity of 800B-BC1:2 at 25 °C, 40 °C, 55 °C are 50.02 mg/g, 95.09 mg/g, 132.78 mg/g, respectively. Pseudo-second-order kinetic model can better describe the adsorption process, the adsorption process is mainly chemical adsorption. Chemical complexation, ions exchange, and co-precipitation may be the main mechanisms for Fe2+ removal.

This paper critically reviewed the current knowledge and challenges of rice husk biochar (RHB) production and its effects on soil properties, plant growth, immobilization of heavy metals, reduction of nutrient leaching and mitigation of greenhouse gas emissions. The characteristics of RHBs produced at various pyrolysis temperatures were discussed and compared to biochars derived from other agro- industrial wastes. RHBs produced at higher pyrolysis temperatures show lower hydrogen/carbon ratio, which suggests the presence of higher aromatic carbon compounds. The increase of pyrolysis temperature also results in production of RHBs with higher ash content, lower yield and higher surface area. RHB usually has higher silicon and ash contents and lower carbon content compared to biochars derived from other feedstocks at the same pyrolysis conditions. Although it depends on soil type, RHB application can improve soil organic carbon content, cation exchange capacity, available K concentration, bulk density and microbial activity. The effect of RHB on soil aggregation mainly depends on soil texture. The growth of different crops is also enhanced by application of RHB. RHB addition to soil can immobilize heavy metals and herbicides and reduce their bioavailability. RHB application shows a significant capacity in reduction of nitrate leaching, although its magnitude depends on the biochar application rate and soil biogeochemical characteristics. Use of RHB, especially in paddy fields, shows a promising mitigation effect on greenhouse gas (CH4, CO2 and N2O) emissions. Although RHB characteristics are also related to other factors such as pyrolysis heating rate and residence time, its performance for specific applications (e.g. carbon sequestration, pH amendment) can be manipulated by adjusting the pyrolysis temperature. More research is needed on long-term field applications of RHB to fully understand the advantages and disadvantages of RHB as a soil amendment.

International audience; The present research deals with the global challenge of managing industrial sludge with respect to sustainability and circular economy principles. It focuses on raw industrial sludge (IS-R) conversion into valuable biochars that can serve as efficient adsorbents for pharmaceuticals in industrial wastewater. Three biochars were produced through sludge pyrolysis at 750 degrees C either without modification (IS-R-B), or after pre-treatment with 1 M solution of ZnCl2 (IS-ZnCl2-B) or FeCl3 (IS-FeCl3-B). Compared to the pristine biochar, the modified sludge-derived biochars (SDBs) showed improved structural, textural, and surface chemical properties. As a result, ISZnCl2-B and IS-FeCl3-B had AMX adsorption capacities of 31.9 and 32.1 mg g-1 which were 41.2% and 42.0% higher than the non-modified biochar, respectively. Moreover, both modified SDBs effectively removed AMX under various experimental conditions, including the presence of competitive ions and over a wide pH range. The AMX removal was found to be spontaneous, endothermic, and primarily controlled by chemical reactions on a monolayer system. These findings suggest that biochars generated from pyrolysis of salt-modified industrial sludge can be used as effective materials for removing pharmaceuticals from water. Therefore, this study supports the concepts of circular economy and sustainable development by offering engineering solutions.

A novel green composite catalyst was prepared by doping CuFe2O4 nanoparticles in the malt bagasse biochar. Composites with different ratios of malt biochar and CuFe2O4 were produced and characterized by XRD, FE-SEM, EDS, HR-TEM, UV–vis, and Zeta potential. The results revealed that CuFe2O4 was successfully supported on the malt biochar surface. The prepared composites showed the band gap energies were narrower than of CuFe2O4, increasing the photocatalytic activity. At 60 min of heterogeneous photo-Fenton, tests under visible light indicated CuFe2O4 removed 39 % of the rhodamine B color, while composites CFO1B3, CFO1B1, and CFO3B1 removed 88 %, 81 %, and 44 % of the dye, respectively. The recycling of the CFO1B3 composite indicated that it can be used in eight cycles without major losses in efficiency. In sunlight, the CFO1B3 composite achieved efficiencies of 100 % for 10 mg L−1 and 50 mg L−1 of rhodamine B at 10 and 20 min of reaction, respectively. In the proposed mechanism, it was verified that the radical OH, O2 − and h+ were the predominant reactive species involved in the degradation to intermediates of low m/z. Results showed that the novel composite formed is a promising photocatalyst for removing organic pollutants in water.

The quality of compost is drastically reduced due to the loss of carbon, which negatively impacts the environment. Carbon emission reduction and carbon dioxide (CO2) fixation have attracted much attention in composting research. In this study, the relationship between CO2 emission, humic substances (HS) formation and cbbL-containing autotrophic microbes (CCAM) was analyzed by adding biochar during cow manure composting. The results showed that biochar can facilitate the degradation of organic matter (OM) and formation of HS, as well as reinforce the diversity and abundance of CCAM community, thereby promoting CO2 fixation and reducing carbon loss during composting. High-throughput sequencing analysis revealed significant increase in Actinobacteriota and Proteobacteria abundance by 30.97 % and 10.48 %, respectively, thus increasing carbon fixation by 32.07 %. Additionally, Alpha diversity index increased significantly during thermophilic phase, while Shannon index increased by 143.12 % and Sobs index increased by 51.62 %. Redundancy analysis (RDA) indicated that CO2 was positively correlated with C/N, temperature, HS and dissolved organic matter (DOM), while the abundance of Paeniclostridium, Corynebacterium, Bifidobacterium, Clostridium, Turicibacter and Romboutsia were positively correlated with temperature, CO2, C/N and E2/E4 (p

