From this observation, the conversion of CaO to
Ca(OH)2 due to the moisture was calculated as 15 and 33 wt.%
for three-month and one-year old catalysts, respectively. Nevertheless,
the amount of Ca(OH)2 in the catalysts (formed due to
the moisture) did not affect the catalytic performance and the
FAME yield for three months and caused a 10% decrease in FAME
yield after a year (Fig. 5). According to Kouzu et al., Ca(OH)2 can
be used successfully as a catalyst in transesterification reactions
and produce the same FAME yield as CaO; however, it takes more
time due to longer induction period [15]. Since the desired FAME
yield in the current study was obtained after 11 h of reaction