Types of refined oil feedstock which contain
FFAs 3 wt%
will lead to soap formation due to the reaction between the
FFA and the catalyst. Consequently, stable emulsion will formpreventing the separation of biodiesel from glycerine and
consequently reducing the final yield (Canakci and Gerpen,
2001). For FFA >2.5 wt%, a pre-treatment process is usually
required before further processing is carried out (Leung et al.,
2010; Talebian-Kiakalaieh et al., 2013). Based on these studies,
biodiesel producers using any type of feedstock with FFA
content above 2.5 wt% need to handle problems of those mentioned.