Paddy soil and irrigation water are commonly contaminated with hexavalent chromium [Cr(VI)] near urban industrial areas, thereby threatening the safety of agricultural products and human health. In this study, we develop a porous and high specific area bone char (BC) to support nanoscale zero-valent iron (nZVI) and apply it to remediate Cr(VI) pollution in water and paddy soil under anaerobic conditions. The batch experiments reveal that BC/nZVI exhibits a higher removal capacity of 516.7 mg/(g•nZVI) for Cr(VI) than nZVI when normalized to the actual nZVI content, which is 2.8 times that of nZVI; moreover, the highest nZVI utilization is the nZVI loading of 15% (BC/nZVI15). The Cr(VI) removal efficiency of BC/nZVI15 decreases with increasing pH (4 – 10). Coexisting ions (phosphate and carbonate) and humic acid can inhibit the removal of Cr(VI) with BC/nZVI15. Additionally, BC exhibits a strong advantage in promoting Cr(VI) removal by nZVI compared to the widely used biochar and activated carbon. Our results demonstrate that reduction and coprecipitation are the dominant Cr(VI) removal mechanisms. Furthermore, BC/nZVI15 shows a significantly higher reduction and removal efficiency as well as a strong anti-interference ability for Cr(VI) in paddy soil, as compared to nZVI. These findings provide a new effective material for remediating Cr(VI) pollution from water and soil.

In order to enhance the removal performance of graphitic carbon nitride (g-C3N4) on organic pollutant, a simultaneous process of adsorption and photocatalysis was achieved via the compounding of biochar and g-C3N4. In this study, g-C3N4 was obtained by a condensation reaction of melamine at 550°C. Then the g-C3N4/biochar composites were synthesized by ball milling biochar and g-C3N4 together, which was considered as a simple, economical, and green strategy. The characterization of resulting g-C3N4/biochar suggested that biochar and g-C3N4 achieved effective linkage. The adsorption and photocatalytic performance of the composites were evaluated with enrofloxacin (EFA) as a model pollutant. The result showed that all the g-C3N4/biochar composites displayed higher adsorption and photocatalytic performance to EFA than that of pure g-C3N4. The 50% g-C3N4/biochar performed best and removed 45.2% and 81.1% of EFA (10 mg/L) under darkness and light with a dosage of 1 mg/mL, while g-C3N4 were 19.0% and 27.3%, respectively. Besides, 50% g-C3N4/biochar showed the highest total organic carbon (TOC) removal efficiency (65.9%). Radical trapping experiments suggested that superoxide radical (•O2−) and hole (h+) were the main active species in the photocatalytic process. After 4 cycles, the composite still exhibited activity for catalytic removal of EFA.

Cortaderia selloana (CS), is an invasive and exotic species that is generating significant invasive problems in the Iberian Peninsula ecosystems. The objective of this research was to study this plant potential thorough a pyrolytic process helping to reduce its expansion. Stems and leaves were subjected to conventional and flash pyrolysis. These processes were carried out in an original design oven using a 25 °C/min heating ramp at a 750 °C temperature and during 60 min at the pyrolysis temperature for conventional pyrolysis and with 750 °C and 850 °C pyrolysis temperatures for flash. Gas-fraction obtained by flash pyrolysis had higher HHV data when compared with conventional ones (∼17 MJ/kg vs ∼5 MJ/kg) due to their less CO2 and higher CO, CH4 and H2. The greater bio-oil yield was obtained for CSS-P (33.58%). The composition of conventional pyrolysis bio-oils had an overbearing of nonaromatic and monoaromatic hydrocarbons nature whereas bio-oils from flash pyrolysis were composed mainly of polycyclic aromatic hydrocarbons. Bio-char fraction was higher in CSL than CSS with HHV similar to lignite and bituminous coals (22.74–29.12 MJ/kg). After done the quantification and characterization of the fractions, it was concluded that a possible energetic valorization of Cortaderia selloana biomass was possible.

The present study investigated the bio-effects and fate of the chiral pesticide fipronil and its three primary metabolites, fipronil desulfinyl, fipronil sulfide and fipronil sulfone on Chlorella pyrenoidosa and Danio rerio in the absence and presence of biochar. The results revealed that fipronil and its metabolites exhibited high toxicity to algae and fish. Enantioselectivity was observed with regard to the toxicity and degradation of fipronil and its metabolites. For Chlorella pyrenoidosa, R-fipronil was more toxic than S-fipronil and degraded preferentially during the toxicity and degradation experiments. For Danio rerio, S-fipronil exhibited higher toxicity than R- and rac-fipronil. The toxicities of fipronil sulfide and sulfone were 3–6 and 5–6 times higher, respectively, than that of rac-fipronil, and the metabolites also exhibited longer persistence. The remediation capacity for water and leachate contaminated by fipronil with the application of biochar was investigated. Biochar significantly mitigated the toxicity of fipronil and its metabolites to nontarget organisms, and reduced residues by 90 % for fipronil, 72 % for sulfone, 65 % for sulfide and 60 % for desulfinyl, whereas mitigation of only 30 %-51 % was observed in the absence of biochar. This study demonstrates that biochar has strong potential as an ideal material for the removal of fipronil and its metabolites from contaminated aquatic environments.

