Biochar as a Multifunctional Component of the Environment—A Review

Fabrication of engineered biochar for remediation of toxic contaminants in soil matrices and soil valorization

Biochar has emerged as an efficacious green material for remediation of a wide spectrum of environmental pollutants. Biochar has excellent characteristics and can be used to reduce the bioavailability and leachability of emerging pollutants in soil through adsorption and other physico-chemical reactions. This paper systematically reviewed previous researches on application of biochar/engineered biochar for removal of soil contaminants, and underlying adsorption mechanism. Engineered biochar are derivatives of pristine biochar that are modified by various physico-chemical and biological procedures to improve their adsorption capacities for contaminants. This review will promote the possibility to expand the application of biochar for restoration of degraded lands in the industrial area or saline soil, and further increase the useable area. This review shows that application of biochar is a win-win strategy for recycling and utilization of waste biomass and environmental remediation. Application of biochar for remediation of contaminated soils may provide a new solution to the problem of soil pollution. However, these studies were performed mainly in a laboratory or a small scale, hence, further investigations are required to fill the research gaps and to check real-time applicability of engineered biochar on the industrial contaminated sites for its large-scale application.

Revitalizing the Biochemical Soil Properties of Degraded Coastal Soil Using Prosopis juliflora Biochar

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

Preparation, Modification, and Application of Biochar in the Printing Field: A Review

Biochar is a solid material enriched with carbon produced by the thermal transformation of organic raw materials under anoxic or anaerobic conditions. It not only has various environmental benefits including reducing greenhouse gas emissions, improving soil fertility, and sequestering atmospheric carbon, but also has the advantages of abundant precursors, low cost, and wide potential applications, thus gaining widespread attention. In recent years, researchers have been exploring new biomass precursors, improving and developing new preparation methods, and searching for more high-value and meaningful applications. Biochar has been extensively researched and utilized in many fields, and recently, it has also shown good industrial application prospects and potential application value in the printing field. In such a context, this article summarizes the typical preparation and modification methods of biochar, and also reviews its application in the printing field, to provide a reference for future work.

Quantitative analysis of the current status and research trends of biochar research - A scientific bibliometric analysis based on global research achievements from 2003 to 2023

Biochar has excellent physical and chemical properties such as porosity, high carbon content, high cation exchange capacity, and rich surface functional groups and has been widely used in environmental remediation. Over the past 20 years, although various reviews have described the application of biochar as an environmentally friendly multifunctional material in environmental remediation, no comprehensive summary and analysis of the research trends in this field exists. To promote the rapid and stable development of the field of biochar, the current state of research on biochar is clarified using the bibliometric method in this report, and potential development directions and challenges for the future are identified. All relevant biochar literature from 2003-2023 was collected from the Chinese National Knowledge Infrastructure and Web of Science Core Collection. A total of 6,119 published Chinese papers and 25,174 English papers were selected for the quantitative analysis. CiteSpace, VOSviewer, and Scimago graphics software was used to summarize the numbers of papers published over the years, as well as the countries, institutions, and authors that published the most articles. Secondly, using keyword co-occurrence and emergence analysis, the recognized research hotspots in different areas such as adsorbents, soil remediation, catalytic oxidation, supercapacitors, and "biochar-microbial" synergy were analyzed. Finally, the prospects and challenges of biochar were assessed to provide new perspectives for further promoting its development in technological, economic, environmental, and other aspects.

