Biochar as a sorbent for contaminant management in soil and water: A review

Effects of rice straw biochar on sorption and desorption of di-n-butyl phthalate in different soil particle-size fractions

The transformation of agricultural waste into biochar that is both eco-friendly and cost-effective is not only a wise recycling strategy but also a solution to environmental pollution management. Due to its low cost, high efficiency, simplicity of use, ecological sustainability, and reliability in terms of public safety, biochar from agricultural residues can be a useful alternative technique for controlling contaminants. Biochars have achieved significant progress in the following areas: reducing greenhouse gas emissions, reducing soil nutrient dispersion, sequestering atmospheric carbon into the soil, increasing agricultural productivity, and reducing the bioavailability of environmental contaminants. A comprehensive scientific assessment of the relationship between the properties of biochars and their impact on soil properties, environmental pollutant remediation, plant growth, yield, and resistance to biotic and abiotic stresses is warranted by recent advancements in the understanding of biochars. The primary factors influencing biochar's properties are the feedstock nature, heat transfer rate, residence duration, and pyrolysis temperature. The efficacy of biochar in the management of pollutants is significantly influenced by its elemental composition, ion-exchange capacity, pore size distribution, and surface area, which are contingent upon the nature of the feedstock, preparation conditions, and procedures. The chapter investigated the potential of biochar derived from agricultural refuse as a viable alternative for the long-term application of biochar in the environment, soil conditioning, and the remediation of environmental pollutants.

Biochar shows significant potential to serve as a globally applicable material to remediate water and soil owing to the extensive availability of feedstocks and conducive physio-chemical surface characteristics. This review aims to highlight biochar production technologies, characteristics of biochar, and the latest advancements in immobilizing and eliminating heavy metal ions and organic pollutants in soil and water. Pyrolysis temperature, heat transfer rate, residence time, and type of feedstock are critical influential parameters. Biochar’s efficacy in managing contaminants relies on the pore size distribution, surface groups, and ion-exchange capacity. The molecular composition and physical architecture of biochar may be crucial when practically applied to water and soil. In general, biochar produced at relatively high pyrolysis temperatures can effectively manage organic pollutants via increasing surface area, hydrophobicity and microporosity. Biochar generated at lower temperatures is deemed to be more suitable for removing polar organic and inorganic pollutants through oxygen-containing functional groups, precipitation and electrostatic attraction. This review also presents the existing obstacles and future research direction related to biochar-based materials in immobilizing organic contaminants and heavy metal ions in effluents and soil.Graphical

Conversion of agricultural wastes into eco-friendly and low cost biochar is not only a smart recycling strategy but a panacea to environmental pollution management. Agricultural wastes biochar can be an effective alternative technique for controlling contaminants due to its low cost, high-efficiency, simple to use, ecological sustainability and reliability in terms of public safety. Biochars have made substantial breakthroughs in reducing greenhouse gases emissions, reducing soil nutrient leaching, sequester atmospheric carbon into the soil, increasing agricultural productivity, and reducing bioavailability of environmental contaminants. Recent advances in the understanding of biochars warrant a proper scientific evaluation of the relationship between its properties and impact on soil properties, environmental pollutant remediation, plant growth, yield, and resistance to biotic and abiotic stresses. The main factors controlling biochar properties include the nature of feedstock, heat transfer rate, residence time and pyrolysis temperature. Biochar efficacy in pollutants management largely depends on its elemental composition, ion-exchange capacity, pore size distribution and surface area, which vary with the nature of feedstock, preparation conditions and procedures. The chapter explored the possibility of using biochar from agricultural wastes as a suitable alternative for the remediation of environmental pollutants, soil conditioning and the long-term biochar application in the environment.

Combustion of biological residue under less condition of oxygen resulting in less density carbon material is biochar. As thermal decomposition of biomass under limited oxygen condition is responsible for producing biochar, this method is getting attention in soil remediation and waste disposal in recent years. On the advantages of biochar, interest increases nowadays and it may discover multidisciplinary field in science and engineering. Biochar has large area of surface and has greater capacity to absorb heavy metals from contaminated soil. It can be used to reduce the availability of heavy metals and organic pollutants in soil through adsorption as well as other physicochemical reactions. Basically, biochar is an alkaline material which can increase the pH of soil and responsible for heavy metal stabilization. Phytoremediation and biochar are two sound environmental technologies which could be at the forefront to mitigate soil pollution. For remediation of polluted soil, biochar applications may provide new solution for contaminated soil problems. The provided biochar application may include sequestration of carbon, improvement fertility of soil, remediation, and recycling of agricultural waste. For controlling its properties, the key parameters include pyrolysis temperature, time of residence, heat transfer rate, and feedstock type. This article will provide an overview of the biochar impact on the environment and movement of heavy metals in polluted soil as well as methods for remediation of contaminated soil through biochar. Also, in this review, a succinct overview of current biochar use as a sorbent for contaminant management in soil will be summarized and discussed.