Low agricultural productivity and electricity shortages continue to plague Africa. Brewer's spent grain (BSG) as a food source and precursor for biochar production via hydrothermal carbonization (HTC) can offer solutions. HTC involves the artificial coalification of biomass by direct injection of steam in a pressurized vessel to produce an upgraded biofuel with characteristics similar to coal. Demand for food security and energy are likely to lead to competing interests and uses of BSG. Therein lies the fundamental dilemma that constitutes the central issue here, which of the two options food or biofuel production from BSG will have the least impact on the environment? From a stochastic model supported by 50,000 Monte Carlo simulations BSG generation, biochar yield and energy potential for Africa were estimated up to the year 2040. This was coupled with model to assess the Global Warming Potential (GWP) of BSG treatment. Apart from a regional evaluation, detailed information at the country level was provided. Total BSG generation is estimated at 698,000 Mg (At a 90% confidence level roughly 0.52 - 0.91 million Mg/yr) for 2020 in Africa. By 2040 it is expected to rise to 852,000 Mg/yr (0.57 - 1.19 million Mg/yr at a 90% confidence level). Flour production can be expected to have a lower GWP compared to biochar production. The GWP of BSG conversion to biochar is more than 1,400 million CO2eq for a 20-year time horizon which is 3. 90 times higher than the alternative, BSG milling to flour for one case study.

In this study, activated biochar prepared using Taihu blue algae was adopted to facilitate cathodic hydrogenotrophic denitrification in bioelectrochemical system (BES). It was found that addition of algal biochar (ABC)-800N (treated with nitric acid) at biocathode reached the highest nitrate removal constant (21.79), while the control reached only 6.94. Besides, activity of nitrous oxide reductase attained 5.16 U/L for the control in day 7, while group ABC-800N reached 16.06 U/L by then. Importantly, chronoamperometry (CA) detect indicated an electron exchange capacity for group ABC-800N as 872.68 μmol e−/gBC, compared to 162.81 μmol e−/gBC for the control. Through chronocoulomb (CC), better charge/discharge stability can be concluded in BES reactor using ABC-800N. Therefore, activated biochar could be implemented to enhance denitrification process at biocathode in BES.

Biochar has been considered as a promising material to enhance the anaerobic digestion of organic wastes, whereas the critical mechanism of biochar promoting interspecies electron transfer is still unclear. The study presented here performed a side-by-side comparison of the three types of biochar (BC300, BC400, and BC500, the pyrolytic temperatures) with the different properties in enhancing the anaerobic digestion of kitchen wastes. The results showed that, in the presence of biochar with the properties of the higher electrical conductance but less redox-active organic functional groups (BC500), the improved performances involved in methane production rates (673.6 mL/d vs 956.8 mL/d) and organic removal efficiencies (69.9% vs 76.4%) were lower than that in the presence of biochar with the properties of the lower electrical conductance but more redox-active organic functional groups (BC400). Biochar (BC400) with the properties of more redox-active organic functional groups enriched the higher abundance of Petrimonas species and Anaerolineaceae capable of electron transfer to the conductive materials than biochar (BC500) with the properties of the higher electrical conductance. The study proposed a strategy of engineering a better anaerobic digestion of kitchen wastes via optimizing the pyrolytic temperature of biochar to form more redox-active organic functional groups as possible.

In this study, the generation of hydrogen from synthesis gas through the pyrolysis of modified Water Hyacinth (Eichhornia Crassipes) biomass was investigated. The modified Water Hyacinth feedstocks were prepared by immersing its dried samples into Iron Chlorides (III) solution under different concentrations (0.5, 1, 1.5, and 2 M). After a 60 min pyrolysis at 540 °C, each created biochar sample also generates a different volume of synthesis gas depending on the properties of the feedstock that were applied to the system. In that manner, it is clear that the value of ferric chloride concentration plays an important role in the generating of synthesis gas. The study indicates that the increase of ferric chloride concentration may also raise the production of synthesis gas, and the amount of hydrogen as well. The result indicates that the 2WH sample (with 2 M of ferric chloride catalyst) exhibited the highest conversion for Water Hyacinth pyrolysis volatiles, with 280 mL of total gas production (42% of hydrogen included, 23% of carbon dioxide, 22% of carbon monoxide and 7% of methane). Therefore, the main objective of the work is achieved by revealing the influence of the metal catalyst over the production of gases via the pyrolysis. On the other hand, the fact that the Water Hyacinth can be utilized effectively also contributes greatly to the matter of environmental betterment.

There is now increasing interest in the creation of a more ‘circular economy’, with a particular aim to eliminate waste – by design, within which products are optimised to be reused, restored or returned. Here, a sulphur functionalised microporous biochar was synthesised from an abundant biomass waste material (cherry kernels), for the selective removal of Pb(II) from landfill leachate as a representative heavy metal. The production process utilises renewable waste material and removes toxic chemicals. Characterisation of the biochar showed that pyrolysis and functionalisation formed an adsorbent with a microporous structure and rich surface chemical functionality. The adsorption process was optimised using a ‘response surface methodology – Box-Behnken Design’. Lead removal efficiency approached 99.9% under optimised experimental conditions, i.e., where the solution pH was 6.0, the biochar dose was 4.0 g/L and the contact time was 47 min. The adsorption process was best described using a Freundlich model. The maximum amount of Pb(II) adsorbed was 44.92 mg/g. The main adsorption mechanisms occurred through outer-sphere (electrostatic attraction) and inner-sphere complexation. Desorption studies showed that three successful regeneration cycles (with acidic deionised water) could be used post pyrolysis. The biochar removed 97% of Pb(II) from landfill leachate samples, as compared to 9.4%, and 7.6% for two commercial activated carbon adsorbents. These findings demonstrate the high selectivity of this biochar towards Pb(II) and its applicability even in the presence of high concentrations of many potentially interfering inorganic and organic ions and compounds.