Nickel Hyperaccumulator Biochar Sorbs Ni(II) from Water and Wastewater to Create an Enhanced Bio-ore

Nickel (Ni) hyperaccumulators make up the largest proportion of hyperaccumulator plant species; however, very few biochar studies with hyperaccumulator feedstock have examined them. This research addresses two major hypotheses: (1) Biochar synthesized from the Ni hyperaccumulator Odontarrhena chalcidica grown on natural, metal-rich soil is an effective Ni sorbent due to the plant's ability to bioaccumulate soluble and exchangeable cations; and (2) such biochar can sorb high concentrations of Ni from complex solutions. We found that O. chalcidica grew on sandy, nutrient-poor soil from a Minnesota mining district but did not hyperaccumulate Ni. Biochar prepared from O. chalcidica biomass at a pyrolysis temperature of 900 °C sorbed up to 154 mg g-1 of Ni from solution, which is competitive with the highest-performing Ni sorbents in recent literature and the highest of any unmodified, plant-based biochar material reported in the literature. Precipitation, cation exchange, and adsorption mechanisms contributed to removal. Ni was effectively removed from acidic solutions with initial pH > 2 within 30 min. O. chalcidica biochar also removed Ni(II) from a simulated Ni electroplating rinsewater solution. Together, these results provide evidence for O. chalcidica biochar as an attractive material for simultaneously treating high-Ni wastewater and forming an enhanced Ni bio-ore.

Biochar-plant interaction and detoxification strategies under abiotic stresses for achieving agricultural resilience: A critical review

The unpredictable climatic perturbations, the expanding industrial and mining sectors, excessive agrochemicals, greater reliance on wastewater usage in cultivation, and landfill leachates, are collectively causing land degradation and affecting cultivation, thereby reducing food production globally. Biochar can generally mitigate the unfavourable effects brought about by climatic perturbations (drought, waterlogging) and degraded soils to sustain crop production. It can also reduce the bioavailability and phytotoxicity of pollutants in contaminated soils via the immobilization of inorganic and/or organic contaminants, commonly through surface complexation, electrostatic attraction, ion exchange, adsorption, and co-precipitation. When biochar is applied to soil, it typically neutralizes soil acidity, enhances cation exchange capacity, water holding capacity, soil aeration, and microbial activity. Thus, biochar has been was widely used as an amendment to ameliorate crop abiotic/biotic stress. This review discusses the effects of biochar addition under certain unfavourable conditions (salinity, drought, flooding and heavy metal stress) to improve plant resilience undergoing these perturbations. Biochar applied with other stimulants like compost, humic acid, phytohormones, microbes and nanoparticles could be synergistic in some situation to enhance plant resilience and survivorship in especially saline, waterlogged and arid conditions. Overall, biochar can provide an effective and low-cost solution, especially in nutrient-poor and highly degraded soils to sustain plant cultivation.

Challenges and opportunities of lignocellulosic biomass gasification in the path of circular bioeconomy

The energy deficiency issues and intense environmental pollution have exacted the production of biofuels which are both renewable and sustainable and can be used to displace fossil fuels. The raw material for manufacturing second-generation biofuels is lignocellulosic biomass (LCB), which is widely available. LCB bioprocessing to produce high-value bio-based products has been the subject of attention. Biomass gasification is a powerful technology to achieve sustainable development goals, reduce reliance on fossil fuels, and reduce environmental concerns. This paper, will provide an overview of the LCB structures and the gasification process. Also, consistent with the concept of "circular bio-economy", this study focuses on the role of LCB gasification in the environmental impacts, and how gasification can be effective in the pathway of circular bio-economy. The current challenges to gasification and biorefinery and future perspectives are also presented.

Rice Straw Utilisation for Bioenergy Production: A Brief Overview

Unsustainable rice straw management causes environmental impacts; hence, utilisation of rice straw for bioenergy is a promising strategy for sustainable rice straw management. Although rice straw has a high potential for bioenergy generation, the whole production cycle and application may cause environmental damage that is not fully understood. Hence, environmental performance studies are required to determine the most effective rice straw utilisation options. A comprehensive approach, such as life-cycle assessment (LCA), can give comprehensive information on the possible environmental effects of rice straw utilisation for bioenergy. Therefore, this study briefly overviews the LCA of rice straw utilisation for bioenergy production. It is found that utilisation of rice straw for bioenergy could reduce global warming potential compared to energy production from fossil fuels. However, it is suggested that other impact categories in LCA be evaluated in the bioenergy production from rice straw research to determine the overall sustainability of the production.

