Insights into biochar and hydrochar production and applications: A review

Abstract Recently, there is an upsurge interest of using biomass derived char products in various fields, in order to address some of the most urgent energy and environmental problems we are facing today, such as CO 2 emission, energy crisis and environmental pollution. In this review paper, most recent studies on biochar/hydrochar production, characterization and prospective utilizations are summarized. Fundamentals and reaction mechanisms of biochar/hydrochar formations are discussed in detail. The energy balance and economic flexibility of biochar production technology is also analysed. The effects of reaction temperature, feedstock types, and thermochemical conversion modes on biochar are compared. In addition, we highlighted benefits and potential challenges in promoting biochar application in energy and environmental fields, including the applications in adsorbents, precursor of catalysts, soil amendment, anaerobic digestion and composting, and electrochemical energy storage materials. This paper not only summarises recent advances in engineered biochar technology but also demonstrates insights on new directions for biochar research and development in the future.