The presented work assesses the sorptive efficacy of acid and base activated biochar engineered from bio-waste tropical almond shells for eradicating Ibuprofen (IBP) from aqueous media. Adsorbents were characterized by proximate, FTIR and SEM analyses. Impact of various parameters like IBP concentration, pH, agitation speed, sorbent dose, interaction time and temperature on sorptive expulsion were studied using experiments focussed on elucidating optimal conditions. Batch sorption and optimization studies using central composite design revealed that highest IBP removal of 92.46 % and 92.8 % respectively using TABAB were attainable with a 15 mg/L initial IBP solution containing 3.33 g/L adsorbent dose at pH 2 under 35 °C within 6 h at 150 rpm. Performance of IBP sorptive removal was verified by linearized and non-linearized approaches on kinetic and isotherm models. Langmuir isotherm model was the best fit with maximum adsorption capacities of 2.794 mg/g and 8.77 mg/g under acid activation for linear and non-linear analyses respectively while noted adsorption capacities under base activation were 2.914 mg/g and 9.52 mg/g for linear and non-linear analyses respectively. A pseudo second order kinetic model best fits the findings from both analyses. Thermodynamic studies suggested a randomness with exothermic nature of the viable removal process. With both biochar showing effective reusability for 4–5 cycles, estimated preparation costs were an approximated 0.24 INR for treating 1 L of solution with optimal IBP concentration. Consequently, modified adsorbents obtained from tropical almond shell char can be used as cost-effective adsorbents for IBP removal.

Treatment of dye-containing wastewater is a major challenge for mankind that has gained much interest from the scientific community owing to the growing concerns of environmental safety and legislations. Thus, it becomes imperative to explore green and self-sustainable dye abatement methods. Phycoremediation is emerging as a new age technology with the goal of decolorization and detoxification of the hazardous dye laden effluents. The underlying mechanisms of phycoremediation of dyes are biodegradation, biosorption, and biocoagulation, which are influenced by several physicochemical and biological factors such as pH, temperature, contact time, surface characteristics, concentration and particle size of the algal biomass, chemical composition and concentration of the dye. This review provides a comprehensive insight into the potential, performance, and applications of phycoremediation methods in terms of the mechanisms, major determinants of phycoremediation processes, physical and chemical pretreatment methods of the algal biomass, and their effects on dye removal. The present article also discusses the emerging aspects of phycoremediation such as immobilization of algae, algal nanoparticles, activated carbon, and algal microbial fuel cell (A-MFC) for dye remediation along with the research gaps and future prospects. It was concluded from the literature review that immobilized algae and algal biochar exhibit enhanced dye uptake capacity due to improved porosity and surface characteristics. A-MFC can be used for simultaneous wastewater treatment and electricity generation. Furthermore, the generation of value-added products from algal biomass used in wastewater treatment has the potential for waste to wealth creation resulting in the improvement in economic feasibilities of the treatment process.

Although pyrolysis is a promising way for treating animal manure, the application is restricted with some limitations of biochar. To improve the quality of biochar derived from swine manure and enhance the immobilization of heavy metals (Cu and Zn) in it, swine manure was mixed with four types of Ca-based additives (CaO, CaCO3, Ca(OH)2, and Ca(H2PO4)2) prior to pyrolysis at 300–700 °C. The thermogravimetric characteristics of swine manure were obviously influenced The addition of CaO, CaCO3, and Ca(OH)2 during the whole decomposition process. Furthermore, with the addition of CaO and Ca(OH)2, the emission of CO2 and CO was substantially decreased at 200–500 °C, whereas the formation of CO, H2, CO2, and CH4 was drastically increased at 600–800 °C. The biochar produced with CaO addition had the highest pH, surface area and carbon content. Moreover, by addition of Ca-based additives, except for Ca(H2PO4)2, the transformation of labile Cu and Zn to the stable fraction was promoted, and the leachability and environmental risk of them were simultaneously reduced. In contrast, CaO and Ca(OH)2 were more favorable for the immobilization of Cu and Zn than CaCO3. Our study indicated that the catalytic pyrolysis using CaO was an effective and valuable method of animal manure treatment.

Rapid methanogenesis recovery of an acidified anaerobic digestion (AD) system is a challenging issue in engineering application, due to the unfavorably thermodynamics of volatile fatty acids (VFA) syntrophic oxidation process with hydrogen as electron transfer mediator. To breakthrough this bottleneck, in this study, we developed the strategy with biochar as an additive for rapid methanogenesis recovery of a severely acidified AD system is elucidated. First, with VFA as substrate, it was found that biochar addition shortened lag time and promoted maximum methane production rate, confirming the role of biochar to enhance VFA syntrophic oxidation. Moreover, the addition of biochar to the acidified sludge significantly decreased hydrogen partial pressure, which thermodynamically stimulated VFA oxidation by reducing Gibbs free energy. Microbial community analysis delivered that biochar addition largely altered the dominant microbes. The enrichment of electro-active Syntrophomonas and Methanosarcina suggested the role of biochar as potential redox-active mediator to stimulate potential direct interspecies electron transfer between syntrophic microorganisms, and inhibit hydrogen-based syntrophic pathway simultaneously. Further stable operation confirms that biochar is a promising additive for the rapid methanogenic recovery of acidified AD systems.

