To 2–10 g of blended waste were added 5 ml of distilled water
and 8 ml of 8 M HCl and the mixture was heated at 70–80 C for
1.5 h. After cooling, the mixture was extracted thoroughly; twice
with 50 ml portions of diethyl ether/petroleum ether (1:1, by
volume) and then with a 25 ml portion of the same solvent. The extracts
were combined and dried with anhydrous Na2SO4 and the
organic solvent was removed by evaporation (water bath at
85 C). The dehydrated FOG was examined for its content of free
fatty acids and its fatty acid composition.