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 form preventing the separation of biodiesel from glycerine and
consequently reducing the final yield . For FFA >2.5 wt%, a pre-treatment process is usually
required before further processing is carried out. 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.