Effects of biochars derived from different feedstocks and pyrolysis temperatures on the anaerobic digestion of kitchen waste

Increasing concentrations of greenhouse gases in the atmosphere caused by human activities are the main cause of climate warming. Global warming is a severe challenge confronted by human society today. Reducing greenhouse gas emissions and increasing carbon sinks are the keys to addressing climate warming. Biochar addition is considered to be a promising way to reduce greenhouse gas emissions and increase carbon sinks, due to its unique physical, chemical, and biological properties. Therefore, it is of great significance to study the effects of biochar on soil greenhouse gas emissions to mitigate the greenhouse effect and achieve "carbon neutrality." The long-term and short-term effects of biochar on soil greenhouse gas emissions and their influencing mechanism were reviewed. It was found that the effects of biochar on soil greenhouse gas emissions varied with the types of biochar feedstock, pyrolysis temperature, application ratio, and soil and vegetable types. In addition, due to the different aging times and modes and cultivation methods, the mitigation effect of aged biochar on soil greenhouse gas could be enhanced or weakened or even disappeared. Further, based on the deficiencies of the previous research, the direction and focus of future research on the effects of biochar on soil greenhouse gas emissions were analyzed and prospected. It was proposed to strengthen simultaneous research on the effects of biochar on CO2, N2O, and CH4 emissions; reducing greenhouse gas emissions and carbon sequestration; different aging modes and cultivation methods of biochar; and revealing the influencing mechanism at the process level, through exploring the effects of biochar on soil carbon and nitrogen dynamics and tracing the source of greenhouse gases using 13C and 15N tracer technology.

Emerging nanomedical techniques: Transforming contaminant management in soil and water

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

Generally, waste management and nutrient cycling are constrained by inadequate utilization of crop waste products, erratic supply of energy, lack of knowledge of better processing, low value of some waste/ byproducts, and disorganized disposal in most of our societies. Biochar and animal manure are becoming popular on environmental issues, sustainable agriculture, and food quality concerns globally. Biochar production and application are important in the management of crop residues and livestock wastes that conserve environments and cycle nutrients in agriculture. Production and application of animal manures are very important in the cycling of nutrients in agriculture and management of livestock wastes. The effect of biochar on the improvement of soil fertility, yield, and quality of crops depends on the type of feedstock, pyrolysis temperature, soil characteristics, climate, and crop type. Application of biochar increases soil pH up to two times in highly weathered acidic soils of tropics while in sand desert soils it decreases soil pH depending on the materials used. Biochar may be animal or plant derived. Also, it can be acidic or alkaline depending on the nature of the materials which has a significant effect on soil reaction and nutrient availability. The application of biochar improves soil texture, structure, bulk density, chemical properties, and flora and fauna in the soil which has a positive effect on yields of crops and food quality. The effect of animal manure on soil fertility improvement depends very much on the quality of manure, soil properties, climatic conditions, and crop type. Animal manure and biochar have been reported to improve soil fertility and crop yield with a significant contribution to food quantity and quality.KeywordAnimal manureBiocharCrop yieldFarmyard manureMacronutrientsMicronutrientsPyrolysisResiduesSoil fertilityWaste management

Biochar characteristics, applications and importance in health risk reduction through metal immobilization

