Sanchita Mandal

Engineered/designer biochar for contaminant removal/immobilization from soil and water: Potential and implication of biochar modification

The use of biochar has been suggested as a means of remediating contaminated soil and water. The practical applications of conventional biochar for contaminant immobilization and removal however need further improvements. Hence, recent attention has focused on modification of biochar with novel structures and surface properties in order to improve its remediation efficacy and environmental benefits. Engineered/designer biochars are commonly used terms to indicate application-oriented, outcome-based biochar modification or synthesis. In recent years, biochar modifications involving various methods such as, acid treatment, base treatment, amination, surfactant modification, impregnation of mineral sorbents, steam activation and magnetic modification have been widely studied. This review summarizes and evaluates biochar modification methods, corresponding mechanisms, and their benefits for contaminant management in soil and water. Applicability and performance of modification methods depend on the type of contaminants (i.e., inorganic/organic, anionic/cationic, hydrophilic/hydrophobic, polar/non-polar), environmental conditions, remediation goals, and land use purpose. In general, modification to produce engineered/designer biochar is likely to enhance the sorption capacity of biochar and its potential applications for environmental remediation.

Biochar-induced concomitant decrease in ammonia volatilization and increase in nitrogen use efficiency by wheat

Ammonia (NH3) volatilization is a major nitrogen (N) loss from the soil, especially under tropical conditions, NH3 volatilization results in low N use efficiency by crops. Incubation experiments were conducted using five soils (pH 5.5-9.0), three N sources such as, urea, di-ammonium phosphate (DAP), and poultry manure (PM) and two biochars such as, poultry litter biochar (PL-BC) and macadamia nut shell biochar (MS-BC). Ammonia volatilization was higher at soil with higher pH (pH exceeding 8) due to the increased hydroxyl ions. Among the N sources, urea recorded the highest NH3 volatilization (151.6 mg kg(-1)soil) followed by PM (124.2 mg kg(-1)soil) and DAP (99 mg kg(-1)soil). Ammonia volatilization was reduced by approximately 70% with PL-BC and MS-BC. The decreased NH3 volatilization with biochars is attributed to multiple mechanisms such as NH3 adsorption/immobilization, and nitrification. Moreover, biochar increased wheat dry weight and N uptake as high as by 24.24% and 76.11%, respectively. This study unravels the immense potential of biochar in decreasing N volatilization from soils and simultaneously improving use efficiency by wheat.

Designing advanced biochar products for maximizing greenhouse gas mitigation potential

ABSTRACT Greenhouse gas (GHG) emissions from agricultural operations continue to increase. Carbon (C)-enriched char materials like biochar have been described as a mitigation strategy. Utilization of biochar material as a soil amendment has been demonstrated to provide potentially greater soil GHG suppression due to its interactions in the soil system. However, these effects are variable and the duration of the impact remains uncertain. Various (nano)materials can be used to modify chars to obtain surface functionality to mitigate GHG emissions. This review critically focusses on the innovative methodologies for improving char efficiency, underpinning GHG mitigation and C sequestration.

Designer carbon nanotubes for contaminant removal in water and wastewater: A critical review

The search for effective materials for environmental cleanup is a scientific and technological issue of paramount importance. Among various materials, carbon nanotubes (CNTs) possess unique physicochemical, electrical, and mechanical properties that make them suitable for potential applications as environmental adsorbents, sensors, membranes, and catalysts. Depending on the intended application and the chemical nature of the target contaminants, CNTs can be designed through specific functionalization or modification processes. Designer CNTs can remarkably enhance contaminant removal efficiency and facilitate nanomaterial recovery and regeneration. An increasing number of CNT-based materials have been used to treat diverse organic, inorganic, and biological contaminants. These success stories demonstrate their strong potential in practical applications, including wastewater purification and desalination. However, CNT-based technologies have not been broadly accepted for commercial use due to their prohibitive cost and the complex interactions of CNTs with other abiotic and biotic environmental components. This paper presents a critical review of the existing literature on the interaction of various contaminants with CNTs in water and soil environments. The preparation methods of various designer CNTs (surface functionalized and/or modified) and the functional relationships between their physicochemical characteristics and environmental uses are discussed. This review will also help to identify the research gaps that must be addressed for enhancing the commercial acceptance of CNTs in the environmental remediation industry.

Advances and future directions of biochar characterization methods and applications

ABSTRACT Biochar is a carbon-rich by-product of the thermal conversion of organic feedstocks and is primarily used as a soil amendment. Identification and quantification of biochar properties are important to ensure optimal outcomes for agricultural or environmental applications. Advanced spectroscopic techniques have recently been adopted in biochar characterization. However, biochar characterization approaches rely entirely on the users choice and accessibility to the new technology. The selection of proper methods is vital to accurately and consistently assess biochar properties. This review critically evaluates current biochar characterization methods of proximate, ultimate, physicochemical, surface and structural analyses, and important biochar properties for various applications.

