Biochar is produced as a charred material with high surface area and abundant functional groups by pyrolysis, which refers to the process of thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. The carbon component in biochar is relatively stable, and, hence, biochar was originally proposed as a soil amendment to store carbon in the soil. Biochar has multifunctional values that include the use of it for the following purposes: soil amendment to improve soil health, nutrient and microbial carrier, immobilising agent for remediation of toxic metals and organic contaminants in soil and water, catalyst for industrial applications, porous material for mitigating greenhouse gas emissions and odorous compounds, and feed supplement to improve animal health and nutrient intake efficiency and, thus, productivity. This article provides for the first time an overview of the multifunctional values and unintended consequences of biochar applications.

Recently, biochar has received significant attention, especially for the removal of potentially toxic elements (PTEs) from water and wastewater. No review has been focused on the potential use of wood-based biochar (WB) for the removal of PTEs in water and wastewater. Here, we have critically reviewed the (i) preparation and characterisation of WB; (ii) removal efficiency of WB for PTEs in water with respect to its physicochemical characteristics, biochar/water ratio, pH, and sorption system; (iii) removal mechanisms of PTEs by WB; (iv) fate of the sorbed PTEs onto WB; and (v) recovery of the sorbed PTEs from the resultant sludge of WB. We also discussed the removal of PTEs by engineered/designer WB as compared to pristine WB. This review demonstrates the overarching scientific opportunities for a comprehensive understanding of using WB as an emerging biosorbent and a promising low-cost and effective material for the remediation of PTEs contaminated water.