Biochar is recommended as a soil amendment for its positive influence on soil hydrological properties, which results in improved soil fertility and crop yield. Much research in the last decade has been conducted in field and laboratory conditions on the effect of biochar on the hydraulic properties of soil. However, reported results in the literature are substantially inconsistent. Here we performed a meta‐analysis to capture the variations in change in hydraulic properties of arable soils after application of different rates of biochar. The meta‐analysis revealed that high biochar rates (>50 t ha −1 ) compared to low rates (<20 t ha −1 ) significantly improved dry bulk density in sandy and clay soils, in field and laboratory experiments. However, field capacity only improved in laboratory experiments on sandy soils. The plant available water, permanent wilting point and saturated hydraulic conductivity did not significantly increase at high rates of biochar application compared to the low rates when applied to different types of soils in both field and laboratory experiments. We discuss possible reasons for this, including hydrophobicity of the biochar with future research directions. We concluded that the current evidence does not support the notion that the application of biochar improves soils' available water capacity. Highlights Meta‐analysis clarifies the influence of biochar on soil hydraulic properties. Biochar addition at higher rates only improves the water holding capacity of sandy soils. Biochar types and pyrolysis temperatures do not influence soil hydraulic properties. The efficiency of biochar may depend on its pore size distribution and hydrophobicity.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously distributed throughout the environment, representing a challenge for environmental scientists and decision makers. As soil constitutes a natural sink for contaminants, the control and management of contaminated soil has been the focus of multiple investigations since the last quarter of the 20th century. Within the different approaches that have been developed for this purpose, the use of plants for the remediation of contaminated soil can be considered as a promising technology given its overall low cost and general public acceptance. Although this technology has been studied for over 30 years, the specific mechanisms behind the process have not been fully understood yet. Therefore, the aim of this thesis was to investigate the impact of plant root biomass and components typically found within root exudates on the biodegradation and bioaccessibility of phenanthrene from soil with particular interest in the study of root-induced changes of hydrocarbon bioaccessibility. Results showed that microbial catabolism and biodegradation of 14C-phenanthrene can be promoted by the incorporation of plant roots into the soil, with significant effects most likely to be observed after an adaptation period. Moreover, although chemically assessed bioaccessibility of 14C-phenanthrene was not observed to be affected by root biomass or organic acids typically found within root exudates, the use of high concentrations of citric and malic acid were observed to promote lager desorbable fractions of the hydrocarbon. This thesis contributes evidence supporting the role of root decay, turnover and exudation for the biodegradation of PAHs in contaminated soil as defining mechanisms by which plants can promote the biodegradation of this type of contaminants.

Biochar is a porous solid material produced by pyrolysis (oxygen-free burning) of biomass for the sake of improving soil quality. The aim of this study was to examine the effect of biochar application rate, pyrolysis temperature and feedstock type on the fertility of leached, acidic, clay soil. The biochars used in the study were produced from rice husk (RH) and maize straw (MS) at pyrolysis temperatures of 350, 450 and 550 °C, so in total six biochars were used. To examine the effects of biochar on soil amendment, the six biochars were mixed with the acidic, clay soil at four different levels of applications (0.5, 2.0, 5.0 and 10.0% w/w) then they were chemically characterized. pH, electrical conductivity, CEC, exchangeable basic cations, WHC, organic carbon and total nitrogen content were determined. The increment in the application rate of biochar resulted in a significant increment in soil pH, CEC, exchangeable basic cations, WHC, Organic carbon content. Increasing the biochar production temperature from 350 to 550 °C brought slight increment in pH, Electrical conductivity and Organic carbon content of the soil. Incorporating RH biochar in the soil resulted in higher soil pH but higher organic carbon content of the soil was acquired by incorporating MS biochar.

As a by-product generated from the pyrolysis of biomass, biochar is extraordinary for improving the soil environment of agricultural fields, improving soil fertility, and promoting nutrient uptake and the utilization of crops. In recent years, breakthroughs in progress have been made regarding the fertility value of biochar and in investigations into the physicochemical properties of soil and into plant nutrient utilization. This review focuses on the physicochemical and biological properties of soil, on soil pollution remediation, on greenhouse gas emissions, and on the effects of biochar on the uptake and utilization of soil nutrients and plant nutrients, as well as on the preparation of biochar, and on biochar produced under different conditions. The results of the relevant studies show that the main characteristics of biochar depend on the biochemical properties and pyrolysis temperature of raw materials, which play an important role in nutrient transport and transformation in the soil. At low temperatures (≤400 ℃), the biochar prepared from manure and waste contains a large amount of nitrogen, which can be used as a nutrient source for plants. In addition, biochar enhances soil fertilizer retention by reducing soil nutrient loss, which in turn promotes nutrient uptake and utilization by crops. By controlling pyrolysis temperature and by optimizing biochar input, one can effectively reduce soil respiration, as well as reduce carbon emissions to achieve the goal of controlling carbon sources and increasing carbon sinks. Therefore, a long-term series of mapping studies on the effects of biochar application on agricultural ecosystems should be conducted, which in turn, it is hoped, will provide a theoretical reference for the physiological and ecological effects of biochar croplands.