The effect of biochar feedstock, pyrolysis temperature, and application rate on the reduction of ammonia volatilisation from biochar-amended soil

Ammonia (NH3) volatilisation is one of the most important causes of nitrogen (N) loss in soil-plant systems worldwide. Carbon-based amendments such as biochar have been shown to mitigate NH3 volatilisation in agricultural soils to various degrees. In this study, we investigated the influence of biochar feedstocks (poultry manure, green waste compost, and wheat straw), pyrolysis temperatures (250, 350, 450, 500 and 700°C) and application rates (1 and 2%), on NH3 volatilisation from a calcareous soil. The 15 biochars were chemically characterized, and a laboratory incubation study was conducted to assess NH3 volatilisation from the soil over a period of four weeks. Furthermore, changes to the bacterial and fungal communities were assessed via sequencing of phylogenetic marker genes. The study showed that biochar feedstock sources, pyrolysis temperature, and application rates all affected NH3 volatilisation. Overall, low pyrolysis temperature biochars and higher biochar application rates achieved greater reductions in NH3 volatilisation. A feedstock related effect was also observed, with poultry manure biochar reducing NH3 volatilisation by an average of 53% in comparison to 38% and 35% reductions for biochar from green waste compost and wheat straw respectively. Results indicate that the biogeochemistry underlying biochar-mediated reduction in NH3 volatilisation is complex and caused by changes in soil pH, NH3 sorption and microbial community composition (especially ammonia oxidising guilds).

Soil Mineralogical Perspective on Immobilization/Mobilization of Heavy Metals

Knowledge on the fate and transport of heavy metals is essential for predicting the environmental impact of metal contamination on agricultural soils. This chapter presents an overview of various factors that are involved in controlling the retention and mobility of heavy metals in soils with a special reference to soil mineralogy. The bioavailability of most elements, in particular heavy metals, in soils is governed by adsorption-desorption, complexation, precipitation and ion-exchange processes. The most important surfaces involved in metal adsorption in soils are active inorganic colloids such as clay minerals, oxides and hydroxides of metals, metal carbonates and phosphates and organic colloids. In addition to soil mineralogy, other important parameters controlling heavy metal retention and their distribution are soil texture, structure, pH, redox condition, cation and anion concentration, ionic strength, organic matter, microbial and root activity and climatic conditions. However, the ultimate fate of elements depends on a combination of several factors that are working together in the soil system. Finally, several remediation strategies have also been highlighted based on the fundamental principles of metal immobilization on mineral containing soil amendments.

Clay Minerals—Organic Matter Interactions in Relation to Carbon Stabilization in Soils

Abstract Stabilization of C in soil is important for minimizing greenhouse gas emission into the atmosphere and for improving the soil fertility. The physical, chemical, and biological properties of soil greatly influence the C protection capacity. Both the physical and chemical properties of soils are directly or indirectly governed by clay minerals, which are the most reactive soil particles. Apart from the amount of clays, clay types are also very important in protecting soil C. Clay minerals provide both permanent and variable surface charges and different specific surface areas that are crucial to determine the C protection capacity of soils. They form organo–mineral complexes, promote aggregate establishment, and protect soil organic matter against microbial decomposition. This chapter aims to provide an overview of the role of various clay minerals in protecting organic C in soils and highlights the mechanisms of C sequestration by clay minerals.

Use of Soil Amendments in an Integrated Framework for Adaptive Resource Management in Agriculture and Forestry

Agricultural practices involving intensive applications of chemical fertilizers can be harmful to the environment. Soil amendments can serve as an alternative source of plant nutrients and simultaneously improve the physical, chemical and biological properties of soils. Many soil amendments are produced from organic and inorganic waste materials. The amendment application practices therefore not only support the agricultural productivity but also facilitate an environmental friendly disposal and recycling of the wastes. This also helps the farmers to reduce their cost of production. Most of the soil amendments supply nutrients to plants over a longer period of time in a slow release process. However, best management practices should be adapted in order to harness the optimum benefits of soil amendments in agricultural and forestry production systems. This chapter aims to present an overview of various soil amendments in relation to their already existing and/or potential applications for improving the productivity and health of soils.

Application of Biochar Produced From Biowaste Materials for Environmental Protection and Sustainable Agriculture Production

Abstract Biochar has created a lot of interest because of its unique properties of sustainable agricultural production and environmental protection. Biochar is known to reduce nitrogen loss from soil in terms of nitrous oxide emission and ammonia volatilization, improve the nutrient retention capacity and structural and chemical properties of soil, and increase plant growth and productivity. Biowaste materials such as biosolids, municipal waste, and paper mill sludge are effective raw materials for biochar production. These materials are rich in nutrient content, and biochar produced using these waste products is highly effective for agricultural production and environmental remediation.