The single or co-combustion experiments of high-Ca pyrolyzed biochar and high-Si coal were carried out on a drop tube furnace (DTF) at 1300 °C under air and oxyfuel (CO2:O2=50:50, oxy50) conditions. The produced PM10 (of an aerodynamic diameter of 10 µm or less) was analyzed to investigate the interactions during co-combustion. Due to the characteristics of the selected samples (low S and Cl), the PM1 emissions including PM0.1 and PM0.1–1 are very low during single combustion, except for the PM0.1–1 emission during the combustion of biochar under oxy50 condition because of the massive partitioning of Mg, Ca and Fe. The interaction during co-combustion was observed to mainly occur in the generation of PM1–10, and also slightly occur in the formation of PM0.1–1 under oxy50 condition. The capture of Mg, Ca, and Fe from biochar by the Si-containing minerals in coal under the oxy50 condition results in a slight decrease in PM0.1–1 during co-combustion. The higher the proportion of coal blended, the more obvious the reduction of elements. As for the formation of PM1–10 during co-combustion, high-melting minerals of biochar would weaken the coalescence of minerals in coal to cause more PM10, while the large mineral grains of coal would capture the minerals in biochar to generate more PM10+. Under the competition of the above two types of interactions, the experimental value of PM1–10 yields was almost consistent with the theoretically calculated value, except for blended ratio of 80:20 (coal: biochar, air) or 50:50 (oxy50) with prior interaction predominating.

The widespread occurrence of antibiotics in water environment, especially the recalcitrant sulfamethoxazole (SMZ), has sparked increasing concern due to their potential to threat non-target organisms, contaminate food and induce bacterial resistance. In this study, magnetic graphitized biochar (GMBC) was synthesized via a facile one-step strategy employing pine wood-derived biochar as precursor and with potassium ferrate (K2FeO4) modification, and introduced as heterogeneous catalyst for persulfate (PS) activation and SMZ degradation. Utilizing K2FeO4 as both activator (KOH) and catalyst (Fe), porous structure, high graphitization degree, abundant electron-rich functional groups and iron loading of GMBC were simultaneously achieved, which afforded the high catalytic efficiency (almost 100 % degradation of SMZ within 60 min) through accelerating electron transfer. Pyrolysis temperatures affected the structure and catalytic performance of GMBCs. A systematic mechanistic study, including quenching experiment, electron spin resonance analysis and electrochemical measurements, unveiled that both radical pathways (HO , SO4 − and O2 −-mediated oxidation) and non-radical pathways (electron shuttle and 1O2-mediated oxidation) were responsible for the SMZ degradation. Vacancies/defective edges formed on graphitized carbon framework, iron loading sites and the electron-rich ketonic group might be the active sites. In this process, GMBC played versatile roles in accumulating reactants, activating PS as well as mediating the electron transfer from SMZ to PS. Benefited from the multiple mechanisms, the GMBC/PS system can maintain superior oxidation efficiency under various environment conditions, with high anti-interference ability to surrounding compounds and solution pH. This study proposes an economic and green template-free strategy to prepare graphitized biochar catalyst for PS activation and gives underlying insight into the multiple roles of biochar in the eco-friendly remediation of contaminated water.

Phosphorus (P) deficiency is one of the main constraints on crop production in Arenosols (acid sandy soil). The high cost of P fertilizers may represent an insurmountable obstacle in many poor countries, leaving the exploitation of their own calcareous and phosphate rocks as the only low-cost and long-term alternative. Biochar is suggested to have positive effects on soil properties; however, there is no published research on the synergistic effects of biochar and rocky materials in modifying soil properties. The aim of this study was to investigate the chemical and biochemical responses of an acid Arenosol treated with phosphate rock (PR), calcareous rock (CR), and biochar (BC), and the implications for corn yield. A soil from Marracuene District, Mozambique was used, where corn was grown for 90 d with the soil treated with: no addition (control), water-soluble zinc phosphite fertilizer (WSP), PR, WSP+CR, WSP+BC, WSP+CR+BC, PR+BC, and PR+CR+BC. Biochar was produced by pyrolysis of babycorn peels for 4 h at 450 °C and applied at 11 g kg−1. The soil pHH2O increased from about 4.54 in the control to 7.38 in the PR+CR+BC treatment. Easily oxidizable organic carbon, cation exchange capacity, and available P were higher in the treatments containing BC than in the control. The treatments containing CR and/or BC led to the highest activities of alkaline phosphomonoesterase, phosphodiesterase, and α-glucosidase, which increased P availability and gave the greatest biomass and yields. We suggest that biochar provides additional soluble P and supplies adsorption sites for phosphate, preventing its evolution to unavailable forms. Thus, PR applied together with BC contributed to an 840% yield increase compared to the control. The treatments containing WSP and BC facilitated phosphite oxidation to phosphate and increased crop yield.

