Display omitted •Biochar for mitigating GHG emissions is reviewed.•Activity and reactivity are significant for the removal of contaminants.•The involved removal behaviors and mechanisms are reviewed.•Potential negative aspects of biochar applications are also discussed.•Possible improvements and outlooks of biochar applications are proposed. With increased interest in scientific investigations and large-scale applications of lignocellulosic biomass derived biochar for environmental management, a comprehensive understanding of its function in the fragile earth environment is urgently needed. The study on the relationship between biochar properties and potential applications requires continuing research. This review provides new insights into the state-of-the-art accomplishments in the utilization of biochar in environmental management and covers three perspectives: firstly, mitigation of greenhouse gas (GHG) emissions, such as sequestration of CO2 and CH4 in global carbon pools and mitigation of N2O emissions; secondly, pollution control, including adsorptive removal and reactive removal of inorganic and organic contaminants; thirdly, potential negative aspects of biochar applications, including contaminations originated from biochar, negative alterations to soil properties and soil biota, negative impacts of biochar on GHG emissions and negative impacts of biochar migration. From a unique and comprehensive environmental perspective, this article aims to provide a critical review of updated knowledge on both positive and negative impacts of biochar for environmental management, based on an exponentially increased number of publications on the topic over the past decade.