The Use of Wood Pellets in the Production of High Quality Biocarbon Materials

Biomass is one of the most important sources of renewable energy. One of the most widely used biomass biofuels is wood pellets. It is an economical, homogeneous and easy-to-use raw material. Biomass is used to generate low-emission energy utilizing the pyrolysis process. Pyrolysis allows for higher energy efficiency with the use of commonly available substrates. This thesis presents the results of research on the possibility of using the pyrolysis process to produce high-energy biocarbons from wood pellets. Data on basic energy parameters and explosivity of biocarbon dust were compiled as criteria for the attractiveness of the solution in terms of energy utility. The research used pellets made of oak, coniferous, and mixed sawdust, which were subjected to a pyrolysis process with varying temperature and time parameters. Carbon, ash, nitrogen, hydrogen, volatile substances, heavy metals, durability and calorific value of the tested materials were carried out. The highest increase in calorific value was determined to be 63% for biocarbons obtained at 500 ℃ and a time of 15 min, compared with the control sample. The highest calorific value among all analyzed materials was obtained from coniferous pellet biocarbon at 31.49 MJ kg⁻¹. Parameters such as maximum explosion pressure, Pmax, maximum pressure increase over time, (dp/dt)max, and explosion rates, Kst max, were also analyzed. It was noted that biomass pyrolysis, which was previously pelletized, improved the energy parameters of the fuel and did not increase the risk class of dust explosion. The lowest and highest recorded values of Kst max for the analyzed materials were 76.53 and 94.75 bar s⁻¹, respectively. The study concluded that the process used for processing solid biofuels did not affect the increase in the danger of dust explosion. The results presented in this article form the basis for further research to obtain detailed knowledge of the safety principles of production, storage, transport and use of these new fuels.

Biochar-based composites for remediation of polluted wastewater and soil environments: Challenges and prospects

Pharmaceuticals, heavy metals, pesticides, and dyes are the main environmental contaminants that have serious effects on both land and aquatic lives and necessitate the development of effective methods to mitigate these issues. Although some conventional methods are in use to tackle soil contamination, but biochar and biochar-based composites represent a reliable and sustainable means to deal with a spectrum of toxic organic and inorganic pollutants from contaminated environments. The capacity of biochars and derived constructs to remediate inorganic dyes, pesticides, insecticides, heavy metals, and pharmaceuticals from environmental matrices is attributed to their extensive surface area, surface functional groups, pore size distribution, and high sorption capability of these pollutants in water and soil environments. Application conditions, biochar feedstock, pyrolysis conditions and precursor materials are the factors that influence the capacity and functionality of biochar to adsorb pollutants from wastewater and soil. These factors, when improved, can benefit biochar in agrochemical and heavy metal remediation from various environments. However, the processes involved in biochar production and their influence in enhancing pollutant sequestration remain unclear. Therefore, this paper throws light on the current strategies, operational conditions, and sequestration performance of biochar and biochar-based composites for agrochemical and heavy metal in soil and water environments. The main challenges associated with biochar preparation and exploitation, toxicity evaluation, research directions and future prospects for biochar in environmental remediation are also outlined.

Biochar in environmental friendly fertilizers - Prospects of development products and technologies

According to the circular economy concept, the production of fertilizers should be closed in a loop, which prevents excessive emissions and harmful effects to the environment. Biological wastes are problematic to collect and transport. They undergo a biological transformation that causes greenhouse gases emission and sanitary hazards. Biomass sources used for organic or organo-mineral fertilizers must be free of pathogens and rich in macro and microelements. Solid residues can be processed thermally. Biochar is a carbon produced by biomass pyrolysis without oxygen presence and has been used for many years to improve soil quality and enhance the efficiency of fertilization. There are many research works on the use of biochar in fertilization. This study is also extended by the latest developments and technologies from the patent database (recent year) and biochar-based fertilizers market. To the best of our knowledge, there is no such review currently available in scientific databases. Based on the collected data, the best method of biochar management was proposed - soil application. Biochar applied to soil has several advantages: it improves soil structure and its sorption capacity, enhances soil-nutrient retention and water-holding capacity, immobilizes contaminants from soil (sorption), reduces greenhouse gas emissions and soil nutrient leaching losses while stimulating the growth of a plant.