The ability of biochar to enhance the physical and hydrological properties of light textured soils is highly dependent on the characteristics of biochar including its particle size. To investigate the effect of biochar particle size on water characteristics and soil structure of a sandy loam soil, date palm biochar prepared at a pyrolysis temperature of 450–500 °C was fractioned by dry sieving into four sizes: 2–1, 1–0.5, 0.5–0.1, and

Microwave-assisted wet co-torrefaction of food sludge (FS) and six widely produced lignocellulose biowaste samples were performed for biochar production. Factors including the torrefaction temperature, reaction time, biowaste type, and blending ratio of sludge and biowaste were evaluated. Biochar produced from FS torrefied at 150 °C for 20 min exhibited the greatest enhancement of carbon content and higher heating value (HHV). Blending sludge with macadamia husk at a ratio of 25/75 (db%) under the same wet torrefaction condition further improved biochar quality, enhanced the fixed carbon content, caused the highest HHV (19.6 MJ/kg), and considerably decreased the ash content. Thermogravimetric analysis indicated that sludge and biowaste degradation followed first-order kinetics, and the resultant biochar exhibited improved thermal stability, combustion efficiency, and safety for biofuel applications because of the increase in the activation energy, frequency factor, and ignition and combustion temperatures. Biochar is an excellent coal substitute for power generation because of its enhanced energy efficiency (energy return on investment: 7.4) and environmental friendliness (45.2 % reduction in greenhouse gas emissions compared with using bituminous coal). Moreover, the protein and carbohydrate contents in the supernatant of FS co-torrefied with biowaste at different blending ratios increased by 1.8–9.0 and 0.8–3.4, respectively. These contents can be recycled back to the activated sludge unit as a nutrient source, rendering the process green and sustainable without any waste production.

Salt and sodicity of saline-alkali soil adversely affect the construction of ecological landscapes and negatively impact crop production. The reclamation potential of biochar (BC, wheat straw biochar applied at 1% by weight), gypsum (G, 0.4% by weight), and gypsum coupled with biochar (GBC) was examined in this laboratory-based study by evaluating their effects on a saline-alkali soil (silt loam) with no amendment as a control (CK). Saline ice and fresh water (simulated rainfall) were leached through soil columns to investigate changes in salt content, sodium adsorption ratio (SAR), alkalinity, and pH of the leachate and the soil. Results showed that saturated water content and field water capacity (FWC) significantly increased by 4.4% and 5.6%, respectively, in the BC treatment after a short incubation time. Co-application of biochar and gypsum (GBC) increased soil saturated hydraulic conductivity (Ks) by 58.4%, which was also significantly higher than the sole addition. Electrical conductivity (EC) of the leachate decreased sharply after saline ice leaching; subsequent freshwater leaching accelerated the removal of the rest of the salts, irrespective of the amendment application. However, the application of gypsum (G and GB) significantly enhanced the removal of exchangeable Na+ and reduced leachate SAR. After leaching, the soil salt content decreased significantly for all treatments. The application of gypsum resulted in a significantly lower soil pH, exchangeable sodium percentage (ESP), SAR, and alkalinity values than those recorded for the CK and BC treatments. These results demonstrated that the co-application of gypsum and biochar could improve saline-alkali soil hydraulic conductivity and decrease leaching-induced sodicity over a short period.

In this study, we produced modified biochars with enhanced electrochemical properties to increase PCP remediation in soil. Although all biochars enhanced PCP remediation in aerobic conditions, only a few did in anaerobic soil. The most successful modifications were (i) the preloading of biomass with 10% w/w FeCl3, to obtain a biochar rich in redox-active metals (B-Fe); (ii) the oxidation of a conductive biochar pyrolyzed at 1000 ºC with 0.025 M KMnO4, to produce a biochar with both moderate conductivity and redox capacity (B-1000-KMnO4); and (iii) KMnO4 oxidation of an amorphous biochar pyrolyzed at 400 ºC to obtain a biochar with very high redox capacity (B-KMnO4). B-Fe reduced extractable PCP to almost zero after 50 days in both incubations, but showed slow kinetics of remediation in aerobic soil. B-1000-KMnO4 had the highest rate of remediation under aerobic conditions, but no significant effect under anaerobic conditions. B-KMnO4, however, presented high rates of remediation and high removal of extractable PCP under both conditions, which made it the recommended modification strategy for increased PCP remediation. We found that the degree of remediation primarily depends on the redox capacity, while the rate of remediation was determined by both the conductivity and redox capacity of biochar., Financial support of projects Nº CTM2015–67200-R and RTI2018-099417-B-I00, financed by the Spanish Ministry of Economy and Competitiveness and the Spanish Ministry of Science, Innovation and Universities, cofunded with EU FEDER funds, is greatly appreciated

Consuming rice grown in contaminated soil that has an elevated level of cadmium (Cd) is a health risk. This study revealed that using a combination of biochar and zerovalent iron (BZVI) reduces the concentration of Cd and enhances that of the essential elements zinc (Zn) and iron (Fe) in rice. The Cd concentration in brown rice grain cultivated in an untreated paddy was 0.84 ± 0.20 mg kg−1, double the acceptable level (0.4 mg kg−1). Soil amendment with BZVI successfully decreased Cd in brown rice by 83 % compared to the untreated field presumably due to the Cd sorption on biochar (BC) and enhanced ZVI corrosion by-products while ZVI and BC alone achieved only 40 % and 74 % reduction, respectively. Moreover, while using ZVI or BC alone decreased Fe in rice grain by 8–14 %, BZVI enhanced the Fe concentrations in rice grain by 11 % because of Fe2+/Fe3+ release from BC-enhanced ZVI corrosion. Similarly, the presence of BC in BZVI enhanced Zn accumulation in rice grain by 8% due to competitive sorption of Cd2+ on BZVI, which may desorb Zn2+, promoting Zn translocation to rice. Using ZVI alone decreased Zn in rice by 19 %.

