Initially, the binder and water were added into the bio-char proportionally
and the mixtures were thoroughly stirred. The dosage
of the binders varied from 5% to 20% (w/w). The amount of water
added was 20% (w/w). The water reintroduced into the bio-char
before compression enhanced the salutary briquette strength
through capillary binding effects [22]. Then, the mixtures were
filled into the mold cylinder and placed horizontally on the fixed
pedestal of the densification machine. The sample was compressed
by moving the girder down at a speed of 5 mm/min until the compressive
load reached 30 kN. The die was then held for 3 min at a
constant displacement for relaxation. Finally, the bio-char pellet
of 20 mm diameter was ejected from the mold and stored at
55 C. At least five replicates were made at each condition.