After the carbonization of carbonaceous material, the pores are filled with tar. To activate the carbon material, we need activation to get rid of tar and open the pore. The activation can be chemical activation by dissolving the tar in acid or physical activation by evaporating the tar as CO2 in high temperatures and a normal atmosphere.
In some cases, the chemical-activated carbon has some residues in the pores that may be not compatible with bio applications. Biochar ensures that the activated carbon has no harmful residues for bio applications. Normally Biochar has been activated by physical activation so there will be no residues in the pores. Moreover, biochar is normally made from biomass such as bamboo.