Economic and ecological aspects of biodiesel production over homogeneous and heterogeneous catalysts

The objective of this paper is to highlight the economic and ecological differences of biodiesel production over homogeneous and heterogeneous catalysts in large-scale industrial plants. Comparative economic assessment of the two processes revealed the advantage of the heterogeneous process in terms of higher yield of biodiesel and higher purity of glycerine, lower cost of catalyst and maintenance, with an estimated cumulative impact on the reduction of the operating cost of US$59 per tonne of biodiesel, relative to the homogeneous process. The biggest challenge for its economic competitiveness is its higher energy consumption. The analysis showed that if the energy costs are below US$85 per tonne of biodiesel, the heterogeneous process can be economically viable. The environmental benefits of the heterogeneous process include absence of strong acids and of energy intensive and waste generating glycerine purification step. However, its application would contribute to depletion of fossil energy resources and higher emission of greenhouse gases due to higher energy and methanol consumption.