This study investigated the role of surface hydrophobicity/hydrophilicity of biochar on its pollutant leaching potential (pollutants originally in biomass feedstock), including nutrients, organic matter and metals, in water treatment applications. The study outcomes confirmed that biochar with greater hydrophilic surface leached comparatively higher loads of nutrients and organic matter compared to biochar with mostly hydrophobic surface, while biochar with greater hydrophilic surface leached lower metal loads. This trend is attributed to the changes to the physical and chemical properties of biochar including specific surface area and surface functional groups, as well as being related to the binding forces between the biochar surface and the different compounds. Further, the study results substantiated the significant influence of surface characteristics of biochar, and its preparation process on pollutant leaching potential. The study outcomes provide essential guidance on the appropriate use of biochar as an adsorbent in water treatment, including raw biomass selection and the production processes to be adopted.

Lab-scale experiments were carried out to investigate a new approach of preparing biochar-based catalyst for transesterification reaction. Black liquor (BL) from cotton pulping process was used as a precursor for preparing the catalyst via spray drying followed by fast carbonization in a fluidized bed reactor. Response surface methodology (RSM) was employed to statistically analyze and optimize the entire process of catalytic synthesis of biodiesel from a waste frying oil, consisted of the catalyst preparation and transesterification steps. Several major operation parameters of the biodiesel synthesis process, including alkaline loading in biochar, methanol to oil ratio, catalyst loading, and the carbonization temperature of catalyst, were studied for their effects on biodiesel conversion. The optimal condition for achieving the maximum biodiesel conversion (i.e. 91.5 %) was found to be: 27 wt% alkaline loading in biochar, 600 °C carbonization temperature, 7.7 methanol to oil ratio, and 6.5 wt% catalyst loading. Overall, the spry drying fluidized bed carbonization demonstrated its viability for significantly reducing duration of high temperature carbonization, opening up the prospects of manufacturing the catalyst in a much less energy consumption manor.

In this study, a novel adsorbent of lanthanum-modified platanus ball fiber biochar (La-TC) was developed for efficient adsorption and reuse of phosphate from actual wastewater. La-TC adsorbing phosphate could be used as agricultural fertilizer. The saturated adsorption capacity of phosphate on La-TC was 148.11 mg/g at dosage of 0.4 g/L, initial solution pH of 6.0, contact time of 20 min, and temperature of 35 ℃, which was much higher than most phosphate biochar adsorbents. Simultaneously, La-TC had a wide pH (3–9) adsorption stability, a strong ability to resist interference of anti-competitive anion (SO2−4 and NO− 3), and an outstanding regeneration ability. Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to reveal the adsorption mechanism of La-TC to phosphate, including electrostatic adsorption, ligand exchange, and complexation mechanisms. In the fixed bed column experiment of phosphorus removal from real wastewater, the maximum treated bed volume was 420, 440 and 480 (BV) under the bed flow of 1 mL/min and La-TC of 0.5, 0.75 and 1.0 g, respectively. Outcomes suggested that La-TC had a broad prospect of engineering application for removal and reuse of phosphate from wastewater, also realizing the resource utilization of wasted platanus ball.

The acai palm (Euterpe oleracea Mart) is native to the floodplains of central and South America and is cultivated in Brazil for its berries, which are considered to be a ‘superfood’. The waste acai fiber and seeds obtained after fruit processing pose a challenge since they remain unutilised despite being an abundant waste by-product of acai processing.This leads to a build-up of waste, regular dumping and environmental management challenges. Here we examine the potential use of acai seed biochar as a soil conditioner. The biochar was produced from waste seeds in a handmade kiln, incorporated into two soils of different textures and then compacted in volumetric rings with a hydraulic press. The samples were kept in a greenhouse for a 270-day incubation period. After this, the samples were evaluated for their soil physical and chemical attributes. Nine months after the application of the acai seed biochar, soil physical properties were not affected, except for the soil aggregate size distribution, for which the highest dosage resulted in a larger weighted average diameter. However, biochar increased phosphorus, potassium and magnesium contents, and reduced the aluminum content, which was reflected in an increase of the base saturation and a reduction in aluminum saturation. Therefore, within a relatively short time period, the biochar was found to improve soil chemical quality more so than soil physical properties, thus offering potential as a sustainable solution to manage acai waste in the Amazon region.

Bauxite residues, a large volume solid waste, are in urgent need of effective disposal and management. Especially, strategies to alleviate the high alkalinity of bauxite residue remain a big challenge. Here, we developed a synergistic pyrolysis to neutralize the alkalinity of bauxite residue and upgrade the structure of biomass simultaneously. By cooperating the catalytic feature from bauxite residue, rice straw, a cellulose-enriched biomass, could prefer to produce acidic components under a hypothermal pyrolysis temperature (below 250 °C) and partial oxygen-contained atmosphere as evidenced by the synchronous TGA-FTIR analysis. In return, these in-situ produced acidic components neutralized the bauxite residue profoundly (pH decreased from 11.5 to 7.2) to obtain a neutral product with long-term water leaching stability. Also, a higher pyrolysis temperature led to neutral biochar-based products with well-defined carbonization characteristics. Thus, the biomass-driven pyrolysis strategy provides a potential to dispose the alkalinity issue of bauxite residue and further opportunities for the sustainable reuse and continuing management of bauxite residue.