Engineered biochar: A multifunctional material for energy and environment

Biochar is a stable carbon-rich product loaded with upgraded properties obtained by thermal cracking of biomasses in an oxygen-free atmosphere. The pristine biochar is further modified to produce engineered biochar via various physical, mechanical, and chemical methods. The hasty advancement in engineered biochar synthesis via different technologies and their application in the field of energy and environment is a topical issue that required an up-to-date review. Therefore, this review deals with comprehensive and recent mechanistic approaches of engineered biochar synthesis and its further application in the field of energy and the environment. Synthesis and activation of engineered biochar via various methods has been deliberated in brief. Furthermore, this review systematically covered the impacts of engineered biochar amendment in the composting process, anaerobic digestion (AD), soil microbial community encouragement, and their enzymatic activities. Finally, this review provided a glimpse of the knowledge gaps and challenges associated with application of engineered biochar in various fields, which needs urgent attention in future research.

Biochar-induced priming effects in soil via modifying the status of soil organic matter and microflora: A review

Biochar (BC) application has the potential to be integrated into a carbon-trading framework owing to its multiple environmental and economic benefits. Despite the increasing research attention over the past ten years, the mechanisms of BC-induced priming effects on soil organic carbon mineralization and their influencing factors have not been systematically considered. This review aims to document the recent progress in BC research by focusing on (1) how BC-induced priming effects change the soil environment, (2) the factors governing the mechanisms underlying BC amendment effects on soils, and (3) how BC amendments alter soil microbial communities and nutrient dynamics. Here, we carried out a detailed examination of the origins of different biochar, its pyrolysis conditions, and potential interactions with various factors that affect BC characteristics and mechanisms of C mineralization in primed soil. These findings clearly addressed the strong linkage between BC properties and abiotic factors that leads to change the soil microclimate, priming effects, and carbon stabilization. This review offers an overview of a fragmented body of evidence and the current state of understanding to support the application of BC in different soil environments with the aim of sustaining or improving the agricultural crop production.

The Possibility of Using Paulownia elongata S. Y. Hu × Paulownia fortunei Hybrid for Phytoextraction of Toxic Elements from Post-Industrial Wastes with Biochar

The potential of the Paulownia hybrid for the uptake and transport of 67 elements along with the physiological response of plants cultivated in highly contaminated post-industrial wastes (flotation tailings—FT, and mining sludge—MS) was investigated. Biochar (BR) was added to substrates to limit metal mobility and facilitate plant survival. Paulownia could effectively uptake and translocate B, Ca, K, P, Rb, Re and Ta. Despite severe growth retardation, chlorophyll biosynthesis was not depleted, while an increased carotenoid content was noted for plants cultivated in waste materials. In Paulownia leaves and roots hydroxybenzoic acids (C6-C1) were dominant phenolics, and hydroxycinnamic acids/phenylpropanoids (C6-C3) and flavonoids (C6-C3-C6) were also detected. Plant cultivation in wastes resulted in quantitative changes in the phenolic fraction, and a significant drop or total inhibition of particular phenolics. Cultivation in waste materials resulted in increased biosynthesis of malic and succinic acids in the roots of FT-cultivated plants, and malic and acetic acids in the case of MS/BR substrate. The obtained results indicate that the addition of biochar can support the adaptation of Paulownia seedlings growing on MS, however, in order to limit unfavorable changes in the plant, an optimal addition of waste is necessary.

