Biochar obtained from the thermal conversion of biomass has high potential as a substitute material for activated carbon and other carbon-based materials because it is economical, environmentally friendly, and carbon-neutral. The physicochemical properties of biochar can also be controlled by a range of activation methods such as physical, chemical, and hydrothermal treatments. Activated biochar can be used as a catalyst for the catalytic pyrolysis of a biomass and as an absorbent for the removal of heavy metal ions and atmospheric pollutants. The applications of biochar are also expanding not only as a key component in producing energy storage materials, such as supercapacitors, lithium ion batteries, and fuel cells, but also in carbon capture and storage. This paper reviews the recent progress on the activation of biochar and its diverse present and future applications.

Abstract
 1. Introduction
 2. Biochar activation
  2.1. Physical activation
  2.2. Chemical activation
  2.3. Hydrothermal carbonization
  2.4. Other activation methods
 3. Biochar for the catalytic pyrolysis of a biomass
 4. Biochar as an energy storage material
  4.1. SCs
  4.2. Electrodes in lithium-ion batteries
  4.3. Fuel cells
 5. Biochar as an environmental material
  5.1. Carbon capture and storage
  5.2. Removal of heavy metal ions
  5.3. Removal of atmospheric pollutants
 6. Conclusion
 References

• Hyung Won Lee(School of Environmental Engineering, University of Seoul) Co-first author
• Young-Min Kim(Department of Environmental Sciences and Biotechnology, Hallym University) Co-first author
• Seungdo Kim(Department of Environmental Sciences and Biotechnology, Hallym University)
• Changkook Ryu(School of Mechanical Engineering, Sungkyunkwan University)
• Sung Hoon Park(Department of Environmental Engineering, Sunchon National University)
• Young-Kwon Park(School of Environmental Engineering, University of Seoul) Corresponding Author