In this study, the influence of production conditions (i.e., pyrolysis temperature and residence time) on the fundamental properties and the nutritional traits of biochars derived from different feedstocks (corn stalk, rape straw, wheat stalk, and peanut shell) were investigated. The results showed that pyrolysis temperature was a critical parameter affecting biochar properties, whereas the influences of residence time and feedstock were comparatively weaker. Biochar properties, including the pH, ash content, electrical conductivity (EC), oxidation stability, and the ability to retain nutrients, were positively related with increasing temperature and prolonged residence time. However, the water-extractable organic matter and available nutrients were negatively related with temperature and residence time. There was a minimal release of NH4+-N, NO3−-N, and PO43−-P from the generated biochars, and their concentrations were reduced through carbonization. By comparison, the water-soluble K+ content steadily increased with pyrolysis. Generally, the biochars showed a limited capacity for sorbing PO43− and NO3−, although the removal efficiencies were enhanced by pyrolysis. By comparison, higher NH4+ removal was achieved by biochars, and particularly for biochars with a higher pH. These findings suggest that the application of agricultural residue-derived biochars might not provide plants with sufficient nutrients (except for K). Additionally, the biochars generated at 500 °C for a duration of 1 h demonstrated higher potential for carbon sequestration.

Overuse of nitrogen (N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water. Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite (NO−2) or nitrate (NO−3). Although positively charged ammonium (NH+4) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO−2 and/or NO−3. In practice, dicyandiamide (DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH+4. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg−1 d−1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg−1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH+4 in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH+4 and DCD could possibly enhance the effectiveness of DCD.

Vegetation fires are known to have broad geochemical effects on carbon (C) cycles in the Earth system, yet limited information is available for nitrogen (N). In this study, we evaluated how charring organic matter (OM) to pyrogenic OM (PyOM) altered the N molecular structure and affected subsequent C and N mineralization. Nitrogen near-edge X-ray absorption fine structure (NEXAFS) of uncharred OM, PyOM, PyOM toluene extract, and PyOM after toluene extraction were used to predict PyOM-C and -N mineralization potentials. PyOM was produced from three different plants (e.g. Maize-Zea mays L.; Ryegrass-Lollium perenne L.; and Willow-Salix viminalix L.) each with varying initial N contents at three pyrolysis temperatures (350, 500 and 700 °C). Mineralization of C and N was measured from incubations of uncharred OM and PyOM in a sand matrix for 256 days at 30 °C. As pyrolysis temperature increased from 350 to 700 °C, aromatic C 000000000000 000000000000 000000000000 111111111111 000000000000 111111111111 000000000000 000000000000 000000000000 N in 6-membered rings (putative) increased threefold. Aromatic CN in 6-membered oxygenated ring increased sevenfold, and quaternary aromatic N doubled. Initial uncharred OM-N content was positively correlated with the proportion of heterocyclic aromatic N in PyOM (R2 = 0.44; P

Wastewater resource recovery facilities produce wastewater solids that offer potential for energy recovery. This opinion article provides a perspective on state-of-the-art technologies to recover energy from sludge (unstabilized wastewater residual solids) and biosolids (stabilized wastewater solids meeting criteria for application on land). The production of biodiesel fuel is an emerging technology for energy recovery from sludge, whereas advancements in pretreatment technologies have improved energy recovery from anaerobic digestion of sludge. Incineration is an established technology to recover energy from sludge or biosolids. Gasification, and to a greater extent, pyrolysis are emerging technologies well-suited for energy recovery from biosolids. While gasification produces high-energy gases, pyrolysis has the benefit of producing biochar in addition to pyrolysis gas. Research on the use of pyrolysis liquids, however, must proceed to advance pyrolysis implementation efforts. Future research on improvements to dewatering and drying of sewage sludge and biosolids will help advance all technologies reviewed.

Amending growing media with biochar has the potential to sequester carbon and enhance the properties of the receiving substance. However, knowledge of the mechanisms of how biochar amends the physical properties of the material is incomplete. By combining 3D image analysis and more conventional methods, this study aimed to (1) characterise the pore structure properties of three different plant-based biochars and (2) quantify their impact on Sphagnum moss growing media physical properties. The 3D imaging showed that irrespective of the feedstock, the majority (0.80–0.94 m3 m−3) of the biochar pore volume resided in pores with diameters 2–11 μm. Biochar pore properties shared similarities due to the structure of plant tissue. The application of biochar increased the water retention of the growing media by a maximum increase of 0.06 m3 m−3 in the pore diameter range 1–8 μm. This is relevant for plant-available water and microbiological activity, which indicates the usability of the biochar amendments. From methodological point of view, the benefits of combining 3D imaging with conventional measurements and impacts of the water table continuum discontinuity between the biochar and the surrounding growing media were demonstrated. The design of biochar for optimal water retention would benefit from further studies quantifying pore structure characteristics of biochar produced from a wide range of feedstocks.