Sustainable Approach and Safe Use of Biochar and Its Possible Consequences

Biochar is considered as a potential substitute for soil organic matter (SOM). Considering the importance of biochar, the present review is based on the different benefits and potential risks of the application of biochar to the soil. Biochar addition to low organic carbon soils can act as a feasible solution to keep soil biologically active for the cycling of different nutrients. The application of biochar could improve soil fertility, increase crop yield, enhance plant growth and microbial abundance, and immobilize different contaminants in the soil. It could also be helpful in carbon sequestration and the return of carbon stock back to the soil in partially combusted form. Due to the large surface area of biochar, which generally depends upon the types of feedstock and pyrolysis conditions, it helps to reduce the leaching of fertilizers from the soil and supplies additional nutrients to growing crops. However, biochar may have some adverse effects due to emissions during the pyrolysis process, but it exerts a positive priming effect (a phenomenon in which subjection to one stimulus positively influences subsequent stimulus) on SOM decomposition, depletion of nutrients (macro- and micro-) via strong adsorption, and impact on soil physicochemical properties. In view of the above importance and limitations, all possible issues related to biochar application should be considered. The review presents extensive detailed information on the sustainable approach for the environmental use of biochar and its limitations.

Biochars and Engineered Biochars for Water and Soil Remediation: A Review

Biochars (BCs) are considered as ecofriendly and multifunctional materials with significant potential for remediation of contaminated water and soils, while engineered biochars (E-BCs) with enlarged surface areas and abundant surface functional groups can perform even better in environmental remediation. This review systematically summarizes the key physical and chemical properties of BCs that affect their pollutant sorption capacities, major methods employed for modification of E-BCs, the performance of BCs/E-BCs in removing major types of organic (e.g., antibiotics and pesticides) and inorganic pollutants (e.g., heavy metals), and the corresponding removal mechanisms. The physical and chemical properties of BCs—such as ash or mineral contents, aromaticity, surface structures, pH, and surface functional groups (e.g., C=O, -COOH, -OH, and -NH2)—depend primarily on their feedstock sources (i.e., plant, sludge, or fecal) and the pyrolysis temperature. Ion exchange, precipitation, electrostatic attraction, and complexation are the main mechanisms involved in the adsorption of inorganic pollutants on BCs/E-BCs, whereas hydrogen bonding, pore filling, electrostatic attraction, hydrophobic interaction, and van der Waals forces are the major driving forces for the uptake of organic pollutants. Despite their significant promises, more pilot and field scale investigations are necessary to demonstrate the practical applicability and viability of BCs/E-BCs in water and soil remediation.

Effect of the Pyrolysis Process Applied to Waste Branches Biomass from Fruit Trees on the Calorific Value of the Biochar and Dust Explosivity

The article discusses the findings related to the calorific value as well as the explosion and combustion parameters of dust from the raw biomass of fruit trees, i.e., apple, cherry, and pear branches, and from biochars produced using this type of biomass during pyrolysis processes conducted under various conditions. The plant biomass was thermally processed at 400, 450, or 500 °C for a duration of 5, 10, or 15 min. The study aimed to identify the calorific value of the biomass obtained from waste produced in orchards and to estimate the explosion hazard during the processing of such materials and during the storage of the resulting solid fuels. Tests were conducted to assess the total contents of carbon, ash, nitrogen, hydrogen, and volatile substances as well as the calorific value. The findings show a significant effect of the thermal transformation of fruit tree branches on the calorific value of the biochars that were produced. It was found that the mean calorific value of all of the biochars was increased by 62.24% compared to the non-processed biomass. More specifically, the mean calorific values of the biochars produced from apple, cherry, and pear branches amounted to 27.90, 28.75, and 26.84 MJ kg−1, respectively. The maximum explosion pressure Pmax measured for the dust from the biomass and for the biochars was in the range 7.56–7.8 and 7.95–11.72 bar, respectively. The maximum rate of pressure rose over time (dp/dt)max in the case of the dust from the biomass, which was in the range of 274.77–284.97 bar s−1, and the dust from biochar amounted to 282.05–353.41 bar s−1. The explosion index Kst max measured for non-processed biomass and biochars was found to range from 74.46 to 77.23 and from 76.447 to 95.77 bar s−1, respectively. It was also shown that a change in the temperature and duration of the pyrolysis process affected the quality of the biochars that were obtained. The findings show that pyrolysis, as a method of plant biomass processing, positively affects the calorific value of the products and does not lead to an increased risk of explosion during the treatment and storage of such materials. It is necessary, however, to continue research on biomass processing in order to develop practices that adequately ensure safety during the production of novel fuels.

