Citation: Chandra, S.; Medha, I.; Tiwari, A.K. The Role of Modified Biochar for the Remediation of Coal Mining-Impacted Contaminated Soil: A Review. Sustainability 2023, 15, 3973. https://doi.org/10.3390/ su15053973 Academic Editor: Cláudio Moisés Santos e Silva Received: 30 December 2022 Revised: 13 February 2023 Accepted: 15 February 2023 Published: 22 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Review The Role of Modified Biochar for the Remediation of Coal Mining-Impacted Contaminated Soil: A Review Subhash Chandra 1, *, Isha Medha 2,3 and Ashwani Kumar Tiwari 4, * 1 Department of Civil Engineering, GITAM School of Technology, Gandhi Institute of Technology and Management University, Visakhapatnam 530045, India 2 Department of Mining Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India 3 Department of Civil Engineering, Vignan’s Institute of Information Technology, Duvvada, Visakhapatnam 530049, India 4 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India * Correspondence: schandra3@gitam.edu (S.C.); ashwaniktiwari@mail.jnu.ac.in (A.K.T.) Abstract: Land degradation and the release of contaminants such as heavy metals into the environ- ment due to mining activities is a concerning issue worldwide. The bioaccumulation of heavy metals in the environmental matrix can severely damage flora and fauna and negatively impact human health. The poor physicochemical properties of mine spoil generated through mining operations make restoration of such contaminated and degraded lands challenging. In recent years, an exponen- tial growth in the development and applications of biochar and its composites for the remediation of heavy metal-polluted environmental matrices such as soil and water has been observed. The literature review found that 95 review papers were published in the last five years reviewing the utility of biochar for heavy metals removal from the aqueous environment. However, no paper was published focusing on the application of biochar and its composites for the remediation of heavy metal-contaminated coal mine soil. The objective of the present review is to critically review the impact of mining activities on the environment and the role of biochar and its composites in the remediation of heavy metal-contaminated mine soil. This review presented a detailed discussion and sufficient data on the impact of mining practices in India on the environment. In addition, it critically discussed the methods of the production of biochar from various wastes and methods of modifying the pristine biochar to develop functionalized biochar composites. The detailed mechanism through which biochar and its composites remove and immobilize the heavy metals in the soil was discussed. The efficacy of biochar for the remediation of contaminated mine soil was also critically evaluated using various case studies and data from previously published articles. Thus, the major conclusion drawn from the review is that the application of various functionalized biochar composites could effectively manage and remediate heavy metal-contaminated mine soil. Keywords: biochar; heavy metals; mine soil; pollution; remediation 1. Introduction The release of pollutants, particularly heavy metals, into the environment has become ubiquitous due to industrialization and urbanization. In the last decade, rapid growth in the worldwide population has created a massive demand for supply chain systems and energy requirements. To cater to the increased demands, particularly the energy requirement, which has almost doubled, most developing countries rely on coal-based thermal power plants to meet their energy demand [1]. Globally, coal production is around 7.90 billion tonnes (BTs) [2], of which China is the leading producer, followed by India and the USA. Recent energy data estimated that coal produces approximately 40% of the world’s electricity. It has also been forecasted to be the most demanded fuel to fulfill energy needs over the next three decades [2]. India is the world’s seventh-largest economy and the second most populated country [3]. The continuous increase in the population and Sustainability 2023, 15, 3973. https://doi.org/10.3390/su15053973 https://www.mdpi.com/journal/sustainability