Process Systems Engineering for Biofuels Development

5Up‐grading of Waste Oil: A Key Step in the Future of Biofuel Production

Luigi di Bitontoand Carlo Pastore

Istituto di Ricerca Sulle Acque (IRSA), Consiglio Nazionale delle Ricerche (CNR), 70132 Bari, Italy

5.1 Introduction

Biodiesel is a mixture of fatty acid methyl esters (FAMEs), which has very similar physical and chemical properties to petroleum‐derived fuel (Borugadda and Goud 2012; Yusuf et al. 2011). It is industrially produced by transesterification of glycerides (animal and/or vegetal) with methanol (MeOH) under homogeneous alkaline conditions, by using sodium or potassium hydroxide, carbonates, or alkoxides (Figure 5.1; Baskar and Aiswarya 2016; Tubino et al. 2016; Bozbas 2008).

Figure 5.1 General equation to obtain biodiesel from triglycerides.

Despite the fact that the use of a co‐solvent would facilitate the formation of a single phase by improving the reaction rate (tetrahydrofuran, dimethyl sulfoxide, acetone, cyclic esters, and n‐hexane have been thoroughly investigated [Alhassan et al. 2014; Thanh et al. 2013; Liu et al. 2012]), in an industrial context, homogeneous basic catalysis is adopted in the presence of MeOH only, for the cost‐effectiveness and the relevant good performances.

However, such application can only be adopted on refined oils or highly pure fat: free fatty acids (FFAs) content must not exceed 0.1–0.5 wt% and moisture has to be absent ...