Global warming, environmental pollution, and energy shortage are causing severe environmental concerns worldwide. Conversion of various renewable biowastes into value-added carbon-based material can be a promising option to alleviate these issues and ensure sustainable development. The emergence of nitrogen (N)-doped biochar provides a versatile electroactive platform suitable for environmental applications. In this review, we summarise and highlight the customised productions of N-doped biochars and their applications in environmental remediation, energy storage, and biorefinery, etc. With a comprehensive overview of original precursor, interspecies conversion, and ultimate deactivation of various N-dopants in biochar-based carbocatalysis; their formation mechanism, distinct electrochemical characteristics, fate in the environmental applications, and electrochemical behaviours can be comprehensively analysed. Contemporary challenges that require to be addressed, and perspectives on improving N-doping technique on biochar are provided throughout the review. Overall, this review can help to cultivate new insights in the customised production of N-doped biochar for its broader applications in sustainable carbocatalysis and green chemistry.