Potential of tannery fleshings in biodiesel production and mathematical modeling of the fleshing pre-treatment

Abstract

Waste fat produced by tanneries during the processes in which raw hide is transformed into leather represents a very important raw material for biodiesel production. However, the acid number of this feedstock is usually high above the limit 1 mg KOH/g, which makes it unsuitable for direct processing into biodiesel via alkali-catalyzed transesterification. An effective and economically viable pre-treatment method is needed to overcome this disadvantage and at the same time to maintain the advantage of low price of the feedstock. In this paper, we present a pre-treatment method consisting of the refining melting and deacidification steps. The pretreatment processes are part of a complex technology for biodiesel production from low quality fats and oils. Mathematical models of the said processes have been elaborated for the optimization of the pre-treatment procedure, as well as a software application developed for simulation of the deacidification step. Suitability and economic parameters of the pre-treatment technology for feedstocks with various free fatty acid content is discussed. Finally, the waste tannery fat potential in biodiesel production is briefly evaluated from the economic and raw material base point of view.