Analysis and Characterization of Metallic Nodules on Biochar from Single-Stage Downdraft Gasification

Biochar, which is a byproduct of gasification, is used in a wide range of fields such as water filtration, agriculture, and electronics, to name a few. The metals in the biomass were thought to end up either in the ash or distributed throughout the biochar. In this study, the goal was a more thorough characterization of biochar resulting from a single-stage downdraft gasifier. One of the first observations was that some metals actually localize into small (~25 micron diameter) metallic nodules on the biochar surface. Further analysis included ultimate and proximate analysis, Brunauer–Emmert–Teller (BET) analysis, and scanning electron microscopy X-ray spectroscopy (SEM-EDS). Biomass fuel included corn grains, soybeans, and wood pellets, with wood biochar showing the highest fixed carbon content, at 91%, and the highest surface area, at 92.4 m2/g. The SEM analysis showed that certain minerals, including potassium, phosphorus, calcium, iron, nickel, silicon, and copper, formed nodules with over 50% metal mass next to pores in the carbon substrate. Aluminum, chlorine, magnesium, and silicon (in certain cases) were mostly uniformly distributed on the biochar carbon substrate. Corn biochar showed a high concentration in the nodules of 9–21% phosphorus and up to 67% potassium. Soybean biochar showed a similar trend with traces of iron and nickel of 2% and 4.1%, respectively, while wood biochar had a significant amount of potassium, up to 35%, along with 44% calcium, 3% iron, and up to 4.2% nickel concentrations. A morphology analysis was also carried out.

State-of-the-Art Char Production with a Focus on Bark Feedstocks: Processes, Design, and Applications

In recent years, there has been a surge of interest in char production from lignocellulosic biomass due to the fact of char’s interesting technological properties. Global char production in 2019 reached 53.6 million tons. Barks are among the most important and understudied lignocellulosic feedstocks that have a large potential for exploitation, given bark global production which is estimated to be as high as 400 million cubic meters per year. Chars can be produced from barks; however, in order to obtain the desired char yields and for simulation of the pyrolysis process, it is important to understand the differences between barks and woods and other lignocellulosic materials in addition to selecting a proper thermochemical method for bark-based char production. In this state-of-the-art review, after analyzing the main char production methods, barks were characterized for their chemical composition and compared with other important lignocellulosic materials. Following these steps, previous bark-based char production studies were analyzed, and different barks and process types were evaluated for the first time to guide future char production process designs based on bark feedstock. The dry and wet pyrolysis and gasification results of barks revealed that application of different particle sizes, heating rates, and solid residence times resulted in highly variable char yields between the temperature range of 220 °C and 600 °C. Bark-based char production should be primarily performed via a slow pyrolysis route, considering the superior surface properties of slow pyrolysis chars.

Role of Pyrogenic Carbon in Parallel Microbial Reduction of Nitrobenzene in the Liquid and Sorbed Phases

