In this study, low-grade crude palm oil (LGCPO) containing 13.81 wt.% free fatty acid (FFA)
was used as raw material. This study aimed to investigate the eff ects of LGCPO preparation
methods on biodiesel basic properties, easing environmental impacts from sulfur emissions,
and getting to zero-sulfur biodiesel. Hence, hydrochloric acid, which is an eff ective and
environmentally friendly homogeneous acid catalyst, was selected as the catalyst to reduce FFA
in pretreatment and to produce green biodiesel. The results indicate that the use 0.25 wt.% of
hydrochloric acid as a catalyst in biodiesel production could effi ciently reduce the FFA content to
a standard level ( < 2.00 wt.%) at 0.56 wt.% (FFA conversion 95.95%). The fi nal ester contents
were 98.05 and 97.31 wt.% for washed esterifi ed palm oil (EPO) and for rinsed EPO without
washing, respectively. Consequently, hydrochloric acid is a suitable catalyst and could replace
the conventional sulfuric acid in biodiesel production from low quality crude palm oil. This
would reduce the environmental impacts, especially sulfur emissions. High FFA leads to soap
formation in fatty acid methyl ester (FAME) saponifi cation causing problems in phase separation
and emulsion formation during the purifi cation stage, so catalytic preprocessing is a necessity