1. Introduction
Biochar is a kind of charcoal produced at moderate to high temperatures from forest residues, agricultural residues, or organic wastes via torrefaction, pyrolysis or gasification. Biochar has many advantages such as high heating value, slow degradation, and low greenhouse gas emissions [1]. One major disadvantage of biochar is its low volumetric energy density, which increases the transportation cost that limits its final uses. Other problems are fines and dust generated during handling and transportation that may potentially cause fires and explosions. Densification (also called