Abstract: Methods and apparatuses for depositing agents relatively deep within pores of bio-char. Bio-char is first produced in an airtight oven by heating biomass feedstock. The bio-char is then cooled and steam is diffused into the pores of the bio-char. The steam-laden bio-char is immersed in a liquid bath containing soluble agents that are to be deposited in the pores of the bio-char. The liquid bath cools the char to below the condensation temperature of the steam, whereupon the condensing steam generates a partial vacuum within the pores, drawing the liquid into the pores. The bio-char is then removed from the liquid bath and dried so that the liquid within the pores evaporates, leaving behind the soluble agent. Accordingly, the invention yields bio-char that has soluble agent embedded relatively deep within its pores.