Remediation Potential of Biochar: A Physicochemical Perspective

Abstract

Several anthropogenic and weathering activities accumulate different types of organic and inorganic pollutants such as chromium (Cr), lead (Pb), arsenic (Ar), etc in soils, causing adverse effects on soil characteristics, soil microbial activity (diversity), agricultural practices, and underground aquifers. It inhibits plants growth mainly by creating stress of ion toxicity, osmotic imbalances, and high pH causing nutritional disorders and reducing soil water potential, limiting the uptake of essential plant nutrients (K, Ca, Mg, P, etc.) and water, hindering root respiration (Saha, 2017). All these together reduce the crop yield directly or indirectly by affecting the various physiological and developmental stages of crop plants such as photosynthesis, biomass, root and shoot length, etc. Heavy metal-contaminated soil is difficult to manage due to its persistence in soils for a long time, resulting in the deposition and transmission into the food web through agricultural food products, ultimately affecting human health. The remediation of soil by using biochar is a promising approach to mitigate soil contamination via immobilizing heavy metals and organic pollutants. Biochar is a type of charcoal made by the thermal decomposition of biomass, without the availability of oxygen. (Saha et al., 2017a). However, various types of feedstocks such as rice husk, bagasse, animal manure, and urban green waste are used for the production of biochar. Thermal decomposition of this biomass is involved in various methods. Pyrolysis, torrefaction, gasification, and Hydrothermal carbonization are involved in this production process. Pyrolysis is the process of thermal decomposition of biomass at a temperature range from 300-900º C. The good physiochemical properties of biochar possess high water holding capacity, cation exchange capacity, pH, and porosity, etc, improve soil health and crop physiological status. Biochar can increase crop yields by improving the properties of salt-affected soil, increasing the water status of crops, reducing Na+ uptake, increasing mineral uptake, and regulating stomatal conductance and phytohormone (Kumari et al., 2013) Hence, biochar produced from agro environmental waste is attracting huge interest as a low-cost amendment due to its potential numerous benefits to the environment and crop productivity. Thus, biochar addition in the agro-environment emerges as a “winwin strategy” for sustainable soil health and environmental eco-friendly assets.