Surface functional groups and graphitic carbons make up the electroactive components of pyrogenic carbon. The role of pyrogenic carbon with different contents of electroactive components in mediating electron transfer in biochemical reactions has not been systematically studied. Here, we determined the electron exchange capacity (EEC) of pyrogenic carbon to be 0.067-0.120 mmol e^-·(g of pyrogenic carbon)^-1, and the maximum electrical conductivity (EC) was 4.85 S·cm^-1. Nitrobenzene was simultaneously reduced in both the liquid and sorbed phases by Shewanella oneidensis MR-1 in the presence of pyrogenic carbon. Pyrogenic carbon did not affect the aqueous nitrobenzene reduction, and the reduction of sorbed nitrobenzene was much slower than that of the aqueous species. Enhancing contents of oxygenated functional moieties in pyrogenic carbon with HNO₃ oxidation elevated bioreduction rates of the aqueous and sorbed species. Anthraquinone groups were deemed as the most likely oxygenated functional redox compounds on the basis of both voltammetric curve tests and spectroscopic analysis. The reactivity of pyrogenic carbon in mediating the reduction of sorbed nitrobenzene was positively correlated with its EC, which was demonstrated to be related to condensed aromatic structures. This work elucidates the mechanism for pyrogenic carbon-mediated biotransformation of nitrobenzene and helps properly evaluate the role of pyrogenic carbon in biogeochemical redox processes happening in nature.

Techno-Economic Assessment of Bio-Syngas Production for Methanol Synthesis: A Focus on the Water-Gas Shift and Carbon Capture Sections

The biomass-to-methanol process may play an important role in introducing renewables in the industry chain for chemical and fuel production. Gasification is a thermochemical process to produce syngas from biomass, but additional steps are requested to obtain a syngas composition suitable for methanol synthesis. The aim of this work is to perform a computer-aided process simulation to produce methanol starting from a syngas produced by oxygen-steam biomass gasification, whose details are reported in the literature. Syngas from biomass gasification was compressed to 80 bar, which may be considered an optimal pressure for methanol synthesis. The simulation was mainly focused on the water-gas shift/carbon capture sections requested to obtain a syngas with a (H₂ - CO₂)/(CO + CO₂) molar ratio of about 2, which is optimal for methanol synthesis. Both capital and operating costs were calculated as a function of the CO conversion in the water-gas shift (WGS) step and CO₂ absorption level in the carbon capture (CC) unit (by Selexol^® process). The obtained results show the optimal CO conversion is 40% with CO₂ capture from the syngas equal to 95%. The effect of the WGS conversion level on methanol production cost was also assessed. For the optimal case, a methanol production cost equal to 0.540 €/kg was calculated.

Balancing Waste and Nutrient Flows Between Urban Agglomerations and Rural Ecosystems: Biochar for Improving Crop Growth and Urban Air Quality in The Mediterranean Region

Mediterranean ecosystems are threatened by water and nutrient scarcity and continuous loss of soil organic carbon. Urban agglomerations and rural ecosystems in the Mediterranean region and globally are interlinked through the flows of resources/nutrients and wastes. Contributing to balancing these cycles, the present study advocates standardized biochar as a soil amendment, produced from Mediterranean suitable biowaste, for closing the nutrient loop in agriculture, with parallel greenhouse gas reduction, enhancing air quality in urban agglomerations, mitigating climate change. The study’s scope is the contextualization of pyrolytic conditions and biowaste type effects on the yield and properties of biochar and to shed light on biochar’s role in soil fertility and climate change mitigation. Mediterranean-type suitable feedstocks (biowaste) to produce biochar, in accordance with biomass feedstocks approved for use in producing biochar by the European Biochar Certificate, are screened. Data form large-scale and long-period field experiments are considered. The findings advocate the following: (a) pyrolytic biochar application in soils contributes to the retention of important nutrients for agricultural production, thereby reducing the use of fertilizers; (b) pyrolysis does not release carbon dioxide to the atmosphere, contributing positively to the balance of carbon dioxide emissions to the atmosphere, with carbon uptake by plant photosynthesis; (c) biochar stores carbon in soils, counterbalancing the effect of climate change by sequestering carbon; (d) there is an imperative need to identify the suitable feedstock for the production of sustainable and safe biochar from a range of biowaste, according to the European Biochar Certificate, for safe crop production.

