Biochar, a pyrolysis product of biomass transformation processes, has gained increasing attention as a low-cost and eco-friendly method for treating pollutants and amending soils. The high porosity, large surface area, and oxygen-functional groups in biochars facilitate their utilization for adsorption of causal pathogens and pollutants. Nevertheless, due to its great adsorption capacity, a number of drawbacks and gaps in knowledge do regulate its extensive use in the field of environmental remediation. The list of challenges mentioned here is critical, as it is based on the heterogeneity of biochar physicochemically, interaction of the pollutants, reusability and regeneration, long-term stability, environmental and regulatory concerns, and others. Selection of suitable feedstock for biochar production is the premier challenge, and then it mostly depends upon pyrolysis conditions and post-treatment processing. Furthermore, the majority of studies are centered on single-pollutant systems, while natural contamination is always a multifaceted mixture, i.e., co-existing pollutants, with diverse chemical characteristics. The long-term biochar stability and degradation properties in the environment are still a challenge, even post-adsorption of any pollutants. Undoubtedly, in scaling up the use of this potential material, reusability and regeneration would be one of the major concerns. Regulatory and environmental issues complicate the application of biochar as well. Overcoming these limitations will be essential in realizing the determined potential of biochar as a green remediation technology for pollutant removal. Here in this chapter, we will discuss the limitations and the knowledge gap in biochar research and development.