Currently biodiesel is one of the most promising first generation biofuel. It is possible to produce biodiesel from any raw materials containing either vegetable or animal fatty acids or their mono-, di- and triglycerides. In the case of fatty acid glycerides, the most common method for producing the biodiesel is using transesterification reaction with methanol in the presence of homogeneous alkaline catalysts. Inexpensive, but valuable biodiesel feedstock, such as the by-products of vegetable oil refining, used cooking oils, animal fat, fats contained in crude glycerol, etc. contain high levels of free fatty acids which completely eliminate the use of alkaline catalysts, but increase the possibilities of acid catalyst application. Due to the high activity and low cost sulfuric acid has become the most widespread acidic catalyst used in the biodiesel production. Considerable amounts of energy and raw materials could be saved and thus reduction in overall product costs could be attained as a result of optimization of various fatty acids containing mixtures esterification and transesterification in the presence of sulfuric acid.