A critical review of different factors governing the fate of pesticides in soil under biochar application

Pesticides are extensively used in the modern agricultural system. The inefficient and extensive use of pesticides during the last 5 to 6 decades inadvertently led to serious deterioration of environmental quality with health risk to living organisms, including humans. It is important to use some environmentally-friendly and sustainable approaches to remediate, restore and maintain soil quality. Biochar has gained considerable attention globally as a promising soil amendment because it has the ability to adsorb and as such minimize the bioavailability of pesticides in soils. This review emphasizes the recent trends and implications of biochar in pesticide-contaminated soils, as well as highlights need of the pesticides use and associated environmental issues in context of the biochar application. The overarching aim of this review is to signify the role of biochar on primary processes such as effect of biochar on the persistence, mineralization, leaching and efficacy of pesticides in soil. Notably, the effects of biochar on pesticide adsorption-desorption, degradation and bioavailability under various operating/production conditions are critically discussed. This review delineates the indirect impact of biochar on pesticides persistence in soils and proposes key recommendations for future research which are essential for the remediation and restoration of pesticides-impacted soils.

In Situ Synthesis, Characterization, and Catalytic Performance of Polypyrrole Polymer-Incorporated Ag2MoO4 Nanocomposite for Detection and Degradation of Environmental Pollutants and Pharmaceutical Drugs

Material combinations of semiconductor with conducting polymer are gaining growing interest due to their enhanced activities in photocatalysis as well as electrochemical sensing. In this present work, we report a facile in situ synthesis of polypyrrole (PPy) polymer-incorporated silver molybdate (Ag₂MoO₄) nanocomposite that is utilized as a photocatalyst and electrocatalyst for the degradation of pollutant heavy metals, namely, methylene blue (MB) and heavy metal (Cr(VI)), and ciprofloxacin (CIP) and for detection of the drug, azomycin. The synthesized nanocomposite was characterized by various theoretical, spectral, and microscopic studies. Matching of the powder X-ray diffraction pattern with JCPDS no. 76-1747 confirmed the formation of α-Ag₂MoO₄/PPy. The surface topography and spherical morphology of the nanocomposite were studied using field emission-scanning electron microscopy and transmission electron microscopy. Fourier transform infrared spectral detail expounds the smooth incorporation of PPy to Ag₂MoO₄. The as-synthesized nanocomposite performs as an efficient photocatalyst in the degradation of MB (99.9%), Cr(VI) (99%), and CIP drug (99.8%) within 10 min. In addition to this, the Ag₂MoO₄/PPy-modified glassy carbon electrode (GCE) demonstrated excellent electrocatalytic activity in terms of a higher cathodic peak current and lower peak potential when compared with other modified and unmodified GCEs for the detection of azomycin. The Ag₂MoO₄/PPy/GCE displayed a broader linear response range and lower detection limit of 0.5-499 μM and 65 nM, respectively. Moreover, other potentially co-interfering compounds, such as a similar functional group-containing biological substances and inorganic species, have no interference effect toward azomycin sensing.

Biochar as a Stimulator for Germination Capacity in Seeds of Virginia Mallow (Sida hermaphrodita (L.) Rusby)

This article presents the findings of a laboratory study investigating the stimulation and conditioning of seeds with biochar and the effects observed in the germination and emergence of Virginia mallow (Sida hermaphrodita (L.) Rusby) seedlings. The study shows that biochar, applied as a conditioner added to water in the process of seed hydration, improves their germination capacity. When the processed plant material was added to water at a rate of 5 g (approx. 1250 seeds) per 100 mL, the rate of germination increased to 45.3%, and was 23.3% higher when compared to the control group, and 7.3% higher than in the seeds hydrated without biochar. The beneficial effects of biochar application were also reflected in the increased mass of Virginia mallow seedlings. The mass of seedlings increased by 73.5% compared to the control sample and by 25.9% compared to the seeds hydrated without biochar. Given the low cost of charcoal applied during the hydro-conditioning process, the material can be recommended as a conditioner in large-scale production of Virginia mallow.