This chapter focuses on the synthesis and application of agro-waste-based biochar with a perspective of circular bioeconomy. Numerous methods are known for the synthesis of biochar; however, pyrolysis of agro-waste is the highly acclaimed method for biochar production from agro-waste. Biochar production is influenced by multiple factors including nature and source of feedstock, pyrolysis conditions, and the system/device used for thermal treatment. The biochar properties enable it to be applied in several fields including wastewater treatment, soil improvement, reduction of greenhouse gas emissions, carbon sequestration, sludge improvement, etc. The commissioning and erection of production facilities nearby agro-waste production sites, can reduce the supply chain and transport, and also improve the sustainability and development of circular bioeconomy. The application of biochar in water treatment can reduce the burden on market for the production and application of expensive adsorbents and hence, the agro-waste-based green adsorbent (biochar) can enhance bio-sustainability and subsequently circular bioeconomy.