3.4. Biodiesel production from BSFL grease
A two step approach with acid-catalyzed esterification and
sequential alkaline-catalyzed transesterification was used for biodiesel
production. Briefly, as a pretreatment to convert free fatty
acids in the crude grease into biodiesel, acid-catalyzed esterification
was conducted at the following conditions: 1% H2SO4 as the
catalyst, 75 C, methanol to grease ratio (8:1), and reaction for
1 h, to decrease the acid value of the crude grease. Resulted mixture
was poured into a funnel for separation. The upper layer containing
crude grease and biodiesel was further transferred into a
new reactor for alkaline-catalyzed transesterification at the following
conditions: methanol to grease ratio of 6:1, 0.8% NaOH (w/w)
as the catalyst, 65 C, and reaction time of 30 min. After separation
with a funnel, the biodiesel layer was distilled at 80 C to remove
residual methanol. About 3.17 g of biodiesel was extracted from
3.34 g BSFL grease with the extraction yield of 94.91%.