A comprehensive review on dairy waste-scum as a potential feedstock for biodiesel production

The continuous rise in crude oil prices over the last decades and crisis in feedstock availability together with food-versus-fuel debate has directed the utilization of industrial wastes for biodiesel production. Accordingly, the biodiesel or fatty acid methyl ester production has been largely explored and demonstrated with a wide variety of wastes (as feedstock materials) of which the dairy waste scum from dairy industries has been recently shown to be a viable and promising feedstock. Therefore, a critical overview on the salient features, and desirable advancements achieved with regard to dairy waste scum derived biodiesel production has become crucial. In this context, this review gives insights into the dairy scum oil methyl ester (DSOME) production, its engine feasibility and economic viability. With the scientific progress made so far by many researchers, this study compiles and analyzes numerous homogeneous, heterogeneous, nano, and bio catalysts that can be adopted for DSOME production. The feasibility of DSOME usage in engine with and without modification has also been critically discussed. An economic analysis has also been carried out to demonstrate the small-scale production of DSOME to signify its economic viability. Thus, with the possibility of demand for biodiesel, and towards addressing the feedstock crisis, the dairy scum can be potentially developed as viable feedstock as it is abundantly and continuously available waste-material in dairy industries. This also contributes to the effective management of dairy wastes. Finally, a list of suggestions to fill the research and development gap in production, engine feasibility and economic analysis has also been proposed.